• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1730
  • 1712
  • 900
  • 155
  • 153
  • 137
  • 130
  • 64
  • 60
  • 49
  • 46
  • 28
  • 22
  • 21
  • 17
  • Tagged with
  • 6173
  • 664
  • 632
  • 507
  • 397
  • 360
  • 313
  • 310
  • 297
  • 256
  • 237
  • 227
  • 226
  • 216
  • 207
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Dielectric relaxation study of the cellulose solvent system LiCl-N,N-dimethylacetamide

Fernandez, Sarka. January 1900 (has links) (PDF)
Regensburg, Univ., Diss., 2003. / Computerdatei im Fernzugriff.
52

Dielectric relaxation study of the cellulose solvent system LiCl-N,N-dimethylacetamide

Fernandez, Sarka. January 1900 (has links) (PDF)
Regensburg, Univ., Diss., 2003. / Computerdatei im Fernzugriff.
53

Appraisal of Dr. Broom's top management game

Gibberd, John Davidson January 1970 (has links)
The objective of the thesis is to examine Dr. Broom's Top Management Game. The examination covers the realism of model input output relationships, the cost of an application, the design structure utilized and the adequacy of the model presentation. Before the analysis is undertaken two analytical tools are developed. The first of these is a management game typology which provides a standardized, method for describing gaming models. The second tool is a two dimensional matrix which may be employed for design or analytical purposes. The rows of the matrix represent input for the current period and the columns output for the current period. In order to determine the feasibility of converting The Broom Game, to modular design, the structure of a modular game is outline. Dr. Broom's Game, is an educational model which employs the computer to calculate the results for a period. Though the model is supposedly total enterprise the personnel function is absent. The marketing function of the model performs in a highly unrealistic manner. Also the production function is inadequate in that no attempt is made to break production into its component parts. The cost of an application is approximately two dollars. In the authors opinion it is not feasible to convert the model to modular design. Finally the administrators' presentation was found to be inadequate. / Business, Sauder School of / Graduate
54

Metallodendrimers as catalysts for C-C coupling reactions

Mapolie, S. F. January 2011 (has links)
>Magister Scientiae - MSc / In this work, we describe the synthesis of ferrocenylimine and G1 dendrimeric N,N′ ligands, and their palladium(II) complexes. The ligands L1 – L4 were synthesized following Schiff base condensation reactions. The ferrocenylimine ligands L1 and L2 were prepared from ferrocenecarboxaldehyde and 1,3-diaminopropane or DAB-4-(NH2)4, while the G1 dendrimeric N,N′ ligands L3 and L4 were prepared from DAB-4-amine and 2- pyridinecarboxaldehyde or 2-quinolinecarboxaldehyde. The air and moisture stable ligands were obtained in fairly good yields of over 65 %. All the ligands were observed to be soluble in common organic solvents. They were characterized by FTIR spectroscopy, 1H-NMR spectroscopy, 13C-NMR spectroscopy, micro-analysis and ESImass spectrometry.A reaction of the ligands with PdCl2(COD) or PdCl2(MeCN)2 gave palladium(II) complexes C1 – C4 in good yields of over 70%. The complexes were observed to be stable. However,the complexes did not dissolve in common organic solvents. These were characterized by FTIR spectroscopy and 1H-NMR and 13C-NMR spectroscopy.All the complexes were screened for activity towards Heck coupling model reaction of iodobenzene with styrene. The complexes catalyzed the coupling of styrene with iodobenzene, giving over 60 % conversions. However, complex C3 was found to be the most active catalyst, yielding 75% conversion without formation of palladium black.
55

The Charge Dependent and Charge Symmetry Breaking Effects of the γ-π-Exchange Process in N-N and λ-N Interactions

Leung, Jurn-Sun 11 1900 (has links)
<p> Experimental and theoretical investigations on charge dependence and charge asymmetry in N-N and λ-N interactions are reviewed. The γ-π-exchange N-N and λ-N potentials are derived and calculated in the static limit. The γ-π-exchange charge dependent component of the N-N potential is found to be larger than the charge dependent part of OPEP due to pion mass difference up to 3 fm and is of opposite sign, making the explanation of the splitting between p-n and p-p scattering lengths more difficult than was previously thought. Except at very short distances, this potential is of the order of only a few percent of the OPEP. In the light of this result, it is concluded that the very large charge-dependent correction at large distances required by Noyes' phenomenological analysis on the splitting of rpn and rpp is inexplicable as an electromagnetic correction. The γ-π exchange charge asymmetric components of both N-N and λ-N interactions are found to be much weaker than the charge dependent one for the N-N case.</p> / Thesis / Doctor of Philosophy (PhD)
56

Measurements of the 96Zr(α, n) and 65Cu(α, n) Cross Sections at Edwards Accelerator Laboratory for Astrophysics and Applications

Hamad, Gulakhshan M. 16 September 2022 (has links)
No description available.
57

Synthesis, reactions and spectra of thiazolyl- and pyridylthioureas and derivatives

Rousseau, Danielle January 1973 (has links)
No description available.
58

Synthesis, structure and reactivity studies of dinuclear group 11 N-heterocyclic carbene complexes

Wyss, Chelsea Marie 07 January 2016 (has links)
This thesis describes the synthesis, structure and reactivity of singly bridged dinuclear Group 11 metal complexes, supported by N-heterocyclic carbene (NHC) ligands. These complexes include dinuclear copper(I) complexes that demonstrate three-center, two-electron bonding with short intermetallic distances. In the first part of this study, a hydride-bridged dicopper cation, {[(IDipp)Cu]2(μ-H)}+ BF4–, which adopts a bent arrangement about the hydride was isolated. It undergoes facile methanolysis, readily reacts with carbon dioxide to afford a (κ2-formate)-bridged dicopper species, and coordinates carbon monoxide reversibly to form a carbonyl adduct. The [(LCu)2H]+ cation also inserts phenylacetylene to afford a gem-dicopper vinyl cation, a rare example of the insertion of carbon-carbon multiple bonds into a copper hydride. The second part of this thesis describes the synthesis and structural characterization of the first boryl-bridged dicopper cation {[(SIDipp)Cu]2(μ-B(O2C6H4)}+ BF4–. The solid state structure shows a bent arrangement about the boryl with a short intermetallic distance of 2.4082(2) Å. The boryl-bridged dicopper cation deprotonates phenylacetylene to form a phenylacetylide dicopper complex. It also readily reacts with methanol to form the hydride-bridged dicopper cation. Density functional theory (DFT) calculations were applied to give further insight into the nature of the metal–boron bonds in comparison to the mononuclear analogue. The two electrons contributed by the bridging boryl are shared between the boron and the two copper centers in the [(LCu)2B]+ core. This three-center, two-electron bonding orbital is lower-lying in energy in comparison to the Cu−B σ-bonding molecular orbital in the mononuclear analogue, consistent with a less nucleophilic Cu–B bond. The NHC ligand also stabilizes an isoleptic series of dinuclear μ-fluoro cations of copper(I), silver(I), and gold(I). In these complexes, a single fluoride acts as the sole bridging ligand between the two group 11 metal centers of the form [(LM)2(μ-F)]+. All three cations are highly sensitive to adventitious moisture, readily forming the hydroxide-bridged dinuclear cations. The gold(I) complex is the most reactive. It activates the C-Cl bonds of CD2Cl2 and adds rapidly across an allene C=C bond to form an allylic C–F bond, and a vinyl anion bound asymmetrically to the two gold(I) centers.
59

Studies on intramolecular trapping of N-nitrenes

Grimshire, Michael J. January 1986 (has links)
The research described in this Thesis is an investigation of the intramolecular trapping of N-nitrenes by alkenes and alkynes. In the former case, the objective was to try to obtain a description of the transition state geometry for concerted addition of nitrenes to double bonds. This was attempted by a study of intramolecular nitrene additions since in the latter, some control over the approach geometry of the interacting components can be exercised by design of the molecular framework. From the effect of changes in this framework upon the characteristics of the cycloaddition, and in particular upon its concertedness, an ideal configuration for the participating atoms (i.e. transition state geometry) was definable. 2H-azirines are obtained in greatly improved yields in the intramolecular trapping of N-nitrenes by comparison with the analogous inter- molecular trapping. Analysis of the n.m.r. spectra of these azirines together with the X-ray crystal structure of one of them reveals that a preference for near-coplanarity of three of the bonds at the spiro-centre results in conformational anchoring of the five-membered ring. (Examination of all the azirine ring containing structures in the Cambridge crystallographic data file shows that all of these also show the same near-coplanarity of azirine C-C bond and substituent bonds at the spiro-centre). Attempts to trap a presumed 1H-azirine intermediate were unsuccessful. This is probably the result not only of their anti-aromatic character but also that migration of the N-N bond in the 1H-azirine delivers the 2H- azirines, in the cases studied, directly in their most stable conformations.
60

Stability and numerical errors in the N-body problem

Urminsky, David January 2008 (has links)
Despite the wide acceptance that errors incurred in numerical solutions to N-body systems grow exponentially, most research assumes that the statistical results of these systems are reliable. However, if one is to accept that the statistical results of N-body solutions are reliable, it is important to determine if there are any systematic statistical errors resulting from the incurred growth of errors in individual solutions. In this thesis we consider numerical solutions to the 3-body problem in which one of the bodies escapes the system. It is shown for a particular 3-body con guration, known as the Sitnikov problem, that the mean lifetime of the system is dependent on the accuracy of the numerical integration. To provide a theoretical explanation of the phenomenon, an approximate Poincar´e map is developed whose dynamics on a particular surface of section is shown to be similar to the dynamics of the Sitnikov Problem. In fact there is a set on which the approximate Poincar´e map is topologically equivalent, like the Sitnikov Problem, to the shift map on the set of bi-in nite sequences. The structure of the escape regions on the surface of section form a cantor set-like structure whose boundary can more easily be delineated using the approximate Poincar´e map than for the Sitnikov problem. Further it is shown that numerical errors destroy escape regions and can cause orbits to migrate to a region in which escape is faster. Finally, a relationship between the Lyapunov time, tl, and the lifetime, td, of the 3-body problem is discussed. Firstly, the Sitnikov problem and the approximate Poincar´e map of the Sitnikov problem both exhibit a two-part power law relationship beween tl and td like that for a particular case of the general 3-body problem. Further, it is demonstrated that large perturbations to the energy of the escaping body in uences the relationship between tl and td for small tl. Finally, it is shown that the approximate Poincar´e map yields a theoretical explanation of the phenomenon based on the structure of the escape regions the orbits traverse before escape.

Page generated in 0.0396 seconds