高效液相色谱法同时测定异α-酸与四氢异α-酸

1引言啤酒花深加工产品异α-酸与四氢异α-酸近年来已被全国各大啤酒厂广泛使用，但并无统一检测手段。文献报道的方法用乙腈和水作为流动相，单独测定四氢异α-酸。乙腈价格较高，用此方法进行产品质量控制成本高，本法采用甲醇代替乙腈，大大降低成本。分离效果好，并可同时测定异α-酸与四氢异α-酸。2实验部分2．1仪器与试剂P200Ⅱ型高压恒流泵，UV200Ⅱ型紫外可变波长检测器（大连伊力特科学仪器有限公司）。HepersilBDSC185μm柱（150×4.6mmi．d．）。甲醇，85％磷酸，四丁基羟胺10％水溶液，均为分析纯。水为双蒸水。2．2色谱条…     

Doping effects on structural and magnetic evolutions of orthoferrite SmFe（1-x） Alx O3

The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom A1 are investigated. The x-ray diffraction patterns show that SmFe（1-x）AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped A1 concentration. Besides, the octa- hedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard＇s rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 〈 x 〈 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature （Tk） decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior.     

Photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles

The photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles in aqueous solution was comprehensively investigated using various selected wavelength light in the UV-Vis-NIR region.The time-dependent photo-dimerization degree(PD) changes in the photo-dimerization experiments showed saturating behaviors with intensity-independent of PDmax values at 28%,44%,92%,85%,36%,35%,32% and 31% for 254,288,320,360,400,500,650 and 900 nm irradiations,respectively.The irradiation experiments at 254 and 288 nm announced the occurring of an asymmetric equilibrium of photo-dimerization and photo-cleavage at the used conditions.Both the alternative irradiation cycles of 360 and 254 nm,650 and 254 nm showed a partially,but evidently reversible photo-dimerization tendency.     

物理教学中要体现学生的主体作用

本文结合“法拉第电磁感应定律”的教学过程,介绍一下我们在“物理课堂教学中,如何发挥学生主体作用”这一研究课题中的一点尝试. 1 指导预习,培养兴趣,提高课堂效益发现问题,产生疑问,进而寻求答案,这可以说是人类的天性.在教学过程中,如何充分调动学生这种本能的求知欲望呢?组织有计划、有指导的课前预习是一个有效的手段.因为与其在教学中反复强调重点和难点,倒不如让学生们通过预习,自己去发现重点和难点,并主动地通过课堂教学过程去寻找答案.变我教你学为我和你一起去寻找答案.这里的关键是:使学生明确预习的目的是重在发现问     

A SINGULAR BOUNDARY VALUE PROBLEM FROM DRAINING AND COATING FLOWS INVOLVING A THIRD-ORDER ORDINARY DIFFERENTIAL EQUATION

1IntroductionInarecentsurveypaperTuckandSchwarts[3]discussedaseriesofthird-orderordinarydifferentialequationsarisinginthestudyoftheflowofathinfilmofviscousfluidoverasolidsurface.Whensuchafilmdrainsdownaverticalwallandtheeffectsofsurfacetensionandgravityaswellasviscosityaretakenintoaccount,oneisledtoanequationoftheformforthefilmprofiley(x)inacoordinateframemovingwiththefluid.Herethex--axisischosentobepointingupwords.Generallyspeaking,thefunctionf(y)issingularaty=0,thatis,atthetipofthefilm.Its…     

萘满酮类缩氨基硫脲的微波无溶剂快速合成(英文)

在微波辐射无溶剂的条件下,以中性三氧化二铝为载体,快速有效地合成了一系列新的6-甲氧基萘满酮缩氨基硫脲类化合物。这些化合物的结构经核磁,红外,质谱和元素分析所确证,与传统方法相比,微波大大缩短反应时间,从240~300分钟缩短到4~8分钟。而产率从59~70%增加到80~92%。     

POLYMATH软件在化工课程中的应用

以化学工程中的非线性方程、复杂函数的积分、离散数据点的处理、实验数据点的回归分析以及线性微分方程组求解为例,讨论POLYMATH软件在化学与化工课程中的应用。结果表明：利用POLYMATH求解计算问题稳定性好、方便快捷;能把学生从复杂的编程与调试中解脱出来,并能提高学生的学习效率以及分析问题和解决问题的能力。