Reaction of 5-aminopyrazole derivatives with ethoxymethylene-malononitrile and its analogues

A one-pot synthesis using 5-aminopyrazole derivatives 1 with ethoxymethylenemalononitrile (EMMN), ethyl ethoxymethylenecyanoacetate (EMCA) or diethyl ethoxymethylenemalonate (DEMM) gave pyrazolo-[1,5-a]pyrimidine compounds 2,4,8 . Also, the one step reaction of EMCA with hydrazine hydrate afforded ethyl(4-ethoxycarbonyl-5-pyrazolyl)aminomethylenecyanoacetate 3c . On the other hand, the reaction of 1-substituted 5-aminopyrazole-4-carboxamide 9 with EMMN afforded pyrazolo[3,4-d]pyrimidine compounds 10 .     

Magnetic excitations in ferromagnetic semiconductors,and their study by light scattering

The magnetic excitation spectrum of degenerate ferromagnetic semiconductors, described by the s-f interaction model, is investigated by calculating various Green functions which provide the dynamic response of the system. In addition to the usual acoustic spin-wave mode, there are also an optical spin-wave branch and the Stoner-like continuum of excitations. Some estimates are made for the first order light scattering from ferrmagnetic semiconductors at low temperatures T?T_c.     

New three- and four-armed flexible bridging ligands for use in metallosupramolecular chemistry: syntheses and X-ray structures

Preparations are described of twelve new tritopic and tetratopic ligands by coupling of two phenolic precursors with a range of heterocyclic units. X-ray crystal structures of four representative examples revealed the conformations in the solid state with the nitrogen donor atoms separated by distances ranging from 10.9 to 18.2 Å.     

荧光寿命的快速傅里叶变换拟合方法

介绍了一种利用快速傅里叶变换算法对稀土掺杂物质的荧光寿命进行数据拟合的方法。稀土掺杂物质可用来制备多种光学传感器,用于温度、pH值等多种参量测量领域。本方法利用快速傅里叶变换(FFT)结果作为基础,从非零项的相位角的正切值得出被测的荧光寿命,具有速度快、误差小、不受本底干扰等一系列优点。以掺铒光纤为例,通过数字仿真将本方法与其它几种传统的拟合方法进行了比较。快速傅里叶变换方法的测量偏差不到Prony方法的50％,为对数似合(log-fit)方法测量偏差的1／6。另外,快速傅里叶变换方法由于不受本底噪声影响,可以不必在信号处理时去掉本底噪声,因而可以明显缩短测量时间。