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Synthesis and Reactivity of N,N,N’,N’-Tetramethyldiaminomethane (TMDM) Complexes of Tricarbonylrhenium(I). X-Ray Molecular Structures of [ReBr(CO)₃(TMDM)] and [{Re(bipy)(CO)₃}₂(μ-OH)][SbF₆].
Get PDFN,N,N′,N′-Tetramethyldiaminomethane (TMDM) is known to act as a source of Me₂NCH in carbonyl substitution reactions, but the reaction of TMDM with the neutral halogenopentacarbonylrhenium(I) compounds gave unexpectedly fac-[ReX(CO)₃(TMDM)] (X=Cl, Br or I), in which the intact TMDM ligand acts in a chelating fashion. The complexes are stable both in the solid-state and in solution, but rapidly decompose on dehalogenation, yielding Re metal. Under anaerobic conditions, the reaction of TMDM with [Re(CO)₃(bipy)]⁺also leads to decomposition. In the presence of oxygen the system is stable. Three Re(bipy) containing species were identified in the reaction mixture: [{Re(CO)₃(bipy)}₂(μ-OH)][SbF₆] (1), which was characterised by X-ray crystallography, [{Re(CO)₃(bipy)}₂(μOH)₂][SbF₆]₂(2) and [Re(OH)(CO)₃(bipy)] (3). Graphical Abstract Reaction of neutral [ReX(CO)₅] (X=Cl, Br or I) with N,N,N′,N′-tetramethyldiaminomethane ((TMDM)) gave unexpectedly fac-[ReX(CO)₃(TMDM)] (X=Cl, Br or I), in which the intact TMDM ligand acts in a chelating fashion. Reaction of TMDM with [Re(CO)₃(bipy)]⁺ under aerobic conditions yields three complexes: [{Re(CO)₃(bipy)}₂(μ-OH)][SbF₆] (1), which was characterised by X-ray crystallography, [{Re(CO)₃(bipy)}₂(μOH₂)][SbF₆]₂(2) and [Re(OH)(CO)₃(bipy)] (3)
On the origin of compositional fluctuations in ZnSe1-xSx alloys grown by metal-organic vapour-phase epitaxy
No full textPeriodic vertical modulations of the sulphur concentration have been observed in epitaxial layers of ZnSe1-xSx grown by metal-organic vapour-phase epitaxy. High-spatial-resolution microanalysis has shown that the sulphur variation is of the order of 1 at.% with a period of about 44 ± 0.1 nm. A detailed analysis of the possible causes of this modulation is presented which shows that periodic temperature fluctuations of the substrate are the most likely source
Voices of Older People in Wales: a qualitative study of health and wellbeing among over 50's
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HySenS data exploitation for urban land cover analysis
Get PDFThis paper addresses the use of HySenS airborne hyperspectral data for environmental urban monitoring. It is known that hyperspectral data can help to characterize some of the relations between soil composition, vegetation characteristics, and natural/artificial materials in urbanized areas. During the project we collected DAIS and ROSIS data over the urban test area of Pavia, Northern Italy, though due to a late delivery of ROSIS data only DAIS data was used in this work. Here we show results referring to an accurate characterization and classification of land cover/use, using different supervised approaches, exploiting spectral as well as spatial information. We demonstrate the possibility to extract from the hyperspectral data information which is very useful for environmental characterization of urban areas
Elucidation of the Emulsification Properties of Sugar Beet Pectin
No full textA protocol has been developed to fractionate sugar beet pectin using hydrophobic affinity chromatography. Three samples eluted from the column using 4 M NaCl as solvent (fractions 1A, 1B, and 1C), two fractions eluted using 2 M NaCl (fractions 2A and 2B), and one fraction eluted using water (fraction 3). The fractions were shown to be very polydisperse, and differences between the GPC refractive index and UV absorbance (214 nm) elution profiles demonstrated chemical heterogeneity. They were found to contain significantly different proportions of protein (1A, 2.79%; 1B, 0.97%; 1C, 0.77%; 2A, 1.41%; 2B, 5.09%; and 3, 5.89%) and ferulic acid (approximately 1A, 0.5%; 1B, 0.5%; 1C, 0.9%; 2B, 1.5%; and 3, 2%). The weight-average molecular mass, Mw, of the fractions also varied (1A, 153 kDa; 1B, 155 kDa; 1C, 306 kDa; 2A, 562 kDa; 2B, 470 kDa; 3, 282 kDa). Three fractions, that is, 1A, 1B, and 3, produced orange oil emulsions with a relatively small droplet size that were stable over a period of weeks. The other three fractions (1C, 2A, and 2B with higher Mw values) produced emulsions with an initially larger droplet size, and the droplet size increased considerably over time. The increased droplet size may be influenced by the viscosity of the aqueous continuous phase. There was no simple relationship between protein or ferulic acid content and emulsification ability. For example, fraction 1B, which contained the lowest proportion of both protein and ferulic acid, produced stable emulsions of similar droplet size to fraction 3, which contained the largest proportion of protein and ferulic acid. The role of protein in the emulsification process was investigated by measuring the amount of protein in the aqueous phase before and after emulsification. It was clearly demonstrated that proteinaceous material adsorbed at the oil−water interface. It is evident that the emulsification properties of sugar beet pectin are influenced by the accessibility of the protein and ferulic acid groups to the surface of the oil droplets, the proportion of ester groups, and the molecular mass distribution of the fractions
Physical performance and decision making in association football referees: A naturalistic study.
Get PDFAlthough researchers have independently investigated the physical and decision-making (DM) demands experienced by sports officials, the combined impact of locomotion and physiological factors upon DM has received little attention. Using an innovative combination of video and Global Positioning System (GPS) technology this study explored the movement, heart rate (HR) and DM of experienced football referees in their natural performance environment. A panel of independent referees analysed incidents (n = 144) taken from five referees in seven games in the New Zealand Football Championship (2005/06). The match-day referees made accurate decisions on 64% of the incidents, although their accuracy levels were not related to variables such as movement speed, HR, and cumulative distance covered. Interestingly, referees were on average only 51% accurate in the opening fifteen minutes of each half compared to 70% accuracy at all other times. This study demonstrated that it is possible to combine new emerging technologies to conduct a comprehensive study of naturalistic decision-making in sport
Deposition in Supercritical Fluids: From Silver to Semiconductors
No full textThere is great interest in developing new routes to novel functional materials, particularly for heterogeneous nanocomposites of metals or semiconductors with polymeric hosts. Supercritical fluids have become important media for the synthesis of such nanocomposites largely because of their unique properties, but also through their perceived environmental benefits over conventional routes. In this feature article, we focus on the deposition of silver and semiconductor nanoparticles into polymer substrates by use of supercritical fluids. These processes develop nanocomposites with distinct characteristics for optical and biomedical applications. The preparation and characterisation of silver and semiconductor nanoparticles is described and a brief discussion is also extended to some other novel deposition systems in supercritical fluids
Real-time optimisation of access control lists for efficient internet packet filtering
Get PDFThis paper considers an optimisation problem encountered in the implementation of traffic policies on network routers, namely the ordering of rules in an access control list to minimise or reduce processing time and hence packet latency. The problem is formulated as an objective function with constraints and shown to be NP-complete by translation to a known problem. Exact and heuristic solution methods are introduced, discussed and compared and computational results given. The emphasis throughout is on practical implementation of the optimisation process, that is within the tight constraints of a production network router seeking to reduce latency, on-line, in real-time but without the overhead of significant extra computation
Sixth form religion in Northern Ireland: the Protestant profile 1968–1998
No full textThe aim of the present study was to build on John Greer’s systematic set of studies concerned with teenage beliefs and values conducted among samples of sixth form students attending County and Protestant voluntary schools in Northern Ireland in 1968, 1978 and 1988. The present study replicated the earlier surveys for a further time in 1998. The results provide a unique snapshot of the persistence of religious affiliation, belief and practice across the latter part of the twentieth century in a nation which has continued to resist the secularisation process so eroding the place of religion in the neighbouring nations of England, Wales and Scotland
SAR and radiation performance of balanced and unbalanced mobile antennas using a hybrid computational electromagnetics
Get PDFThe procedure that is required to ensure that the effect of the mobile antenna on the handset can be reduced by using balanced antennas was investigated. However, using this type of antenna may degrade the antenna performance, such as bandwidth and gain, although these antennas can cause less effect on the body to which they are adjacent. Moreover, if these antennas are well-designed, then the maximum specific absorption rate (SAR) values are likely to be reduced when placed next to the human head, since the coupling of such antennas to the body of the handset is very weak. In this paper, a study on balanced and unbalanced antennas for mobile handsets next to the human head is presented, using a hybrid electromagnetic method for the analysis. The method uses the hybridisation technique between the frequency domain Method of Moments (MoM) and the Finite Difference Time Domain method (FDTD). The antenna was modelled using MoM whereas the head tissues were modelled using FDTD. Two antennas were designed and investigated with respect to the SAR and radiation performance for two different antenna positions on the top edge of mobile handsets. Radiation patterns are presented and compared, with and without the human head, and the maximum SAR values and field distribution inside the human head for both antennas are discussed. The balanced antenna shows good improvements with respect to the unbalanced antenna in terms of the SAR values and variations of the input impedances