学堂乐歌的回响——钱君匋儿童歌曲研究

文章以钱君匋的儿童歌曲为研究对象,在分析歌词和考证曲调来源基础上,阐述其跟近现代中国文化与教育变迁之间的紧密联系,从而展现这些歌曲产生的历史必然性、先进性、局限性,以利于客观、公正地认识和评价钱君匋儿童歌曲的历史价值和艺术价值。通过钱君匋的儿童歌曲,也可以观察到在中外、新旧文化的碰撞下,人们在思想观念方面呈现出的变化。

Power source–power grid coordinated typhoon defense strategy based on multiagent dynamic game theory

A power source–power grid coordinated typhoon defense strategy is proposed in this study to minimize the cost of power grid anti-typhoon reinforcement measures and improve defense efficiency.It is based on multiagent dynamic game theory.This strategy regards a typhoon as a rational gamer that always causes the greatest damage.Together with the grid planner and black start unit(BSU)planner,it forms a multiagent defense–attack–defense dynamic game model naturally.The model is adopted to determine the optimal reinforcements for the transmission lines,black start power capacity,and location.Typhoon Hato,which struck a partial coastal area in Guangdong province in China in 2017,was adopted to formulate a step-by-step model of a typhoon attacking coastal area power systems.The results were substituted into the multiagent defense–attack–defense dynamic game model to obtain the optimal transmission line reinforcement positions,as well as optimal BSU capacity and geographic positions.An effective typhoon defense strategy and minimum load shedding were achieved,demonstrating the feasibility and correctness of the proposed strategy.The related theories and methods of this study have positive significance for the prevention of uncertain large-scale natural disasters.

Best linear unbiased estimation algorithm with Doppler measurements in spherical coordinates

In an active radar-tracking system,the target-motion model is usually modeled in the Cartesian coordinates,while the radar measurement usually is obtained in polar/spherical coordinates.Therefore the target-tracking problem in the Cartesian coordinates becomes a nonlinear state estimation problem.A number of measurement-conversion techniques,which are based on position measurements,are widely used such that the Kalman filter can be used in the Cartesian coordinates.However,they have fundamental limitations to result in filtering performance degradation.In fact,in addition to position measurements,the Doppler measurement or range rate,containing information of target velocity,has the potential capability to improve the tracking performance.A filter is proposed that can use converted Doppler measurements（i.e.the product of the range measurements and Doppler measurements） in the Cartesian coordinates.The novel filter is theoretically optimal in the rule of the best linear unbiased estimation among all linear unbiased filters in the Cartesian coordinates,and is free of the fundamental limitations of the measurement-conversion approach.Based on simulation experiments,an approximate,recursive implementation of the novel filter is compared with those obtained by four state-of-the-art conversion techniques recently.Simulation results demonstrate the effectiveness of the proposed filter.

Experimental generation and observation of a super-resolution optical tube

We generated a super-resolution optical tube by tightly focusing a binary phase modulated azimuthally polarized laser beam.The binary phase modulation is achieved by a glass substrate with multi-belt concentric ring grooves.We also characterized the 3D beam pro¯le by using a crossshaped knife-edge fabricated on a silicon photo-detector.The size of the super-resolution dark spot in the tube is 0.32
,which remains unchanged for
4
within the tube.This optical tube may¯nd applications in super-resolution microscopy,optical trapping and particle acceleration.

Effect of tillage state of paddy soils with heavy metal pollution on the nosZ gene of N_(2)O reductase

Paddy soils are an important source of atmospheric nitrous oxide(N_(2)O).However,numerous studies have focused on N_(2)O production during the soil tillage period,neglecting the N_(2)O production during the dry fallow period.In this study,we conducted an incubation experiment using the acetylene inhibition technique to investigate N_(2)O emission and reduction rates of paddy soil profiles(0-1 m)from Guangdong Province and Jinlin Province in China,with different heavy-metal pollution levels.The abundance and community structures of denitrifying bacteria were determined via quantitative-PCR and Illumina MiSeq sequencing of nosZ,nirK,and nirS genes.Our results showed that the potential N_(2)O emission rate,N_(2)O production rate,and denitrification rate have decreased with increasing soil vertical depth and heavy-metal pollution.More importantly,we found that the functional gene type of N_(2)O reductase switched with the tillage state of paddy soils,which cladeⅡnos Z genes were the dominant gene during the tillage period,while cladeⅠnos Z genes were the dominant gene during the dry fallow period.The heavy-metal pollution has less effect on the niche differentiation of the nos Z gene.The N_(2)O emission rate was significantly regulated by the genus Bradyhizobium,which contains both N_(2)O reductase and nitrite reductase genes.Our findings suggests that the nos Z gene of N_(2)O reductase can significantly impact the N_(2)O emission from paddy soils.

Fiber orientation effects on grinding characteristics and removal mechanism of 2.5D C_(f)/SiC composites

Carbon fiber reinforced silicon carbide(C_(f)/SiC)composites are widely used in aerospace for their excellent mechanical properties.However,the quality of the machined surface is poor and unpredictable due to the material heterogeneity induced by complex removal mechanism.To clarify the effects of fiber orientation on the grinding characteristics and removal mechanism,single grit scratch experiments under different fiber orientations are conducted and a three-phase numerical modelling method for 2.5D C_(f)/SiC composites is proposed.Three fiber cutting modes i.e.,transverse,normal and longitudinal,are defined by fiber orientation and three machining directions i.e.,MA(longitudinal and normal),MB(longitudinal and transverse)and MC(normal and transverse),are selected to investigate the effect of fiber orientation on grinding force and micro-morphology.Besides,a three-phase cutting model of 2.5D C_(f)/SiC composites considering the mechanical properties of the matrix,fiber and interface is developed.Corresponding simulations are performed to reveal the micro-mechanism of crack initiation and extension as well as the material removal mechanism under different fiber orientations.The results indicate that the scratching forces fluctuate periodically,and the order of mean forces is MA>MC>MB.Cracks tend to grow along the fiber axis,which results in the largest damage layer for transverse fibers and the smallest for longitudinal fibers.The removal modes of transverse fibers are worn,fracture and peel-off,in which normal fibers are pullout and outcrop and the longitudinal fibers are worn and push-off.Under the stable cutting condition,the change of contact area between fiber and grit leads to different removal modes of fiber in the same cutting mode,and the increase of contact area results in the aggravation of fiber fracture.

微博视角下的MOOCs学习特征：自主性、社会性、多样性与开放性

"互联网+"时代的学习在"社会化"语境中发生了本质的变化。在这样的时代背景下,对社交媒体中MOOCs学习者行为与话语的深度剖析显得尤为重要。微博作为我国重要的社交媒体平台,为研究MOOCs学习提供了丰富的文本资料。本研究在过去八年中先后进行两次抽样,共选取新浪微博平台2010年至2018年间4,000多条有关MOOCs话题的微博,开展内容分析。通过编码与归纳演绎,提炼出MOOCs学习特征的框架图来阐释各主题范畴之间的相互关系。研究发现:微博中的MOOCs学习呈现出自主性、社会性、多样性与开放性四类较为显著的特征,与联通主义抑或心理学中人格理论与自我决定论的探讨有共通之处。

基于类芬顿反应的Mn_(3)O_(4)/DOX@Lip纳米递药体系的构建及应用

利用肿瘤微环境与普通组织的差异,我们设计了一种基于类芬顿反应(Fenton-like reaction)的微环境响应的纳米递药体系(Mn_(3)O4/DOX@Lip).首先利用热分解法制备得到锰的氧化物(Mn_(3)O4)纳米粒子,基于化疗药物阿霉素(DOX)与Mn原子的配位作用,该纳米粒子可以负载并递送DOX,其最外层包裹的酸敏脂质体能有效防止药物在递送过程中的泄露.在肿瘤细胞的弱酸性和高浓度谷胱甘肽的微环境中,脂质体膜破裂,其中的Mn_(3)O4纳米粒子被谷胱甘肽还原、分解,并释放出DOX.共聚焦成像结果表明,MCF-7细胞与Mn_(3)O4/DOX@Lip共孵育后,细胞中活性氧探针的荧光显著增加,表明该递药体系可以通过下调细胞中的谷胱甘肽的含量引发细胞中的活性氧含量增加.噻唑蓝(MTT)和流式细胞实验结果表明,相比于单一的化疗药物,Mn_(3)O4/DOX@Lip的细胞毒性增强,这可能归因于还原产物Mn2+触发了类芬顿反应从而将细胞中内源性的H2O2转化为毒性更强的•OH.氧化活性物质介导的细胞凋亡与化疗药物的细胞毒性相互促进,增强了对细胞的凋亡能力.本体系利用外源性的物质激发内源性的细胞毒性,增强了化疗药物的治疗效果,为肿瘤治疗提供了新的研究策略.

Enhanced magnetostrictive properties of lightly Pr-doped Fe83Ga17 alloys

Fe83Ga17Prx alloys,where x=0,0.2,0.4,0.6 and 1.0,were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere.The crystal structure and surface morphologies of the alloys were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM),respectively.Local compositional variations were measured by energy dispersive X-ray spectroscopy(EDXS).The magnetostriction coefficients of the alloys were measured by means of a differential resistive strain sensor.The magnetism of the sample was measured by a vibrating sample magnetometer(VSM).The results show that the parent Fe83Ga17 alloy consists of a single A2 phase of bcc symmetry,whereas the Pr doped Fe83Ga17 alloys are composed of the A2 phase of bcc structure and a small volume fraction of PrGa2 as a secondary phase.Most importantly,with increasing x,the magnetostriction coefficient of the Fe83Ga17Prx alloys first increases reaching a maximum saturation magnetostriction coefficient of192 ppm for x=0.6 at a magnetic field strength of 486 kA/m,then decreased.This maximum represents a 400% increase over the parent alloy with a mere 0.6 at% Pr doping.

Myoprotective effects of bFGF on skeletal muscle injury in pressure-related deep tissue injury in rats

Background:Pressure ulcers(PUs)are a major clinical problem that constitutes a tremendous economic burden on healthcare systems.Deep tissue injury(DTI)is a unique serious type of pressure ulcer that arises in skeletal muscle tissue.DTI arises in part because skeletal muscle tissues are more susceptible than skin to external compression.Unfortunately,few effective therapies are currently available for muscle injury.Basic fibroblast growth factor(bFGF),a potent mitogen and survival factor for various cells,plays a crucial role in the regulation of muscle development and homeostasis.The main purpose of this study was to test whether local administration of bFGF could accelerate muscle regeneration in a rat DTI model.Methods:Male Sprague Dawley(SD)rats(age 12 weeks)were individually housed in plastic cages and a DTI PU model was induced according to methods described before.Animals were randomly divided into three groups:a normal group,a PU group treated with saline,and a PU group treated with bFGF(10μg/0.1 ml)subcutaneously near the wound.Results:We found that application of bFGF accelerated the rate of wound closure and promoted cell proliferation and tissue angiogenesis.In addition,compared to saline administration,bFGF treatment prevented collagen deposition,a measure of fibrosis,and up-regulated the myogenic marker proteins MyHC and myogenin,suggesting bFGF promoted injured muscle regeneration.Moreover,bFGF treatment increased levels of myogenesis-related proteins p-Akt and p-mTOR.Conclusions:Our findings show that bFGF accelerated injured skeletal muscle regeneration through activation of the PI3K/Akt/mTOR signaling pathway and suggest that administration of bFGF is a potential therapeutic strategy for the treatment of skeletal muscle injury in PUs.

Sonochemical Synthesis of Two Dimensional C3N4 Nanosheets Supported Palladium Composites and Their Electrocatalytic Activity for Oxygen Reduction and Methanol Oxidation Reaction

The preparation of highly active electrocatalysts with good durability and low cost for fuel cells is highly desir- able but still remains a significant challenge. Here we synthesized two dimensional （2D） C3N4 nanosheets supported palladium composites （C3N4/Pd） via a simple and convenient sonochemical approach. We have systematically stud- ied the electrocatalytic performance of as-prepared catalysts. We found that the prepared C3N4/Pd composites pos- sessed excellent catalytic activity and stability for oxygen reduction reaction （ORR） in alkaline media. Encourag- ingly, the C3N4/Pd catalysts exhibit the excellent electrocatalytic activity for methanol oxidation reaction （MOR） in alkaline media, even better than that of the commercial Pt/C catalyst, The excellent electrocatalytic performance of the 2D C3N4 nanosheets supported palladium composites catalysts results from their synergy effect between the ul- trathin substrate material with large surface area and excellent dispersion of palladium nanoparticles. This study demonstrates that sonochemical method opens up a new avenue for the preparation of electrocatalysts for fuel cells. We expect these materials are likely to find uses in a broad range of applications, for example, fuel cells, solar cells, batteries and other electrochemical analysis.

miR-133b targets NCAPH to promote β-catenin degradation and reduce cancer stem cell maintenance in non-small cell lung cancer

Dear Editor,Non-small cell lung cancer(NSCLC),one of the most common lung cancers,is well known to have diverse pathological features.Cancer stem cells(CSCs)have been identified to play critical roles in tumor metastasis and drug resistance,while its potential clinical significance and molecular mechanism are still unclear.In addition,numerous findings have also shown that miRNAs play pivotal roles in CSCs during tumor progression.

Hyaluronidase-triggered anticancer drug and siRNA delivery from cascaded targeting nanoparticles for drug- resistant breast cancer therapy

Drug resistance renders standard chemotherapy ineffective in the treatment of connective tissue growth factor （CTGF）-overexpressing breast cancer. By co-embedding the breast tumor cell-penetrating peptide （PEGA-pVEC） and hyaluronic acid （HA） as a targeting media, novel cascaded targeting nanoparficles （HACT NPs） were created on a rattle mesoporous silica （rmSiO2） scaffold for the pinpoint delivery of siRNAs along with an anticancer drug, aiming at overcoming the drug resistance of CTGF-overexpressing breast cancer in vivo. The targeting nanoparticles selectively accumulated in the vasculature under the guidance of the PEGA-pVEC peptide, cascaded by receptor-mediated endocytosis with the aid of another targeting agent, HA, presenting a greater in vivo tumor targeting ability than single targeting ligand vectors. In addition, an HA shell prevented the leakage of therapeutic drugs during the cargo transport process, until the hyaluronidase （HAase）-triggered degradation upon lysosomes entering, guaranteeing a controllable drug release inside the target cells. When the protective shell disintegrates, the released siRNA took charge to silence the gene associated with drug resistance, CTGF, thus facilitating doxorubicin-induced apoptosis. The cascaded targeting media （PEGA-pVEC and HA） advances precision-guided therapy in vivo, while the encapsulation of siRNAs into a chemotherapy drug delivery system provides an efficient strategy for the treatment of drug resistance cancers.

脂肪组织的生物医用前景

Adipose tissue is a highly specialized connective tissue that typically contributes to 10%-29%of body weight in an adult[1].Fat cells,including white adipocytes responsible for lipid storage and brown and beige adipocyte responsible for thermogenesis,play important roles in systemic lipid metabolism and energy supply.