Debris flow modeling: A review

A debris flow represents a mixture of sediment particles of various sizes and water flowing down a confined, channel-shaped region (e.g., gully, ravine or valley) down to its end, at which point it becomes unconfined and spreads out into a fan-shaped mass. This review begins with a survey of the literature on the physical-mathematical modeling of debris flows. Next, we discuss the basic aspects of their phenomenology, such as dilatancy, internal friction, fluidization, and particle segregation. The basic characterization of a debris flow as a mixture motivates the application of the continuum thermodynamical theory of mixtures to formulate a model for a debris flow as a viscous fluid-granular solid mixture. A major advantage of such a formulation, which goes beyond the most general models in the literature, e.g., Takahashi (1991), is that it can be used to expose and better understand the assumptions underlying existing models, as well as to derive new, more sophisticated models. Finally, we delve into the issue of how such models have been or can be implemented numerically, as well as general boundary conditions for debris flows.Dedicated to Professor Reint de Boer upon the occasion of his 60^th birthday     

Mutual stabilisation between MII 4L6 tetrahedra and MIIX4 2– metallate guests

A complex host–guest equilibrium employing metal ions incorporated into both the host and guest is discussed. M^IIX₄ ^2– metallate guests are shown to provide a good size and shape match for encapsulation within the M₄L₆ tetrahedral capsules, facilitating the generation of previously unreported Zn₄L₆ complexes. Displacement of the initial, primary template anion (ZnBr₄ ^2–) by a secondary template anion (ClO₄ ^–) is shown to result in the formation of a pentagonal-prismatic Zn₁₀L₁₅ structure that incorporates both Br^– and ClO₄ ^–. Furthermore, the formation of heterometallic complexes provides direct evidence for metal exchange between the guest and host complex.     

Optimization and Evaluation of 5-Styryl-Oxathiazol-2-one Mycobacterium tuberculosis Proteasome Inhibitors as Potential Antitubercular Agents

This is the first report of 5-styryl-oxathiazol-2-ones as inhibitors of the Mycobacterium tuberculosis (Mtb) proteasome. As part of the study, the structure–activity relationship of oxathiazolones as Mtb proteasome inhibitors has been investigated. Furthermore, the prepared compounds displayed a good selectivity profile for Mtb compared to the human proteasome. The 5-styryl-oxathiazol-2-one inhibitors identified showed little activity against replicating Mtb, but were rapidly bactericidal against nonreplicating bacteria. (E)-5-(4-Chlorostyryl)-1,3,4-oxathiazol-2-one) was most effective, reducing the colony-forming units (CFU)/mL below the detection limit in only seven days at all concentrations tested. The results suggest that this new class of Mtb proteasome inhibitors has the potential to be further developed into novel antitubercular agents for synergistic combination therapies with existing drugs.     

Designed Enclosure Enables Guest Binding Within the 4200 Å3 Cavity of a Self‐Assembled Cube

Metal–organic self‐assembly has proven to be of great use in constructing structures of increasing size and intricacy, but the largest assemblies lack the functions associated with the ability to bind guests. Here we demonstrate the self‐assembly of two simple organic molecules with Cd^II and Pt^II into a giant heterometallic supramolecular cube which is capable of binding a variety of mono‐ and dianionic guests within an enclosed cavity greater than 4200 ų. Its structure was established by X‐ray crystallography and cryogenic transmission electron microscopy. This cube is the largest discrete abiological assembly that has been observed to bind guests in solution; cavity enclosure and coulombic effects appear to be crucial drivers of host–guest chemistry at this scale. The degree of cavity occupancy, however, appears less important: the largest guest studied, bound the most weakly, occupying only 11 % of the host cavity.     

Nanosized iron and chromium oxides supported on mesoporous CeO2 and SBA-15 silica: Physicochemical and catalytic study

Mesoporous ceria and SBA-15 silica were modified with iron and chromium oxide nanoparticles and characterized by XRD, N₂-physisorption, FTIR, UV-vis, Moessbauer spectroscopy and TPR-TG in hydrogen. Their catalytic behaviour in methanol decomposition to CO and hydrogen was also studied. Stabilization of mono- and bi-chromate species, FeO_x patches or isolated iron ions as well as Fe₂O₃ and Cr₂O₃ nanoparticles in different ratio depending on the nature of the porous matrix was observed. The simultaneous presence of iron and chromium oxides lead to change in their dispersion, providing easier reducibility, higher catalytic activity and stability of the obtained materials in comparison with the corresponding mono-component ones. The “intimate contact” at the interface of both loaded metal oxide nanoparticles and the support was discussed with respect to explain the differences in the state of the active ingredient and its specific catalytic behaviour.     

Experimental pool boiling investigations of FC-72 on silicon with artificial cavities and integrated temperature microsensors

In this experimental study, fluorinert FC-72 is boiled on a silicon chip with artificial cavities and integrated microsensors. The horizontal silicon chip with dimensions of 39.5 × 19 × 0.38 mm is completely immersed in FC-72. The integrated nickel–titanium temperature microsensors on the back of the chip are calibrated individually and exhibit a near-linear increase of electrical resistance with temperature. The applied heat fluxes and the resulting wall superheat at the boiling surface are varied by means of an integral thin-film resistance heater (95% Al, 4% Cu and 1% Si), also on the back of the silicon chip. Artificial cylindrical cavities with a mouth diameter of 10 μm and depths of 40, 80 or 100 μm situated above the microthermometers serve as artificial nucleation sites, due to trapped vapour. Bubble growth rates, frequencies, departure diameters of bubbles and waiting times between bubbles from an isolated cavity for different wall superheats and pressures were obtained by analysing high-speed video images and the simultaneously measured temperature below the artificial cavity.     

The structures of four new himbacine-like Galbulimima alkaloids

The structures of four new alkaloids isolated from the bark of the rain forest trees Galbulimima belgraveana and Galbulimima baccata have been determined by a combination of NMR spectra and single crystal X-ray crystallography. Two of the alkaloids are simple oxygenated derivatives of himbacine, while the remaining two are based on a novel 7,19-cyclo-himbacine skeleton.