简介:制备了锌修饰铂电极,建立了一种新的测定Zn(Ⅱ)的示波双电位滴定法。在六次甲基四胺溶液(1.0mol/L)中(pH=5.5),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Zn(Ⅱ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。在3.0×10^-4~2.0×10^-3mol/L的浓度范围内,Zn(Ⅱ)的回收率为99.9%~100.2%。该修饰电极具有良好的稳定性和重现性,对Zn(Ⅱ,1.0×10-3mol/L)溶液连续11次测定,所得终点电位值均在10.1mV左右,其相对标准偏差(RsD)为0.5%。用来测定含锌的实际样品,其结果与指示剂法测定的值基本一致。
简介:PhasesandmicrostructuresofthreehighZncontainingAl–Zn–Mg–Cualloyswereinvestigatedbymeansofthermodynamiccalculationmethod,opticamicroscopy(OM),scanningelectronmicroscopy(SEM)energydispersivespectroscopy(EDS),X-raydiffraction(XRD),anddifferentialscanningcalorimetry(DSC)analysis.TheresultsindicatethatsimilardendriticnetworkmorphologiesarefoundinthesethreeAl–Zn–Mg–Cualloys.Theas-cast7056aluminumalloyconsistsofaluminumsolidsolution,coarseAl/Mg(Cu,Zn,Al)2eutecticphases,andfineintermetalliccompoundsg(MgZn2).Bothofas-cast7095and7136aluminumalloysinvolvea(Al)eutecticAl/Mg(Cu,Zn,Al)2,intermetallicg(MgZn2),andh(Al2Cu).Duringhomogenizationat450°C,fineg(MgZn2)candissolveintomatrixabsolutely.Afterhomogenizationat450°Cfor24h,Mg(Cu,Zn,Al)2phasein7136alloytransformsintoS(Al2CuMg)whilenochangeisfoundin7056and7095alloys.ThethermodynamiccalculationcanbeusedtopredictthephasesinhighZncontainingAl–Zn–Mg–Cualloys.
简介:Inapreviousgreenhouseexperiment,weshowedthattherewasaninteractionbetweencuandZn,whichaffectedgrowthandmetaluptakebyyoungbarleyplantsgrownonsoiltowhichCd,Cu,Pb,andZnhadbeenadded.Wesuggestedthattheunderlyingmechanismwasthecontroloftheamountofplant-availableZnbycompetitiveadsorptionbetweenCuandZn,Inordertotestthishypothesis,theadsorptionofZnalone,andinthepresenceofaddedCd,CuandPb,hasbeenmeasuredusingthesamesoil.Followingadsorption,theextractabilityoftheZninCaCl2solutionwasmeasured.TheadsorptionisothermsshowedthatoftheaddedmetalsonlyCuhadalargeeffectonZnadsorption.TheeffectofCuwastoreduceZnadsoptionandtoincreasetheamountofCaCl2-extractable(i.e.plant-available)Zn,inagreementwiththeconclusionsfromthegreenhouseexperiment.ThemagnitudeoftheeffectofCuonplant-avalilableZnwassimilarinbothexperiments.
简介:摘要目的分别利用体表电极和食道电极监测阻塞性睡眠呼吸暂停(OSA)患者夜间不同睡眠状态的呼吸中枢驱动、呼吸中枢驱动的有效性及上气道阻力,评估两者是否具有一致性。方法共招募24例OSA患者,分别利用体表电极和食道电极测量受试者清醒期(W)、稳定的非快速眼动2期(N2)、稳定的非快速眼动2期伴打鼾期(SNORING)、低通气期(HYPOPNEA)、暂停事件前低通气期(PREAPNEA)的呼吸中枢驱动。流速用流量计测量。所有受试者行标准的全夜睡眠多导图检查。结果我们的研究结果发现从W到N2,到SNORING,到HYPOPNEA,到PREAPNEA,标化后的食道膈肌肌电(EMGdi%max)和标化后的体表膈肌肌电(SEMGdi%max)的变化趋势一致。从W到N2,到SNORING,EMGdi%max、SEMGdi%max依次增高。呼吸中枢驱动在SNORING期高于HYPOPNEA,PREAPNEA期高于HYPOPNEA。EMGdi%max/V和SEMGdi%max/V从W到N2,到SNORING,到HYPOPNEA,到PREAPNEA依次增高。VE/EMGdi%max、VE/SEMGdi%max从W到N2,到SNORING,到HYPOPNEA,到PREAPNEA依次降低。结论体表电极可以代替多导食道电极评估OSA患者的呼吸中枢驱动、呼吸中枢驱动有效性及上气道阻力。