Stabilization of anti-aromatic and strained five-membered rings with a transition metal

1981年诺贝尔化学奖获得者、美国康奈尔大学RoaldHoffmann教授评价该项工作说：'The　paper is an excellent one--it's　quite a mazing that the parent Os　system,molecule 1,chooses to give the osmapentalyne'。德国化学家Uwe Rosenthal教授等在同期《自然—化学》杂志的《News and Views》栏目以《Breaking the rules》为题撰文评述了这一研究成果。全文地址：http://www.nature.com/nchem/journal/vaop/ncurrent/pdf/nchem.1702.pdfAnti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hückel anti-aromaticity into Craig-type Möbius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal–carbon triple bond. Moreover, these metal–aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement

Graphical Presentation and Their Characteristics of the Coupled Zones for Optimal Supplies of Water and Nutrients to Crops

用中国科学院安塞实验站田间试验数据 ,建立了水肥供应与玉米产量、耗水量的关系模型。以作物水分利用效率与产量为目标 ,得到了两类作物水肥优化耦合区域。在水肥坐标面上 ,取两种方向 (与产量达到最大的点的连线的方向及产量曲面的梯度方向 ) ,得到的水分生产弹性系数等于 1和等于 0的点所形成的区域均呈椭圆形 ,分别称为第一类椭圆和第二类椭圆。第二类椭圆与第一类椭圆相比 ,短轴缩小 ,长轴没有变化。最大产量与最大水分利用效率处于长轴的两个端点上。由此椭圆 ,根据节肥要求等条件 ,得到了水肥优化耦合区域。可在此区域内决策水肥的优化投

Potential productivity of dryland spring corn on Loess tableland.

在黄土高原南部长武旱塬所做的田间试验结果表明 ,玉米的水分效应函数为 :Pw =1 .0 0 - 5.2 93( 1 -k) 2 .把式中k取为农田干湿指数 (旱作玉米全生育期内高肥水平下耗水量与需水量的比值 ) ,则Pw即为旱作玉米生产潜力指数 .试验中k值的表现区间为0 .78至 1 .1 0 ,k值的理论上界与局部农田潜在蒸散有关 .1 985～ 1 988年 ,旱作玉米的Pw的平均值为 0 .87.旱作玉米生产潜力的远期值与近期值变化趋势相似 ,前者 4年平均值为1 1 2 4 7kg·hm- 2 ,后者为 7696kg·hm- 2 .由于试区近年来物质能量向农田的不断强化投入以及对作物品种的改良 ,试区大田实际产量连年来向潜力值逼近

智慧之油 民族之业

有一种营养物质叫α-亚麻酸(α-linolenic?acid,ALA),属于ω-3系列多不饱和脂肪酸,是机体必需的生命活性因子EPA和DHA的合成前体,人体不能自身合成,主要从膳食中摄取,对人体健康起着至关重要的作用。它是构成人体脑细胞和组织细胞的重要成分,拥有"血液营养素""维生素F"和"植物脑黄金"的美誉,对于防治21世纪威胁人类生命的"四大杀手"——心脑血管病、癌症、糖尿病、痴呆症有着显著的作用

钛电解精炼中阳极过程的研究

本文通过测定金属 Ti、Ti-6Al-4V 合金及氢化-脱氢处理后的 Ti-6Al-4V 合金三种不同阳极的极化曲线,分析了合金组分 Al、V 对金属钛极化行为和阴极产品粒度的影响,并探讨了钛及其合金中钛的溶解过程

Spatial variability of soil moisture and aboveground biomass of Medicago sativa under long term continuous planting

基于苜蓿长期连续种植定位试验,研究了不同施肥与采样位置差异对苜蓿草地地上部分生物量和土壤水分的影响。苜蓿长期连续种植19年后,施肥对苜蓿地上部分生物量的影响不显著;试验样地内呈由外及内植株高度逐渐下降、地上部分生物量积累逐渐减小的"生物漏斗"现象,距样地中心位置不同引起的差异远远超过施肥处理引起的差异。中下层土壤水分也呈类似的漏斗状分布。相关分析表明,苜蓿地上部分生物量与1 m以下土壤水分含量呈显著相关,表明在长期连续种植条件下下层土壤水分状况是决定苜蓿草地生长状况的主要因素

一种用于被动型小氢钟快速调制锁定的数字移相装置

本发明涉及一种用于被动型小氢钟快速调制锁定的数字移相装置，包括：一可编程控制芯片，所述可编程控制芯片接收由一压控晶体振荡器提供的输入参考时钟信号；所述可编程控制芯片分别输出一用于控制所述被动型小氢钟的数字调制的调制控制信号，以及用于分离信号的具有相位差的两个移相信号；所述可编程控制芯片包括对所述输入参考时钟信号移动第一相位的第一移相电路，以输出第一移相信号，以及将所述第一移相信号滞后第二相位的第二移相电路，以输出第二移相信号。采用本发明可实现简单可行、成本低的数字移相

The effects of loose top-coal on the mining pressure of support in longwall top-coal caving mining

The peak value of mining pressure on hydraulic support is supposed to increase with the mining height in the longwall top-coal caving mining. The supporting pressure of hydraulic support is therefore selected based on the mining height. However, it is also known that the pressure may not significantly increase as expected. This study mainly aims to clarify the effects of the loose top-coal on the reduction of the mining pressure of the hydraulic support for the geological conditions of Jiaozuo Coal Mine in Henan Province, China. A series of dynamic loading tests for loose top-coal, which was simulated by particles having different types and sizes, with different thicknesses, was carried out. It was found that the buffering effect became more prominent for softer or larger particles, or with the thickness within a certain value. The interaction model between the support and loose top-coal was built and the constitutive equations between them were derived. In the analysis using the constitutive equations, it was confirmed that the top-coal became more stable with the stiffness of the support. It was found from the numerical analysis using ANSYS software that the stratification of stress occurred during the propagation of loading in the top-coal and that the buffering effect became better with the thickness within a certain value.一般社団法人資源・素材学会 2020年度 春季大会、2020年3月15日～17日、千葉工業大学 津田沼キャンパス、習志野市（開催中止