基于可见/近红外能量光谱的苹果褐腐病和水心鉴别

快速无损鉴别苹果内部品质的优劣是当前苹果行业亟待解决的一项重要课题.针对这一现状,提出了直接采用可见一近红外能量光谱对苹果褐腐病、水心鉴别的新方法,考察了不同判别分析方法对苹果类别判定的准确性.在能量光谱经MSC或者一阶导数处理后,分别采用了峰面积判别法(PADA)、主成分分析判别法(PCADA)、偏最小二乘判别法(PLSDA)建立判别模型.结果显示,三种方法对褐腐病苹果判别正确率都为100%;对水心苹果分别是79.2%,95.0%和96.7%;对正常苹果分别是88.6%,98.2%和98.8%.其中,PCADA和PLSDA明显优于PADA,而PLSDA总判别率最高,达到98.1%,其建模标准差RMSEC为0.449,预测标准差RMSEP为0.392,说明可见一近红外能量光谱结合化学计量学算法可以快速、无损鉴别苹果褐腐病和水心.     

碱性藏花红T荧光猝灭法测定痕量过氧化氢

在NH3·H2O-NH4CI缓冲溶液中,Cu2 催化下,H2O2氧化碱性藏花红,使其荧光猝灭,荧光猝灭程度与H2O2在一定范围内呈线性关系.建立了荧光光度法测定痕量H2O2的新方法,用正交法确定最佳测定条件.方法的激发波长为528nm,发射波长为587nm,在最佳条件下该法测定H2O2的线性范围为0.5-25μg/25mL,检出限为7.2×10-7g/L.方法操作简单,用于雨水中H2O2含量的测定.     

采用罗戈夫斯基线圈诊断径向束流

 罗戈夫斯基线圈具有结构简单、高频特性好等特点而被广泛应用于脉冲电流测量。提出了用两个自积分式罗戈夫斯基线圈诊断径向束流的方法,在此基础上设计了两个用于径向束流诊断的自积分式罗戈夫斯基线圈,对其进行了标定。当标准电流的上升沿为30 ns时,罗氏线圈响应时间约为10 ns;整个系统的测量误差约为4.7%。从标定结果来看,该系统的频率响应特性和测量精度能够满足ns级束流诊断的要求,该方法可以用于径向结构高功率微波器件的束流强度测量。     

Mechanical Properties of Breast Cancer Cell Membrane Studied with Optical Tweezers

Membrane tethers are extracted from breast cancer cells using a force generated by an optical trap. It is experimentally obtained that the radius of tether is about 0.1μm and the static tether force is about 8.5 pN. Calculations based on the experimental measurements give a bending modulus for the tether of 1.35 x 10^-19 N.m and a surface membrane tension of 6.76 x 10^-6 N/m in the breast cancer cell. The treatment with cytochalasin D results in the decreasing bending modulus and decreasing apparent surface tension. When the membrane protein caveolin is over-expressed, similar cases occur in bending modulus and apparent surface tension. In addition, the viscous resistance coefficient of the membrane is calculated to be 1.15pN.s/μm according to the dynamic tether forces obtained under different pulling velocities.     

Possible triggering of solar activity to big earthquakes (Ms ≥ 8) in faults with near west-east strike in China

A big earthquake (Ms = 8.1) occurred at western Kunlun Mts gap on November 14, 2001. It is the biggest earthquake in China in the past 50 years and the only one with a magnitude bigger than 8 in China after Dangxiong Earthquake (M = 8) in Tibet in 1951. The big earthquake has drawn wide attention of scientists in seismological, geophysical, geological and astro-geodynamic circles. Scientists are interested in the occurrence regularity of the very big earthquakes and try to find out the fac…     

Liquid Nuclear Magnetic Resonance Implementation of Quantum Computation in Subspace

Based on the logical labelling method, we prepare an effective pure state in a subsystem of a three spin system via liquid nuclear magnetic resonance technique. Then with this subspace effective pure state we implement the Deutsch-Jozsa algorithm. The tomography for the subspace effective pure state and the corresponding spectrum of the output for the Deutsch-Jozsa algorithm agree with theoretical predictions, which shows that we have successfully implemented the Deutsch-Jozsa algorithm in a subsystem of a nuclear spin system and demonstrated a subspace quantum computation.     

近红外光谱技术测定紫花苜蓿青贮鲜样的发酵品质

及时了解青贮饲草的发酵品质,如青贮饲草中氨态氮(NH₃-N),乳酸(LA), 乙酸(AA),丁酸(BA)含量,对畜牧业生产具有重要意义。应用偏最小二乘回归法(PLS)、傅里叶变换近红外光谱技术和液氮冷冻制样技术,建立了适合不同品种,不同生育期,不同茬次和不同青贮方法即时测定青贮苜蓿鲜样中氨态氮,乳酸,乙酸,丁酸的近红外校正模型,以期对NIRS在测定紫花苜蓿青贮样品中这些物质的可行性进行分析。所建模型的交叉检验决定系数(R2_CV)为0.602 4～0.949 7,交叉检验标准误(RMSECV)为0.559～3.78 g·kg-1鲜重。用检验集样品对模型进行外部检验,预测相关系数(r)为0.882 6～0.985 3,预测标准误为0.571～3.15 g·kg-1鲜重。结果表明,采用适当的样品处理方法和光谱分析技术可以实现近红外光谱技术对苜蓿青贮样品发酵品质的评定。     

Improved Resistive Switching Characteristics of Ag-Doped ZrO2 Films Fabricated by Sol-Gel Process

Ag-doped and pure ZrO₂ thin films are prepared on Pt/Ti/SiO₂/Si substrates by sol-gel process for resistive random access memory application. The highly reproducible resistive switching is achieved in the 10% Ag-doped ZrO₂ devices. The improved resistive switching behaviour in the Ag doped ZrO₂ devices could be attributed to Ag doping effect on the formation of the stablefilamentary conducting paths. In addition, dual-step reset processes corresponding to three stable resistance states are observed in the 10% Ag doped ZrO₂ devices, which may be implemented for the application of multi-bit storage.     

人教版高中化学必修教科书的内容呈现方式及特点分析*

高中化学教科书是发展学生化学学科核心素养的重要载体和资源平台。依据《普通高中化学课程标准(2017年版)》编写的人教版普通高中化学必修教科书作为分析文本,着重从栏目系统、图像系统、习题系统角度对其呈现方式进行分析,具体特点表现为:栏目系统强化功能性,图像系统凸显直观性,习题系统体现针对性、情境性、开放性,以期为高中化学教师有效使用教科书、落实化学学科核心素养的培养发挥积极作用。     

国内外化学相异构想研究的进展与启示*

国内外有关化学学科的相异构想研究主要包括对学生相异构想进行诊断及其原因分析,以及开发有效的教学模式或策略对学生相异构想进行概念转变。通过对国内外相关研究现状的分析,为相异构想的后续研究提供思路。