Investigation of electrochemical behavior and development of a validated adsorptive stripping square wave voltammetry method for 3-nitrotyrosine in human plasma and cerebrospinal fluid

An adsorptive stripping square wave voltammetric (AdSqW) method was developed for the determination of 3-nitrotyrosine (3-NT), a biomarker of in vivo oxidative damage in Alzheimer, ALS, Parkinson’s, cardiovascular diseases and cancer, in some biological fluids. Voltammetric measurements were performed in 0.30 M (pH 9.0) phosphate solution as supporting electrolyte, a reduction peak was observed at–0.487 V (vs. Ag/AgCl–3 M KCl) with a hanging mercury drop electrode by square wave voltammetry. Cyclic voltammetric measurements showed that the current was adsorption-controlled. LOD and LOQ values were as 0.25 and 1.5 nM, respectively, for the AdSqW method. 3-NT was determined in plasma and cerebrospinal fluid using AdSqW method, which allowed to work at low concentrations. Recovery value was measured as 96.3 ± 2.3%.     

超低温高电场下GaAs的电子太赫兹功耗谱的研究

利用自由空间太赫兹电光取样方法,测量了在高电场下,GaAs中受飞秒激光脉冲激发的电子所辐射出的太赫兹电磁波,发现从样品中辐射出的和电子加速度成正比的太赫兹电磁波电场强度E_THz（t）,表现出双极特性.通过分析GaAs中辐射出的太赫兹电磁波的傅里叶变换谱,首次实验上得到在阶跃电场下的GaAs的电子太赫兹功耗谱.研究发现,当电场小于50 kV/cm时,由电子谷间散射引起的负功耗（即增益）的截止频率ν_c,随着电场的增大而增大;当电场大于50 kV/cm时,负功耗的截止频率ν_c开始在750 GHz（10 K）附近饱和. 关键词： 太赫兹 非平衡载流子 功耗谱 谷间散射     

Errors in measuring the linear sizes of structures when detecting backscattered electrons in an SEM

The determining of element width and localization of the edge of nanostructures from the intensity of backscattered electron signal using nonreference measurement methods is discussed.     

Surface tension evolution during early stages of drying of sol–gel coatings

Striation defects in spin-coated thin films have been blamed on unfavorable capillary forces that occur due to solvent evaporation commonly experienced during coating deposition. Solvent evaporation during spinning causes predictable composition changes at the surface and these can either stabilize or de-stabilize the surface with respect to convective motions within the coating solution. The present work examines the surface tension changes while adding the most volatile component rather than removing it. This is then a “reverse drying” process, but it provides us with the slope of the surface tension change during normal coating drying. We have examined coating solutions for a case where a specific solvent addition has previously been shown to prevent the formation of striation defects. By measuring both the starting solution (one that produces bad striation defects) and the co-solvent-modified solution (that produces much flatter coatings), we are able to demonstrate the correlation between surface tension changes during spinning and the striation defect formation (or prevention). For the present case, an aluminum-titanate sol–gel recipe, the solvent that eliminated the striation defects is also responsible for a continuous, gradual, reduction in surface tension during the spin-on process, consistent with a model proposed earlier (D. P. Birnie, J Mater Res 16:1145–1154, 2001).     

On the existence of solid solutions based on magnesium diboride

Dense samples of pure magnesium boride and of the compositions Mg_(1–x)A _x B₂ (A = Na, K, Ca, Sr, Ba, Sn, Ti; 0.05 < x < 0.15) were prepared by sintering and using high temperature—high pressure treatment. The lattice parameters of most of the doped MgB₂ samples vary only slightly as compared to those of the pure MgB₂ irrespective of the sample preparation procedure, high temperature—high pressure treatment conditions, and the amount of dopant, thus indicating the absence of extended solid solution regions. The superconducting transition temperatures of all the samples did not exceed the value characteristic of MgB₂ (39±1 K). The results obtained for the dense MgB₂ samples using the Andreev reflection and tunneling spectroscopies confirm the two-gap nature of superconductivity in magnesium diboride and point to analogy between the superconductivity mechanisms in this compound and in cuprates.     

Thermal conductivity and interfacial energy of solid Bi solution in the Bi–Al–Zn eutectic system

The equilibrated grain boundary groove shapes for solid Bi solution (Bi–6.1 at.%Zn–0.38 at.%Al) in equilibrium with the Bi–Al–Zn eutectic liquid have been observed from quenched sample with a radial heat flow apparatus. The Gibbs–Thomson coefficient, solid–liquid interfacial energy and grain boundary energy of solid Bi solution have been determined from the observed grain boundary groove shapes. The variations of thermal conductivity with temperature for solid Bi solution (Bi–6.1 at.%Zn–0.38 at.%Al) has been measured up to five degree below the melting temperature by using radial heat flow technique. The ratio of thermal conductivity of equilibrated Bi–Al–Zn eutectic liquid phase to solid Bi solution (Bi–6.1 at.%Zn–0.38 at.%Al) phase has also been measured with a Bridgman type growth apparatus at the melting temperature.     

The Transformed Nonparametric Flood Frequency Analysis

1.IntroductionFloodmagnitudeandthecorrespondingfrequencycanbeestimatedfromtheawiLabedatesamplebytheparamofricmethodwherebyvarioustheoreticaldistributions(i.e-,LogPearsonTypeIII)areemployed.DuringthepastseveraJyearsparametricmodelinghasbeenasubjectofintensiveinvestigationsbymanyresearchers(Singh,1986).Itisnowwellrecognizedthatthemainproblem8ofparametricproceduresareduetothepresenceofasymmetricaJandmultimodaJdensitiesintheobservedflooddata.Thedataalsomightbeofsuchatypethatthereisnosuitablep…     

Determination of thermal conductivity and interfacial energy of solid Zn solution in the Zn-Al-Bi eutectic system

The equilibrated grain boundary groove shapes for solid Zn solution (Zn-3.0 at.% Al-0.3 at.% Bi) in equilibrium with the Zn-Al-Bi eutectic liquid (Zn-12.7 at.% Al-1.6 at.% Bi) have been observed from quenched sample with a radial heat flow apparatus. Gibbs-Thomson coefficient, solid-liquid interfacial energy and grain boundary energy for solid Zn solution in equilibrium with Al-Bi-Zn eutectic liquid have been determined to be (5.1 ± 0.4) × 10⁻⁸ K m, (80.1 ± 9.6) × 10⁻³ and (158.6 ± 20.6) × 10⁻³ J m⁻² from the observed grain boundary groove shapes, respectively. The thermal conductivity variation with temperature for solid Zn solution has been measure with radial heat flow apparatus and the value of thermal conductivity for solid Zn solution has been determined to be 135.68 W/km at the eutectic melting temperature. The thermal conductivity ratio of equilibrated eutectic liquid to solid Zn solution, R = K_L(Zn)/K_S(Zn) has also been measured to be 0.85 with Bridgman type solidification apparatus.     

Scanning electron microscopes Microscan of the MS20 series

A new series of scanning electron microscopes Microscan (MS20) has been developed at the Institute of Microelectronics Technology and High-Purity Materials, Russian Academy of Sciences. The main distinctive feature of these instruments is the modular design of all units and systems, which ensures a high level of unification.