ALBERT

Description: Hysteresis in the capillary pressure-saturation relationship (Pc–Sw) for a porous medium has contributions from the complex geometry of the pore network as well as the physical chemistry of the grain surfaces. To isolate the role of wettability on hysteresis, we fabricated microfluidic cells that contain a single wedge-shaped channel that simulates a single pore throat. Using confocal microscopy of the three-dimensional interfaces under imbibition and drainage, we demonstrate an accurate balance between mechanical work and surface free energy that was evaluated using measured advancing and receding contact angles. The closed-loop mechanical work per surface water molecule is 95 kJ/mol, which is consistent with physisorption. Therefore, the hysteresis in the Pc–Sw relationship for a single pore throat is defined by advancing and receding contact angles that are controlled by dissipative surface adsorption chemistry.

Description: Intersections in a fracture network control the connectivity of the flow paths through rock. The long near-linear geometric nature of fractures makes them difficult to identify and characterized. We present a new type of elastic wave, an intersection wave, which travels along an intersection and is sensitive to the coupling between two orthogonal fractures that define the intersection. Group theory for C 2 v and C 4 v point groups predict sets of propagating elastic waves confined to the fracture intersection. Along with the use of the wave equation and displacement discontinuity boundary conditions, the dispersion relationships for intersection waves were predicted. Experimental ultrasonic measurements on a non-welded linear intersection between two orthogonal, synthetic fractures in aluminum confirm the existence of multiple modes that travel between the speed of wedge waves (sub-Rayleigh waves) when the intersection is completely open or decoupled, and bulk shear waves, when the intersection is closed, as predicted by theory. In between these two limits, the intersection behaves as a non-welded contact and yields these new intersection waves that are dispersive and sensitive to the coupling along the intersection. Intersection waves provide the foundation for new geophysical approaches for characterizing the hydraulic connectivity of fracture networks.

Description: [1]  Seismic characterization of fluid flow through fractures requires a fundamental understanding of the relationship between the hydraulic and mechanical properties of fractures. A finite-size scaling analysis was performed on fractures with weakly correlated random aperture distributions to determine the fundamental scaling relationship between fracture stiffness and fracture fluid flow. From computer simulations, the dynamic transport exponent, which provides the power law dependence, was extracted and used to collapse the flow-stiffness relationships from multiple scales into a single scaling function. Fracture specific stiffness was determined to be a surrogate for void area that is traditionally used in percolation studies. The flow-stiffness scaling function displays two exponentially decaying regions above and below the transition into the critical regime where the hydromechanical properties become scale dependent. The transition is governed by the stressed flow paths when the flow path geometry deforms from a sheet-like topology to a string-like topology. The resulting hydro-mechanical scaling function provides a link between fluid flow and the seismic response of a fracture.

Description: Abstract Fracture pattern development has been a challenging area of research in the earth sciences for more than 100 years. Much has been learned about the spatial and temporal complexity inherent to these systems but severe challenges remain. Future advances will require new approaches. Chemical processes play a larger role in opening‐mode fracture pattern development than has hitherto been appreciated. This review examines relationships between mechanical and geochemical processes that influence the fracture patterns recorded in natural settings. For fractures formed in diagenetic settings (ca. 50 to 200 °C), we review evidence of chemical reactions in fractures and show how a chemical perspective helps solve problems in fracture analysis. We also outline impediments to subsurface pattern measurement and interpretation, assess implications of discoveries in fracture history reconstruction for process‐based models, review models of fracture cementation and chemically assisted fracture growth, and discuss promising paths for future work. To accurately predict the mechanical and fluid‐flow properties of fracture systems, a processes‐based approach is needed. Progress is possible using observational, experimental, and modeling approaches that view fracture patterns and properties as the result of coupled mechanical and chemical processes. A critical area is reconstructing patterns through time. Such datasets are essential for developing and testing predictive models. Other topics that need work include models of crystal growth and dissolution rates under geological conditions, cement mechanical effects, and subcritical crack propagation. Advances in machine learning and 3D imaging present opportunities for a mechanistic understanding of fracture formation and development, enabling prediction of spatial and temporal complexity over geologic timescales. Geophysical research with a chemical perspective is needed to correctly identify and interpret fractures from geophysical measurements during site characterization and monitoring of subsurface engineering activities.

Description: The synthesis, crystal structure, photophysical properties, and biological activity of the novel bis-cyclometalated complexes [Ir(ptpy) 2 (vnsc)] ( 2 ) and [Ir(ptpy) 2 (acsc)] ( 3 ) [ptpy = 2-( p -tolyl)pyridinato, vnsc = vanillin semicarbazone, acsc = acetone semicarbazone] are described. The new compounds were prepared by the reaction of [{Ir(μ-Cl)(ptpy) 2 } 2 ] ( 1 ) with the corresponding semicarbazone ligands under basic conditions. The molecular structure of compound 3 was confirmed by a single-crystal X-ray diffraction study. The complex crystallized from chloroform as a mono- solvate in the orthorhombic space group Pcab with eight molecules in the unit cell.

Description: A model formulated in terms of both conservation and kinematic equations for phases and interfaces in two-fluid-phase flow in a porous medium system is summarized. Macroscale kinematic equations are derived as extensions of averaging theorems and do not rely on conservation principles. Models based on both conservation and kinematic equations can describe multiphase flow with varying fidelity. When only phase-based equations are considered, a model similar in form to the traditional model for two-fluid-phase flow results. When interface conservation and kinematic equations are also included, a novel formulation results that naturally includes evolution equations that express dynamic changes in fluid saturations, pressures, the capillary pressure, and the fluid-fluid interfacial area density in a two-fluid-system. This dynamic equation set is unique to this work, and the importance of the modeled physics is shown through both microfluidic experiments and high-resolution lattice Boltzmann simulations. The validation work shows that the relaxation of interface distribution and shape toward an equilibrium state is a slow process relative to the time scale typically allowed for a system to approach an apparent equilibrium state based upon observations of fluid saturations and external pressure measurements. Consequently, most pressure-saturation data intended to denote an equilibrium state is likely a sampling from a dynamic system undergoing changes of interfacial curvatures that are not typically monitored. The results confirm the importance of kinematic analysis in combination with conservation equations for faithful modeling of system physics. This article is protected by copyright. All rights reserved.

Description: Nanostructuring of phthalocyanine-based materials is a powerful tool towards the preparation of new materials with outstanding properties. It has been previously shown that porphyrin-functionalized and phthalocyanine-functionalized polymers give rise to nanosized aggregates. With the goal in mind of searching new phthalocyanine-containing polymeric materials that are able to self-organize into stable supramolecular nanostructures, we have prepared unsymmetrically functionalized Zn(II) phthalocyanines that are able to behave as initiators in the atom transfer radical polymerization of styrene. Hybrid phthalocyanine–polystyrene materials of different tail lengths have been prepared, and their self-organization behavior was studied by means of UV–Vis spectroscopy and transmission electron microscopy. Copyright © 2012 John Wiley & Sons, Ltd. Polymerization of styrene by ATRP using a series of Zn(II) phthalocyanine initiators proceeds in a controlled fashion and yields well-defined Zn(II)Pc-polystyrene hybrids with low polydispersities which form well-organized nanoarchitectures.

Description: Nanostructuring of phthalocyanine-based materials is a powerful tool towards the preparation of new materials with outstanding properties. It has been previously shown that porphyrin-functionalized and phthalocyanine-functionalized polymers give rise to nanosized aggregates. With the goal in mind of searching new phthalocyanine-containing polymeric materials that are able to self-organize into stable supramolecular nanostructures, we have prepared unsymmetrically functionalized Zn(II) phthalocyanines that are able to behave as initiators in the atom transfer radical polymerization of styrene. Hybrid phthalocyanine–polystyrene materials of different tail lengths have been prepared, and their self-organization behavior was studied by means of UV–Vis spectroscopy and transmission electron microscopy. Copyright © 2012 John Wiley & Sons, Ltd. Polymerization of styrene by ATRP using a series of Zn(II) phthalocyanine initiators proceeds in a controlled fashion and yields well-defined Zn(II)Pc-polystyrene hybrids with low polydispersities which form well-organized nanoarchitectures.

Description: Slow crystallisation at lowered temperature yielded crystals of the “third-generation” tris (pyrazolyl)borate transfer agent p -BrC 6 H 4 TpCs (Tp′Cs) 1 (triclinic; P ; a = 8.540(4), b = 15.045(6), c = 15.879(7) Å; α = 65.853(8), β = 88.457(8), γ = 75.056(8)°; V = 1791.4(13) Å 3 ; Z = 4). The central caesium ion in 1 interacts with three individual p -BrC 6 H 4 Tp ligands in two different chelating fashions.In particular, κ 1 - N -coordination and η 5 -π-coordination of pyrazole moieties as well as η 6 -π-coordination of the p -BrC 6 H 4 substituent are observed. Further, comparable coordination of neighbouring caesium ions leads to the formation of polymeric structures connected by two bridging modes.