No description available.

We have revisited the general constructing schemes for a large family of stable hollowboron fullerenes with 80 + 8n (n = 0,2,3,...) atoms. In contrast to the hollow pentagon boron fullerenes with 12 hollow pentagons, the stable boron fullerenes constitute 12 filled pentagons and 12 additional hollow hexagons, which are more stable than the empty pentagon boron fullerenes including the “magic” B80 buckyball. Based on results from first-principles density-functional calculations, an empirical rule for filled pentagons is proposed along with a revised electron counting scheme to account for the improved stability and the associated electronic bonding feature. We have also studied the relative stability of various boron fullerene structures and structural and electronic properties of B80 bucky ball and boron nanotubes via dispersion-corrected density-functional calculations. Our results reveal that the energy order of fullerenes strongly depends on the exchange-correlation functional employed in the calculation and the vibrational stability for the icosahedral B80 with the inclusion of dispersion corrections, in contrast to the instability to a tetrahedral B80 with puckered capping atoms from preceding density functional theory calculations. Similarly, the dispersion-corrected density-functional calculations yield non-puckered boron nanotube conformations and an associated metallic state for zigzag tubes. A systematic study elucidates the importance of incorporating dispersion forces to account for the intricate interplay of two and three centered bonding in boron nanostructures.

Poly[4-(4-vinylbenzyloxy-2-hydroxybenzaidehyde)i and Po]y[1 -(2-pyridyl)-3-[4- (4-vinyihenzyloxy)phenyl]im.idazo( I ,5-a)pyridine-co-methacrylate] were synthesized and characterized and have been evaluated to he effective sorbent materials for [he removal of heavy metats from aqueous solution. Batch adsorption experiments were performed for several divalent metal ions, namely Pb24, Cd2t. Cu24, Ni2~, Zn2~ and Co2~. Preliminary batch adsorption screening test revealed that the adsorbents being evaluated had the highest adsorption capacities for Pb and Cd ions, hence they were studied in much greater detail. Upon applying the equilibrium data to the Langmuir and Freundlich isotherm models, the adsorption of the Pb ions on both the polymer and the copolymer fitted well to the Langmuir model. This means that there occurred homogeneous and. complete monolayer coverage of the Ph2~ ions on the polymer surface as well as on the copolymer surface. Two kinetic models, pseudo-first-order and pseudo-second-order were also tested to investigate the adsorption mechanisms and the kinetics was found to be second order and equilibrium adsorption occurred within 15 seconds. This suggests that the adsorption sites are either near the adsorbent or on the adsorbent surface therefore the metal ions have easy access to them thereby resulting in a high frequency of collision between the metal ions and the adsorption sites. The metal removal was also found to be strongly dependent on pH and this is reflected in the gradual increase in percent adsorption as pH increases from 1.0 to 5.5.

This research effort is focused on the development of new transition-metal salencomplexes bearing bulky t-pentyl groups to further understand their role in the directing of substrates to the reactive metal centers. These new chiral and achiral transition-metal salen complexes also possess the ability to be novel asymmetrical catalysts. A series ofsalen ligands were prepared by the condensation of 3,5-di-t-pentyl salicylaldehyde with five different diamines: (1) 1,3-diamino-propan-2-01, (2) benzene-l,2-diamine, (3) ethylene-l,2-diamine, (4) (S,S)-1,2-diamino-l,2-diphenylethane, and (5) 1,2- diaminocyclohexane. These ligands were treated with transition metal salts to give the corresponding transition-metal salen complexes. As a result, five new systems with three crystal x-ray structures were obtained.

A one-pot and straightforward synthesis, which results in the formation of imidazo[l,5-a]pyridines, has been intensely investigated. This methodology has been applied to 2,2'-pyridil, a- pyridoin and 2-benzoylpyridne ketone systems respectively.Treatment of 2,2'-pyridiI, a -pyridoin or 2-benzoylpyridine with aromatic aldehydes, and ammonium acetate in the presence of hot acetic acid has been shown to give l-(2-Pyridoyl)-3-phenylimidazolesand l,3-di-phenylimidazo[l,5-a]pyridines in good to excellent yields. These reactions were carried out without the use of metal catalysts, which is a commonly used methodology for imidazo[l,5-a]pyridine synthesis. A new and efficient synthesis of l,3-diaryl-[l,5-a]imidazopyridines has also been developed based on the reaction of 2-benzoylpyiridne with aldehydes in the presence of ammonium acetate and hot acetic acid Aldehydes applicable to this reaction include aryl aldehydes, heteroaromatic aldehydes, salicylaldehydes.

In 1996 we set out to show that primary teachers could teach the new physical science curriculum with no further training if they had the right books. We searched the literature for didactics which had been shown to positively impact learning so that we could incorporate those features into any books we would make. We conducted a pilot project for which we wrote and printed 30 workbooks for one activity. Next, we sent out a book survey to find what books were available for the subject in New Zealand at that time. Simultaneously, we scoured Europe, Asia and North America for good lesson material. We found material which incorporated the didactic criteria from our literature search and adapted some of it for our study, producing about 12,000 guided workbooks for each of the last four pre-secondary years, 3000 for each age nine to twelve. The books were made available to all New Zealand schools. Two groups of about 12 teachers each formally trialled the books. One group answered questionnaires and the other kept action research journals. Both groups confirmed the principal research premise- teaching hours increased with no further training. Once good books were in hand other problems became apparent. A nationwide resources survey revealed a lack of equipment and other problems such as poor classroom design, awkward grouping of children of different ages and abilities, lack of time, dysfunctional open plan classes of 100 pupils, two-year teaching cycles, competition from free resource packs, and lack of support material such as videos. From this study it can be concluded that the books made a positive impact for teaching physical science. The books gave teachers an international standard of lessons to work from. It was shown by this study that a teacher with no background in physics or chemistry can teach primary physical science at an international standard once good books are in hand as long as poor equipment, space and facilities are not too serious a set of impediments.

The research is focussed on wide bandgap 11-VI semiconductors, and more specifically on ZnS and CdS, with applications as thin film electroluminescent displays in the expanding display device market. The science of electroluminescent semiconductors and inorganic salt precipitation is combined with a unique, thin film laser processing technique known as laser induced forward transfer or direct writing (the later terminology used mostly in the case of metal films). Zinc sulfide and cadmium zinc sulfide films with a thickness ranging between 70 and 400 nin have been prepared in an aqueous chemical bath, on optically smooth, silica, or silica based, substrates. The chemical bath contained zinc and cadmium chlorides, thioacetamide, and urea, and the most successful combination of concentrations was found to be 2.6 mM, 56.36 mM and 167.71 mM, respectively. The solution was only slightly acidic, with a pH between 5 and 6.5, and a bath temperature of 90 to 92°C (as measured at I cm from the water surface of the bath) was found to be the most efficient. The films were doped with impurities, such as Cu, Ag and Mn in order to achieve specific luminescent characteristics. A KrF excimer laser at 248 nin was used to transfer the films from their original substrate to a new one. The laser pulse was focussed on the chemically deposited films through the back of the transparent silica substrate. The detached film was transported across a gap of 15 µm and attached to the new substrate. A fluence between 0.5 and 0.7 jCM⁻² was found to give the best transfers, and also able to achieve multiple layer transfers over the same area of the target substrate. The transfers were performed in an argon atmosphere of 4x 10⁻² mbar pressure. Ellipsometry and film reflectivity measurements were used to model and determine the film thickness of the chemically deposited films and the values obtained were confirmed by scanning electron microscopy. Ile latter, together with optical microscopy, atomic force microscopy and interferometry were exploited to investigate the structure of the chemically deposited and laser transferred films. It was found that a very thin ZnO film initially adhered to the substrate in the bath, on which the ZnS or CdZnS main film was attached as homogenously grown cluster beads or grown via ion by ion deposition. The homogeneously grown beads had a phase separation, containing the sulfide with the lowest Ksp in the centre, enclosed by highest Ksp sulfides, with the highest one as a shell. The phase separation between CuS and ZnS was also confirmed by extended X-ray absorption fine structure. The elemental composition of the chemically-prepared and laser-transferred films was investigated by energy dispersive X-ray analysis (EDX), inductively coupled plasma mass spectrometry and Raman microspectrometry, while the EDX and Raman methods also helped to confirm the phase separation between US and ZnS. Cathodoluminescence and photoluminescence measurements were employed to investigate the luminescence properties of the films, and the Mn doped films that were annealed at 700°C were found to be the most efficient cathode ray excited phosphors, while the Cu doped phosphors came next in efficiency, performing equally well under an electron or a UV laser beam (from a HeCd laser at 325 rim). Smaller luminescence peaks were also detected in Ag doped films. Transferred films showed similar luminescent properties to their original films, but with lower intensity. Thus the chemical bath deposition and laser transferring were successful, but the methods can be further improved.

No description available.

In this thesis we provide a better understanding of the role of the inter-cluster filamentary environment in the evolution of galaxy properties, relating that to the physical mechanisms involved. We examine a poorer supercluster structure and describe how it compares with the richer regime, deciding whether the same processes are responsible for driving galaxy evolution in both cases. We develop a new approach to automated galaxy morphology classification, undertake an extensive observational survey of a nearby supercluster and investigate the evolution of galaxy properties within this structure, considering the filamentary environments that we confirm exist. Firstly, we present an application of Mathematical Morphology (MM) for the classification of astronomical objects, both for star/galaxy differentiation and galaxy morphology classification. We demonstrate that, for CCD images, 99.3 ± 3.8% of galaxies can be separated from stars using MM, with 19.4±7.9% of the stars being misclassified. We demonstrate that, for photographic plate images, the number of galaxies correctly separated from the stars can be increased using our MM diffraction spike tool, which allows 51.0±6.0% of the high-brightness galaxies that are inseparable in current techniques to be correctly classified, with only 1.4 ± 0.5% of the high-brightness stars contaminating the population. We demonstrate that elliptical (E) and late-type spiral (Sc-Sd) galaxies can be classified using MM at an accuracy of 91.4 ± 7.8%. It is a method involving less ‘free parameters’ than current techniques, especially automated machine learning algorithms. The limitations of MM due to seeing and distance are also discussed. We examine various star/galaxy differentiation and galaxy morhpology classification techniques commonly used today, and show that the above MM techniques compare very favourably. Secondly, we present a wide-field photometric and spectroscopic study of the supercluster SCL266 (z = 0.068). We have obtained CCD imaging in B-, R- and I-bands covering 5 clusters within the structure, and spectroscopy within the region of 3 of the clusters and the filamentary environment between them. We have over 950 redshifts obtained and 161 galaxies confirmed as members of the supercluster structure. The galaxy morphologies are derived using the MM techniques we have developed. We show that the population of passive, early-type galaxies extends into the dense regions of the filaments and is not just confined to the higher-density clusters, indicating that the denser filamentary environment hastens the galaxy evolution within it. The star-forming, late-type galaxies are distributed throughout the entirety of the supercluster structure. We show that both the mean star formation rate and the fraction of star-forming galaxies decrease strongly as a function of distance along the filaments towards the cluster centres. Given these observations we conclude that the evolution occurring within this poor supercluster begins within the filaments up to 4 Mpc away from the cluster centres, and is driven by long time-scale mechanisms involving encounters between neighbouring galaxies.

No description available.