基于“腾讯会议+课堂派”的有机化学课程在线教学实践

新冠疫情期间,开展在线教学是响应教育部“停课不停学,停课不停教”号召的重要举措,而如何保障在线教学的效果是亟待解决的关键问题。本研究基于“腾讯会议+课堂派”平台,辅以其他过程性评价平台,从重组教学资源、创新教学活动、重整教学评价三个维度,构建有机化学课程的在线教学新模式,为有效实施在线教学提供参考。

Soil water repellency and influencing factors of Nitraria tangutorun nebkhas at different succession stages

Abstract： Soil water repellency （WR） is an important physical characteristic of soil surface. It is capable of largely influencing the hydrological and geomorphological processes of soil, as well as affecting the ecological processes of plants, such as growth and seed germination, and has thus been a hot topic in recent research around the world. In this paper, the capillary rise method was used to study the soil WR characteristics of Nitraria tangutorun nebkhas. Soil water repellencies at different succession stages of Nitraria tangutorun were investigated, and the relationships between soil WR and soil organic matter, total N, and total P, soil texture, pH, and concentrations of CO32, HCO3-, CI, SO42-, Na~, K~, Ca2~ and Mg2＋ were discussed. Soil WR may be demonstrated at the following nebkhas dune evolvement stages： extremely degraded〉degraded〉stabilized〉well developed〉newly developed〉quick sand. Apart from some soil at the bottom, the WR of other soils （crest and slope of dune） was found to be largest at the topsoil, and decreased as the soil depth increased. The results showed that multiple factors affected soil WR characteristics e.g. WR increased significantly as the contents of soil organic matter and total N increased, but did not change as the total P content increased. Soil texture was a key factor affecting soil WR; soil WR increased significantly as clay content increased, and decreased significantly as sand content increased. Low pH was shown to be more suitable for the occurrence of soil WR. Four cations （Ca2＋, Mg2＋, K＋ and Na＋） and two anions （CI and SO42） enhanced soil WR, while CO32-decreased it. HCO3- did not show any observable effect. Finally, we established a best-fit general linear model （GLM） between soil-air-water contact angle （CA） and influencing factors （CA=5.606 sand＋6.496 （clay and silt）-2.353 pH＋470.089 CQ2＋11.346 Na＋-407.707 Cl--14.245 SO42-＋0.734 total N-519.521 ）. It was concluded that all soils contain subcritical WR （0°〈CA〈90°）. The development and succession of Nitraria tangutorun nebkhas may improve the formation of soil subcritical WR. There exist significant relationships between soils subcritical WR and soil physical or chemical properties.

Soil restoration research advances of artificial sand-binding vegetation ecosystem in the Tengger Desert, Northern China

Soil plays an important role in desert ecosystem, and is vital in constructing a steady desert ecosystem. The management and restoration of desertified land have been the focus of much discussion. The soil in Shapotou desert region has developed remarkably since artificial sand-binding vegetation established in 1946. The longer the period of dune stabilization, the greater the thickness of microbiotic crusts and subsoil. Meanwhile, proportion of silt and clay increased significantly, and soil bulk density declinced. The content of soil organic matter, N, P, and K similarly increased. Therefore, soil has developed from aeolian sand soil to Calcic-Orthic aridisols. This paper discusses the effects brought about by dust, microbiotic soil crust and soil microbes on soil-forming process. Then, we analyzed the relation between soil formation and sand-binding vegetation evolution, in order to provide a baseline for both research on desert ecosystem recovery and ecological environment governance in arid and semi-arid areas.

Impact of global warming on drought in China

Spatial and temporal change pattems of air temperature （7）, precipitation （P）, relative humidity （RH）, lower vapor pressure （VP）, potential evapotranspiration （PET） and drought situation of 690 meteorological stations for all of China were evaluated in this study to understand the effects of warming on regional drought and hydrological processes. Here, the drought extent is expressed by aridity index （AI）, which is the ratio of precipitation and reference crop evapotranspiration （ETo） calculated by FAO Pen- man-Monteith equation, taking into account air temperature, atmospheric humidity, solar radiation, and wind. Our results indicate that there are different patterns of climate change from 1961 to 2008 and from 1981 to 2008. Little precipitation change occurred in China and ETo decreased from 1961 to 2008. But, the warming trend has intensified and the area with significant increasing precipitation has reduced since the early 1980＇s and ETo has increased in most areas of China from 1981 to 2008 and decreased from 1961 to 2008. The areas affected by drought have shifted from North China and Northeast China to East China and South China since 1981. It is speculated that the increasing warming intensity after 1981 possibly strengthened the power of potential evapotmnspiration and resulted in drought in most areas of Northeast China, North China, eastem Southwest China, and especially in East China and South China.

Analysis of the mechanical transfer characterization between lodged sugarcane and the cutter by simulation modeling with UMAT subroutine

Cutting the roots of sugarcane using cutters is a critical part of sugarcane harvesting,and the degree of breakage of the roots after cutting affects the germination and growth of sugarcane to a certain extent in the following year.However,the intricate interactions between the cutter and the stalk remain unclear.In order to fill this gap,this study first analyzed the conditions for no missed cuts during the operation of a double-disk cutter.Secondly,the research established a model of sugarcane stalk with anisotropy using the User-defined Material Mechanical Behavior(UMAT)subroutine based on the secondary development module of ABAQUS/Explicit.The cutting force curves obtained from simulation and test show a high correlation coefficient(R^(2)=0.9621),indicating the reliability of the model of sugarcane stalk in mechanical transfer.Subsequently,the simulation test of the blade rotating cutting characteristics in this study indicates that at a blade tilt angle of 11.3°,a blade rotating speed of 659.3 r/min,and a forward speed of 1.5 km/h,the maximum shear force on the blade is the largest,while the maximum cutting force is the smallest.Finally,based on the simulation results,this paper discussed the internal factors affecting the breakage rate of sugarcane stalks and predicted the damage location and damage force of the stalks by studying the stress wave transmission effect.Additionally,it analyzed the effects of single-knife cutting and multi-cutting on stalk incisions.The results indicated that multi-cutting causes more damage to the stalks and increases the breakage rate of sugarcane.The results of this study can provide a theoretical basis and technical reference for exploring the reduction of sugarcane residual cutting rate.

Recognition of tea buds based on an improved YOLOv7 model

The traditional recognition algorithm is prone to miss detection targets in the complex tea garden environment,and it is difficult to satisfy the requirement for tea bud recognition accuracy and efficiency.In this study,the YOLOv7 model was developed to improve tea bud recognition accuracy for some extreme tea garden scenarios.In the improved model,a lightweight MobileNetV3 network is adopted to replace the original backbone network,which reduces the size of the model and improves detection efficiency.The convolutional block attention module is introduced to enhance the attention to the features of small and occluded tea buds,suppressing the interference of the complex tea garden environment on tea bud recognition and strengthening the feature extraction capability of the recognition model.Moreover,to further improve recognition accuracy for dense and occlusive scenarios,the soft non-maximum suppression strategy is integrated into the recognition model.Experimental results show that the improved YOLOv7 model has the precision,recall,and mean average precision(mAP)values of 88.3%,87.4%,and 88.5%,respectively.Compared with the Faster R-CNN,SSD,and original YOLOv7 algorithms,the mAP of the improved YOLOv7 model is increased by 7.4,7.9,and 3.9 percentage points,respectively,and its recognition speed is also promoted by 94.9%,46.2%,and 16.9%.The proposed model can rapidly and accurately identify the tea buds in multiple complex tea garden scenarios-such as dense distribution,being close to the background color,and mutual occlusion-with high generalization and robustness,which can provide theoretical and technical support for the recognition of tea-picking robots.

Mouse knockout models reveal largely dispensable but context-dependent functions of IncRNAs during development

Dear Editor, In mammalian genomes, pervasive transcription produces thousands of long non-coding RNA （IncRNA） transcripts （Olebali et al., 2012; Hon et al., 2017）. Compared to protein-coding mRNAs, IncRNAs are less conserved, and often exhibit low-level, developmental stage-and tissue-specific expression （Pauli et al., 2011; Hu et al., 2012; Lee, 2012; Ulitsky and Bartel, 2013; Cech and Steitz, 2014; Hon et al., 2017）. Many IncRNAs are strongly correlated with their neighboring mRNA genes in terms of expression and function, and tend to regulate nearby transcription （Orom et al., 2010; Engreitz et al., 2016; Luo etal., 2016）. It has been implicated that IncRNAs play versatile roles in regulating diverse aspects of cell biology through mechanisms at multiple levels （Pauli et al., 2011; Lee.

IDH1 fine-tunes cap-dependent translation initiation

The metabolic enzyme isocitrate dehydrogenase 1(IDH1)catalyzes the oxidative decarboxylation of isocitrate to a-ketoglutarate(a-KG).Its mutation often leads to aberrant gene expression in cancer.IDH1 was reported to bind thousands of RNA transcripts in a sequence-dependent manner;yet,the functional significance of this RNA-binding activity remains elusive.Here,we report that IDH1 promotes mRNA translation via direct associations with polysome mRNA and translation machinery.Comprehensive proteomic analysis in embryonic stem cells(ESCs)revealed strikingenrichmentof ribosomal proteins and translation regulators in IDH1-bound protein interactomes.We performed ribosomal profiling and analyzed mRNA transcripts that are associated with actively translating polysomes.Interestingly,knockout of IDH1 in ESCs led to significant downregulation of polysome-bound mRNA in IDH1 targets and subtle upregulation of ribosome densities at the start codon,indicating inefficient translation initiation upon loss of IDH1.Tethering IDH1 to a luciferase mRNA via the MS2-MBP system promotes luciferase translation,independently of the catalytic activity of IDH1.Intriguingly,IDH1 fails to enhance luciferase translation driven by an internal ribosome entry site.Together,these results reveal an unforeseen role of IDH1 in fine-tuning cap-dependent translation via the initiation step.