ВИКОРИСТАННЯ ІМПУЛЬСНОГО МЕТОДУ ВИМІРЮВАННЬ ДЛЯ ВИЗНАЧЕННЯ ПОШКОДЖЕННЯ КАБЕЛЬНИХ ЛІНІЙ

В даній роботі розглядаються особливості використання приладу ІКЛ-5 для швидкого визначення точності імпульсних вимірювань в пошкодженнях кабельних ліній і точного знаходження міста пошкодження кабелю. Для досягнення поставленої мети запропонований імпульсний метод, який визначає місце і характер пошкодження кабельних ліній. Обраний у роботі підхід дає можливість вимірювання при будьякому складному характері ушкодження. Завдяки цьому забезпечується зручність, простота і швидкість вимірювань

Coordination chemistry of amide-functionalised tetraazamacrocycles: structural, relaxometric and cytotoxicity studies

Three different tetraazamacrocyclic ligands containing four amide substituents that feature groups (namely allyl, styryl and propargyl groups) suitable for polymerisation have been synthesised. Gadolinium(III) complexes of these three ligands have been prepared as potential monomers for the synthesis of polymeric MRI contrast agents. To assess the potential of these monomers as MRI contrast agents, their relaxation enhancement properties and cytotoxicity have been determined. A europium(III) complex of one of these ligands (with propargyl substituents) is also presented together with its PARACEST properties. In addition, to gain further insight into the coordination chemistry of the tetra-propargyl substituted ligand, the corresponding zinc(II) and cadmium(II) complexes have been prepared. The X-ray crystal structures of the tetra-propargyl ligand and its corresponding gadolinium(III), zinc(II) and cadmium(II) complexes are also presented

Optimization of a catalyst system through the sequential application of experimental design techniques

The selective oligomerisation of ethylene to higher alpha olefins is an area of much recent interest. In this regard, Sasol Technology R{&}D has developed a homogeneous catalyst system based on bis-sulfanylamine (SNS) complexes of chromium for the selective trimerisation of ethylene to 1-hexene. It is activated by methylaluminoxane (MAO), which is an extremely expensive activator. This paper discusses how, through the sequential application of experimental design and response surface techniques, the activator requirements of the catalyst system were reduced 12 times, whilst improving the catalyst activity on a g/g Cr/h basis ca. three times and the activity on a g/g MAO basis ca. nine times. This reduction in the amount of MAO required led to economically attractive catalyst activities for the production of 1-hexene, and would not have been possible without the use of experimental design techniques. This paper will demonstrate the process of investigation through the use of sequential experimental design in practice.experimental design, methylaluminoxane, oligomerisation, response surface modelling,

Carbon-bridged diphosphine ligands for chromium-catalysed ethylene tetramerisation and trimerisation reactions

The use of carbon-bridged diphosphine ligands in chromium-catalysed ethylene tri- and tetramerisation reactions has been investigated. Two- and three-carbon spacer ligands all showed activity for selective oligomerisation, with a structure-selectivity correlation between P-Cr-P bite angle and 1-octene: 1-hexene ratio evident. Activated chromium complexes of single carbon spacer diphosphines were also shown to be effective tetramerisation catalysts, provided that the ligand is innocent under the conditions of catalyst activation. A catalyst with the bis(diphenylphosphino)benzene ligand was found to be exceptionally active, although the combined 1-hexene and 1-octene selectivity was lower than with the best diphosphinoamine (PNP) ligands. The yield losses to by-products can to an extent be minimised by the use of high reaction temperatures and pressures. Unlike with the PNP-based systems, attempts to activate the Cr/bis(diphenylphosphino)benzene catalyst in situ from a chromium salt and free ligand resulted in low activity and high polymer formation. The effect of different phosphine substitution on catalyst selectivity was explored. Steric constraints around the catalytic centre (ortho-alkylphenyl phosphines) resulted in a shift towards 1-hexene formation, as with PNP catalysts. Additionally, the basicity of the phosphines appears to influence catalyst selectivity, with alkyl phosphines favouring trimerisation. An interplay between phosphine basicity and bridge structure is in evidence, however, as a catalyst containing a ligand with both basic phosphine atoms and a small bite angle was shown to be selective towards I-octene. (c) 2007 Elsevier B.V. All rights reserved.</p