Literatura académica sobre el tema "Structure porale complexe"

Dans un contexte de changements globaux et de transitions écologiques et énergétiques, le changement climatique induit une sècheresse récurrente et de crise de la ressource en eau dans plusieurs régions et continents. Il est donc crucial d'étudier les aquifères d'eaux douces afin d'accompagner ces transitions et assurer une gestion et une utilisation durable et raisonnée de cette ressource vitale. En l'occurrence, la zone vadose qui joue un rôle important dans la recharge de ces aquifères et le transfert d'éventuels polluants et d'intrants. La plupart du temps, cette zone non saturée en eau, se caractérise par la présence d'hétérogénéités (structure de pores, fractures, variation minéralogique) multi-échelles notamment lorsqu'il s'agit d'un milieu calcaire. Ces hétérogénéités sont complexifiées par les processus diagenétiques liés principalement à l'altération physico-chimique et minéralogique. La surimposition de ces phénomènes primaires et secondaires rend difficile l'estimation des propriétés pétrophysiques (porosité, perméabilité, saturation en eau) à partir des méthodes géophysiques. Parmi ces méthodes couramment utilisées, les méthodes acoustique et électrique sont bien adaptées car il existe, à priori, un lien étroit entre les hétérogénéités et les propriétés mesurées.Les travaux de recherche menés dans le cadre de cette thèse s'appuient ainsi sur une approche multi-géophysique permettant de mieux caractériser un réservoir carbonaté complexe en se basant notamment sur une analyse pétrophysique combinée à une description microstructurale fine.Dans ce travail, nous avons démontré l'influence de la microstructure sur la prédiction et la modélisation des propriétés pétroacoustiques ce qui conduit à une bonne discrimination de certains faciès, utile pour améliorer les modèles de simulation d'écoulements. De plus, ce travail a aussi permis de montrer la pertinence de la conductivité complexe dans la caractérisation des calcaires et la prédiction de leur perméabilité. Cependant, des développements supplémentaires sont nécessaires concernant la problématique du changement d'échelles des réservoirs complexes et hétérogènes<br>In a context of global changes and ecological and energy transitions, climate change induces recurrent drought and water resource crisis in several regions and continents. It is crucial to study groundwaters in order to support these transitions and ensure effective management and use of this vital resource. In particular, the vadose zone which plays an important role in the recharge of these groundwaters and the transfer of possible pollutants and inputs. Most of the time this unsaturated zone is characterized by multi-scale heterogeneities (e.g., pore structure, fractures, mineralogical variation) particularly in a limestone environment. These heterogeneities are complexified by diagenetic processes linked mainly to physicochemical and mineralogical alteration which leads to uncertainty in reservoir property (e.g., porosity, permeability, water saturation) estimation from geophysical methods. Among these methods, acoustic and electrical methods are well suited because of the strong relation between heterogeneities and the measured properties.This thesis relies on a multi-geophysical approach in order to better characterize a complex carbonate reservoir using petrophysical measurements combined with microstructural descriptions. Based on this approach, we demonstrated the influence of rock structure on the prediction and modeling of petroacoustic properties. This work leads to a good discrimination of some facies, which can be used to improve simulation and flow models. In addition, we demonstrate the relevance of complex conductivity measurements in limestone characterization and permeability prediction. However, additional developments are needed to understand the upscaling problematic for heterogeneous and complex reservoirs

With the advent of high-throughput technology there has been a large increase in the availability of biological data, such as interaction data of genes, proteins and metabolites. It is therefore necessary to develop ways in which these data can be efficiently modelled and analysed. Networks over a natural modelling framework for complex biological systems and as such, network theory and related computational approaches have proven important in bioinformatics. A particular facet of network theory that has been employed to analyse biological networks is community structure detection. Community structure is a modular network topology where communities are defined as groups nodes with dense intra-community connections and less dense inter-community connections. Methods to uncover such communities in complex biological networks have the potential to contribute towards a better understanding of the underlying organisation of a system. Consequently, this thesis focuses on the development of a series of mathematical programming models to address various manifestations of the community structure detection problem. The aim is to produce more information-rich models that can accurately represent the features of biological systems; with weighted and unweighted interactions, disjoint and overlapping communities and network dynamics all being considered. First, the detection of disjoint communities in unweighted networks is approached through a two-stage procedure, known as iMod. A mixed integer nonlinear programming (MINLP) model optimises modularity to find an initial partition which is then improved by iteratively solving a mixed integer quadratic programming (MIQP) model. A comparative analysis shows that iMod finds globally optimal solutions for networks of up to 512 nodes and outperforms all other methods tested when applied to larger networks. Subsequently, the MINLP model is generalised to weighted networks, known accordingly as WeiMod. Competitive results are found when WeiMod is compared with several other well known methods from the literature. Next, the work on disjoint community structure is extended to _nd overlapping modules. An MINLP model, known as OverMod, transforms disjoint to overlapping communities through the optimisation of the community strength metric. OverMod is compared with similar methods from the literature and is further assessed on protein-protein interaction (PPI) networks to test the method's ability to extract meaningful biological results. It is shown that proteins assigned to more than one module exhibit topological and functional properties indicative of their strategically important role in the organisation of the PPI networks. The work on disjoint and overlapping community structure concludes with the investigation of a network generated from sequence, protein interaction and co-expression data, for the fungal pathogen, Fusarium graminearum. The functional coherence of communities, properties of multiclustered genes and aspects of virulence-associated genes are all explored in an attempt to link topological and functional features. Finally, the concept of community structure in dynamic networks is explored. Consensus clustering is tackled; de_ned as detecting a single partition of a dynamic network that is relevant across multiple snapshots. This is addressed by extending the previously proposed MIQP and MINLP models such that average modularity across network snapshots is now optimised. A comparison is made with a similar method from the literature showing that the proposed approaches achieve competitive results for small to medium sized networks. Overall, this thesis demonstrates that the exible nature of mathematical programming lends itself well to developing versatile solution procedures for community structure detection. The method evaluations show the proposed algorithms to be comparable to other approaches from the literature and able to detect meaningful results in biological applications. Finally, the methods described in this thesis have the potential to infer important topological-functional relationships and help to provide insight into the organisation and evolution of biological systems.

This is a historic structure report for the C-47 Nike missile launch site in Wheeler, Indiana. This report provides a description, condition assessment, and recommendation for restoration of the site since it has sustained damage from weather, fire, and vandals. The site is listed on the State Register and National Register of Historic Places and the Nike Preservation Group desires to turn the site into a Cold War museum and memorial.A history of the Cold War and development of the Nike missile systems and C-47 site provides the background of the project. Each structure and feature is described and the condition recorded. Recommendations for treatment and maintenance are provided. Suggestions are made for a phased restoration of the site to accommodate a Cold War museum. Since it is recommended the site be open to the public, issues regarding public health, safety, security, and handicap accessibility are addressed. This project does not provide a full management and preservation plan, measured HABS/HAER drawings, or a structural analysis.<br>Department of Architecture

We investigate global pattern-switching effects in 2D cellular solids in which the voids are arranged in a square lattice. Uniaxial compression of these structures triggers an elastic instability which brings about a period-doubling transformation of the void shapes at a critical strain. Specifically, a square array of circular voids forms a pattern of mutually orthogonal ellipses and a similar effect is observed for diamond-shaped voids. The onset of instability is governed by the void fraction and size-effects are found for the experimental samples. We establish empirical laws which characterise the stiffness, strength and stability of cellular structures comprising square arrays of circular voids. A comparison of these with predictions from a discrete model implies underestimation of the resistance of the lattice to buckling, although the size effects are replicated. We find similar pattern-switching effects in the cubic lattice, which is a three-dimensional porous cube. The effect of buckling in this system is to produce a 2D pattern in one plane of voids. In two-phase granular crystals, rearrangement of a square lattice of particles results in a new, period-doubled, structural pattern. This switch can occur via an intermediate phase depending on the size ratio of the particles as shown in experiments and numerical simulations.

In this thesis we study the problem of determining the possible cobordism types of r-fold self-intersection manifolds associated to self-transverse immersions f: M^{n-k} -> \R^n for certain values of n, k, and r. Namely, we study the double-point self-intersection manifolds of immersions M^{n+2} -> \R^{2n+2} and M^{n+4} -> \R^{2n+4}, focusing on the case when $n$ is even. In the case of self-transverse immersions f : M^{n+2} -> \R^{2n+2}, we see that when n is even the double-point self-intersection manifold is a boundary, which is a result originally due to Szucs. In the case of self-transverse immersions f : M^{n+4} -> \R^{2n+4}, we show than when n is even the double-point self-intersection manifold is either a boundary or cobordant to RP^2 x RP^2, which is a new result. We then show that for even n such that the binary expansion of n+4 contains 5 or more 1s, the double-point self-intersection manifold of a self-transverse immersion M^{n+4} -> \R^{2n+4} is necessarily a boundary. We also survey the case when n is odd. We also set up and study the complex versions of the above problems: self-transverse immersions f : M^{2k+2} -> \R^{4k+2} and f : M^{2k+4} -> \R^{4k+4} of stably complex manifolds with a given complex structure on the normal bundle of f$. In these cases, the double-point self-intersection manifold L associated to the immersion inherits a stably complex structure, and we attempt to determine which complex cobordism classes of stably complex manifolds may arise in this way. This is all new work. In the case of self-transverse complex immersions f : M^{2k+2} -> \R^{4k+2}, we show that the first normal Chern number of the double-point self-intersection manifold is a multiple of 2^{\lambda_{k+1}} for some integer \lambda_{k+1}, and provide upper and lower bounds for the value of \lambda_{k+1}. We also determine the exact value of \lambda_{k+1} in certain cases. In the case of self-transverse complex immersions f : M^{2k+4} -> \R^{4k+4}, we identify a large class of stably complex manifolds that may arise as the double-point self-intersection manifold of such an immersion and also identify a class of manifolds that may not. Additionally, in both cases we identify a necessary (and sometimes sufficient) condition for a stably complex manifold of the appropriate dimension to admit a complex immersion of the appropriate codimension.

Earth-abundant first-row transition metals have seen a renaissance in chemistry in recent years due to their relatively low toxicity and cost in comparison to precious metals. Furthermore open-shell transition metal complexes exhibit useful one-electron redox processes which contrasts to their heavier d block anologues. This thesis aims to synthesize and analyse the structure and reactivity of low-coordiante first-row transition metal complexes of from groups 7-9 with an aim to utilize these species in catalysis. The divalent compound [Co{N(SiMe3)2}2] reacts with the primary phosphines PhPH2 in the presence of an NHC ligand (IMe4) to yield the phosphinidene bridged dimer [(IMe4)2Co(µ-PMes)]2. The complex has interesting magnetic properties due to strong antiferromagnetic coupling between the two cobalt(II) centres. Increasing the steric bulk of the NHC yielded carbene-phosphinidene adducts (NHC·PAr). This transformation was shown to be catalytic. The structure and reactivity of complexes of the type [(NHC)xMn{(N(SiMe3)2}2] were investigated. The complexes exhibit similar structural properties to their iron and cobalt analogues; however their reactivity has been shown to differ. The addition of primary phosphines to complexes of the type [(NHC)xMn{N(SiMe3)2}2] yielded a range of manganese phosphide complexes. [Mn{N(SiMe3)2}2] also reacts with imidazolium salts at elevated temperatures to yield heteroleptic manganese NHC complexes. The reaction of [Mn{N(SiMe3)2}2] with IPr·HCl afforded the abnormal carbene complex [(aIPr)Mn{N(SiMe3)2}µ-Cl]2. A new monoanionic bidentate ligand is reported which has shown to be a useful ligand system to stabilize three-coordiante iron(II) complex. The reaction of [(L)Fe(Br)] with mesitylmagnesium Grignard or n-butyllithium yield the iron hydrocarbyls [(L)Fe(Mes)] and [(L)Fe(nBu)] with the latter being stable to β-hydrogen elimination. Finally [(L)Fe(nBu)] has been utilized as a pre-catalyst in the hydrophosphination of internal alkynes, showing selectivity for the E-isomeric vinylphosphine.

IgE plays a central role in the pathogenesis of immediate hypersensitivity reactions through interacting with its receptors, in particular the high affinity receptor FcεRI. The low-affinity IgE receptor, CD23, affects IgE-dependent immune responses by regulating the synthesis of IgE, facilitating allergen presentation to the immune system, and influencing the activation and differentiation of B- and T-cells. Surprisingly, CD23 is different from other Ig receptors and belongs to the C-type (calcium-dependent) lectin family. Calcium binding to CD23 affects IgE binding to CD23, but previous NMR and crystal structures of CD23 gave conflicting results concerning the calcium binding sites. Investigation of calcium binding site(s) in CD23 and its complexes may assist CD23- targeted drug design. DerCD23 (a fragment of human CD23 that consists of the lectin domain and part of the C-terminal tail) and derCD23 mutants designed to remove each of the two potential calcium binding sites, were expressed and purified. The crystal structures of Ca2+-bound wild type derCD23, the complex with the Fcε3-4 sub-fragment of IgE-Fc, and four putative calcium binding site mutants of derCD23 were solved. Binding affinities of derCD23 and its mutants for calcium and for IgE-Fc were measured with ITC and SPR. The results indicate a loop of derCD23 (loop 4) is stabilized upon calcium binding to “site 2” and thereby contributes to the increased binding affinity for IgE. In addition, a residue (D258) in the non-conserved “site 1” is observed to bind IgE directly in the Ca2+-bound derCD23/Fcε3-4 complex. Thus, Ca2+ bound to site 2 in CD23 stabilizes loop 4 for IgE binding, whereas site 1 has evolved to bind IgE directly. Clinical studies of IDEC152 (also known as Lumiliximab), a primatized IgG1, anti- CD23 monoclonal antibody (IDEC Pharmaceuticals, San Diego, CA) show positive clinical effects in patients with allergic asthma and chronic lymphocytic leukemia. The Fab fragment of IDEC152 was prepared by enzymatic digestion from IDEC152 and crystals of the complex of derCD23 with IDEC152-Fab were grown, which diffracted to 2.4 Å resolution.

Chemistry of the early actinides has undergone a lot of developments in recent years, and due to the need of specialised laboratories to handle these often highly radioactive complexes, computational chemistry has become a powerful aid in understanding the physical properties of these unique systems. This thesis describes a systematic computational study of organoactinide and organometallic model complexes of the form [LAnX]n+ where L is the macrocyclic trans- calix[2]benzene[2]pyrrolide ligand using density functional theory (DFT) in conjunction with a variety of partition-based methods – Mulliken populations analysis (MPA), Hirshfield population analysis (HPA), natural population analysis (NPA) and the quantum theory of atoms in molecules (QTAIM) – with the aim of probing the electronic structure of the An-X and An-arene bonds as a function of the X ligand. Natural bond orbital (NBO) analysis was also used to study the nature of the An-X bonds, with these results compared to the QTAIM descriptions of covalency and ionicity in the [LAnX]n+ complexes. Analogous transition metal complexes of the form [LMX]n+ (M = Hf, W) have also been studied with the QTAIM and NBO approaches to compare with the actinide-based systems. Nucleus independent chemical shift (NICS) analysis was carried out to probe the extent of aromaticity of the arene rings of the L2- ligand in the closed-shell [LThX]+ complexes as a function of X ligand, and was compared with QTAIM measurements of aromaticity. The MPA also revealed Î ́-bonding to the arene rings of the L2- ligand and was compared to the NICS data. Bond energies and bond energy decomposition analysis (EDA) of An-X were further analysed and compared to the QTAIM data. These same analyses were carried out on complexes where the X-type ligand series was extended to include a larger set of first and second-row p-block based ligands. Finally, other, bi-metallic actinide-based complexes including the L2-/4- ligand were studied with the aim of understanding the thermal stabilities of these experimentally-characterised complexes, with analogous model complexes modelled to find potential synthetic targets. The Kohn-Sham molecular orbitals (KS-MOs) of some of these complexes were also analysed to try and find a rationale, based on their electronic structure, for the energetic preference for one binding mode of L-An over another.

The new ligand L1 [2-[(E)-2,6-diisopropylphenyl-phenyimino]-2H-acenaphthylen-(1E)-ylidene]-(2,4,6-trimethyl-phenyl)-amine was prepared by stepwise addition of 2,6-diisopropylaniline and 2,4,6 trimethylaniline to acenaphthenequinone. The L1NiBr2 complex crystallized as a pseudo tetrahedral monomer, as determined by single crystal X-ray diffraction. This new catalyst L1NiBr2 and 3 related catalysts, bis(2,6-diisopropylphenyl)acenaphthenediimineNiBr2 (L2NiBr2), [(N,N'-bis-(2,6-diisopropylphenyl)-phenanthrene-9,10-diylidendiamineNi-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} [(L3Ni-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and N-(2,6-diisopropylphenyl)-N'-(2,4,6-trimethylphenyl)-phenanthrene-9,10-diylidenediamineNiBr2 (L4NiBr2) were tested for activity in ethylene polymerization. The super-bulky α-diimine nickel catalysts [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and L4NiBr2 successfully produced higher molecular weight polyethylene with a high level of linearity compared to the less bulky α-diimine nickel catalysts (L1NiBr2 and L2NiBr2). The super bulky α-diimine backbone helped to compress the reaction space and therefore impede the ethylene insertion to active centre of the catalyst. For this reason, the catalyst activity for super- bulky backbone ligands (L3 and L4) is lower than for their analogous less-bulky backbone ligands (L1 and L2). In general, for both backbones, the nickel catalysts with all-isopropyl substituents produced higher molecular weight polyethylene with less linearity compared to the nickel catalysts with methyl substituents. Moreover, for the acenaphthene backbone, the nickel catalysts with all isopropyl substituents (L2NiBr2) got a higher activity compared to the nickel catalysts with methyl substituents (L1NiBr2). A similar catalyst activity trend was not observed for phenanthrene backboned catalysts. In contrast, L4NiBr2 showed a higher activity compared to [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} For all catalysts, the majority of branches, as characterized by 13C nuclear magnetic resonance, were methyl branches. Polymers with a high level of branches showed a sharp intensity in the loss modulus measured by dynamic mechanical analysis due to a high level of interfacial chains. A reduction in catalyst activity was observed with all nickel catalysts when supported on silica. However, supporting nickel catalysts helps to improve the linearity of the polymer. The same ligands L3 and L4 were used with palladium and successfully produced two new catalysts [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} and [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-. Catalyst [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} was more active and produced higher molecular weight and less branched polymer than catalyst [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} in the polymerization of ethylene.

Five ansa-tris(allyl) complexes [(PhSi{C3H3(SiMe3)}3)(Li?tmeda)3] (2.1), [(MeSi{C3H3(SiMe3)}3)(Li?pmdeta)3] (2.2), [(MeSi{C3H3(SiMe3)}3)-(Na.tmeda)3] (2.3), [(PhSi{C3H3(SiMe3)}3)(Na?tmeda)2Na]2 [2.4]2 and [(MeSi-{C3H3(SiMe3)}3)(K?OEt2)2(KLi{OtBu})]2 [2.5]2 have been synthesised, and studied by X-ray crystallography and NMR spectroscopy. A collaboration was undertaken to study some of the complexes by DFT. Crystallographic studies have shown that the overall structure of the complex is dependent on a combination of several factors: the metal cation; the substituent on the central silicon atom for the ansa-tris(allyl) ligands; and the co-ligand, tmeda or pmdeta. (tmeda = N,N,N?,N?¬-tetramethylethylenediamine and pmdeta = N,N,N?,N?,N??-pentamethyldiethylene-triamine). Solution studies of the ansa-tris(allyl) complexes showed that the solid-state structures are maintained in solution. The first examples of donor-functionalised allyl pro-ligands have been synthesised and coordinated to a variety of s-block metals; [Li{(SiMe3)2C3H2(1-CH2C4H7O)}]2 [4.1]2, [Li{(SiMe3)2C3H2(1-CH2CH2OCH3)}]2 [4.2]2, [(thf)K{(SiMe3)2C3H2(1-CH2C4H7O)}]2 [4.5]? and [Mg{(SiMe3)2C3H2(1-CH2C4H7O)}2] (4.6). As with the ansa-tris(allyl) complexes, both X-ray crystallographic and NMR spectroscopy studies have been undertaken, and the structures of the donor-functionalised allyl complexes were found to be dependent on the metal cation, with each cation coordinated in a different manner by the allyl ligand. For the potassium allyl complex 4.5 there is complete delocalisation of the allyl negative charge, and it is ?3-coordinated in a polymeric structure. However for lithium complexes, [4.1]2 and [4.2]2, the donor-functionalised allyl ligand is ?2-coordinated, and the negative charge is only partially delocalised. The magnesium complex 4.6 has the allyl ligand coordinated via a ?-bond to the metal and the allyl has localised single and double bonds.Finally, the synthesis of the first two donor-functionalised pentadienyl ligands and their lithium complexes are reported. Complexes [(tmeda)Li{1,5-(SiMe3)2C5H4(CH2C4H7O)}] (6.1) and [(tmeda)Li{1,5-(SiMe3)2C5H4(CH2CH2OCH3)}] (6.2) are the first structurally characterised lithium pentadienyl complexes, and are the first donor-functionalised pentadienyl complex of any metal. As well as structural characterisation, complexes 6.1 and 6.2 have been investigated by NMR spectroscopy and collaborative DFT studies. X-ray crystallography revealed that both complexes have the W-conformation of the pentadienyl ligand ?2-coordinated to the lithium cation, as well as the ether oxygen atom and the tmeda nitrogen atoms. DFT studies showed that the most stable gas-phase structure of the 1,5-bis(trimethylsilyl)-pentadienyl anion is the W-conformation, but its lithium complex is most stable in the U-conformation. The [Li{1,5-(SiMe3)2C5H4(CH2CH2OCH3)}]? anion has the W-conformation and the U-conformation is isoenergetic, but the addition of tmeda gives the W-conformation as the most stable in both the gas-phase and in toluene. Finally NMR spectroscopy studies showed that in solution complexes 6.1 and 6.2 are either in the symmetrical U-conformation or in fluxional process with a very low activation energy.