Who expects what from whom? : a gender based study on expectations and secondary school administration

This study is about expectations and aspirations of secondary school teachers. It is an investigation of why some teachers aspire to become administrators and why some teachers do not. My research compares expectations and existing attltudes regarding aspirations toward administration which are held by three distinct groups within the secondary school system: 1) principals/vice-principals, 2) aspiring teachers, and 3) non-aspiring teachers. This study questions why, in the late 60's, secondary school administration is still predominated by men. The conclusions and recommendations were based on interviews with thirty men and women in the Hamilton Secondary School System. In addltion, Mr. Keith Rielly, Superintendent of Operations, made valuable contributions to my work. The interviews revealed experiences and percept ions of men and women in di scourse about f amil y re lat i onshi ps, educational choices and perceived internal and external barriers which inhiblted or enhanced their decision to aspire to secondary school administration. Candidates spoke about their personal and professional Hves wlth respect to encouragement, perceived images of an administrator, netWOrking and the effect of marriage and children on their careers. Historically, women have not accepted the challenge of administration and It would appear as if this is still the case today. My research suggests that women are under-represented in secondary school administration because of internal and external barriers which discourage many women from aspiring. I conclude that many of women's internal barrlers are reinforced by external roadblocks which prevent women from aspiring to secondory school administration. Thus. many women who do not envision a future in educational administration establish priorities outside the general realm of education. I recommend that males and females recognize that women make valuable contributions to educational theory and design based on their experiences which may be "differene from mole experiences. but just as significant. Mole and female representation in secondary school administration represents a balance between attitudes and behaviours which can not be accomplished when an administrative offlce is dominated by on all ma1e or all female staff.

Mass spectrometric studies on aryltin compounds and alkali halides /

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.

Postglacial water levels in the Great Lakes Region in relation to Holocene climate change : Thecamoebian and Palynological evidence /

Various lake phases have developed in the upper Great Lakes in response to isostatic adjustment and changes in water supply since the retreat of the Laurentide Ice Sheet. Georgian Bay experienced a lowstand that caused a basin wide unconformity approximately 7,500 years ago that cannot be explained by geological events. Thecamoebians are shelled protozoans abundant in freshwater environments and they are generally more sensitive to changing environmental conditions than the surrounding vegetation. Thecamoebians can be used to reconstruct the paleolimnology. The abundance of thecamoebians belonging to the genus Centropyxis, which are known to tolerate slightly brackish conditions (i.e. high concentrations of ions) records highly evaporative conditions in a closed basin. During the warmer interval (9000 to 700 yBP), the Centropyxis - dominated population diminishes and is replaced by an abundant and diverse Difflugia dominate population. Historical climate records from Tobermory and Midland, Ontario were correlated with the Lake Huron water level curve. The fossil pollen record and comparison with modem analogues allowed a paleo-water budget to be calculated for Georgian Bay. Transfer function analysis of fossil pollen data from Georgian Bay records cold, dry winters similar to modem day Minneapolis, Minnesota. Drier climates around this time are also recorded in bog environments in Southem Ontario - the drying of Lake Tonawanda and inception of paludification in Willoughby Bog, for instance, dates around 7,000 years ago. The dramatic impact of climate change on the water level in Georgian Bay underlines the importance of paleoclimatic research for predicting future environmental change in the Great Lakes.

ESI-MS[n] of anticancer pt[iv] organoamido complexes and their interactions with DNA-model compounds /

The general solution behaviour and" the major fragmentation pathways of the anticanceractive PtIV coordination complexes, trans, trans, cis, cis-[PtCIOH{N(pFC6F4) CH2h(pY)2] (1), trans, cis, cis-[Pt(OH)2{N(p-FC6F4)CH2h(Py)2] (2), trans, cis, cis-[Pt(OH)2{N(p-HC6F4)CH2h(Py)2] (3), trans, trans, cis, cis-[PtCIOH{N(pHC6F4) CH2h(Py)2] (4), and trans, trans, cis, cis-[PtOH(OCH3){N(p-HC6F4)CH2h(PY)2] (5) (Py = pyridine) have been deduced by positive-ion tandem-in-time ESI-MS. Overall, the acquired full-scan, positive-ion ESI-MS spectra of 2, 3, and 5 were characterized by the presence of relatively low-intensity [M+Nar and [M+Kt mass spectral peaks, whereas those of 1 and 4 were dominated by extremely intense [M+Hr peaks. Complexes 2 and 3 were also noted to form [2M+Ht and [2M+Nat dilneric cations. The source of Na + and K+ ions is believed to be the sample, the solvent systems used or the transport line carrying the sample solutions into the ES ion source. Further, the fragmentation pathway of all complexes studied was found to be almost identical with concurrent loss of py and H20 molecules, loss of a {N(p-YC6F4)CH2} (Y = F, H) group and/or concomitant release of the latter group and a py ligand being the most conunon. The photochemical degradation behaviour of 1 and 2 was also investigated using either fluorescent or ultraviolet light and some products of that degradation were positively identified. Altogether, light irradiation of solutions of both complexes resulted in cation cationisation, reductive-elimination, ligand-release, ligand-exchange and ligand-addition reactions. Finally, positive- and negative-ion ESI-MSn spectra of 5' -GMP, guanosine, inosine and products of their reactions with 1, 2,3, and 4 were also recorded. On the whole, full-scan ESI-MS spectra of the pure nucleobases revealed the presence of cationic and anionic species that are highly reflective of both their solution ionic composition and their propensity t9 form polymeric clusters. Analyses of mass spectra acquired from their reaction solutions with the aforementioned platinum complexes indicated very slow kinetics. However, all complexes investigated formed, to various degrees, Pt-nucleobase adducts with guanosine and inosine, but not with 5'-GMP. The products included species having coordination numbers of III, IV, V, and VI, among which the first-time�� observed, coordinatively saturated, jive-coordinate PtlI-nucleobase complexes were of most interest. The latter complexes are presumably stabilized by 7tback- donation involving the filled d orbitals of the PtII centre and the empty pz�� orbital of MeCN. All products, whose peaks appeared inlull-scan ESI-MS spectra, are believed to represent solution species rather than artifacts of gas-phase processes. Finally, negativeion ESI-MSn spectra recorded in reaction solutions of 1 and 4 with guanosine and of the latter complex with inosine revealed the negative-ion-ESI-MS first-time observed, noncovalent, nucleoside-chloride adducts, with the source of chloride anion being complexes 1 and 4 theillselves. In contrast, no such adducts were observed to form with Na25'-GMP or its protonated fonn. Few suggestions are offered for the possible cause(s) behind the absence of such adduct ions.

Honey proteins and their interaction with polyphenols

This project aimed to determine the protein prof i les and concent rat ion in honeys, ef fect of storage condi t ions on the protein content and the interact ion between proteins and polyphenols. Thi r teen honeys f rom di f ferent botanical or igins were analyzed for thei r protein prof i les using SDS-PAGE, protein concent rat ion and phenol ic content , using the Pierce Protein Assay and Fol in-Ciocal teau methods, respectively. Protein-polyphenol interact ions were analyzed by a combinat ion of the ext ract ion of honeys wi th solvents of di f ferent polar i t ies fol lowed by LCjMS analysis of the obtained f ract ions. Results demonst rated a di f ferent protein content in the tested honeys, wi th buckwheat honey possessing the highest protein concent rat ion. We have shown that the reduct ion of proteins dur ing honey storage was caused, partially, by the protein complexat ion wi th phenolics. The LCjMS analysis of the peak elut ing at retent ion t ime of 10 to 14 min demonst rated that these phenolics included f lavonoids such as Pinobanksin, Pinobanksin acetate, Apigenin, Kaemferol and Myricetin and also cinnamic acid.

Molecular Magnetism: The Design, Synthesis, and Characterization of New Building Blocks for Molecule-based Magnetic Materials

Two classes of building blocks have been prepared and characterized and their coordination chemistry explored working towards the preparation of new molecule-based magnetic materials. In the first project, the amine functionality of 3,3'-diamino-2,2'- bipyridine was exploited for the preparation of a new family of ligands (H2L 1)-(H2L 4). The molecular structures of three ligands have been fully characterized by X-ray crystallography. [molecular structure diagram will not copy here, but is available in full pdf.] The coordination chemistry of these ligands with divalent first row transition metal ions was investigated. For ligand (H2L1), the molecular structures of four coordination complexes with stoichiometries [Zn2(Ll)(OAc)(MeO)]2 (I), [Cu2(L1)(OAc)2 (II), [Li(L1)]3 (III), and [Ni(L1)]3 (IV) were determined by X-ray crystallography. For ligand (H2L2), a Cu(II) complex of stoichiometry [Cu3(L2)(OAc)3MeO] (V) was determined by X-ray crystallography. The magnetic properties of complexes (II), (III), and (V) have been fully elucidated. In project two, synthetic strategies for the preparation of porphyrin molecules bearing triol substituents is presented. Following this approach, three new porphyrin derivatives have been prepared and characterized [Zn(HPTPP-CH2C(CH20H)3)] (VI), [P(TPP)(OCH2C(CH2)H)3)2]+CL- (VII), and [P(OEP)(C6H5)(OCH2C(CH2OH)3)]+Cl- (VIII). Attempts to exchange the labile methoxide bridges of a tetraironIIl single molecule magnet of stoichiometry [Fe4(OMe)6(dpm)6] (Hdpm = dipivaloylmethane) with the triol appended porphyrins will be discussed. [molecular structure diagram will not copy here, but is available in full pdf.]

The Synthesis and Coordination Chemistry of Two Families of Polydentate Ligands - Exploring Their Potential for the Preparation of Molecule-Based Magnets

The synthesis and studies of two classes of poly dentate ligands are presented as two projects. In project 1, four new carboxamide ligands have been synthesised via the condensation of 2,2',6,6'-tetrachloroformyl-4,4'-bipyridine or 2,6-dichloroformyl pyridine together with heterocyclic amines containing pyridine or pyrazole substituents. The coordination chemistry of these ligands has been investigated and studies have shown that with a Cu(II) salt, two carboxamide ligands LJ and L2 afford large clusters with stoichiometries [Cu8(L1)4Cl16].CHCl3.5H2O.7CH3OH (I) and [Cu9(L2)6Cl6].CH3OH.5H2O.(C2H5)3N (II) respectively. [molecular diagram availabel in pdf]. X-ray diffraction studies of cluster (I) reveal that it has approximate S4 symmetry and is comprised of four ligands and eight copper (II) centers. Here, coordination takes place via amide 0 atoms, and pyrazole nitrogens. This complex is the first reported example of an octanuclear copper cluster with a saddle-shaped structure. The second cluster comprises nine copper ions that are arranged in a cyclic array. Each ligand coordinates three copper centers and each copper ion shares two ligands to connect six ligands with nine copper ions. The amide nitrogens are completely deprotonated and both amide Nand 0 atoms coordinate the metal centres. The cluster has three-fold symmetry. There are six chloride ions, three of which are bridging two neighbouring Cu(II) centres. Magnetic studies of (I) and (II) reveal that both clusters display weak antiferromagnetic interactions between neighbouring Cu(II) centers at low temperature. In the second project, three complexes with stoichiometries [Fe[N302](SCN)2]2 (III), R,R-[Fe[N3O2](SCN)2 (IV) and R,R-]Fe[N3O2](CN)2] (V) were prepared and characterized, where [N302] is a pentadentate macrocycle. Complex (III) was prepared via the metal templated Schiff-base condensation of 2,2',6,6'-tetraacetyl-4,4'-bipyridine together with 3,6-dioxaoctane-I,8-diamine and comprises of a dimeric macro cycle where the two Fe(II) centres are in a pentagonal-bipyramidal environment with the [N302] ligands occupying the equatorial plane and two axial NCS ligands. Complexes (IV) and (V) were prepared via the condensation of 2,6-diacetylpyridine together with a chiral diamine in the presence of FeCh. The synthetic strategy for the preparation of the chiral diamine (4R,5R)-4,5-diphenyl-3,6-dioxa-I,8-octane-diamine was elucidated. The chirality of both macrocycles (IV) and (V) was probed by circular dichroism spectroscopy. The crystal structure of (IV) at 200 K contains two independent molecules in the unit cell, both of which contain a hepta-coordinated Fe(II) and axial NCS ligands. Variable temperature magnetic susceptibility and structural studies are consistent with a high spin Fe(II) complex and show no evidence of any spin crossover behaviour. In contrast, the bis cyanide derivative (V) crystallizes with two independent molecules in the unit cell, both of which have different coordination geometries consistent with different spin states for the two Fe(II) centres. At 250 K, the molecular structure of (V) shows the presence of both 7- and a 6-coordinate Fe(II) complexes in the crystal lattice. As the temperature is lowered, the molecules undergo a structural change and at 100 K the structural data is consistent with a 6- and 5-coordinate Fe(II) complex in the unit cell. Magnetic studies confirm that this complex undergoes a gradual, thermal, spin crossover transition in the solid state. Photomagnetic measurements indicate this is the first chiral Fe (II) sea complex to exhibit a LIESST.

Structural, Magnetic and Thermal Studies of Ce1-xEuxCrO3 Nano-Powders

A new series of nano-sized Ce1-xEuxCrO3 (x = 0.0 to 1.0) with an average particle size of 50 - 80 nm were synthesized using a solution combustion method. Nano-powders Ce1-xEuxCrO3 with the canted antiferromagnetic property exhibited interesting magnetic behaviours including the reversal magnetization and the exchange bias effect. The effect of europium doping as the ion with the smaller radius size and different electron con figuration on structural, magnetic and thermal properties of Ce1-xEuxCrO3 were investigated using various experimental techniques, i.e. DC/AC magnetic susceptibility, heat capacity, thermal expansion, Raman scattering, X-ray photoemission spectroscopy, transmission/scanning electron microscopy, X-ray powder diffraction and neutron scattering. An exchange bias effect, magnetization irreversibility and AC susceptibility dispersion in these samples confirmed the existence of the spin disorder magnetic phase in Ce1-xEuxCrO3 compounds. The exchange bias phenomenon, which is assigned to the exchange coupling between glassy-like shell and canted antiferromagnetic core, showed the opposite sign in CeCrO3 and EuCrO3 at low temperatures, suggesting different exchange interactions at the interfaces in these compounds. The energy level excitation of samples were examined by an inelastic neutron scattering which was in good agreement with the heat capacity data. Neutron scattering analysis of EuCrO3 was challenging due to the large neutron absorption cross-section of europium. All diffraction patterns of Ce1-xEuxCrO3 showed the magnetic peak attributed to the antiferromagnetic Cr3+ spins while none of the diffraction patterns could detect the magnetic ordering of the rare-earth ions in these samples.

Single-Molecule Magnets and Multifunctional Molecular Magnetic Materials Based on Polynuclear Metal Complexes

Our work on single molecule magnets and multifunctional magnetic materials is presented in four projects. In the first project we show for first time that heteroatomic-type pseudohalides, such as OCN-, can be employed as structure-directing ligands and ferromagnetic couplers in higher oxidation state metal cluster chemistry. The initial use of cyanato groups in Mn cluster chemistry has afforded structurally interesting MnII/III14 (1) and MnII/III/IV16 (2) clusters in which the end-on bridging cyanates show a preference in binding through their O-atom. The Mn14 compound shows entirely visible out-of-phase alternating currect signals below 5 K and large hysteresis loops below 2 K. Furthermore, the amalgamation of azido groups with the triethanolamine tripodal ligand in manganese carboxylate cluster chemistry has led to the isolation of a new ferromagnetic, high-nuclearity and mixed-valence MnII/III15Na2 (3) cluster with a large ground-state spin value of S = 14. In the second project we demonstrate a new synthetic route to purely inorganic-bridged, transition metal-azido clusters [CoII7 (4) and NiII7 (5)] and coordination polymers [{FeII/III2}n (6)] which exhibit strong ferromagnetic, SMM and long-range magnetic ordering behaviors. We also show that access to such a unique ferromagnetic class of inorganic, N-rich and O-free materials is feasible through the use of Me3SiN3 as the azido-ligand precursor without requiring the addition of any organic chelating/bridging ligand. In the last projects we have tried to bring together molecular magnetism and optics via the synthesis of multifunctional magnetic materials based on 3d- or 4f-metal ions. We decided to approach such challenge from two different directions: firstly, in our third project, by the deliberate replacement of non-emissive carboxylato ligands in known 3d-SMMs with their fluorescent analogues, without perturbing the metal-core structure and SMM properties (complexes 7, 8, and 9). The second route (last project) involves the use of naphthalene or pyridine-based polyalcohol bridging ligands for the synthesis of new polynuclear LnIII metal clusters (Ln = lanthanide) with novel topologies, SMM behaviors and luminescent properties arising from the increased efficiency of the ���antenna��� organic group. This approach has led us to the isolation of two new families of LnIII8 (complexes 10-13) and LnIII4 (complexes 14-20) clusters.

The Effects of Magnetic Dilution and Applied Pressure on Several Frustrated Spinels

The effects of magnetic dilution and applied pressure on frustrated spinels GeNi2O4, GeCo2O4, and NiAl2O4 are reported. Dilution was achieved by substitution of Mg2+ in place of magnetically active Co2+ and Ni2+ ions. Large values of the percolation thresholds were found in GeNi(2-x)MgxO4. Specifically, pc1 = 0.74 and pc2 = 0.65 in the sub-networks associated with the triangular and kagome planes, respectively. This anomalous behaviour may be explained by the kagome and triangular planes behaving as coupled networks, also know as a network of networks. In simulations of coupled lattices that form a network of networks, similar anomalous percolation threshold values have been found. In addition, at dilution levels above x=0.30, there is a T^2 dependency in the magnetic heat capacity which may indicate two dimensional spin glass behaviour. Applied pressures in the range of 0 GPa to 1.2 GPa yield a slight decrease in ordering temperature for both the kagome and triangular planes. In GeCo(2-x)MgxO4, the long range magnetic order is more robust with a percolation threshold of pc=0.448. Similar to diluted nickel germanate, at low temperatures, a T^2 magnetic heat capacity contribution is present which indicates a shift from a 3D ordered state to a 2D spin glass state in the presence of increased dilution. Dynamic magnetic susceptibility data indicate a change from canonical spin glass to a cluster glass behaviour. In addition, there is a non-linear increase in ordering temperature with applied pressure in the range P = 0 to 1.0 GPa. A spin glass ground state was observed in Ni(1-x)MgxAl2O4 for (x=0 to 0.375). Analysis of dynamic magnetic susceptibility data yield a characteristic time of tau* = 1.0x10^(-13) s, which is indicative of canonical spin glass behaviour. This is further corroborated by the linear behaviour of the magnetic specific heat contribution. However, the increasing frequency dependence of the freezing temperature suggests a trend towards spin cluster glass formation.

High-Spin and Emissive Molecular Materials: Synthesis and Characterization of New Polynuclear Ni(II) Complexes from the Use of Aromatic Schiff Bases as Bridging Ligands

The employment of the bridging/chelating Schiff bases, N-salicylidene-4-methyl-o-aminophenol (samphH2) and N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in nickel cluster chemistry has afforded eight polynuclear Ni(II) complexes with new structural motifs, interesting magnetic and optical properties, and unexpected organic ligand transformations. In the present thesis, Chapter 1 deals with all the fundamental aspects of polynuclear metal complexes, molecular magnetism and optics, while research results are reported in Chapters 2 and 3. In the first project (Chapter 2), I investigated the coordination chemistry of the organic chelating/bridging ligand, N-salicylidene-4-methyl-o-aminophenol (samphH2). The general NiII/tBuCO2-/samphH2 reaction system afforded two new tetranuclear NiII clusters, namely [Ni4(samph)4(EtOH)4] (1) and [Ni4(samph)4(DMF)2] (2), with different structural motifs. Complex 1 possessed a cubane core while in complex 2 the four NiII ions were located at the four vertices of a defective dicubane. The nature of the organic solvent was found to be of pivotal importance, leading to compounds with the same nuclearity, but different structural topologies and magnetic properties. The second project, the results of which are summarized in Chapter 3, included the systematic study of a new optically-active Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in NiII cluster chemistry. Various reactions between NiX2 (X- = inorganic anions) and nacbH2 were performed under basic conditions to yield six new polynuclear NiII complexes, namely (NHEt3)[Ni12(nacb)12(H2O)4](ClO4) (3), (NHEt3)2[Ni5(nacb)4(L)(LH)2(MeOH)] (4), [Ni5(OH)2(nacb)4(DMF)4] (5), [Ni5(OMe)Cl(nacb)4(MeOH)3(MeCN)] (6), (NHEt3)2[Ni6(OH)2(nacb)6(H2O)4] (7), and [Ni6(nacb)6(H2O)3(MeOH)6] (8). The nature of the solvent, the inorganic anion, X-, and the organic base were all found to be of critical importance, leading to products with different structural topologies and nuclearities (i.e., {Ni5}, {Ni6} and {Ni12}). Magnetic studies on all synthesized complexes revealed an overall ferromagnetic behavior for complexes 4 and 8, with the remaining complexes being dominated by antiferromagnetic exchange interactions. In order to assess the optical efficiency of the organic ligand when bound to the metal centers, photoluminescence studies were performed on all synthesized compounds. Complexes 4 and 5 show strong emission in the visible region of the electromagnetic spectrum. Finally, the ligand nacbH2 allowed for some unexpected organic transformations to occur; for instance, the pentanuclear compound 5 comprises both nacb2- groups and a new organic chelate, namely the anion of 5-chloro-2-[(3-hydroxy-4-oxo-1,4-dihydronaphthalen-1-yl)amino]benzoic acid. In the last section of this thesis, an attempt to compare the NiII cluster chemistry of the N-naphthalidene-2-amino-5-chlorobenzoic acid ligand with that of the structurally similar but less bulky, N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2), was made.

Towards the nanomechanical actuation and controlled assembly of nanomaterials using charge-transfer reactions in electroactive self-assembled monolayers

Les microcantileviers fonctionnalis��s offrent une plateforme id��ale pour la nano- et micro-m��canique et pour le d��veloppement de (bio-) capteurs tres sensible. Le principe d���op��ration consiste dans des ��v��nements physicochimiques qui se passent du c��t�� fonctionnalis�� du microcantilevier induisant une diff��rence de stress de surface entre les deux c��t��s du cantilevier qui cause une d��flexion verticale du levier. Par contre, les facteurs et les ph��nom��nes interfacials qui r��gissent la nature et l'intensit�� du stress de surface sont encore m��connus. Pour ��claircir ce ph��nom��ne, la premi��re partie de cette th��se porte sur l'��tude des r��actions de microcantileviers qui sont recouverts d'or et fonctionnalis��s par une monocouche auto-assembl��e (MAA) ��lectroactive. La formation d'une MAA de ferroc��nylund��canethiol (FcC11SH) �� la surface d'or d'un microcantilevier est le mod��le utilis�� pour mieux comprendre le stress de surface induit par l�����lectrochimie. Les r��sultats obtenus d��montrent qu'une transformation r��dox de la MAA de FcC11SH cr��e un stress de surface qui r��sulte dans une d��flexion verticale du microcantilevier. D��pendamment de la flexibilit�� du microcantilevier, cette d��flexion peut varier de quelques nanom��tres �� quelques microm��tres. L���oxydation de cette MAA de FcC11SH dans un environnement d'ions perchlorate g��n��re un changement de stress de surface compressive. Les r��sultats indiquent que la d��flexion du microcantilevier est due �� une tension lat��rale provenant d'une r��orientation et d'une expansion mol��culaire lors du transf��rt de charge et de pairage d���anions. Pour v��rifier cette hypoth��se, les m��mes exp��riences ont ��t�� r��p��te��s avec des microcantileviers qui ont ��t�� couverts d'une MAA mixte, o�� les groupements ��lectroactifs de ferroc��ne sont isol��s par des alkylthiols inactifs. Lorsqu���un potentiel est appliqu��, un courant est d��tect�� mais le microcantilevier ne signale aucune d��flexion. Ces r��sultats confirment que la d��flexion du microcantilevier est due �� une pression lat��rale provenant du ferroc��nium qui se r��organise et qui cr��e une pression sur ses pairs avoisinants plut��t que du couplage d���anions. L���amplitude de la d��flexion verticale du microcantilevier d��pend de la structure mol��culaire de la MAA et du le type d���anion utilis��s lors de la r��action ��lectrochimique. Dans la prochaine partie de la th��se, l�����lectrochimie et la spectroscopie de r��sonance de plasmon en surface ont ��t�� combin��es pour arriver �� une description de l���adsorption et de l���agr��gation des n-alkyl sulfates �� l���interface FcC11SAu/��lectrolyte. �� toutes les concentrations de solution, les mol��cules d'agent tensio-actif sont empil��es perpendiculairement �� la surface d'��lectrode sous forme de monocouche condens�� entrecrois��. Cependant, la densit�� du film sp��cifiquement adsorb�� s'est av��r��e ��tre affect��e par l'��tat d'organisation des agents tensio-actifs en solution. �� faible concentration, o�� les mol��cules d'agent tensio-actif sont pr��sentes en tant que monom��res solvat��s, les monom��res peuvent facilement s'adapter �� l�����volution de la concentration en surface du ferroc��nium lors du balayage du potential. Cependant, lorsque les mol��cules sont pr��sentes en solution en tant que micelles une densit�� plus faible d'agent tensio-actif a ��t�� trouv��e en raison de l'incapacit�� de r��pondre effectivement �� la surface de ferrocenium g��n��r��e dynamiquement.

Pr��paration d'��chantillons pour l'��tude par GISAXS des m��canismes de d��formation des mat��riaux par faisceaux d'ions lourds de haute ��nergie.

Le m��canisme menant �� des d��formations structurales suivant le bombardement d'��chantillons de a-Si d'un faisceau d'ions lourds et rapides est sujet de controverses. Nous nous sommes pench��s sur l'hypoth��se de la formation d'une zone liquide caus��e par la d��position d'��nergie des ions incidents dans le contexte de la th��orie du pic thermique. Des ��chantillons de silicium amorphe furent pr��par��s dans le but d'observer les indices d'une transition de phase l-Si/a-Si suivant la d��position locale d'��nergie sur le parcours d'un ion lourd ��nerg��tique dans le a-Si. Les ��chantillons furent implant��s d'impuret��s de Cu ou d'Ag avant d'��tre expos��s �� un faisceau d'ions Ag12+ de 70 MeV. L'utilisation de l'analyse GISAXS est projet��e afin d'observer une concentration locale d'impuret��s suivant leur s��gr��gation sur la trace de l'ion. Des masques d'implantation nanom��triques d'oxide d'aluminium ont ��t�� fabriqu��s afin d'augmenter la sensibilit�� de l'analyse GISAXS et une m��thode d'alignement de ces masques selon la direction du faisceau fut d��velopp��e. Le bombardement d'��chantillons au travers de ces masques a donn�� lieu �� un r��seau de sites d'impacts isol��s presque ��quidistants.

Analytical strategies for the comprehensive profiling of histone post translational modifications by mass spectrometry and implications for functional analyses

Le long bio-polym��re d'ADN est condens�� �� l���int��rieur du noyau des cellules eukaryotes �� l'aide de petites prot��ines appel��es histones. En plus de leurs fonctions condensatrices,ces histones sont ��galement la cible de nombreuses modifications post-traductionnelles(MPT), particuli��rement au niveau de leur section N-terminale. Ces modifications r��versibles font partie d���un code d���histones ��pi-g��n��tique transmissible qui orchestre et module dynamiquement certains ��v��nements impliquant la chromatine, tels l���activation et la d��sactivation de g��nes ainsi que la duplication et la r��paration d���ADN. Ces modifications sont impliqu��es subs��quemment dans la signalisation et la progression de cancers, tels que la leuc��mie. En cons��quence, l'��lucidation des modifications d���histones est importante pour comprendre leurs fonctions biologiques. Une m��thodologie analytique a ��t�� mise au point en laboratoire pour isoler, d��tecter, et quantifier les MPT d���histones en utilisant une approche rapide �� deux volets �� l���aide d���outils bioinformatiques sp��cialis��s. La m��thodologie d��velopp��e en laboratoire a ��t�� valid��e en utilisant des histones de souche sauvage ainsi que deux types d���histones mutants d��ficients en enzymes ac��tyltransferase. Des trois sources d���histones utilis��es, la seule MPT qui a d��montr�� un changement significatif est l���ac��tylation de l���histone H3 �� lysine 56 (H3K56ac). L���expression et la stoechiom��trie de cette MPT, issue de cellules de souche sauvage et de cellules mutantes, ont ��t�� d��termin��es avec pr��cision et compar��es. Les fonctions de balayage polyvalentes d'un instrument �� trappe ionique quadrup��le lin��aire hybride ont ��t�� utilis��es pour am��liorer la d��tection de prot��ines intactes. Le mode de balayage �� enhanced multiply charged �� (EMC) a ��t�� modifi�� pour contenir et d��tecter les ions de prot��ines intactes situ��es dans la trappe ionique lin��aire. Ce mode de balayage nomm�� �� targeted EMC �� (tEMC) a permis de quadrupler le niveau de sensibilit�� (signal/interf��rence), et quintupler la r��solution du mode de balayage conventionnel. De plus, la capacit�� de s��paration des charges du tEMC a r��duit de fa��on significative les effets de �� space charge �� dans la trappe ionique lin��aire. La r��solution sup��rieure du mode tEMC a permis de diff��rencier plusieurs isoformes modifi��es, particuli��rement pour l���histone H3. L���analyse des peptides d���histones trypsiques �� l���aide du mode de balayage �� MRM �� a permis le s��quen��age et la quantification de MPT avec un haut degr�� de pr��cision. La seule MPT qui ��tait sous-exprim��e entre l���histone de souche sauvage et le mutant DOT1L fut la m��thylation de l���histone H3 lysine 79(H3K79me1). Les effets de deux inhibiteurs d���enzymes HDAC (HDACi) sur l���expression de MPT d���histone ont ��t�� ��valu��s en utilisant la m��thodologie analytique mentionn��e. Les histones extraites de cellules normales et canc��reuses ont ��t�� expos��es �� du Vorinostat(SAHA) ou du Entinostat (MS-275) pour une p��riode de 24 �� 72 heures. Deux histones furent principalement affect��es, soit H3 et H4. ��tonnamment, les m��mes effets n'ont pas ��t�� d��tect��s lorsque les cellules normales ont ��t�� trait��es avec le HDACi pour une p��riode de 48 �� 72 heures. Une m��thode absolue de quantification avec une courbe d�����talonnage a ��t�� d��velopp��e pour le peptide H3K56ac. Contrairement �� certaines publications, nos r��sultats d��montrent que cette MPT est pr��sente dans les cellules mammif��res avec une stoechiom��trie tr��s basse (< 0,1%) et n'est pas surexprim��e de fa��on significative apr��s le traitement au HDACi.

Actin cytoskeleton regulates pollen tube growth and tropism

La fertilisation chez les plantes d��pend de la livraison des cellules spermatiques contenues dans le pollen �� l���ovule. Au contact du stigmate, le grain de pollen s���hydrate et forme une protub��rance, le tube pollinique, charg�� de livrer les noyaux spermatiques �� l���ovule. Le tube pollinique est une cellule �� croissance rapide, anisotrope et non autotrophe; ainsi tout au long de sa croissance �� travers l���apoplaste du tissu pistillaire, le tube pollinique puise ses sources de carbohydrates et de min��raux du pistil. Ces ��l��ments servent �� la synth��se des constituants de la paroi qui seront achemin��s par des v��sicules de s��cr��tion jusqu����� l���apex du tube. Ce dernier doit aussi r��sister �� des pressions m��caniques pour maintenir sa forme cylindrique et doit r��pondre �� diff��rents signaux directionnels pour pouvoir atteindre l���ovule. Mon projet de doctorat ��tait de comprendre le r��le du cytosquelette dans la croissance anisotrope du tube pollinique et d���identifier les ��l��ments responsables de sa croissance et de son guidage. Le cytosquelette du tube pollinique est compos�� des microfilaments d���actine et des microtubules. Pour assurer une bonne croissance des tubes polliniques in vitro, les carbohydrates et les ��l��ments de croissance doivent ��tre ajout��s au milieu �� des concentrations bien sp��cifiques. J���ai donc optimis�� les conditions de croissance du pollen d���Arabidopsis thaliana et de Camellia japonica qui ont ��t�� utilis��s avec le pollen de Lilium longiflorum comme mod��les pour mes exp��riences. J���ai d��velopp�� une m��thode rapide et efficace de fixation et de marquage du tube pollinique bas��e sur la technologie des microondes. J���ai aussi utilis�� des outils pharmacologiques, m��caniques et mol��culaires coupl��s �� diff��rentes techniques de microscopie pour comprendre le r��le du cytosquelette d���actine lors de la croissance et le tropisme du tube pollinique. J���ai trouv�� que le cytosquelette d���actine et plus pr��cis��ment l���anneau d���actine localis�� dans la partie sub-apicale du tube est fortement impliqu�� dans la croissance et le maintien de l���architecture du tube �� travers le contr��le de la livraison des v��sicules de s��cr��tion. J���ai construit une chambre galvanotropique qui peut ��tre mont��e sur un microscope invers�� et qui sert �� envoyer des signaux tropistiques bien pr��cis �� des tubes polliniques en croissance. J���ai trouv�� que les filaments d���actine sont impliqu��s dans la capacit�� du tube pollinique �� changer de direction. Ce comportement tropistique d��pend de la concentration du calcium dans le milieu de croissance et du flux de calcium �� travers des canaux calciques. Le gradient de calcium ��tabli dans le tube pollinique affecte l���activit�� de certaines prot��ines qui se lient �� l���actine et dont le r��le est la r��organisation des filaments d���actine. Parmi ces prot��ines, il y a celles de d��polym��risation de l���actine (ADF) dont deux sp��cifiquement exprim��es dans le gam��tophyte m��le d���Arabidopsis (ADF7 et ADF10). Par marquage avec des proteins fluorescents, j���ai trouv�� que l���ADF7 et l���ADF10 ont des expressions diff��rentielles pendant la microsporogen��se et la germination et croissance du tube pollinique et qu���elles partagent entre elles des r��les importants durant ces diff��rents stades.