En l’absence de traitements de protection, de nombreux objets et éléments patrimoniaux en attente de restauration se dégradent sous l’effet de la corrosion atmosphérique. Ainsi les témoignages de notre histoire disparaissent lentement. Il est nécessaire de développer des traitements de protection temporaires, peu coûteux, réversibles et répondant aux normes environnementales actuelles, afin d’enrichir le panel de solutions dont disposent les professionnels de la conservation restauration. Ces recherches sont également motivées par les conservateurs du patrimoine qui souhaitent éviter des travaux de restauration complexes et onéreux sur des collections importantes. L’enjeu de cette étude est in fine de pouvoir proposer un traitement alternatif pour la protection du patrimoine ferreux soumis à la corrosion atmosphérique sous abri. Les molécules choisies pour réaliser ces nouveaux traitements sont des acides carboxyliques. Ces composés sont mis en œuvre dans différents types de solutions, dont les performances anti-corrosion sont prouvées par des mesures électrochimiques et des tests de vieillissement artificiels et naturels. Parallèlement à ce travail, le carboxylate de fer, responsable de l’inhibition de la corrosion est étudié aux points de vue morphologique, thermique, chimique et structural grâce à la combinaison de plusieurs techniques d’analyses. Ces travaux permettent de proposer des traitements protecteurs, adaptés à l’état de surface de l’élément à protéger, au type d’intervention envisagée (dépendant notamment de l’urgence de l’intervention, et des moyens humains et financiers à disposition), et aux conditions de conservation de l’élément. / Without any protection treatment, lots of artefacts or elements from our cultural heritage slowly decay because of atmospheric corrosion. Therefore there is a need for temporary, cheap, easy-to-use and non-toxic protection systems, fitting to the actual environmental laws. These treatments could give new solutions to the conservators for protecting the artefacts and sometimes avoid them complex and expensive restoration works. Long chain carboxylic acids have been chosen for this purpose, and used in different kinds of treatments. Their good performances are proved by electrochemical measurements and artificial and natural ageing tests. In parallel with this work, the iron (III) carboxylate, which is the compound responsible for the inhibition properties, has been studied in term of morphology, structure, and chemical properties, thanks to many analytical techniques. This work finally leads to propose a specific and adapted solution for each element or artefact that has to be treated- depending on its surface, its environmental conditions of exposure, the emergency of its treatment, and the financial and human means available.

Abstract A theoretical study of the Kolbe-Schmitt reaction mechanism, performed using a DFT method, reveals that the reaction between sodium phenoxide and carbon dioxide proceedswith the formation of three transition states and three intermediates. In the first step of the reaction, a polarized ONa bond of sodium phenoxide is attacked by the carbon dioxide molecule, and the intermediate NaPh-CO2 complex is formed. In the next step of the reaction the electrophilic carbon atom attacks the ring primarily at the ortho position, thus forming two new intermediates. The final product, sodium salicylate, is formed by a 1,3-proton shift from C to O atom. The mechanism agrees with the experimental data related to the Kolbe-Schmitt reaction.

Compared to SO42-(H2O)n, the solute-solvent interaction is favorable by C2O4 2- (H2O)n, n = 6∼12, due to two charges separation and more space in C2O42-. Because of the extensive hydration bonds, the stepwise solvation energy is around 15 kcal/mol even for larger clusters. The solvation dynamics for C 2O42-(H2O)n is influenced by the coupling between torsional movement along C-C bond and solute-solvent interaction. / For Na(H2O)n, the "constant IP" observed experimentally for Na(H2O)n is due to autoionization through Rydberg transition induced by the release of large relaxation energy after the removal of unpaired electron. In contrast, the reorganization is less extensive in Na(NH3)n, as both the electron-NH3 and NH 3-NH3 interactions are weaker, and the structure of Na(NH 3)n is determined by the maximization of Na+-NH 3 interaction. The autoinization is no important and the threshold measured in experiment is indeed for ionization of Na(NH3)n. / In the size-dependant charge separation of SO42-(H 2O)n with n = 3∼7, the key factor governing the charge separation is the difference in the strength of solvation interaction: while interaction with water is strong for SO42- and OH-, it is relatively weak for HSO4-. It gives rise to a barrier for charge separation as SO42- is transformed into HSO4- and OH-, although the overall reaction energy is exothermic. The barrier is high when more than two H2O are left to solvate HSO4-. The entropy is another important factor, which leads to the eventual switch-off of charge separation as cluster size increases. / The equilibrium structures of SO42-(H 2O)n with n = 6∼12 are determined by the competition between the solute-solvent and solvent-solvent interactions. Facilitated by SO42- in symmetry, the extensive hydrogen bonds are formed. The stepwise solvation energy is quite large (often exceeding 15 kcal/mol). AIMD simulation shows "crowding" effects in the first solvation of SO42-(H2O)12 at raised temperature. / The structure and solvation of hydrated di-anion (SO4 2-, C2O42-) clusters and solvated Na clusters are explored computationally by the quantum chemical calculation using Gaussian programme, and by the density functional theory based ab initio molecular dynamics (AIMD) method using Vienna Ab Initio Simulation Package (VASP). / Gao Bing. / "May 2006." / Adviser: Zhi-feng Liu. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6420. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 131-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

No description available.

The epithelial sodium channel (ENaC) is a key regulator of salt homeostasis. The classic ENaC consists of three subunits: α, β and γ, which are highly expressed in the kidney and colon where they mediate electrogenic Na⁺ influx into cells under the tight hormonal regulation of aldosterone. A fourth ENaC subunit named [delta]ENaC also generates Na⁺ influx with the β- and γENaC subunits in Xenopus oocytes. However [delta]ENaC differs to the other subunits in its channel properties and tissue distribution, suggesting that [delta]ENaC may possess a physiological role other than salt regulation. A copper-toxicosis related protein called COMMD1/Murr1 was previously identified to directly interact with [delta]ENaC and downregulate [delta]ENaC activity. COMMD1 is linked with multiple ubiquitination pathways, therefore we hypothesised that COMMD1 directly interacts with [delta]ENaC through novel protein-protein interaction motifs and promotes internalisation of [delta]ENaC from the cell surface through enhanced ubiquitination. With the use of GST pulldown assays and coimmunoprecipitation, it was found that the binding of COMMD1 to [delta]ENaC is mediated by the COMM domain of COMMD1, primarily through amino acids 120-150 of COMMD1. Immunocytochemical studies showed that the intracellular interaction between [delta]ENaC and COMMD1 predominantly occurred in the early and recycling endosomes, suggesting that COMMD1 may promote the retrieval of [delta]ENaC from the cell surface to the intracellular pool. COMMD1 mediated a decrease in the [delta]ENaC cell surface population, as shown by a biotinylation surface labelling assay. This may be driven by an ubiquitin-regulated endocytosis, as COMMD1 increased ubiquitination, but not proteasomal/lysosomal degradation, of [delta]ENaC. COMMD1 may promote [delta]ENaC ubiquitination through the action of the ubiquitin ligase Nedd4-2 as coexpression with Nedd4-2 enhanced the COMMD1-mediated decrease in surface [delta]ENaC expression. This is abolished by the addition of the Nedd4-2 downregulator kinase sgk1, suggesting that COMMD1 may downregulate [delta]ENaC through the Nedd4-2/sgk1 pathway. Surface levels of [delta]ENaC may also be affected by XIAP, a RING domain ubiquitin ligase which is able to decrease the levels of COMMD1. Coimmunoprecipitation of endogenous [delta]ENaC and COMMD1 proteins, and the enhanced colocalisation of endogenous [delta]ENaC in the recycling endosomes with transfected COMMD1, indicate that interaction between transfected [delta]ENaC and COMMD1 reflect the intracellular interactions of the endogenous proteins. Taken together, these findings suggest that COMMD1 downregulates [delta]ENaC activity by promoting the internalisation of surface [delta]ENaC into early and recycling endosomes and this may be mediated by enhanced [delta]ENaC ubiquitination via the ubiquitin ligase Nedd4-2.

Thesis (M.S.)--University of Wisconsin -- La Crosse, 1984. / Includes bibliographical references (leaves 54-59).

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Robert A. Sikes, Dept. of Biological Sciences. Includes bibliographical references.

25 years after the first sodium images of the human brain were created, sodium MRI remains on the periphery of MR research, despite intimate sodium involvement in cellular metabolism and implicated abnormal concentrations in numerous disorders. The difficulties of sodium MRI include not only tissue concentration, ~1750x less than proton, but also rapid biexponential signal decay. The purpose of this work was to optimize human brain sodium MRI and facilitate a study of sodium increase following onset of acute human stroke, with potential timing application for those patients who present with unknown time-of-onset, as effective treatment is currently bound by a 4.5 hour time-window. Optimization begins with radial center-out k-space acquisition, which minimizes echo time (TE) and signal loss, and in particular concerns the twisted projection imaging (TPI) technique, which has not found wide use. This thesis first considers a new application of TPI, i.e. k-space filtering by sampling density design to minimize detrimental ringing artifact associated with cerebral spinal fluid. Image noise correlation is addressed next, and a method for measuring volumes of statistical noise independence presented, as this correlation together with signal-to-noise ratio (SNR) defines the confidence of signal-averaging measurements. Radial acquisition is then considered with respect to a new imaging metric, i.e. the minimum object volume that can be precisely (with respect to noise) and accurately (with respect to image intensity modulation with object volume) quantified. It is suggested that TPI is a highly beneficial radial acquisition technique when implemented with long readout duration (countering common thought), reduced SNR (i.e. small voxel volumes), and in particular small TPI parameter p. Sequence optimization for bulk-tissue sodium analysis demonstrates a large SNR/voxel-volume advantage for TPI implementation in a steady-state approach, even though excitation pulse length and TE must be increased to mitigate power deposition. Finally, an inversion-recovery based fluid-nulling method that facilitates sodium environment separation based on rapid relaxation during soft inversion pulses is presented, with possible application for intracellular weighted imaging. On high quality sodium images a clear trend of lesion intensity increase with time-after-onset is demonstrated for the first time in acute stroke patients, as expected from animal models.

No description available.

ABSTRACT A purge and trap concentrator coupled to gas chromatography-pulsed flame photometric detector(GC-PFPD) after in situ ethylation with sodium tetraethylborate(NaBEt4) was used to analyze organotin compounds in water samples. The sample glassware with 5.5 ml water sample, 1.5 ml derivatizing reagent as well as 2 ml buffer solution was installed to purge and trap system, and then all steps were performed automatically, including ethylation, purge and trap, concentration, chromatography seperation and detection. Parameters including NaBEt4 concentration, purge flow rate, purge time, desorb time, the pH of buffer solution, H2 flow rate and the voltage of photomultiplier tube(PMT) of PFPD , which influence the speciation of organotin compounds were optimized. Method detection limits for dibutyltin and tributyltin were 0.50 and 0.46 ng as Sn/L, respectively. The calibration graphs were linear up to 2 orders of magnitude. Surface water samples collected from fourteen different locations of Kaohsiung harbor were analyzed. The concentration of dibutyltin ranged from nondetected(ND) to 272.2 ng as Sn/L and tributyltin ranged from nondetected to 105.4 ng as Sn/L. Recovery percentage for dibutyltin and tributyltin ranged from 88.9-95.3 %.