Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.     

Determination of small amounts of tungsten by atomic absorption spectrometry after extraction separation

Small amounts of tungsten can be determined by atomic absorption spectrometry, after reduction with tin(II) and separation of the thiocyanate complex into methyl isobutyl ketone. The organic phase is aspirated into an acetylene-nitrous oxide flame There are no interferences from 1000-fold amounts of Zr or Cr(III), 200-fold amounts of U or Ti. 100-fold V or 10-fold Mo. Interference from large amounts of iron(III) is avoided by prior reduction. The method was successfully applied to the determination of tungsten in steels and zirconium alloys.     

Induction heating of cylindrical nonmagnetic ingots by rotation in static magnetic field generated by permanent magnets

Induction heating of cylindrical nonmagnetic billets by their rotation in static magnetic field is modeled. The magnetic field is produced by a system of appropriately arranged permanent magnets. The numerical model is solved by our own full adaptive higher-order finite element method in a monolithic formulation, i.e., both magnetic and temperature fields are solved simultaneously, respecting their mutual interaction. All principal nonlinearities are included in the model (permeability of ferromagnetic parts of the system as well as temperature dependences of physical parameters of the heated metal). The methodology is illustrated by two examples whose results are discussed.     

Synthesis,characterization and antitumour activity of copper(II) 6-(4-chlorobenzylamino)purine complexes. X-ray structure of 6-(4-chloro-benzylamino)purinium perchlorate

Copper(II) complexes with 6-(4-chlorobenzylamino)purine (HL) have been prepared and characterized by elemental analysis, electronic, i.r., ES + mass and ¹³C-n.m.r. spectra, and by magnetic and conductivity data. Based on these physical methods, mainly the temperature dependence of magnetic susceptibility data, we conclude that the complexes are: [Cu₂(-Cl)₂(-HL)₂Cl₂] (1) and [CuCl₃(H⁺L)₂]Cl (2). They have been studied for their possible antitumour activity against human malignant melanoma G-361, human osteogenic sarcoma HOS, human chronic myelogenous leukaemia K-562 and human breast adenocarcinoma MCF7 cells in vitro. The IC₅₀ values were determined by calcein AM assay. The molecular structure of 6-(4-chlorobenzylamino)purinium perchlorate, i.e. a protonated form of the free HL ligand, has been determined by a single crystal X-ray analysis.     

Oszillopolarographischer nachweis und bestimmung von jodat und perjodat

The oscillopolarographic behaviour of periodate and iodate has been investigated in acid, neutral and alkaline electrolytes. The detection and determination of periodate in iodate may be carried out using iodate as electrolyte and the detection and determination of iodate in periodate may be carried out using 5 M sodium hydroxide as electrolyte.     

On optimal control problems with general boundary conditions

It is shown that the necessary optimality conditions for optimal control problems with terminal constraints and with given initial state allow also to obtain in a straightforward way the necessary optimality conditions for problems involving parameters and general (mixed) boundary conditions. In a similar manner, the corresponding numerical algorithms can be adapted to handle this class of optimal control problems.This research was supported in part by the Commission on International Relations, National Academy of Sciences, under Exchange Visitor Program No. P-1-4174.The author is indebted to the anonymous reviewer bringing to his attention Ref. 9 and making him aware of the possible use of generalized inverse notation when formulating the optimality conditions.     

Distributional chaos and factors

We show the existence of a dynamical system without any distributionally scrambled pair which is semiconjugated to a distributionally chaotic factor.     

Microdetermination of aromatic nitro compounds with iron(II) in alkaline sorbitol media

In titrations with iron(II) sulphate in alkaline solutions of sorbitol, the iron(III) formed is bound in a strong complex and the formal redox potential of the Fe(III)/Fe(II) system is decreased to —1.10 V (SCE; 0.5 M sorbitol, 2 M KOH). This permits reducing titrations with a stable reagent, of systems which would otherwise require unstable strong reductants (e.g. Cr(II), Sn(II), V(II), etc.). Determinations of organic mono-, di- and tri-nitro compounds are described; these can be carried out directly on the microscale, with potentiometric, bipotentiometric or biamperometric end-point detection. Nitrate does not interfere; the method can also be employed for indirect determinations of various aromatic compounds after their conversion to nitro derivatives.