An Efficient Boron Source Activation Strategy for the Low‑Temperature Synthesis of Boron Nitride Nanotubes

Lowering the synthesis temperature of boron nitride nanotubes(BNNTs)is crucial for their development.The primary reason for adopting a high temperature is to enable the effective activation of highmelting-point solid boron.In this study,we developed a novel approach for efficiently activating boron by introducing alkali metal compounds into the conventional MgO–B system.This approach can be adopted to form various low-melting-point AM–Mg–B–O growth systems.These growth systems have improved catalytic capability and reactivity even under low-temperature conditions,facilitating the synthesis of BNNTs at temperatures as low as 850℃.In addition,molecular dynamics simulations based on density functional theory theoretically demonstrate that the systems maintain a liquid state at low temperatures and interact with N atoms to form BN chains.These findings offer novel insights into the design of boron activation and are expected to facilitate research on the low-temperature synthesis of BNNTs.

Rapid Detection of Accelerants in Fire Debris Using a Field Portable Mid-Infrared Quantum Cascade Laser Based Analyzer

Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.

Protection efficiency assessment and quality of coastal shelterbelt for Dongshan Island at the coastal section scale

The coastal shelter forest in China is under threat of destruction and degradation because of the impact of human activities. Protection efficiency assessment of the coastal shelterbelt is an important component of shelterforest remediation planning and sustainable management. In this study, a protection efficiency index （PEI） model was established using the projection pursuit method to assess the protective quality of the coastal shelter forest at the coastal section scale of Dongshan Island, China. Three criteria were used, including forest stand structure, forest belt structure, and windbreak effect; each criterion further comprised multiple factors. Based on survey data of 31 plots in the coastal shelter forest of Dongshan Island, we calculated PEI values using a projection of a pursuit model. The result showed 64.5 % of the PEIs fell at or below the middle level, which can indicate the status of the coastal shelterbelt is unsatisfactory. To further explore whether the different bays and land use types create significant differences in PEIs and evaluation indices, we used an ANOVA to test the influence of various bays and forms of land use on coastal shelterbelts. The results showed that PEI and most of the indices differed significantly by bay; mean tree height, mean DBH, mean crown width, stand density, vegetation coverage, and wind velocity reduction differed significantly by land use. Therefore, relevant measures for different locations, bays and surrounding land use can be proposed to improve the existing conditions of the coastal shelterbelt. The results of this study provide a theoretical and technical framework for future changes and sustainable management of coastal shelterbelt on Dongshan Island.

“Three‐in‐one”strategy:Heat regulation and conversion enhancement of a multifunctional separator for safer lithium-sulfur batteries

The safety problems encountered with lithium–sulfur batteries(LSBs)hinder their development for practical applications.Herein,a highly thermally conductive separator was constructed by cross‐weaving super‐aligned carbon nanotubes(SA‐C)on super‐aligned boron nitride@carbon nanotubes(SA‐BC)to create a composite film(SA‐BC/SA‐C).This separator was used to fabricate safe LSBs with improved electrochemical performance.The highly aligned separator structure created a uniform thermal field that could rapidly dissipate heat accumulated during continuous operation due to internal resistance,which prevented the development of extremely high temperatures.The array of boron nitride nanosheets endowed the composite separator with a large number of adsorption sites,while the highly graphitized carbon nanotube skeleton accelerated the catalytic conversion of high‐valence polysulfides into low‐valence polysulfides.The arrayed molecular brush design enabled the regulation of local current density and ion flux,and considerably alleviated the growth of lithium dendrites,thus promoting the smooth deposition of Li metal.Consequently,a battery constructed with the SA‐BC/SA‐C separator showed a good discharge capacity of 685.2 mAh g−1 over 300 cycles(a capacity decay of 0.026%per cycle)at 2 C and 60°C.This“three‐in‐one”multifunctional separator design strategy constitutes a new path forward for overcoming the safety problems of LSBs.

磁性Co/C纳米复合材料的合成及其对水中刚果红吸附性能研究

介绍一个由科研成果转化形成的大学综合化学实验,本综合实验设计以金属有机框架材料ZIF-67为前驱体,通过高温热解法合成磁性Co/C纳米复合材料,并将其应用于水中刚果红有机染料的吸附性能研究。在本实验中用X射线粉末衍射仪和扫描电镜对材料的基本结构和形貌进行了表征,利用紫外-可见分光光度计绘制了刚果红的标准曲线,并详细考查了磁性Co/C纳米复合材料对刚果红染料的吸附性能,且对吸附动力学和吸附等温线进行了拟合和分析。本实验操作简单,实验结果稳定,适用于大学生综合化学实验。本实验涵盖了无机-有机杂化材料合成、结构表征、有机染料浓度定量分析、动力学和吸附等温线的测定以及数据拟合分析等化学专业基础和实验操作技能,不仅有利于提高学生的综合实验能力,也可以培养学生的科研兴趣,拓展学生的视野。

Petal-assisted artificial pollination method enhanced the fruit setting ratios in tea plant(Camellia sinensis)

Pollination methods play an important role in developing F1 populations.Our study presents an improved method of petal-assisted artificial pollination in tea plants.The field operation using this method exhibited high efficiency in which more than 500 pistillate flowers per day can be pollinated per capita,and the pollen amount from only one staminate flower was sufficient to pollinate more than five pistillate flowers.Additionally,we surveyed the fruit-setting ratio in three F1 groups,which were established using this method and the influence of rainfall on the fruit-setting ratio.The results indicate that the fruit-setting ratio was superior among the tested F1 population with an average value of 12.90%,and a significant negative correlation was observed between rainfall and fruit-setting ratio.By analyzing the growth states of each F1 population,both a high germination rate and survival rate were observed.Furthermore,the purity for 184 individuals in the F1 population of'Jiaming 1'×'Longjing 43'(J×L)were analyzed with 32 selected simple sequence repeats(SSRs).The purposes of this paper are(1)to demonstrate that this method is beneficial to establish high purity F1 populations and(2)to identify the number of SSR markers that are suitable for identification.The parentage analysis detected nine false-hybrid individuals,and the rate of false-hybrid was only 4.89%at 95%confidence,demonstrating that a low false-hybrid rate can be achieved using the method.Furthermore,one to two SSR markers randomly selected from each linkage group or chromosome were recommended as a sufficient quantity for SSR identification.

An integrative analysis of metabolomics,DNA methylation and RNASeq data reveals key genes involved in albino tea'Haishun 2'

Albino tea,a type of tea closely associated with the chlorophyll-deficient phenotype is of great interest due to its multiple benefits to human health.To explore the potential mechanisms involved in albino tea,we performed metabolomics,DNA methylation and RNA-Seq analysis of green and albino leaves in a special tea mutant'Haishun 2'.The albino leaves accumulated significantly less catechins compared with the green leaves,which is closely associated with their difference in chlorophyll formation.A total of 385 candidate genes were identified by the integrative analysis.Two NAC transcription factors were less methylated and highly up regulated in the albino leaves of'Haishun 2',which was the first identification of the key roles of NAC transcription factors in albino tea and worth further study.Many genes involved in catechin biosynthesis were down regulated in albino leaves,such as 4-coumarate-CoA ligase,flavonol synthase and leucoanthocyanidin reductase genes,suggesting chlorophyll formation is important for catechin biosynthesis.Furthermore,CsMYB5 and CsGSTF11 were found to be differentially methylated and expressed in albino and green leaves,indicating their potential roles in catechin accumulation.This was the first report of the integrative analysis of transcriptome and DNA methylation data in tea plants and the results suggest that the integrative analysis is useful for exploring key genes associated with epigenetic changes in tea plants.

Construction of multiple heterogeneous interfaces boosting alkaline hydrogen evolution

Alkaline hydrogen evolution reaction(HER)is suppressed by the water dissociation,leading to more sluggish kinetics than acidic HER.Developing multifunction catalysts via constructing heterogeneous interfaces is a feasible tactic to accelerate the alkaline HER.Herein,NiO coupled with Ni and MoxN(NMN)nanorods were prepared via a hydro-thermal synthesis combined with a thermal decomposition under ammonia atmosphere.The low crystalline NMN nanorods are rich in heterointerfaces,and have sufficient high active sites for HER.The synergistic effect between NiO and Ni-MoxN promotes the water dissociation the hydrogen adsorption,and the charge transfer,contributing to excellent alkaline HER activity.The overpotential on NMN is only 36 and 150 mV for the current density of 10 and 300 mA cm^(-2),respectively,and the Tafel slope is 48 mV/dec,demonstrating a superior performance for alkaline HER,which is even comparable to the commercial electrocatalysts.

Research on the Selection of Supply Chain Marketing Models Based on E-commerce Service Levels

Based on the game theory,the service sensitivity coefficient is introduced to construct four marketing game models,which include a single flagship store,a single self-operated store,a direct sales-flagship store,and a direct sales-self-operated store,in combination with numerical analysis methods to analyze manufacturers and e-commerce platforms in different situations.The study found that the service levels affected the profit of each entity in the supply chain.The service levels of self-operated stores were higher than those of the flagship stores,and the opening of direct sales channels had a stimulating effect on the service levels of e-commerce platforms to a certain extent.In consideration of the service levels and the ability to build direct sales channels,the direct sales-flagship store marketing model is the best choice for manufacturers whereas e-commerce platforms are more inclined to open self-operated stores.However,the opening of manufacturers'direct sales channels is not necessarily beneficial to e-commerce platforms.

Impact of Quality and Government Subsidies on Elderly Care Services

In order to solve the problem of imbalance resource allocation and service income in the elderly care service industry,this article establishes three service income models in different situations for a single provider and a single integrator while considering the quality as well as government subsidies.The results showed that government subsidies can significantly improve quality efforts and service income with a mutual restriction between quality and service income.Government subsidies would have an impact on the quality,and they are more conducive to the service income of providers.When government subsidies are less than 80% of the service income,the incentive effect is better.

正电子发射粒子示踪的关键技术与进展

多相流参数检测对工业过程装置的设计和优化至关重要,但其多尺度与内在复杂性限制了对多相流动过程的理解,在流动机制方面仍有许多关键问题尚未明晰。正电子发射粒子示踪(PEPT)是一种面向工业过程中复杂多相流的新型无扰、无损的核成像方法,利用γ光子探测对放射性标记的示踪颗粒进行三维动力学成像。由于γ光子具有高穿透性、不受电磁场影响等特点,使得PEPT在非透明复杂多相流检测上具有独特优势。目前主要应用于化工、食品、制药等工业领域内多相流动现象的测量和系统物理参数提取。然而,小型化示踪颗粒制备困难、多个示踪颗粒同时定位效果差等问题严重阻碍了PEPT技术的进一步应用和推广。本工作首先介绍了PEPT技术的基本原理;然后重点从示踪颗粒、算法、硬件系统、数据处理及应用等方面讨论了PEPT关键技术及其研究进展,并指出其中存在的问题和潜在的发展方向;最后,对PEPT技术的发展和应用进行总结和展望。

A New Class of Partial Orders

Let R be a unital*-ring.For any a,w,b∈R,we apply the w-core inverse to define a new class of partial orders in R,called the w-core partial order.Suppose that a,b∈R are w-core invertible.We say that a is below b under the w-core partial order if a_(w)^(#)a=a_(w)^(#)b and a_(w)a_(w)^(#)=bwa_(w)^(#),where a_(w)^(#)denotes the w-core inverse of a.Characterizations of the w-core partial order are given,and its relationships with several types of partial orders are also considered.In particular,we show that the core partial order coincides with the a-core partial order,and the star partial order coincides with the a*-core partial order.

Growth of boron nitride nanotubes from magnesium-based catalysts

This study reports an efficient method for growing high-quality boron nitride nanotubes(BNNTs)via chemical vapor deposition of low-melting-point precursors—magnesium diboride(MgB_(2)),magnesium nitride(Mg_(3)N_(2)),and diboron trioxide(B_(2)O)at a growth temperature of 1000–1300℃.The strong oxygen-capturing ability of Mg_(3)N_(2)inhibits the formation of high-melting-point Mg_(3)B_(2)O_(6),which helps MgB_(2)to maintain an efficient and stable catalytic capacity,thereby enhancing its growth efficiency and utilization of the boron source.Moreover,polydimethylsiloxane(PDMS)composites formed from these BNNTs demonstrated much greater thermal conductivities than pure PDMS.Thus,this novel strategy for preparing BNNTs is efficient,and they have great potential for application as thermal interface materials.

A study of the temporal and spatial variations in the suitability of the environment in Chinese cities for tourism and in strategies for optimizing the environment

With the aim of guaranteeing the interests and health of tourists,this study comprehensively evaluates the suitability of the environment in different cities in China for tourism by considering the impacts of climate,vegetation and environmental factors on health.The Universal Thermal Climate Index(UTCI),total precipitation(PREC),Vegetation Leaf Area Index(LAI),concentration of particulate matter with a diameter of less than 2.5μm(PM2.5),and the downward UV radiation at the surface(UVB)are used as indices.In addition,the Delphi–AHP–TOPSIS algorithm is introduced and is used for the comprehensive evaluation of the environmental suitability of 684 cities in China for tourism in 2019.It is found that Chinese cities vary greatly in terms of the suitability of their environments for tourism.Among the factors that affect the environmental suitability,the LAI is important,with an increase in the LAI generally being advantageous.In contrast,an increase in the PM2.5 concentration is a key factor that limits the environmental suitability of an area.Thus,urban landscaping and control of the atmospheric quality are essential and effective ways of improving the suitability of the environment of cities in China for tourists.