Solvation processes in steam: Ab initio calculations of ion-solvent structures and clustering equilibria

Reports of the high ion content of steam and low-density supercritical fluids date back to the work of Carlon [Carlon H. R. (1980) Ion content of air humidified by boiling water.J. Appl.Phys.51, 171-173], who invoked ion and neutral-water clustering as mechanism to explain why ions partition into the low-density aqueous phase. Mass spectrometric, vibrational spectroscopic measurements and quantum chemical calculations have refined this concept by proposing strongly bound ion-solvent aggregates and water clusters such as Eigen- and Zundel-type proton clusters H₃O⁺·(H₂O)_m and the more weakly bound water oligomers (H₂O)_m. The extent to which these clusters affect fluid chemistry is determined by their abundance, however, little is known regarding the stability of such moieties in natural low-density high-temperature fluids. Here we report results from quantum chemical calculations using chemical-accuracy multi-level G3 (Curtiss-Pople) and CBS-Q theory (Peterson) to address this question. In particular, we have investigated the cluster structures and clustering equilibria for the ions and H₃S⁺·(H₂O)_m(H₂S)_n, where m ? 6 and n ? 4, at 300-1000 K and 1 bar as well as under vapor-liquid equilibrium conditions between 300 and 646 K. We find that incremental hydration enthalpies and entropies derived from van’t Hoff analyses for the attachment of H₂O and H₂S onto H₃O⁺, and H₃S⁺ are in excellent agreement with experimental values and that the addition of water to all three ions is energetically more favorable than solvation by H₂S. As clusters grow in size, the energetic trends of cluster hydration begin to reflect those for bulk H₂O liquids, i.e. calculated hydration enthalpies and entropies approach values characteristic of the condensation of bulk water (ΔH^o = −44.0 kJ mol⁻¹, ΔS^o = −118.8 J K mol⁻¹). Water and hydrogen sulfide cluster calculations at higher temperatures indicate that a significant fraction of H₃O⁺, and H₃S⁺ ions exists as solvated moieties.     

Climate and material controls on periglacial soil processes: Toward improving periglacial climate indicators

One of the distinguished efforts of A.L. Washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators. This paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies, with a focus on solifluction and thermal contraction cracking and associated landforms/structures. Landforms resulting from solifluction reflect both the depth subjected to freeze-thaw and the thickness of frost-susceptible soils. The thickness of a solifluction structure can be used to infer the dominant freeze-thaw regime and minimum seasonal frost depth. Ice-wedge pseudomorphs have limited potential as a climate indicator because (1) they mainly reflect extreme winter temperatures, (2) their thermal thresholds depend on the host material, and (3) they need to be distinguished from frost wedges of other origin produced under different thermal and/or material conditions. Monitoring studies of currently active ice wedges suggest that ice-wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer. Further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed, however, to improve the resolution of periglacial paleoclimate indicators.     

Microstructural interpretations of modern and Pleistocene subglacially deformed sediments: the relative role of parent material and subglacial processes

Analysis of till micromorphology represents a relatively new technique that has been used most frequently to infer the importance of subglacial shear in till genesis. This study aims to calibrate the technique by comparing Pleistocene tills from United Kingdom with a modern till (the UpB till) from beneath Ice Stream B, West Antarctica. Despite the fact that all of the tills examined have been interpreted as deforming‐bed deposits, the modern till has significantly less abundant and diverse microstructures than those found in the Pleistocene tills. Seventeen examined thin‐sections of the UpB till contain recognisable microstructures over only 0–30% of individual thin‐section area. The most common microstructures are: (i) birefringent clay patterns that are interpreted as shear zones and (ii) adherent matrix structures, which we interpret as uncomminuted remnants of the parent glacial/glaciomarine diamictons. Fourteen thin‐sections of the Pleistocene tills were covered by microstructures in 10–95% of their area. The Pleistocene microstructures include birefringent clays and adherent matrix structures, as in the UpB till, but also laminations and deformed pods made of chalk and sorted sediments. We conclude that the same till‐forming process, i.e. subglacial deformation, may result in distinctly different till micromorphology. This is a consequence of the fact that microstructural characteristics are strongly influenced by factors other than shear deformation. We identify three controls that may be important for forming contrasting microstructural assemblages: (i) strain magnitude, (ii) the degree of heterogeneity of parent material, and (iii) relative importance of sediment sorting by flowing water in the subglacial environment. Thus till micromorphology is sensitive to multiple factors, which with proper calibration may enhance the existing capability to interpret past subglacial conditions from microstructures. Copyright © 2001 John Wiley & Sons, Ltd.     

Tunnel valley deposits from the southern North Sea – material provenance and depositional processes

This study offers new insights into the origin and depositional history of the mixture of sediments infilling one of the largest offshore, northward‐orientated, clinoform‐structured, tunnel valleys (TVs) of Elsterian age in the southern North Sea (SNS). Specifically, the study sheds light on the provenance of TV deposits based on K‐Ar dating of illite, QEMSCAN^® heavy mineral assemblage study, and U‐Pb and fission track dating on single grains of apatite. Early Pleistocene substrate and the TV infill demonstrate provenance from the Scandinavian and Baltic realms as well as from Renish central Europe and the Alps. Prior to Elsterian glaciation fluvial transport to the SNS increasingly switched from Baltic sources to a more central European influence. However, based on similar provenance of both the substrate and TV infill, the episode of subglacial tunnel valley formation interrupted this central European influence. Glacial erosional processes associated with the expansion of the Elsterian ice sheet to the SNS reworked a large amount of sediment from the Early Pleistocene deposits of the SNS. The sediment was eventually deposited as the tunnel valley infill. Taking into account a high uncertainty related to the facies of TV sedimentary infill, which thus far has been inferred from seismic reflection surveys only, this study offers the first comprehensive set of data on the composition and provenance of the offshore Elsterian TV sediment.     

An assessment of the material point method for modelling large scale run-out processes in landslides

This paper demonstrates the predictive capabilities of a numerical model based on continuum mechanics for the simulation of run-out processes during landslides. It assesses a particle-based method that takes advantage of a double Lagrangian-Eulerian discretization and known as the material point method (MPM). Attention is given to the post-failure behaviour and, in particular, to the computation of important quantities such as run-out distance, maximum velocity and energy release. The MPM is a step forward in computational solid mechanics and has the potential to simulate large deformations such as those occurring during landslides. A validation is conducted based on simulations of two case studies of different scales, namely the Tokai-Hokuriku expressway failure in Japan and the Vajont landslide in Italy. The results show a very good agreement with field and other numerical observations.     

The Sea of Azov: Recent abrasion processes and problems of coastal protection

The abrasion processes of the Sea of Azov have been assessed on the basis of long-term monitoring. The coast has been zoned by the degree of abrasion. The current condition of coast protection measures has been studied.     

模糊聚类分析法在油气评价中的应用

文章介绍了模糊聚类分析在石油勘探决策中的应用,选用了烃源岩9个评价参数,利用模糊聚类方法对烃源岩进行分类评价,并对评价过程进行了详细的论述.通过对评价结果与实际地质情况进行比较,评价结果与实际情况完全符合,证明模糊聚类方法用于油气资源评价是完全可靠的.     

Smoothing and re-roughening processes: The geometric evolution of a single fault zone

The geometry of a fault zone exerts a major control on earthquake rupture processes and source parameters. Observations previously compiled from multiple faults suggest that fault surface shape evolves with displacement, but the specific processes driving the evolution of fault geometry within a single fault zone are not well understood. Here, we characterize the deformation history and geometry of an extraordinarily well-exposed fault using maps of cross-sectional exposures constructed with the Structure from Motion photogrammetric method. The La Quinta Fault, located in southern California, experienced at least three phases of deformation. Multiple layers of ultracataclasite formed during the most recent phase. Crosscutting relations between the layers define the evolution of the structures and demonstrate that new layers formed successively during the deformation history. Wear processes such as grain plucking from one layer into a younger layer and truncation of asperities at layer edges indicate that the layers were slip zones and the contacts between them slip surfaces. Slip surfaces that were not reactivated or modified after they were abandoned exhibit self-affine geometry, preserving the fault roughness from different stages of faulting. Roughness varies little between surfaces, except the last slip zone to form in the fault, which is the smoothest. This layer contains a distinct mineral assemblage, indicating that the composition of the fault rock exerts a control on roughness. In contrast, the similar roughness of the older slip zones, which have comparable mineralogy but clearly crosscut one another, suggests that as the fault matured the roughness of the active slip surface stayed approximately constant. Wear processes affected these layers, so for roughness to stay constant the roughening and smoothing effects of fault slip must have been approximately balanced. These observations suggest fault surface evolution occurs by nucleation of new surfaces and wear by competing smoothing and re-roughening processes.     

Selling green militarization: The discursive (re)production of militarized conservation in the Virunga National Park,Democratic Republic of the Congo

In recent years, the militarization of nature conservation has intensified, especially in protected areas located in conflict zones or plagued by ‘poaching crises’. Such ‘green militarization’ is enabled by a range of discursive techniques that allow it to be seen as a ‘normal’ and ‘legitimate’ response. This article analyzes these techniques in relation to the Virunga National Park, located in the war-ridden east of the Democratic Republic of the Congo, where militarized approaches to conservation have a long lineage. It demonstrates that many of the discursive techniques that are currently at play show strong continuities with the past. These include moral boundary-drawing grounded in colonial tropes that accomplish the (racial) Othering of poachers and rebels, and the long-established practice of invoking states of emergency as part of wider mechanisms of securitization. However, the rise of neoliberal conservation, with its emphasis on marketing and marketization, has induced transformations in the employed discursive techniques. Notably, it has intensified the spectacularization of militarized conservation and anchored it in everyday consumer practices, by actively inviting individual supporters to directly fund militarized interventions, thus generating ‘militarization by consumption’. This shows that ‘green militarization’ is not only driven by the growing commodification of nature conservation, but is increasingly subject to commodification itself.     

The sandy channel-lobe depositional systems in the Gulf of Cadiz: Gravity processes forced by contour current processes

The sedimentation in the Gulf of Cadiz (NE Atlantic Ocean) is significantly controlled by the Mediterranean Outflow Water (MOW). Along its pathway onto the continental slope, the MOW is canalized by contourite channels, some of them feeding gravity sandy channel-lobe depositional systems firstly recognized in previous study [Habgood et al., 2003. Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic. Sedimentology 50(3), 483-510.].Using very high resolution acoustic data and cores, a detailed characterization and a new evolution pattern of these channel-lobe depositional systems is established. Complex internal geometry of the lobes shows several depositional units revealing a polyphase evolution of these systems, with a general progradation punctuated by retrogradation and avulsion phases. A gravity origin controlled by contouritic processes and climatic changes is demonstrated for the feeding and the evolution of these sandy channel-lobe depositional systems. Climate oscillations, via the MOW variations, act as a major forcing of the activity of the channel-lobe depositional systems during the Late Quaternary.     

Grounding the virtual: The material effects of electronic grocery shopping

This paper addresses the materiality of computer-mediated retailing. The paper uncovers the “hidden geography” of e-commerce, considering how the seemingly simple act of doorstep food delivery is explicated in urban form, and in transportation and communication infrastructures. The paper categorises electronic grocery shopping (EGS) enterprises into three types: “bricks and clicks”, “pure-play” and the “infomediary”, and examines how each type of operation has been materialised in the urban landscape, and the infrastructure upon which each draws. The paper then considers the strategies EGS operations have used to offset the “killer costs” of logistics for electronic commerce. The paper concludes by considering how electronic grocery shopping is embedded within broader trends in consumer behaviour, and how these trends are manifested in the materiality of urban life. The paper argues that online grocers are in the vanguard of ventures habituating customers to the remote ordering and delayed delivery of products to the home. Through controlling this “last mile”, online retailers hope to extend the product offer to higher-margin and more problematic products, which are in themselves unprofitable to distribute direct to the customer, but which can be profitably combined with a grocery shop.     

The parent material of Sydney laterites

The petrography of laterites in the Sydney district shows that source rocks range from shales—in which quartz grains are not common and average about 0.03 mm in diameter—to sandstones, with generally abundant quartz grains which may average up to 0.5 mm in diameter. Ferricretes or iron‐cemented duricrusts occur in rocks with coarser quartz grains, such as the Tertiary river gravels of the Maroota area. The porosity and permeability of these rocks have considerably influenced the nature and profiles of the laterites. Two possible sources of sesquioxides in the laterites appear to be the Wianamatta Shale and, perhaps more importantly, basic igneous rocks.     

The geopolitics of military material supply

The advent of the New World Order has raised a number of key logistical concerns for the defence industries of the West. To ensure the procurement of supplies of material, whether raw materials or finished components, for production, and particularly surge production, introduces a variety of geographical and geopolitical problems. Resources for which there are potential supply problems are designated strategic and this paper summarizes the author's work in the US and the UK on the identification of such resources.     

Boundaries of air mass trajectory clustering: key points and applications

Calculating air mass trajectories is common in atmospheric analyses. However, if explainable results are to be achieved, several procedures are needed to process the vast amount of information handled. Clustering methods are statistical tools usually considered for such a purpose. Although they are based on rigorous algorithms, certain questions still remain when these methods are applied. The current review is organised in sections according to the sequence followed by such procedures. First, the types of clustering methods are described, with their core being the distance used. One key point is the stopping rule, which determines the final number of clusters. A simple classification based on this number is then suggested. Finally, the graphical presentation of the results is examined and the main drawbacks are commented on. A range of applications and results are considered to illustrate each section, and certain caveats and recommendations are also presented.     

The synchronous nature of geologic processes

IGR Report on Volume XIV of Geologiya Rudnykh Mestorozhdeniy [GEOLOGY OF ORE DEPOSITS], nos. 1–6. Bi-monthly periodical; V. I. Smirnov, Chief Editor. By Dr. V.P. Sokoloff     

The dynamics of a river bend: a study in flow and sedimentary processes

Comprehensive field measurements of flow and sedimentary processes have been made with the aid of stable scaffolding bridges spaced along the length of a bend of the River South Esk, Scotland. At river stages between about two-thirds full and bankfull, channel width, mean depth and mean flow velocity at a cross-section vary little in the streamwise direction. Flow resistance reaches a maximum at these stages, and the bed topography is stable and in equilibrium with flow and bedload transport. Stable flow geometry is thus related in some way to energy conservation, and to maximization of flow resistance. Detailed observations over a large range of river stages of mean velocity distributions, secondary circulation, water surface configuration, bed shear stress and resistance to flow, bed configurations and bed load transport rates agree with much (but not all) of the comparable published experimental studies and selected theoretical work. Generalized physical models of flow and sediment transport in natural curved channels (Engelund, 1974; Bridge, 1977) are demonstrated to be sound in basis and can simulate the bend studied very well. Although there is a pressing need for further development of these models, the results lend confidence to their use in simulating ancient river sedimentation. Sediment deposited on point bars is the result mainly of bedload transport over a range of near-bankfull stages. The areal distribution of grain-size characteristics and bed configurations at these stages give rise, with lateral deposition, to vertical facies sequences that vary substantially in the streamwise direction.