8 resultados para Black Studies|Health Sciences, Obstetrics and Gynecology|Health Sciences, Public Health

em Brock University, Canada


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Floral nectar is thought to be the primary carbohydrate source for most dipteran species. However, it has been shown that black flies (Burgin & Hunter 1997 a,b,c), mosquitoes (Foster 1995; Burkett et al. 1999; Russell & Hunter 2002), deer flies (Magnarelli & Burger 1984; Janzen & Hunter 1998; Ossowski & Hunter 2000), horse flies (Schutz & Gaugler 1989; Hunter & Ossowski 1999) and sand flies (MacVicker et al. 1990; Wallbanks et al. 1990; Cameron et al. 1992, 1995; Schlein & Jacobson 1994, 1999; Hamilton & EI Naiem 2000) feed on homopteran honeydew as well as floral nectar. Prior to 1997 floral nectar was thought to be the main source of carbohydrates for black flies. However, Burgin & Hunter (1 997a) demonstrated that up to 35% of black flies had recently consumed meals of homo pte ran honeydew. This information has necessitated a re-assessment of many life history aspects of black flies. Attempts are being made to examine the effects of nectar versus honeydew on black fly fecundity and parasite transmission (Hazzard 2003). Recently, Stanfield and Hunter (unpublished data) have shown that in female black flies, honeydew sugars produce flights of longer distance and duration than do nectar sugars. This thesis examines two aspects of black fly biology as it relates to sugar meal consumption. First, the effects of honeydew and nectar on black fly longevity are examined. Second, the proximate causation behind longer flight performances in honeydew-fed flies will be examined. The comparison between these two sources is important because nectar is composed of mainly simple sugars (monosaccharides and disaccharides) whereas honeydew is composed of both simple and complex sugars (including trisaccharides and tetrasaccharides ).

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Nuclear magnetic resonance spectroscopy has been used to study donor-acceptor complexes of boron trifluoride with several ureas, tetramethylthiourea, tetramethylselenourea, and tetramethylquanidine as well as adducts of tetramethyl- -urea with BF2Cl, BFC1 2 , and BC1 3 - A large number of mixed tetrahaloborate ions, including some of the ternary ones such as BF2CIBr-,have been obtained by ligand exchange reactions and studied by NMR techniques. The bonding in these ions is of the same inherent interest as the bonding in the isoelectronic tetrahalomethanes which have been the subject of many detailed studies and have been involved in a controversy concerning the existence of and the nature of "fluorine hyperconjugation" or C-F P1T- Pn bonding_ Ligand exchange reactions also gave rise to the difluoroboron cation, (TMU)20BF2+o The difluoroboron cation has been observed in solutions of TMU-BF3 , and has been proposed as a possible intermediate for fluorine exchange reactions in BF3 adducts.

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The fragmentation behavior of aryltin compounds [(p-ThAnis)nSnPh4.n (n=l-4); (p-ThAnis)3SnX (X=C1, Br, I); (o-CH30C6H4)3SnCl; Ph3Sn(o-pyr)] have been studied comparatively under EI and FAB ionization modes. Alkali halides were run under FAB mode. For the aryltin compounds, the effect of ligand type on the spectra have been explored in both EI and FAB modes. The fragmentation mechanisms have been examined with linked scans, such as fragment ion scans (B/E) and parent ion scans (B^/E). Ab Initio molecular orbital calculations were used to determine the structures of the fragments by comparing their relative stabilities. In the EI MS studies, negative ion EI mode has also been used for some of the aryltin compounds, to examine the possible ion molecule reactions under low pressures at 70eV. In the positive ion FAB MS studies, matrix optimization experiments have been carried out. Negative ion FAB experiments of all the compounds have been done in two different ways. Finally, the comparison of the two methods, EI MS and FAB MS, have been made.For alkali halides, the studies focused on the FAB MS behavior under different conditions. The intensities of cluster ions were reported, and the anomalies in the intensity distribution was also discussed.

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The formation and the isolation of fluoroboron salts, (D2BF2+)(PF6-), (DD'BF2+)(PF6-) and (D3BF2+)(PF6-)2, have been carried out. 1,8-Diazabicyclo [5,4.0]undec-7-ene (DBU) and 1,5-diazabicyclo[4,3,O]non-5-ene (DBN), extremely strong organic bases, were introduced into the fluoroboron cation systems and induced a complicated redistribution reaction in the D/BF3/BC13 systems. The result was the formation of all BFnCI4-n-, D.BFnCI3-n and fluoroboron cation species which were detected by 19p and 11B NMR spectrometry. The displacement reaction of CI- from these D.BFnCI3-n (n = 1 and 2) species by the second entering ligand is much faster than in other nitrogen donor containing systems which have been previously studied. Tetramethylguanidine, oxazolines and thiazolines can also produce similar reactions in D/BF3/BCI3 systems, but no significant BFnC4-n- species were observed. As well as influences of their basicity and their steric hindrance, N=C-R(X) (X = N, 0 or S) and N=C( X)2 (X = N or S) structures of ligands have significant effects on the fonnationof fluoroboron cations and the related NMR parameters. D3BF2+ and some D2BF2+ show the expected inertness, but (DBU)2BF2+ shows an interestingly high reactivity. (D2BF2+)(X-) formed from weak organic bases such as pyridine can react with stronger organic bases and form DD'BF2+ and D'2BF2+ in acetone or nitromethane. Fast atom bombardment mass spectrometry is doubly meaningful to this work. Firstly, FABMS can be directly applied to the complicated fluoroboron cation containing solution systems as an excellent complementary technique to multinuclear NMR. Secondly, the gas-phase ion substitution reaction of (D2BF2+)(PF6-) with the strong organic bases is successfully observed in a FABMS ion source when the B-N bond is not too strong in these cations.

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Letter to W.D. Woodruff from E.E. Black of N.W. Harris and Co. Bankers of New York (1 page, printed), which accompanied a bill showing $10,000 due on the Dominion Power Company, July 23, 1907.

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Letter to W.D. Woodruff from E.E. Black of N.W. Harris and Co. Bankers of New York (1 page, printed) stating that they have applied the $961.55 balance to the amount owing, Oct. 29, 1907.

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Letter to W.D. Woodruff from E.E. Black of N.W. Harris and Co. Bankers of New York (1 page, printed) regarding $41,000 in Dominion Power Company bonds that they have put in safekeeping, Oct. 30, 1907.