Influence of iron-subgroup metals on the atomization of silicon in a graphite furnace

The regime of atomization of Si in the presence of Fe-subgroup metals was investigated with the use of a “Saturn” spectrophotometer and a “Graphit-2” electrothermic atomizer. The optimal operating parameters of the atomizer have been determined. It was established that the optimal value of the ashing and the atomization temperatures are, respectively, 900–1000°C and 2400°C, the optimal rate of temperature rise at the stage of atomization is 1400 K/sec, and the appropriate amount of Fe, Co and Ni additions is 1–2 μg. It was established that the formation of gaseous silicides of the Fe-subgroup metals, the dissociation energies of which are lower than the dissociation energies of Si oxides and carbides, increases the sensitivity for determination of Si. To whom correspondences should be addressed. Institute of Single Crystals, National Academy of Sciences of Ukraine, 60, Lenin Ave., Khar'kov, 310001, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 153–157, March–April, 1999.     

Trigger System of the NUCLEON Experiment

Physics of Particles and Nuclei Letters - The NUCLEON experiment is aimed at measuring the spectrum and the elemental composition of cosmic rays (CR) in the 1011–1015 eV energy range. The...     

Nontransversality of the gluon polarization tensor in a chromomagnetic background field

We investigate the problem of the transversality of the gluon polarization tensor in a homogeneous Abelian chromomagnetic background field. Using the Slavnov-Taylor identities, we rederive the nontransversality known from a one-loop calculation in the Feynman gauge. In addition, we generalize the whole procedure to an arbitrary gauge-fixing parameter ξ and calculate the ξ-dependent part of the polarization tensor. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 148, No. 1, pp. 42–56, July, 2006.     

Comparative investigation of the electronic structure and acidic properties of aluminophophates and of silicoaluminophosphates

The spatial and electronic structures of alumino- and silicoaluminophosphates have been investigated by quantum chemical SCF MO LCAO MNDO method. The implantation of silicon atoms into aluminophosphate matrix affects mainly the structure of aluminophosphate tetrahedra. The hydroxy groups at phosphorus atoms which possess the main Brönsted acidity are the sites of the strongest water molecule binding.     

Quantum-chemical investigation into the geometric and energetic characteristics of kaolinite cluster models

A method of constructing molecular models for layered aluminosilicate crystals is put forward. The geometric and energetic characteristics of cluster models are calculated for the elementary kaolinite crystal layer using the MNDO approximation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 3, pp. 214–218, May–June, 1993.     

Sulfonation of 4′-acetyl-, 4′-(<Emphasis Type="Italic">tert</Emphasis>-butyl)-dibenzo-18-crown-6 and (dibenzo-18-crown-6)-4′-sulfonic acid with potassium sulfate in polyphosphoric acid

The sulfonation of monosubstituted derivatives of dibenzo-18-crown-6 with potassium sulfate in polyphosphoric acid has been carried out. Sulfonic acids with various functional groups in the second nucleus of dibenzo-18-crown-6 have been obtained. A qualitative comparison of the reactivity of the substrates gave information on the transfer of the electronic influence of a substituent through the macrocycles. The displacement of electron density in the benzene nuclei of the substrates and the products of sulfonation was assessed from the value of the displacement of the proton signals in the ¹H NMR spectra. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 370–375, March, 2009.     

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响.