Intrusions of sediment laden fluids into density stratified water columns can be an unrecognized source of mixing in many lakes.

<p>When a sediment laden river flows into a stratified water body, the water mass can either intrude as an overflow, interflow, or underflow depending upon the density contrast between the river and the lake. If the river is sufficiently warm or fresh to compensate for the additional mass of sediment, an overflow results, below which convective sedimentation occurs. If the sediment load is sufficiently high, then an underflow initially occurs, from which the warm/fresh interstitial material can subsequently loft as sedimentation reduces the initial density. Such convection can even potentially overturn the water column stratification if there is a very fresh, but very high sediment load turbidity current. For intermediate cases, an interflow can occur. Here it is possible for both lofting and sediment driven convection to occur above and below the pycnocline. All these different regimes can be described in terms of two dimensionless parameters: R<sub>S</sub> and R<sub>A</sub>, which are ratios that compare the density contrast due to sediment between the river and the upper layer with the density contrast between the upper and lower layers and the density contrast between the river and upper layer, respectively. We used laboratory experiments to describe the vigour of convection in terms of these dimensionless parameters, which then allows the behaviour in various rivers inflows into lakes to be predicted. We also apply our observations to predict how a turbidity current could lead to lofting and possible overturn of the stratification of meromictic Lake Kivu.</p>

Nanopore Structure Distribution of the Upper Paleozoic Tight Sandstones and Its Controls on Gas Production Performance in the Shenfu Area, Northeastern Ordos Basin, China

Based on X-ray diffraction, thin section and scanning electron microscopy observation, helium porosity and permeability tests and high-pressure mercury intrusion experiments, the pore and throat distributions of tight sandstone reservoirs were revealed on a nm–μm scale, and their control on gas productivity in the Shenfu area, northeastern Ordos Basin, China was discussed. The results show that lithic sandstones are the main rock types. As the burial depth increases, the quartz content increases, while the feldspar content decreases. There is approximately 5–25% of interstitial material varying between the different layers, and this interstitial material is mainly composed of mud, kaolinite and Fe-calcite. These tight sandstone reservoirs generally have porosities <10% and permeabilities <1 mD. Except for the Shiqianfeng Formation, the dissolution pores in other Upper Paleozoic strata all account for more than 80% of pores. The main pore types are mainly intragranular dissolution pores, intergranular dissolution pores and cement dissolution pores. Generally, the pore radius is approximately 500 nm, while the pore throats are much smaller are variable in size. Wells with high amounts of sandstones but low gas production rate are generally characterized by dominant intercrystalline pores, few macropores, and low effective porosity. The lithology and reservoir characteristics, which are controlled by primary deposition and secondary diagenesis, are speculated to be main factors controlling the gas contents.

O PROCESSO DE ANALCIMIZAÇÃO DE UM KAMAFUGITO (LUZ262) DO CENTRO-OESTE MINEIRO

Resumo:O presente trabalho é um estudo petrográfico das fases primárias e secundárias de uma rocha kamafugítica, intrusão nomeada Luz262, de um afloramento próximo a BR 262, nos arredores da cidade de Luz, no centro-oeste mineiro. A rocha é composta por olivina, parcialmente substituída por serpentina, clinopiroxênio, perovskita, flogopita, opacos, pseudomorfos de leucita (analcima), vênulas de natrolita e material intersticial (vidro vulcânico/feldspatóide). A rocha apresenta xenólitos sedimentares de siltitos, compostos principalmente por ortoclásio, provenientes da Formação Serra da Saudade; além de autólitos constituídos basicamente por clinopiroxênio, perovskita, opacos, apatita, pseudomorfos de leucita e natrolita. A rocha foi classificada como leucita-mafurito com base na presença limitada de leucita (cerca de 10% modal), além da provável presença de kalsilita intersticial, como já descrito anteriormente em rochas semelhantes do Grupo Mata da Corda, da Província Ígnea do Alto Paranaíba. A partir de análises petrográficas por microscópio óptico, mineralógicas por difratometria de raios-x e químicas por microssonda eletrônica foi determinado que os feldspatóides originalmente potássicos, sofreram um processo secundário de troca do K pelo Na, representado na substituição de leucita e kalsilita por analcima.Palavras-chave: Kamafugito, petrografia, analcimização, Minas Gerais AbstractTHE ANALCIMIZATION PROCESS OF A KAMAFUGITE (LUZ262) FROM THE MIDWEST OF MINAS GERAIS. The present paper is a petrographic study of the primary and secondary phases of a kamafugitic rock, intrusion named as Luz262, found in an outcrop nearby BR-262, nearby the town of Luz in the middle west of Minas Gerais. The kamafugite is composed by olivine partially replaced by serpentine, clinopyroxene, perovskite, flogopite, opaques, leucite pseudomorphs (analcime), veins of natrolite and interstitial material (volcanic glass/feldspathoid). The rock contains sedimentary xenoliths of siltite, mainly constituted of orthoclase from the Serra da Saudade Formation, as well as autoliths composed basically of clinopiroxene, perovskite, opaques, apatite, leucite pseudomorphs and natrolite. The rock is classified as leucite-mafurite based on the limited presence of leucite (around 10% modal), besides the probable presence of interstitial kalsilite, as previously described on similar rocks of the Mata da Corda Group from the Alto Paranaíba Province. By using petrographic analysis with optical microscope, mineralogical analysis by x-ray diffraction and chemical microanalysis with electron microprobe it was determined that the feldspathoids originally potassic, suffered a secondary change process of K by Na, with transformation of leucite and kalsilite to analcime. Keywords: Kamafugite, Petrography, Analcimization, Minas Gerais

Technological Processes for Manufacturing Cellular Concrete Products for Construction

Cellular concrete occupies one of the leading places in world practice of a high-rise construction as the constructional heat-insulating material used in case of construction and reconstruction of buildings and constructions of different purpose. In this artificial stone construction material pores (air cells with diameter 0.1-3.0mm) are distributed rather regularly and occupy from 20 to 90% of amount of concrete, providing high heatphysical qualities (coefficient of heat conductivity of 0.07-0.2 W/ms) that allows cellular concrete houses to keep heat well. Excessive (reserve) porosity of cellular concrete provides its frost resistance (compensates expansion of water when freezing and the formed ice without material destruction). Vapor permeability of cellular concrete provides fast removal of technological moisture from material and maintenance of normal moisture conditions in rooms, and rather high air permeability promotes preserving in rooms of fresh air. Significant growth in production the cellular concrete of products is caused by use of rather simple technologies allowing (due to change of degree of porosity and properties of interstitial material) to receive cellular concrete for thermal insulation or sound insulation, to make wall constructional heat-insulating products with a density 250-1200 kg/ m3 and strength of a 1-25 MPa.

Adcumulate mafic dykes in layered intrusions: a case study of a late-stage dyke in the Bayantsagaan layered intrusion, Mongolia

We have discovered an adcumulate late-stage dyke in the Bayantsagaan layered intrusion. The 11-cm-thick dyke is composed of fresh troctolite with no signs of chilling against the host leucotroctolite. Texturally, both the dyke and its host are medium-grained plagioclase-olivine-magnetite cumulates. The dyke is however finer grained and contains less interstitial material. Two geochemical features characterize the dyke: it is compositionally more evolved than the host, as indicated by its lower real and normative An-content in plagioclase, whole-rock Cr and Mg-number; and it is highly depleted in all incompatible components (e.g. K2O, Y and rare earth elements or REEs) that have much lower concentrations than in the host. The depletion in REEs is extreme and has not been reported earlier for any troctolitic rocks. It has an internal reverse zonation with an inwards increase in compatible MgO and TiO2 and a decrease in all incompatible elements, suggesting an inwards decrease in the amount of trapped melt. We interpret this late-stage dyke as having formed from a residual melt that was channelled along a fissure in solidifying cumulates. The flow of the melt resulted in the very efficient removal of a boundary layer of evolved liquid from crystals growing on the walls of the dyke. This resulted in an almost perfect adcumulate that is extremely depleted in incompatible components.

Measurements and Models for the Thermal Conductance Through Surfaces Joined by Screws

In electronics cooling with limited local convective or irradiative cooling, conduction path optimization is critical. Decreased junction temperatures (resulting in increased performance and reliability) can be achieved by maximizing the conductance through screw joints. Thermal contact conductance across an Aluminum-Aluminum screw joint was experimentally measured which compared well with published data for uniformly distributed pressure, with increasing conductance versus the published data as the screw preload was applied. The geometry was modeled using a meshed surface application of an available model for thermal conductance of contacts with uniformly-applied pressure, resulting in a poor correlation due to limitations in the applied technique. Modifications to the model were explored, including capping pressure, imposing a non-zero pressure in the area not influenced by screw pressure, simplifying the pressure distribution, and scaling the model to match experimental results. Each resulted in somewhat better correlation between calculated and experimental results. Recommendations are made regarding the calculation of conductance in general, leaning toward more simplified models. Further work is suggested in the area of experimentally-verified modeling of other materials and surface conditions, geometry, and with an interstitial material other than air.

ON REYNOLDS' DILATANCY AND SHEAR BAND EVOLUTION: A NEW PERSPECTIVE

Dense granular media exhibit rich phenomenology when subject to imposed stresses and strains. This is a result of the many degrees of freedom present in an assembly of grains and the nonlinear interactions between the grains. Their complex behavior include the self-organization of load-bearing columnar structures known as force chains across a wide range of spatial scales. Behavior akin to phase transitions from a strong solid-like to a weak liquid-like response can also be observed with shear bands, i.e. regions where force chains collectively buckle, being the signature microstructure in this transition from the stable to the failure regime. An inherent aspect of shear bands and dense granular failure is the phenomenon of dilatancy, i.e. expansion in volume, when the material is subjected to a combined compression and shear. To understand the origins of dilatancy, it is useful to consider the granular material as a mixture of two components: grains and the interstitial material filling the voids or pores between the grains. The grains within a dense granular material respond to applied loads by rearranging to create local zones which contract and dilate. Extant studies of this mechanical response are typically focused on the solid skeleton, in particular, the topology of the network representing the physical contacts between grains. Here, we propose an alternative perspective which is to consider network representations of the evolving anisotropic pore space. We demonstrate how to construct pore space networks that express the local size of voids about a grain through network edge weights. We investigate sectors of the loading history when a percolating giant component of the pore space network exists. By defining two weight functions for edge properties, we: (i) discover via a recurrence plot-based analysis a temporal time scale for jamming–unjamming (contractant-dilatant) dynamics in shear bands; and show that (ii) the formation of a persistent shear band in response to the deformation places grains in a configuration predisposed to the efficient transport of interstitial material as evidenced by the location of percolating shortest path routes through the most dilatant sites. A proper understanding of the micromechanics of pore evolution with respect to shear bands and dilatancy is key to a range of applications such as modeling ground water flow, dewatering systems, carbon capture and sequestration.

‘This is FilmFour – Not Some Cheesy Pseudo-Hollywood Thing!’: The Opening Night Simulcast of FilmFour on Channel 4

Channel 4's tradition of supporting, promoting and contributing to British cinema culture entered a new phase in 1998. Its film-making operations were consolidated into a single, semi-vertically integrated studio called FilmFour. On 1 November it launched a brand-new pay-TV channel of the same name. This channel programmed a variety of cinema, premiering world cinema films, FilmFour's own productions and independent films. It was the first digital channel in Britain affiliated to a public service broadcaster. The new channel was introduced on its opening night with a simultaneous broadcast with terrestrial Channel 4. Scheduled on this evening was a representative selection of films and programmes to entice viewers to take up the new channel, including the UK television premiere of The Usual Suspects (1995). This article presents a detailed textual analysis of this opening night simulcast. It examines how the new channel was presented to the audience, focusing particularly on interstitial material: the introductory programme, interviews with well-known faces from the British film industry, and additional material broadcast between the films. Evaluating the evening's output, the paper argues that the opening night simulcast represented both a marketing tool for the new channel and a means of extending the Channel 4 corporation's brand. This article offers a case study in how a public service broadcaster began to negotiate for itself a space in the new digital broadcasting environment by targeting a specific, discriminating audience.

Performance Study on Alumina Red Mud-Cement Stabilized Macadam Base

Based on the analysis of chemical constituents and mineral composition, a new disposal method of alumina red mud added in cement stabilized macadam base was put forward. Through experiments of compressive strength, dynamic elastic modulus, splitting intensity and resilient modulus, mechanical properties of alumina red mud- cement stabilized macadam base and base performance affected by alumina red mud dosage were studied. Also, the strength formation micro-mechanism of alumina red mud-cement stabilized macadam mixture was explored by scanning electron microscopy (SEM). The results indicate that alumina red mud-cement stabilized macadam mixture has good mechanical properties; its early compressive strength, early splitting intensity, dynamic elastic modulus, resilient modulus are improved obviously with alumina red mud mixing; the mixing amounts of alumina red mud and cement are significantly affected mixture strength and the optimum mixing amount is respectively 10~12% and 5~6%; alumina red mud can promote cement hydration and hydrates generation. it not only is used as interstitial material among aggregates，also as binder closely linked aggregates through the spatial reticular structure formed by red mud and cement hydrates, which enhance mixture strength.

3-Omega-T-Type Method for Measuring the Thermophysical Properties of Micro/Nanowires

A novel 3ω-T type probe method is developed to investigate the thermal effusivity of micro/nanowires. In this method, a short hot wire subjected to an alternating current serves simultaneously as a heater and a thermometer, and a test wire is attached to the midpoint of the hot wire with an interstitial material. A measurement system based on a virtual lock-in is developed to measure the thermal impedance of the interposer and the thermal effusivity of the test wire. The same value of thermal effusivity is obtained with the presence of different interposers, and the interposer with small thermal impedance gives a decrease of the temperature oscillation of the hot wire. Using this method, the thermal resistances of bare metallic junctions are measured as a function of temperature. For the junction established by two crossed platinum wires with small diameters, the thermal contact resistance is found to decrease as temperature increases, which can possibly be explained the plastic deformation of the microscopic contacts.