Indirect Electrochemical Determination of Ribavirin Using Boronic Acid-Diol Recognition on a 3-Aminophenylboronic Acid-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode (APBA/ERGO/GCE)

A novel method for the indirect electrochemical determination of ribavirin based on boronic acid-diol recognition was developed using the platform as the sensing element. The device was constructed using a 3-aminophenylboronic acid (APBA)-electrochemically reduced graphene oxide (ERGO) modified electrode. When the electrode was immersed in a solution of ribavirin, complexation of boronic acid groups of APBA with ribavirin occurred at the surface of the electrode and simultaneously caused steric hindrance, resulting in a current decrease because the ferricyanide redox probe was unable access the surface. Under the optimized conditions, a linear relationship was obtained between the relative change in current (%Δi) of [Fe(CN)₆]^3?/4?and the concentration of ribavirin at levels from 10.0 to 7.50?×?10²?ng mL^?1. The proposed electrochemical sensor performed with acceptable sensitivity and reproducibility and was successfully used to determine the content of ribavirin in an injection with satisfactory results.     

Determination of antihyperglycemic drugs in nanomolar concentration levels by micellar electrokinetic chromatography with non-ionic surfactant

A method for the separation of six selected antihyperglycemic (antidiabetic) drugs (tolbutamide, gliclazide, glimepiride, glibenclamide, repaglinide, and glipizide) was developed with use of micellar electrokinetic chromatography. Two non-ionic poly(ethylene glycol)-based surfactants Genapol X-080 and Triton X-114 (reduced) were studied as neutral pseudostationary phases. High alkaline pH 10.0 was used to obtain negative charges of separated antidiabetic drugs and non-ionic surfactants were employed for selectivity alteration. Both non-ionic surfactants provided good selectivity at concentration 0.2% (v/v) in sodium borate buffer and the separation of six drugs was obtained within 5 min. An on-line preconcentration method based on reversed electrode polarity switching was employed for the determination of antihyperglycemic drugs in blood serum after acetonitrile protein precipitation. The limits of detection ranged from 20.8 nmol L⁻¹ for tolbutamide to 6.5 nmol L⁻¹ for glibenclamide, respectively.     

Thermal investigations of direct iron ore reduction with coal

In this paper, fundamental mechanisms for iron ore reduction in coal–ore mixtures have been investigated using several advanced experimental techniques. Firstly, the thermal properties of coal–ore mixtures were studied and apparent specific heat of coal–ore mixtures against temperature was obtained at a heating rate of 10 °C/min. Several exothermic and endothermic peaks were observed which were related to the decomposition reactions and reduction. The flue gases from the mixture were analysed using a mass spectrometer. Secondly, the X-ray diffraction (XRD) and the iron phase analytical techniques were applied to identify the iron phase changes with the temperature. It has been found that coal devolatilisation and iron oxides reduction occur simultaneously during the heating of the mixture. H₂ and CO gases produced from coal devolatilisation and char gasification were responsible for the reduction of iron oxides at these temperatures. Iron oxides undergo step-wise reduction over the whole process. The results in this work provide a fundamental understanding for the direct reduced ironmaking processes.     

三维二硫化钼/还原氧化石墨烯气凝胶用作宏观可见光催化剂

近年来,光催化技术在解决环境污染和能源短缺方面展现出巨大潜力.二硫化钼(MoS2)作为一种二维层状光催化材料受到广泛关注.MoS2具有可调的带隙(1.2–1.9 eV)、低的成本和高的存储量,是一种可替代铂的理想助催化剂.然而,MoS2本身光催化活性较低.理论和实验已经证明,MoS2只有暴露的边缘具有催化活性,并且MoS2的光生电子-空穴对容易复合,导致其光催化效率低.增加暴露的活性边缘以及有效分离电子-空穴对是提高MoS2光催化活性的关键.而石墨烯气凝胶是一种理想的催化剂载体,其高比表面积和高空隙率可以有效提高催化剂利用率.同时,其高导电性可以促进光生电子-空穴对分离.因此,将MoS2负载到石墨烯气凝胶上制备宏观可回收光催化材料具有广阔的应用前景.然而,目前尚未见到有关MoS2/石墨烯气凝胶光催化产氢以及还原Cr(VI)的报道.本文以钼酸铵为钼源,硫脲为硫源和还原剂,同时加入氧化石墨烯及其还原剂氨水,通过一步水热法制备出二硫化钼/还原氧化石墨烯(MoS2/RGO)水凝胶.最后通过冷冻干燥得到MoS2/RGO气凝胶.经光催化测试发现其产氢达到38.9μmol/g,光还原Cr(VI)达到92%,明显高于MoS2粉体.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见-近红外吸收光谱(UV-Vis-NIR)及红外光谱(FTIR)等手段研究了其光催化性能提高的原因.XRD测试显示,过量的NH4+离子插入到MoS2层与层之间增加了(002)面的晶面间距;SEM观察到在形成气凝胶后,MoS2从粉末的片状转变成花状,这是因为氧化石墨烯上的含氧官能团促进MoS2成核同时限制其生长导致的;TEM观察到MoS2上存在大量的脱节和扭曲,这是由于过量硫脲阻碍了MoS2晶体的取向生长而产生缺陷;XPS发现,除了形成MoS2之外,还形成了MoO2,同时大量的暴露边缘导致不饱和硫产生;FTIR表明MoS2与RGO之间通过氢键链接在一起;UV-Vis-NIR吸收光谱显示,MoS2/RGO气凝胶在可见光区具有很强的吸收,这是黑色的RGO以及光在花状结构的不断反射共同作用导致的.综合以上结果,我们提出了MoS2/RGO光催化性能增强的机理.首先,三维的气凝胶网状结构以及花状结构的MoS2所带来的高比表面积(599.7 m2/g)使得材料对H+和Cr(VI)吸附量增加;其次,黑色的RGO以及入射光在花状结构层片间的不断反射增加了MoS2/RGO气凝胶对可见光的吸收;最后,RGO本身的高导电性促进了光生电子-空穴有效分离,电子通过RGO快速转移到材料表面参与光催化反应.因此,将MoS2负载在RGO上可提高光催化效率.另外,低密度的MoS2/RGO气凝胶(56.1 mg/cm3)可以有效吸附有机溶剂且容易回收.综上所述,本文制备的MoS2/RGO气凝胶光催化材料在环境与能源方面表现出潜在的应用前景.     

Charge localization in organic conductors (TM)X: The influence of anion ordering

An investigation of the different contributions leading to charge localization in a 1/2 or 1/4 filled band 1D conductor has been conducted through a study of transport properties in the solid solution [(TMTSF)_1-x (TMTTF) _x]₂ReO₄. The existence of an ordering transition of the anions allows to identify two contributions to the electronic potential with wave vector 4k_F. A dominant on-site 4k_F potential besides the bond contribution is revealed when Umklapp scattering is pertinent via the weakening of the localization arising at the (0, 1/2, 1/2) anion ordering which is stabilized under pressure in the compound [(TMTSF) _0.5 (TMTTF)_0.5]₂ReO₄ at variance with the enhancement of localization observed in the homomolecular (TMTTF)₂ReO ₄ material. Received: 13 May 1998 / Revised: 8 July 1998 / Accepted: 9 July 1998     

约化环和半交换环

讨论了在约化条件下,比平凡扩张更广泛的一类扩张环的半交换性.通过给出半交换模的定义,得到平凡扩张是半交换环的一个充要条件.     

Reduced Norm Map of Division Algebras over Complete Discrete Valuation Fields of Certain Type

We study a ramification theory for a division algebra D of the following type: The center of D is a complete discrete valuation field K with the imperfect residue field F of certain type, and the residue algebra of D is commutative and purely inseparable over F. Using Swan conductors of the corresponding element of Br(K), we define -function of D/K, and it describe the action of the reduced norm map on the filtration of D-. We also gives a relation among the Swan conductors and the ramification number of D, which is defined by the commutator group of D-.     

Exact ground-state for the periodic Anderson model in dimensions at finite value of the interaction and absence of the direct hopping in the correlated f-band

We report for the first time exact ground-states deduced for the D = 2 dimensional generic periodic Anderson model at finite U, the Hamiltonian of the model not containing direct hopping terms for f-electrons ( t ^f = 0). The deduced itinerant phase presents non-Fermi liquid properties in the normal phase, emerges for real hybridization matrix elements, and not requires anisotropic unit cell. In order to deduce these results, the plaquette operator procedure has been generalised to a block operator technique which uses blocks higher than an unit cell and contains f-operator contributions acting only on a single central site of the block. Received 1st July 2002 / Received in final form 16 September 2002 Published online 19 December 2002 RID="a" ID="a"e-mail: gulacsi@heavy-ion.atomki.hu     

Density Matrix in Quantum Mechanics and Distinctness of Ensembles Having the Same Compressed Density Matrix

We clarify different definitions of the density matrix by proposing the use of different names, the full density matrix for a single-closed quantum system, the compressed density matrix for the averaged single molecule state from an ensemble of molecules, and the reduced density matrix for a part of an entangled quantum system, respectively. We show that ensembles with the same compressed density matrix can be physically distinguished by observing fluctuations of various observables. This is in contrast to a general belief that ensembles with the same compressed density matrix are identical. Explicit expression for the fluctuation of an observable in a specified ensemble is given. We have discussed the nature of nuclear magnetic resonance quantum computing. We show that the conclusion that there is no quantum entanglement in the current nuclear magnetic resonance quantum computing experiment is based on the unjustified belief that ensembles having the same compressed density matrix are identical physically. Related issues in quantum communication are also discussed.