“互联网+”背景下基础化学原理实验在线学习与考试系统的开发与实践

在移动互联网的飞速发展与智能手机等移动终端日趋普及的情况下,设计开发了基于移动端的基础化学原理实验在线学习与考试系统。该系统包括化学实验室安全教育与考试、实验基础理论学习、试题库资源、移动端在线考试、成绩管理和统计分析等五大功能。该系统的开发建设顺应了“互联网+教育”的发展趋势,有利于学生自主学习,节约考试资源。

Protective effects of taurine against muscle damage induced by diquat in 35 days weaned piglets

Background: Oxidative stress is a key factor that influences piglets' health. Taurine plays an imperative role in keeping the biological system from damage. This study was conducted to investigate the protective effect of taurine against muscle injury due to the secondary effect of diquat toxicity.Results: Our study found that taurine effectively and dose-dependently alleviated the diquat toxicity induced rise of feed/gain, with a concurrent improvement of carcass lean percentage. The plasma content of taurine was considerably increased in a dose-dependent manner. Consequently, dietary taurine efficiently improved the activity of plasma antioxidant enzymes. Furthermore, taurine attenuated muscle damage by restoring mitochondrial micromorphology, suppressing protein degradation and reducing the percentage of apoptotic cells in the skeletal muscle. Taurine supplementation also suppressed the genes expression levels of the antioxidant-, mitochondrial biogenesis-, and muscle atrophy-related genes in the skeletal muscle of piglets with oxidative stress.Conclusions: These results showed that the dose of 0.60% taurine supplementation in the diet could attenuate skeletal muscle injury induced by diquat toxicity. It is suggested that taurine could be a potential nutritional intervention strategy to improve growth performance.

Porous Rh/BINAP polymers as efficient heterogeneous catalysts for asymmetric hydroformylation of styrene:Enhanced enantioselectivity realized by flexible chiral nanopockets

A new chiral monomer,(S)‐5,5′‐divinyl‐BINAP,was successfully synthesized and embedded intotwo different porous organic polymers(Poly‐1and Poly‐2).After loading a Rh species,the catalystswere applied for the heterogeneous asymmetric hydroformylation of styrene.Compared with thehomogeneous BINAP analogue,the enantioselectivity of Rh/Poly‐1catalyst was drastically increasedby approximately70%.The improved enantioselectivity of the porous Rh/BINAP polymerswas attributed to the presence of flexible chiral nanopockets resulting from the increased bulk ofthe R groups near the catalytic center.

Enhancing the activity,selectivity,and recyclability of Rh/PPh_(3) system‐catalyzed hydroformylation reactions through the development of a PPh_(3)‐derived quasi‐porous organic cage as a ligand

In contrast to heterogeneous network frameworks(e.g.,covalent organic frameworks and metal‐organic frameworks)and porous organic polymers,porous organic cages(POCs)are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis.Herein,we report a triphenylphosphine‐derived quasi‐porous organic cage(denoted as POC‐DICP)as an efficient organic molecular cage ligand for Rh/PPh_(3) system‐catalyzed homogeneous hydroformylation reactions.POC‐DICP not only displays enhanced hydroformylation selectivity(aldehyde selectivity as high as 97%and a linear‐to‐branch ratio as high as 1.89)but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems.We speculate that the reason for the high activity and good selectivity is the favorable geometry(cone angle=123.88°)and electronic effect(P site is relatively electron‐deficient)of POC‐DICP,which were also demonstrated by density functional theory calculations and X‐ray absorption fine‐structure characterization.

Chiral BINAP-based hierarchical porous polymers as platforms for efficient heterogeneous asymmetric catalysis

Two vinyl‐functionalized chiral2,2'‐bis(diphenylphosphino)‐1,1'‐binaphthyl(BINAP)ligands,(S)‐4,4'‐divinyl‐BINAP and(S)‐5,5'‐divinyl‐BINAP,were successfully synthesized.Chiral BINAP‐based porous organic polymers(POPs),denoted as4‐BINAP@POPs and5‐BINAP@POPs,were efficiently prepared via the copolymerization of vinyl‐functionalized BINAP with divinyl benzene under solvothermal conditions.Thorough characterization using nuclear magnetic resonance spectroscopy,thermogravimetric analysis,extended X‐ray absorption fine structure analysis,and high‐angle annular dark‐field scanning transmission electron microscopy,we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores.Ru was introduced as a catalytic species into the POPs using different synthetic routes.Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous asymmetric hydrogenation ofβ‐keto esters revealed their excellent chiral inducibility as well as high activity and stability.Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis.

Three-stage tectonic subsidence and its implications for the evolution of conjugate margins of the southwest subbasin,South China Sea

To reveal the tectonic characteristics of the continental margins in the southwest subbasin(SWB)of the South China Sea,a long high-resolution seismic profile was studied using empty basin subsidence.We find that tectonic subsidence features on both margins are uniformly divided into three stages:(1)slow subsidence from Tg to 18.5 Ma(synrift stage);(2)extremely slow subsidence/uplift from18.5 to 16 Ma(spreading stage);and(3)accelerated subsidence from 16 to 0 Ma(post-spreading stage).This feature differs from the classic tectonic subsidence pattern of rifted basins,which exhibits fast subsidence during synrift stage and slow subsidence during the post-rift stage.The tectonic uplift occurred during the spreading stage and the magnitude increased from the continent to the ocean,which is likely related to mantle flow during seafloor spreading.We propose that lower crustal flow played a significant role in the tectonic evolution of the continental margins of the SWB.The lower crust of the SWB margins was warmer and therefore weaker,and more prone to flow beneath the faulting center,which compensated for the upper crustal thinning caused by brittle faulting during the synrift period and thus reduced the tectonic subsidence rate.During the spreading stage,faulting attenuated rapidly,and a necking zone appeared at the continentocean transition formed by lithospheric extension.With upwelling asthenosphere,small-scale secondary mantle convection occurred under the necking zone,which raised the continental margin isotherms and increased the buoyancy.Simultaneously,secondary mantle convection lifted the overriding crust,thus the overall subsidence rate decreased sharply or even reversed to uplift.After seafloor spreading,the effect of mantle convection faded away,and sediment loading drove the lower crust to flow landward.Thermal relaxation,lower crust flow,and vanish of secondary mantle convection together led to rapid subsidence in this stage.

Landscape Evaluation Based on Gaofen Satellite in the Southern Part of the Nile Delta, Egypt

Landscape segmentation and classification is fundamental to landscape research because it provides an important frame of reference for researchers to communicate and compare their work. Anthropogenic human activities mainly lead to landscape changes. The present study aims to assess the impact of anthropogenic activities on landscape classification of the Nile Delta using remote sensing and GIS techniques. Field survey, digital databases and GIS capabilities are applied for landscapes classification. Vector data using a lot of maps and raster data using satellite image have the ability to give obvious classification about landscape. Results showed that the anthropogenic impacts affect negatively on the landscape classification. Using GF2, landscapes are classified into major eight classes: cultivated land, garden land, woodland, grassland, bare land, urban land, water bodies and mining land. It was showed that the urban occupies the highest percentage of the study area. Urban construction and development areas centered on the capital Cairo city and the city of Giza are dumbbell-shaped to the east. Bare lands occupy the second percentage of the study area, and it may be distributed on around the Nile Delta, southeast of Cairo City and southwest of Giza City. According to vegetation cover, three classes were applied as the sequence: Cultivated land > Garden land > Grass land. These classes depend mainly on the River Nile. Vegetation cover may be based mainly on the water from the Nile River. In addition, mining land occupies the least percentage of the study area. The main distribution of mines and mineral exploration is also very small, but it is distributed on the edge of the city. Landscape metric as Fractal Dimension (Frac) and the Square Pixel (SqP) was applied to validate the segmentation and classification. These metrics indicated that the landscape classification is related to natural and human changes. These changes were related to unplanned management of new projects and some anthropogenic activities.

Optically manipulated nanomechanics of semiconductor nanowires

Opto–electromechanical coupling at the nanoscale is an important topic in new scientific studies and technical applications. In this work, the optically manipulated electromechanical behaviors of individual cadmium sulfide(CdS) nanowires are investigated by a customer-built optical holder inside transmission electron microscope, wherein in situ electromechanical resonance took place in conjunction with photo excitation. It is found that the natural resonance frequency of the nanowire under illumination becomes considerably lower than that under darkness. This redshift effect is closely related to the wavelength of the applied light and the diameter of the nanowires. Density functional theory(DFT) calculation shows that the photoexcitation leads to the softening of CdS nanowires and thus the redshift of natural frequency, which is in agreement with the experimental results.

哺乳动物卵子与早期胚胎中全转录组poly(A)尾研究进展

在哺乳动物卵子向胚胎转变过程中,卵子和胚胎中的转录在合子基因组激活之前都是沉默的,因此mRNA转录后修饰在此过程发挥着重要的作用。poly(A)尾巴是影响mRNA命运和翻译效率的一种重要的转录后修饰。随着测序技术和分析工具的进步,尤其是三代测序技术的发展,poly(A)尾的长度和组成能够被精确测量,极大地拓展了人们对于poly(A)尾在哺乳动物早期胚胎发育过程中的认识。本文对poly(A)尾研究方法的发展及其在卵子向胚胎转变中的研究进展进行评述,以期为哺乳动物早期胚胎发育和不孕不育相关疾病的研究带来新的思路。

Origin of submarine canyon-channel systems along the middle segment of West Mariana Ridge,Philippine Sea

Submarine canyon-channel systems have been documented in the Parece Vela Basin,West Mariana Ridge;however,the mechanism of the formation and controlling factors remain poorly understood.Based on high-resolution multibeam bathymetric data and two-dimensional(2D)seismic profiles,we identified and mapped the submarine canyon-channel system along the middle segment of West Mariana Ridge in the Philippine Sea.These submarine canyon-channels show a main W-E orientation at depth of 2000–4500 m.They are approximately 72–128 km in length and 1.3–15 km in width,and their canyon heads are adjacent to the seamounts with several branches.The upper reaches of submarine canyon-channels are characterized by deeply incised,narrow,V-shaped thalwegs,suggesting the powerful erosion of gravity flows.The distinguished sediment waves are suggested to be resulted from the interaction of turbidity currents and seafloor.Our observations demonstrate that gravity flows originated from the collapses of seamount flanks plays a vital role in developing the submarine canyonchannel system along the West Mariana Ridge.This work provides better understanding of erosion,transport,and deposition of sediments from subducting ridges to deep-water basins,and also new insights into the origin and evolution of submarine canyon-channel systems along subducting ridges.

Termination of Recurrent Atrial Fibrillation by Superior Vena Cava Isolation: A Case Report

Background:Paroxysmal atrial fibrillation can be triggered by non-pulmonary vein foci,such as the superior vena cava.Here,we report the case of a patient with a 6-year history of paroxysmal atrial fibrillation who received cryoballoon ablation in 2012 but relapsed in 2014.He then received cardiac radiofrequency ablation,which successfully isolated the left pulmonary vein and superior vena cava,but the arrhythmia recently relapsed again.The tachycardia was finally successfully terminated by ablation on the free wall without recurrence during a 2-year following up.Conclusion:Superior vena cava isolation may not require ablation isolation with a full circle way and can be accomplished by ablating several connection points between the superior vena cava and the right atrium.

The Role of Sleep Deprivation in Arrhythmias

Sleep is essential to the normal psychological and physiological activities of the human body.Increasing evidence indicates that sleep deprivation is associated with the occurrence,development,and poor treatment effects of various arrhythmias.Sleep deprivation affects not only the peripheral nervous system but also the central nervous system,which regulates the occurrence of arrhythmias.In addition,sleep deprivation is associated with apoptotic pathways,mitochondrial energy metabolism disorders,and immune system dysfunction.Although studies increasingly suggest that pathological sleep patterns are associated with various atrial and ventricular arrhythmias,further research is needed to identify specific mechanisms and recommend therapeutic interventions.This review summarizes the findings of sleep deprivation in animal experiments and clinical studies,current challenges,and future research directions in the field of arrhythmias.

大功率GHz重复频率飞秒光纤激光技术及前沿应用

与kHz~MHz重复频率飞秒激光相比,GHz重复频率飞秒激光具有更大的频率间隔、更易获得高平均功率,是光谱学、生物光子学、微波光子学、精密加工等基础研究与工业应用领域的崭新工具.光纤型飞秒激光在光束质量、紧凑性、鲁棒性等方面具有先天优势,是大功率GHz重复频率飞秒激光的重要发展方向,有望拓展激发超快激光在尖端领域应用,支撑核心工业、生命医学、航空航天等领域持续创新.本文从大功率GHz重复频率飞秒光纤激光器的技术难点、最新进展、前沿应用等方面进行综述,并展望未来发展前景.

TaSRO1 interacts with TaVP1 to modulate seed dormancy and pre-harvest sprouting resistance in wheat

Dormancy is an adaptive trait which prevents seeds from germinating under unfavorable environmental conditions.Seeds with weak dormancy undergo pre-harvest sprouting(PHS)which decreases grain yield and quality.Understanding the genetic mechanisms that regulate seed dormancy and resistance to PHS is crucial for ensuring global food security.In this study,we illustrated the function and molecular mechanism of TaSRO1 in the regulation of seed dormancy and PHS resistance by suppressing TaVP1.The tasro1 mutants exhibited strong seed dormancy and enhanced resistance to PHS,whereas the mutants of tavp1 displayed weak dormancy.Genetic evidence has shown that TaVP1 is epistatic to TaSRO1.Biochemical evidence has shown that TaSRO1 interacts with TaVP1 and represses the transcriptional activation of the PHS resistance genes TaPHS1 and TaSdr.Furthermore,TaSRO1 undermines the synergistic activation of TaVP1 and TaABI5 in PHS resistance genes.Finally,we highlight the great potential of tasro1 alleles for breeding elite wheat cultivars that are resistant to PHS.

Construction of the particle simulation model for ginger-soil system using discrete element method

In order to systematically obtain the excavation characteristic parameters for ginger harvesting, experimental analysis was conducted on the discrete elemental parameters in a particle simulation model of the ginger-soil system. Through stacking tests, the surface energy of soil-ginger tuber JKR was determined to be 3.7 J/m2, the coefficient of static friction of soil-steel (65 Mn) was 0.56, the coefficient of rolling friction was 0.03, and the coefficient of restitution of collision was 0.40. Utilizing normal and lateral compression tests conducted on the soil body, the soil base parameters required for the Bonding model were determined. Subsequently, a three-dimensional model of ginger root and stem was constructed using these parameters. With the aid of 3D scanning technology, a discrete element parameter model was established for the ginger field during the harvesting period. On the basis of the measured parameters, a three-dimensional model of ginger rhizome was established and finally a discrete parameter model of ginger field was constructed in the harvesting period. The calibration parameters are highly reliable after the model’s tightness and field harvesting test, which provides reliable data support for the soil flow and the force of the soil-touching parts during the later simulation of ginger harvesting and digging operation.

长程能量传递提升上转换纳米颗粒的量子效率

The integration of lanthanide-doped upconversion nanoparticles(UCNPs)into modern technology has been transformative,finding utility in a broad spectrum of applications ranging from super-resolution imaging and optogenetics to solar energy conversion and lasing[1–4].The core principle underlying these UCNPs involves the process of photon upconversion,which refers to the conversion of low-energy photons into high-energy photons,known as the anti-Stokes shift.

晶格受限Ga~Ⅲ诱导Pt高分散及其催化重整性能

针对催化重整反应中由于Pt分散度低引起氢解等副反应导致异构烷烃选择性差的问题,本文提出利用受限于层状双金属氢氧化物(LDHs)主体层板晶格内的GaⅢ对Pt的诱导效应控制Pt在载体表面原子水平高分散,Pt分散度达到98.8%,其中单原子Pt比例占68%.应用于正庚烷重整反应,高分散的Pt能够有效地抑制氢解副反应和芳构化反应,并大幅度提高异构选择性,在50%转化率下获得了53%的i-C7选择性,同时C1~4产物选择性小于20%.

侧流分析装置的结构改进和化学改性研究进展

侧流分析(lateral flow assay,LFA)是一种重要的纸基快速检测技术,具有操作简便、成本低廉等特点,但存在灵敏度低和信号弱等问题.近年来,对LFA的技术改进与性能改善已成为即时检测领域急需解决的问题.本文综述了利用结构改进、化学改性以及其他辅助手段改善LFA灵敏度的研究工作,分析了相关方法的原理和检测性能,剖析了各种改进手段存在的优缺点,并对LFA技术发展前景进行了展望.

Oxidative stress, nutritional antioxidants and beyond

Free radical-induced oxidative stress contributes to the development of metabolic syndromes(Mets), including overweight,hyperglycemia, insulin resistance and pro-inflammatory state. Most free radicals are generated from the mitochondrial electron transport chain;under physiological conditions, their levels are maintained by efficient antioxidant systems. A variety of transcription factors have been identified and characterized that control gene expression in response to oxidative stress status.Natural antioxidant compounds have been largely studied for their strong antioxidant capacities. This review discusses the recent progress in oxidative stress and mitochondrial dysfunction in Mets and highlights the anti-Mets, anti-oxidative, and antiinflammatory effect of polyphenols as potential nutritional therapy.

Current status of applying microwave-associated catalysis for the degradation of organics in aqueous phase – A review

Interactions between microwaves and certain catalysts can lead to efficient, energy-directed convergence of a relatively dispersed microwave field onto the reactive sites of the catalyst,which produces thermal or discharge effects around the catalyst. These interactions form"high-energy sites"(HeS) that promote energy efficient utilization and enhanced in situ degradation of organic pollutants. This article focuses on the processes occurring between microwaves and absorbing catalysts, and presents a critical review of microwave-absorbing mechanisms. This article also discusses aqueous phase applications of relevant catalysts(ironbased, carbon-based, soft magnetic, rare earth, and other types) and microwaves, special effects caused by the dimensions and structures of catalytic materials, and the optimization and design of relevant reactors for microwave-assisted catalysis of wastewater. The results of this study demonstrate that microwave-assisted catalysis can effectively enhance the degradation rate of organic compounds in an aqueous phase and has potential applications to a variety of engineering fields such as microwave-assisted pyrolysis, pollutant removal,material synthesis, and water treatment.