生成性教学中“真”与“假”的关键:基于生活经验

生活经验是影响教学生成的重要因素。在生成性教学中,脱离了个体生活经验,教学生成必会沦为"假生成",而在教学过程中不断开发和利用个体潜藏的生活经验,使之转化为生成性资源,能够推动教学"真生成"。

生成性:当代课堂教学改革的旨趣

新课程背景下,强调课堂教学的生成性,然而当代基础教育课堂教学的现状却是生成走过头,从传统的课堂教学活动中对孩子“满堂灌”到现代的课堂教学中的“满堂问”、“满堂答”,对生成性课堂教学的盲目倡导造成课堂教学虚假的生成.这样一种对生成的理解毫无情面地抛弃了预成性的课堂教学所具有的价值,真正的课堂教学应是建立在对“伪预成”与“伪生成”两级批判的基础之上,建立在真预成和真生成互动生成的辩证关系之中.

Chemical Constituents of One Species of Endophytic Fungus in Taxus chinensis

Three compounds were obtained from the mycelia of an endophytic fungus Gliocladium sp. (designated as strain F) of Taxus chinensis (Pilg.) Rehd. growing in Fujian Province, China. Their structures were determined on the basis of spectral analysis. (20S,22S)-4a-homo-22-hydroxy-4-oxaergosta-7,24(28)-dien-3-one was a novel compound. 4,8,12,16-tetramethyl-1,5,9,13-tetraoxacyclohexadecane-2,6,10,14-tetraone was firstly isolated from the genus ofGliocladium and 6,9-epoxyergosta-7,22-dien-3-ol was firstly obtained from the strain F.

真问题,真数据,真分析——“疫情中的折线统计图”课堂教学片段和反思

数据分析观念的形成,是当今社会每一个公民不可或缺的数学素养,这也是我们“会用数学的眼光看世界”的体现。庚子鼠年,突如其来的新冠肺炎疫情席卷全球,疫情意外闯进了我们的生活。可谓“人生大课”,也是孩子们必须关注的“大课堂”。媒体对疫情的及时报道,为“折线统计图”的教学提供了真问题和真数据,亟待我们通过教学设计“真生成”“真分析”。

初·名师

教育格言德为神,儒为形,归源求真,因真生成,教学相长。教学主张房德坤主张构建灵动的"生成性"语文课堂,热情带领本校和教学共同体联盟校教师进行探索和实践。他主张,教师和学生各自在生活、学习和情感等方面的经历、经验乃至教训,应是语文课程不可或缺的重要资源。

Chemical constituents of marine mangrove-derived endophytic fungus Alternaria tenuissima EN-192

A chemical investigation of the ethyl acetate extract of the fermentation broth of Alternaria tenuissima EN- 192, an endophytic fungus obtained from the stems of the marine mangrove plant Rhizophora stylosa, resulted in the isolation of nine known secondary metabolites, including four indole-diterpenoids： penijanthine A （1）, paspaline （2）, paspalinine （3）, and penitrem A （4）; three tricycloalternarene derivatives： tricycloalternarene 3a （5）, tricycloalternarene lb （6）, and tricycloalternarene 2b （7）; and two alternariol congeners： djalonensone （8） and alternariol （9）. The chemical structures of these metabolites were characterized through a combination of detailed spectroscopic analyses and their comparison with reports from the literature. The inhibitory activities of each isolated compound against four bacteria were evaluated and compounds 5 and 8 displayed moderate activity against the aquaculture pathogenic bacterium Vibrio anguillarum, with inhibition zone diameters of 8 and 9 mm, respectively, at 100 gg/disk. To the best of our knowledge, this is the first report on the secondary metabolites of mangrove-derived Alternaria tenuissima and also the first report of the isolation ofindole-diterpenoids from fungal genus Alternaria.

A novel process integrating vacuum distillation with atmospheric chlorination reaction for flexible production of tetrachloroethane and pentachloroethane

In this paper, we developed a novel process integrating vacuum distillation with atmospheric chlorination reaction(VD-ACR) to realize the flexible production of tetrachloroethane(TeCA) and pentachloroethane(PCA)from 1,2-dichloroethane(DCA). During the simulation, the distillation column and reactors were operated for separation and chlorination respectively under variable pressures and temperatures. It is interesting to note that VD-ACR processes producing pure TeCA or PCA can exhibit the similar configuration parameters after optimization, which enables the flexible production of TeCA and PCA with different molar ratios via changing operating parameters. The molar ratio of TeC A/PCA can be fine-tuned within the range of 0.9:0.1-0.1:0.9 through adjusting the amount of chlorine pumped into side reactors, giving rise to the increase of the heat duty of reboiler by five times. A pilot-scale experiment was then operated based-upon this VD-ACR process and the result matched well with the simulation. Therefore, the VD-ACR model presented in this study will be beneficial for the industrial-scale flexible production of TeCA and PCA from DCA.

Deriving Changjiang coastal zone wind from C-band SAR and its application to salinity simulation

Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang （Yangtze） River Diluted Water （CDW）, and shelf circulation in the Changjiang estuary. Thus, it is essential to include wind in the numerical simulation of these phenomena. Synthetic aperture radar （SAR） with high resolution and wide spatial coverage is valuable for measuring spatially inhomogeneous ocean surface wind fields. We have collected 87 ERS-2 SAR images with wind-induced streaks that cover the Cbangjiang coastal area, to verify and improve the validity of wind direction retrieval using the 2D fast Fourier transform method. We then used these wind directions as inputs to derive SAR wind speeds using the C-band model. To demonstrate the applicability of the algorithms, we validated the SAR-retrieved wind fields using QuikSCAT measurements and the atmospheric Weather Research Forecasting model. In general, we found good agreement between the datasets, indicating the reliability and applicability of SAR- retrieved algorithms under different atmospheric conditions. We investigated the main error sources of this process, and conducted sensitivity analyses to estimate the wind speed errors caused by the effect of speckle, uncertainties in wind direction, and inaccuracies in the normalized radar cross section. Finally, we used the SAR-retrieved wind fields to simulate the salinity distribution off the Changjiang estuary. The findings of this study will be valuable for wind resource assessment and the development of future numerical ocean models based on SAR images.

Evaluation on safety performance of a millimetre wave radar-based autonomous vehicle

This paper presents a method using range deception jamming to evaluate the safety performance of the autonomous vehicle with millimetre wave(MMW)radar.The working principle of this method is described.Combined with a waveform edition software,an experimental platform is developed to generate a deceptive signal that contains false distance information.According to related theories and its principle,the configuration parameters of the experimental setup are calculated and configured.The MMW radar of evaluated vehicle should identify an objective when it receives the deceptive signal from the experimental setup.Even if no obstacle,the evaluated vehicle can immediately brake in order that its braking distance is measured.The experimental results show that the proposed method can meet the requirements of the safety performance evaluation for the autonomous vehicle with MMW radar,and it also overcomes some deficiencies of previous methods.

Algorithm for Automatic Generation of Curved and Compound Twills

A new arithmetic using matrix left-shift functions for the quicker generation of curved and compound twills is introduced in this paper. A matrix model for the generation of regular, curved and compound twill structures is established and its computing simulation realization are elaborated. Examples of the algorithm applying in the simulation and the automatic generation of curved and compound twills in fabric CAD are obtained.

MPLPK:A mobile path localization protocol based on key nodes

To alleviate the localization error introduced by irregular sensor network deployment, a new mo bile path localization based on key nodes （MPLPK） protocol is proposed. It can recognize all con cave/convex nodes in the network as fixed anchor nodes, and simplify the following localization process based on these key nodes. The MPLPK protocol is composed of three steps. After all key nodes are found in the network, a mobile node applying improved minimum spanning tree （MST） algorithm is introduced to traverse and locate them. By taking the concave/convex nodes as anchors, the complexity of the irregular network can be degraded. And the simulation results demonstrate that MPEPK has 20% to 40% accuracy improvements than connectivity-based and anchor-free three-di- mensional localization （CATL） and approximate convex decomposition based localization （ACDL）.

“长时间思考”:数学学习应有的状态

小学数学教学一直存在“‘即时思考’盘踞课堂的时空,而‘长时间思考’难寻踪迹”的现象。“长时间思考”被忽视,与学习内容太饱和、学习评价不合理、好课标准不恰当有关。要重视“长时间思考”,是因为:时代发展倒逼学生思维转型,教育本质呼唤课堂静默生长,学科特点要求教师放慢脚步。培养学生“长时间思考”的习惯和能力,核心策略包括:课前预设“大问题”,课中预约“真生成”,课后预留“长作业”;操作要义包括:控制快与慢的节奏,认识多与少的关系,把握动与静的内涵。

Large-eddy simulation of the generation and propagation of internal solitary waves

A modified large-eddy simulation model,the dynamic coherent eddy model(DCEM)is employed to simulate the generation and propagation of internal solitary waves(ISWs)of both depression and elevation type,with wave amplitudes ranging from small,medium to large scales.The simulation results agree well with the existing experimental data.The generation process of ISWs is successfully captured by the DCEM method.Shear instabilities and diapycnal mixing in the initial wave generation phase are observed.The dissipation rate is not equal at different locations of an ISW.ISW-induced velocity field is analyzed in the present study.The structure of the bottom boundary layer(BBL)of internal wave packets is found to be different from that of a single ISW.A reverse boundary jet instead of a separation bubble exists behind the leading internal wave while separation bubbles appear in other parts of the wave-induced velocity field.The boundary jet flow resulting from the adverse pressure gradients has distinctive dynamics compared with free shear jets.

MicroRNAs in tomato plants

MicroRNAs (miRNAs) are a specialized class of small silencing RNAs that regulate gene expression in eukaryotes.In plants,miRNAs negatively regulate target mRNAs containing a highly complementary sequence by either mRNA cleavage or translational repression.As a model plant to study fleshy fruit ripening,miRNA studies in tomato have made great progress recently.MiRNAs were predicted to be involved in nearly all biological processes in tomato,particularly development,differentiation,and biotic and abiotic stress responses.Surprisingly,several miRNAs were verified to be involved in tomato fruit ripening and senescence.Recent studies suggest that miRNAs are related to host-virus interactions,which raises the possibility that miRNAs can be used as diagnostic markers for response to virus infection in tomato plants.In this review,we summarize our current knowledge systematically and advance future directions for miRNA research in tomato.

Biosynthesis and combinatorial biosynthesis of antifungal nucleoside antibiotics

There is an urgent need for new antifungal agents to treat or combat fungal infection in humans and plants.Antifungal nucleoside antibiotics are an important family of natural products with distinctive structural features.Understanding their biosynthetic machinery is of great importance for the improvement of antibiotics titers.More importantly,it is a requisite for combinatorial biosynthesis to create hybrid nucleoside antibiotics.We herein focus on findings on the natural and designed biosynthesis of this important family of nucleoside antibiotics.

Synthesis and biological activities of thio-triazole derivatives as novel potential antibacterial and antifungal agents

A series of novel thio-triazole derivatives including thiols, thioethers and thiones as well as some corresponding triazolium compounds were conveniently and efficiently synthesized from commercially available halobenzyl halides and thiosemicarbazide. All the new compounds were characterized by 1 H NMR, 13 C NMR, FTIR, MS and HRMS spectra. Their antibacterial and antifungal activities in vitro were evaluated against four Gram-positive bacteria, four Gram-negative bacteria and two fungi by two-fold serial dilution technique. The preliminary bioassay indicated that some prepared triazoles exhibited effective antibacterial and antifungal activities. Especially, 3,4-dichlorobenzyl triazolethione and its triazolium derivatives displayed the most potent activities against all the tested strains.

VdPKS1 is required for melanin formation and virulence in a cotton wilt pathogen Verticillium dahliae

Verticillium dahliae is a soil-borne phytopathogenic fungus that causes vascular wilt disease in a broad range of hosts. This pathogen survives for many years in soil in the form ofmelanized microsclerotia. To investigate the melanin synthesis in V.. dahliae, we identified a polyketide synthase gene in V. dahliae, namely VdPKS1. PKS1 is known to involve in the dihydroxynaphthalene melanin synthesis pathway in many fungi. We found that VdPKS1 was required for melanin formation but not for microsclerotial production in E dahliae. The VdPKS1 gene-disruption mutant （vdpksl） formed melanin-deficient albino microsclerotia, which did not affect the fungal colonization in host tissues but significantly reduced the disease severity. Gene transcription analysis in the wild-type and the vdpks1 strains suggested that VdPKS1 gene-disruption influenced the expression of a series of genes involved in ethylene biosynthesis, microsclerotial formation and pathogenesis. Our results suggest that the VdPKS1-mediated melanin synthesis is important for virulence and developmental traits of E dahliae.

Growth and micromagnetic simulation of magnetite nanoparticles

Magnetite nanoparticles with different sizes and different assemblies were synthesized via hydrothermal method.Micromagnetic simulation shows the magnetite nanocubes with different sizes have different energy states,which determines the assembly mode.Magnetite nanocubes with the side length of 30-60 nm tended to be dispersed while both nanochains and dispersed nanoparticles were found to grow for the nanocubes with the side length less than 30 nm,which can be explained in the fact that the above two assembly modes have very close energies.The assembly mode of nanocubes with the size bigger than 60 nm is generally nanorings consisting of connected inter-grown nanocubes and the nanocubes are no longer single domain.The simulations are consistent with the experimental results.

Sparse current source reconstruction in MCG

Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently, the computational demands and the accuracy of sparse source reconstruction are improved simultaneously. The simulation results demonstrate that the FGS method is capable of reconstructing sparse equivalent current sources using the magnetic field data generated by a single current source with varying orientation or multiple current sources generated randomly. In addition, we analyze the cardiac current source reconstructed with real MCG data at typical instants and discuss the electrical excitation conduction during the QRS complex based on moving sparse source imaging.