989 resultados para library materials


Relevância:

30.00% 30.00%

Publicador:

Resumo:

The central theme of this thesis is the use of imidazolium-based organic structure directing agents (OSDAs) in microporous materials synthesis. Imidazoliums are advantageous OSDAs as they are relatively inexpensive and simple to prepare, show robust stability under microporous material synthesis conditions, have led to a wide range of products, and have many permutations in structure that can be explored. The work I present involves the use of mono-, di-, and triquaternary imidazolium-based OSDAs in a wide variety of microporous material syntheses. Much of this work was motivated by successful computational predictions (Chapter 2) that led me to continue to explore these types of OSDAs. Some of the important discoveries with these OSDAs include the following: 1) Experimental evaluation and confirmation of a computational method that predicted a new OSDA for pure-silica STW, a desired framework containing helical pores that was previously very difficult to synthesize. 2) Discovery of a number of new imidazolium OSDAs to synthesize zeolite RTH, a zeolite desired for both the methanol-to-olefins reaction as well as NOX reduction in exhaust gases. This discovery enables the use of RTH for many additional investigations as the previous OSDA used to make this framework was difficult to synthesize, such that no large scale preparations would be practical. 3) The synthesis of pure-silica RTH by topotactic condensation from a layered precursor (denoted CIT-10), that can also be pillared to make a new framework material with an expanded pore system, denoted CIT-11, that can be calcined to form a new microporous material, denoted CIT-12. CIT-10 is also interesting since it is the first layered material to contain 8 membered rings through the layers, making it potentially useful in separations if delamination methods can be developed. 4) The synthesis of a new microporous material, denoted CIT-7 (framework code CSV) that contains a 2-dimensional system of 8 and 10 membered rings with a large cage at channel intersections. This material is especially important since it can be synthesized as a pure-silica framework under low-water, fluoride-mediated synthesis conditions, and as an aluminosilicate material under hydroxide mediated conditions. 5) The synthesis of high-silica heulandite (HEU) by topotactic condensation as well as direct synthesis, demonstrating new, more hydrothermally stable compositions of a previously known framework. 6) The synthesis of germanosilicate and aluminophosphate LTA using a triquaternary OSDA. All of these materials show the diverse range of products that can be formed from OSDAs that can be prepared by straightforward syntheses and have made many of these materials accessible for the first time under facile zeolite synthesis conditions.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

A faccile and efficient one-pot synthesis of highly substituted thiophenes has been developed and employed for the preparation of a small focused library. Treatment of 1,3-dicarbonyl compounds 1 with CS2 in the presence of K2CO3 in DMF at room temperature, followed by stepwise addition of alkyl bromides 2 and methylene active bromides 3, provided via intramolecular cyclization 2,3,4,5-tetrasubstituted thiophenes 4 in yields of 77-94%. This protocol, combining construction and modification of the thiophene ring, increases the structural diversity of final products from readily available materials. A mechanism for the one-pot synthesis of thiophenes of type 4 has been proposed. A small focused library of thiophenes is prepared using the sequential addition of reagents to achieve unique substitution in the 2 and 5 position of the thiophene ring

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Thomas, R. & Urquhart, C. NHS Wales e-library portal evaluation. (For Informing Healthcare Strategy implementation programme). Aberystwyth: Department of Information Studies, University of Wales Aberystwyth Follow-on to NHS Wales User Needs study Sponsorship: Informing Healthcare, NHS Wales

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Cooper, J., Spink, S., Thomas, R. & Urquhart, C. (2005). Evaluation of the Specialist Libraries/Communities of Practice. Report for National Library for Health. Aberystwyth: Department of Information Studies, University of Wales Aberystwyth. Sponsorship: National Library for Health (NLH)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Tedd, L.A. (2007). Library management systems in the UK: 1960s-1980s. Library History, 23(4),301-316 Originally published (as above) by Maney Publishing.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This thesis is concerned with several aspects of the chemistry of iron compounds. The preparation (with particular emphasis on coprecipitation and sol-gel techniques) and processing of ferrites are discussed. Chapter 2 describes the synthesis of Ni-Zn ferrites with various compositions by three methods. These methods include coprecipitation and sol-gel techniques. The Ni-Zn ferrites were characterised by powder X-ray diffactometry (PXRD), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), Mössbauer spectroscopy and resistivity measurements. The results for the corresponding ferrites prepared by each method are compared. Chapter 3 reports the sol-gel preparation of a lead borosilicate glass and its addition to Ni-Zn ferrites prepared by the sol-gel method in Chapter 2. The glass-ferrites formed were analysed by the same techniques employed in Chapter 2. Alterations in the microstructure, magnetic and electronic properties of the ferrites due to glass addition are described. Chapter 4 introduces compounds containing Fe-O-B, Fe-O-Si or B-O-Si linkages. The synthesis and characterisation of compounds containing Fe-O-B units are described. The structure of [Fe(SALEN)]2O.CH2Cl2 (17), used in attempts to prepare compounds with Fe-O-Si bonds, was determined by X-ray crystallography. Chapter 4 also details the synthesis of three new borosilicate compounds containing ferrocenyl groups, i.e. [FcBO)2(OSiBut2)2] (19), [(FcBO)2(OSiPh2)2] (20) and [FcBOSiPh3] (21). The structure of (19) was determined by X-ray Crystallographic analysis. Chapter 5 reviews the intercalation properties of the layered host compound iron oxychloride (FeOCI). Intercalation compounds prepared with the microwave dielectric heating technique are also discussed. The syntheses of intercalation compounds by the microwave method with FeOCI as host and ferrocene, ferrocenylboronic acid and 4-aminopyridine as guest species are described. Characterisation of these compounds by powder X-ray diffractometry (PXRD) and M{ssbauer spectroscopy is reported. The attempted synthesis of an intercalation compound with the borosilicate compound (19) as guest species is discussed. Appendices A-E describe the theory and instrumentation involved in powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM0, vibrating sample magnetometry (VSM), Mössbauer spectroscopy and electrical resistivity measurements, respectively. Appendix F details the attempted syntheses of compounds with Fe-O-B and Fe-O-Si linkages.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The thesis is focused on the magnetic materials comparison and selection for high-power non-isolated dc-dc converters for industrial applications or electric, hybrid and fuel cell vehicles. The application of high-frequency bi-directional soft-switched dc-dc converters is also investigated. The thesis initially outlines the motivation for an energy-efficient transportation system with minimum environmental impact and reduced dependence on exhaustible resources. This is followed by a general overview of the power system architectures for electric, hybrid and fuel cell vehicles. The vehicle power sources and general dc-dc converter topologies are discussed. The dc-dc converter components are discussed with emphasis on recent semiconductor advances. A novel bi-directional soft-switched dc-dc converter with an auxiliary cell is introduced in this thesis. The soft-switching cell allows for the MOSFET's intrinsic body diode to operate in a half-bridge without reduced efficiency. The converter's mode-by-mode operation is analysed and closed-form expressions are presented for the average current gain of the converter. The design issues are presented and circuit limitations are discussed. Magnetic materials for the main dc-dc converter inductor are compared and contrasted. Novel magnetic material comparisons are introduced, which include the material dc bias capability and thermal conductivity. An inductor design algorithm is developed and used to compare the various magnetic materials for the application. The area-product analysis is presented for the minimum inductor size and highlights the optimum magnetic materials. Finally, the high-flux magnetic materials are experimentally compared. The practical effects of frequency, dc-bias, and converters duty-cycle effect for arbitrary shapes of flux density, air gap effects on core and winding, the winding shielding effect, and thermal configuration are investigated. The thesis results have been documented at IEEE EPE conference in 2007 and 2008, IEEE APEC in 2009 and 2010, and IEEE VPPC in 2010. A 2011 journal has been approved by IEEE Transactions on Power Electronics.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Presented at the Annual Conference of the Canadian Political Science Association, Brock University, St. Catharines, Ontario, May 27, 2014

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This case study traces the evolution of library assignments for biological science students from paper-based workbooks in a blended (hands-on) workshop to blended learning workshops using online assignments to online active learning modules which are stand-alone without any face-to-face instruction. As the assignments evolved to adapt to online learning supporting materials in the form of PDFs (portable document format), screen captures and screencasting were embedded into the questions as teaching moments to replace face-to-face instruction. Many aspects of the evolution of the assignment were based on student feedback from evaluations, input from senior lab demonstrators and teaching assistants, and statistical analysis of the students’ performance on the assignment. Advantages and disadvantages of paper-based and online assignments are discussed. An important factor for successful online learning may be the ability to get assistance.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The Tyne Digital Library (TDL) provides access to scholarly materials (e.g. papers, book chapters, bibliographic reference lists), databases of hydrological and physical information, maps of key physiographic and environmental data, and electronic journal articles, for students undertaking GEOG3023 River Basin Management. In addition, the TDL utilises technological innovations that enhance services for accessing this information.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The Tyne Digital Library (TDL) provides access to scholarly materials (e.g. papers, book chapters, bibliographic reference lists), databases of hydrological and physical information, maps of key physiographic and environmental data, and electronic journal articles, for students undertaking GEOG3023 River Basin Management. In addition, the TDL utilises technological innovations that enhance services for accessing this information.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The paper presents a content-based evaluation, tracing the historical background of two heritage music collections at the State Library of Victoria (Melbourne, Australia).  In the case of the Gustav Holst and the British Music Society of Victoria Collections, history and content intertwine for the reason that both collections were initiated at the same time and by the same visionary power. During the early 1930s Louise Hanson-Dyer, a patron of Gustav Holst, issued a complete catalogue of the composer’s works and donated to the State Library of Victoria the first batch of Holst scores. This was to be the initial installment of a complete collection of published British music, which, however, was stopped due to duty tax complications. At the same time, the British Music Society of Victoria, founded by Louise Hanson-Dyer in 1921, maintained the first open library of chamber music in Australia. The BMS of Victoria Collection came to the State Library of Victoria in the 1980s. The most valuable materials in the collection are manuscripts of Australian twentieth century works, concert programs and first publications of British music from the 1920s and 1930s, which also supplement the Gustav Holst Collection. The collections are valuable reference and research collections, which document musical taste and music-making in Melbourne from 1920s well into the 1970s. The collections are also sources for studies into Louise Hanson-Dyer’s gift in collection development and her efforts to raise the professional standards of music performance in Melbourne and Australia.