微弱信号检测技术在超导电阻测量方面的应用

随着近年来超导技术应用范围的不断扩大,超导技术的影响已经波及到了各个学科领域.本文通过对超导电阻特性的分析研究,提出了一种基于微弱信号检测的超导体电阻测量的新方案.利用高性能DSP芯片,软件实现了超导体电阻的测量;利用单片机配合双积分A/D转换器测量超导体的环境温度.实验表明,本测量系统可有效地检测微弱的超导电阻信号,本系统充分显示出了自身在超导体电阻测量等微弱信号检测方面的优越性.     

柱状黄杆菌对褶纹冠蚌抗氧化系统主要因子的影响

利用柱状黄杆菌为刺激物,对褶纹冠蚌进行注射感染,在注射后3、6、12、24、48h后分别取血清、肝胰腺,测定其超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPX)的活性和谷胱甘肽(GSH)、过氧化氢(H2O2)、丙二醛(MDA)的含量的变化。结果表明,经柱状黄杆菌感染后,实验组血清中的SOD活性在6h时与对照组有显著性差异;GPX的活力在3h与对照组有明显的差异,GSH的含量在24h明显低于对照组。而实验组肝胰腺中GPX的活力在24和48h时显著高于对照组。实验组血清和肝胰腺中MDA和H2O2的含量与对照组没有明显的差异。褶纹冠蚌注射柱状黄杆菌感染后,血清中各抗氧化指标比肝胰腺中的变化大。更多还原     

Co3+离子自旋态对六方相LaCoO3的低指数晶面稳定性影响的密度泛函理论研究

By the first-principles calculations,most studies indicated that the (11102)-CoO₂ termination of LaCoO₃ cannot be stabilized,which disagrees with the experimental observation.Besides the crystal structure,we found that the spin states of Co³⁺ ions could affect surface stability,which previously were not well considered.By examining the different states of Co³⁺ ions in hexagonal-phase LaCoO₃,including low spin,intermediate spin,and high spin states,the surface grand potentials of these facets are calculated and compared.The results show that the spin states of Co³⁺ ions have an important influence on stability of the LaCoO₃ facets.Different from the previous results,the stability diagrams demonstrate that the (11102)-CoO₂ termination can stably exist under O-rich condition,which can get an agreement with the experimental ones.Furthermore,the surface oxygen vacancy formation energies (E_Ov) of stable facets are computed in different spin states.The E_Ov of these possible exposed terminations strongly depend on the spin state of Co³⁺ ions:in particular,the E_Ov of the HS states is lower than that of other spin states.This indicates that one can tune the properties of LaCoO₃ by directly tuning the spin states of Co³⁺ ions.     

水溶性阳离子卟啉与ctDNA的相互作用及其聚集行为研究

水溶性阳离子卟啉作为多功能DNA结合试剂在光动力学疗法、抗病毒药物等方面得到了越来越多的应用,因此研究阳离子卟啉与DNA的相互作用引起人们极大的兴趣。文章采用吸收光谱、荧光光谱和共振光散射技术研究了meso-四(4-三甲铵基苯基)卟啉(TMAP)和5-苯基-10,15,20-三(N-甲基-4-吡啶基)卟啉(TriMPyP)两种水溶性阳离子卟啉在水溶液中的聚集状态及与小牛胸腺DNA(ctDNA)的相互作用。在R>1时(R=c_TMAP/c_DNA),TMAP在DNA分子表面发生聚集,吸收光谱有明显的减色效应,卟啉的荧光被猝灭。在R<1时,TMAP与DNA以外部结合方式结合,荧光得到增强,共振光信号减弱。DNA的加入,使TriMPyP的聚集程度进一步增加。考察了离子强度对卟啉与DNA相互作用的影响,离子强度增大,卟啉的荧光得到增强,卟啉与DNA的结合方式发生改变。     

超高效液相色谱-串联质谱法检测鸡粪中16种残留抗生素

建立了固相萃取-超高效液相色谱-串联质谱(UPLC-MS/MS)同时检测畜禽粪便中四环素类、磺胺类、氟喹诺酮类和大环内酯类16种抗生素的分析方法.针对目标物化学性质和样品杂质情况,对质谱条件、提取液种类、超声功率等参数进行了优化.最终以50%乙腈(V/V)的磷酸盐缓冲溶液(pH=4)提取3次,经过超声、离心、旋蒸、稀释后,SAX-HLB串联小柱净化富集,用10 mL甲醇-丙酮混合液(80∶20,V/V)洗脱,35℃氮吹近干后,用含0.1%甲酸-甲醇(1∶1, V/V)定容,在UPLC-MS/MS多反应检测模式下进行定性及定量分析.结果表明,粪便中四环素类、磺胺类、氟喹诺酮类和大环内酯类抗生素的平均加标回收率为56.4%~94.6%,相对标准偏差(RSD)在2.6%~19.8%之间,方法检出限(LOD, S/N=3)和定量限(LOQ, S/N=10)分别为0.01~2.50 μg/ kg和0.05~7.90 μg/kg.本方法简便、稳定性好、灵敏度高、重现性好,适用于畜禽粪便中多种抗生素的同时检测.     

Synthesis via Precursor Method and Shape Evolution of Basic Magnesium Carbonate

Basic magnesium carbonate(4 MgCO3·Mg(OH)2·4 H2 O) with spherical-like structure was synthesized through precursors thermal decomposition. The precursor of magnesium carbonate trihydrates(MgCO3·3 H2 O) was synthesized by brine and ammonium bicarbonate, and the thermal decomposition conditions were investigated in detail. The obtained particulate was characterized using SEM, XRD and laser particle analyzer. The result showed that it was easy to obtain spherical-like 4 MgCO3·Mg(OH)2·4 H2 O by precursor thermal decomposition at 80~100 ℃ with thermal decomposition time 90 min, stirring time 15 min and the liquid initial concentration 0.1 mol/L, while rod-like 4 MgCO3·Mg(OH)2·4 H2 O with a surface of "house of card" structure was more likely to be obtained at low temperature(55 ℃), and rosette-like products were obtained at a little higher temperature(80 ℃) by direct synthesis.     

适用于壳体h型自适应有限元分析的一组新单元

推导出一组适用于h型自适应分析的四边形蜕化壳元。对于大多数壳体结构,壳单元的刚度矩阵可分为薄膜、弯曲和剪切三部分。对薄膜部分本文采用杂交应力元方法进行设计,独立假设薄膜应力场以改善其精度;弯曲部分的刚度矩阵则依然由基于位移的应变来获得;而剪切部分则采用假设自然应变的方法来获得能克服薄壳下剪切自锁的新剪应变并用于计算此部...     

蓝链霉菌抗生素次生代谢过程的调控因子研究进展

天蓝链霉菌是抗生素代谢调控研究的模式菌株,它能产生十一烷基灵菌红素(Red)、放线紫红素(Act)、次甲霉素(Mmy)和CDA(Calcium-Dependent Antibiotic)4种抗生素.详细介绍了抗生素生物合成基因簇中途径专一调控基因、形态分化基因、双组份信号传导基因以及其它一些重要的小分子物质对抗生素次生代谢的调控作用,并阐述了其相互协同调节的网络体系.     

Noise-Induced Bursting and Coherence Resonance in Minimal Cytosolic Ca^2＋ Oscillation Model

A stochastic calcium oscillation model based on the minimal calcium oscillation model is investigated by numerical computation. When the extracellular stimulation is sub-threshold and random, the oscillations of cytosolic calcium show complex behaviour: a bursting-like phenomenon induced by noise, that is, the phase of glomerate spikes are separated by phase of quiescence (but fluctuations in the baseline values of calcium with small amplitude during the silent phase), in a pattern that occurs at irregular intervals. By using the histogram of interspike intervals of calcium concentration spikes, it is found that the noise-induced coherence resonance phenomenon occurs at the cellular level.     

巯基葡聚糖凝胶分离富集三甲氧基苯基荧光酮光度法测定痕量铟

1　引　　言铟属于分散元素,在地壳中平均含量为 1×10-8,具有亲石和亲硫性,由于分散性极强,而广布于自然界中,本实验采用显色剂三甲氧基苯基荧光酮建立了在微乳液介质中矿石中测定痕量铟的方法,采用机械性能优于巯基棉的巯基葡聚糖凝胶进行分离富集,消除了共存离子的干扰。2　实验部分2.1　仪器和试剂　UV 3000型紫外可见分光光度计(日本岛津公司)。铟标准溶液: 1. 000g/L贮备液,稀释成 1. 0mg/L工作液;三甲氧基苯基荧光酮(TM PF): 0. 1g/L的乙醇溶液。乙酸 乙酸钠系列缓冲溶液:pH=2. 5~6. 2;溴代十六烷基吡啶(CPB)微乳液:CPB∶正丁…