Mixed Zone Research Articles

Comment on “Soil Moisture Response to Snowmelt and Rainfall in a Sierra Nevada Mixed‐Conifer Forest”

[Bales et al(2011)][1] advance the understanding of soil moisture dynamics in response to water input, especially snowmelt, in the mixed conifer zone of the Sierra Nevada, California. In particular, we appreciate the authors” conclusion that regolith deeper than 1 m is important in supporting base

Theoretical Basis and Technology Development of the Combined Process of Asymmetric Rolling and Plastic Bending

The article focuses at technology development of the vertical asymmetric rolling and combined process of vertical asymmetric rolling and plastic bending. It has been shown that vertical asymmetric rolling peculiarity relates to the presence of a mixed zone, in which friction forces on contact roll surfaces are directed are differently. Experimental research showed serious drawbacks in the rolling technology caused by the growth of dynamic loads arising at the moment of plate contact with the bending roller. For solving the problem it was proposed to make the roller position motile to allow its movement along the required trajectory. The application of the motile roller helps to reduce dangerous torque differentiation at working rolls by the value of 1,5-2,5 compared with the rigidly fixed roller. The most effective bending roller trajectory is a second-order curve that is convex parabola.

ZVI-Clay remediation of a chlorinated solvent source zone, Skuldelev, Denmark: 2. Groundwater contaminant mass discharge reduction

The impact of source mass depletion on the down-gradient contaminant mass discharge was monitored for a 19-month period as a part of a field demonstration of the ZVI-Clay soil mixing remediation technology. Groundwater samples were collected from conventional monitoring wells (120 samples) and a dense network of multilevel samplers (640 samples). The hydraulic gradient and conductivity were determined. Depletion of the contaminant source is described in the companion paper (Fjordbøge et al., 2012). Field data showed four distinct phases for PCE mass discharge: (1) baseline conditions, (2) initial rapid reduction, (3) temporary increase, and (4) slow long-term reduction. Numerical modeling was utilized to develop a conceptual understanding of the four phases and to identify the governing processes. The initial rapid reduction of mass discharge was a result of the changed hydraulic properties in the source zone after soil mixing. The subsequent phases depended on the changed accessibility of the contaminant mass after mixing, the rate of source depletion, and the concentration gradient at the boundaries of the mixed source zone. Overall, ZVI-Clay soil mixing resulted in a significant down-gradient contaminant mass discharge reduction (76%) for the parent compound (PCE), while the overall reduction of chlorinated ethenes was smaller (21%).

A design algorithm for batch stirred tank transesterification reactors

A 50L per batch, stirred tank reactor, suitable for carrying out transesterification of vegetable oils was designed and constructed. The major design assumptions included stainless steel plate thickness of 2mm, reaction temperature of 60–65°C and an initial/final fluid temperature of 25/70°C. The calculated impeller Reynolds number was in the mixed regime zone of 10–104; the power number was varied between 1 and 5, while a typical propeller speed of 22.5rev/s (or 1350rev/min) was adopted. The limiting design conditions were maximum reactor diameter of 1.80m, straight side height-to-diameter ratio in the range of 0.75–1.5 and minimum agitator motor power of 746W (1Hp). Based upon the design, a simple algorithm was developed and interpreted into Microsoft C Sharp computer programming language to enable scale up of the reactor. Performance testing of the realized reactor was carried out while using it to produce Neem oil biodiesel via base – catalyzed methanolysis, which yielded high quality fuel product.

Microstructure and Hydrogen-Induced Failure Mechanisms in Fe and Ni Alloy Weldments

The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-IN625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially mixed zones and a continuous partially mixed zone on the Ni side of the fusion line. Within the partially mixed zone on the Ni side, there exists a 200-nm-wide transition zone within a 20-μm-wide planar solidification region followed by a cellular dendritic region with Nb-Mo–rich carbides decorating the dendrite boundaries. Although there were differences in the volume of the partially mixed zones, the major difference in the metal weld interfaces was the presence of M7C3 precipitates in the planar solidification region, which had formed in AISI 8630-IN625 but not in ASTM A182-F22-IN625. These precipitates make the weldment more susceptible to hydrogen embrittlement and provide a low energy fracture path between the discontinuous partially mixed zones.

Weldability of 780 MPa Super-High Strength Heavy-Duty Truck Crossbeam Steel

CO2-shielded welding experiments of newly developed, 780 MPa super-high strength heavy-duty truck crossbeam steel were conducted, and the microstructure, microhardness, mechanical properties, and impact toughness of the welded joint were studied. The evolution of the microstructure of the welded joint occurred as follows: welding seam (acicular ferrite+proeutectoid ferrite) → fusion zone (granular bainite-long strip M/A island) → coarse grain zone (granular bainite-long strip or short bar M/A island) → grain zone (ferrite+pearlite+blocky M/A island) → mixed grained zone (ferrite+granular bainite+blocky M/A island) → base metal (proeutectoid ferrite+granular bainite-blocky or granular M/A island). Increasing the density of the grain boundaries can effectively improve the impact toughness, and the blocky M/A island hindered crack propagation more effectively than the long strip M/A island. The new hot-rolled 780 MPa super-high strength steel had excellent weldability. The welding technology was applied under the following conditions: welding voltage was 20 to 21V, welding current was 200 to 210 A, and the gas flow rate was 25 L/min.

Division of labor in rhizomatous species: Comparative performance of native and invasive species in the tidal marshes of the Yangtze River estuary, China

We compared reproductive characteristics of Scirpus mariqueter and Spartina alterniflora in monocultures and mixed communities to assess the importance of clonality in the population distribution and colonization of the two species. In the core S. alterniflora zone, individuals were taller and there were fewer underground tillers than in the Spartina–Scirpus zone. Every sexual S. alterniflora individual produced about two underground tillers in the S. alterniflora zone, which was two thirds as many as in the Spartina–Scirpus zone. In contrast, the height of sexual S. mariqueter was the highest in the mixed zone, whereas the numbers of flowering individuals and vegetative individuals were the highest in the core and the Scirpus–tidal flat zones, respectively. In the Scirpus–tidal flat zone each sexual individual produced 14 vegetative individuals, which was 23 times that produced in the mixed zone, and 45 times that in the core zone. Aboveground biomass and density of sexual individuals decreased from the core to the Scirpus–tidal flat zone. The ratio of aboveground to belowground biomass was lower in core zones of the two species than in their mixed zones. From the S. alterniflora to the tidal flat zone there was a decrease in salinity and redox potential and an increase in soil moisture.

MODELING THE X-RAYS RESULTING FROM HIGH-VELOCITY CLOUDS

With the goal of understanding why X-rays have been reported near some high velocity clouds, we perform detailed 3 dimensional hydrodynamic and magnetohydrodynamic simulations of clouds interacting with environmental gas like that in the Galaxy's thick disk/halo or the Magellanic Stream. We examine 2 scenarios. In the first, clouds travel fast enough to shock-heat warm environmental gas. In this scenario, the X-ray productivity depends strongly on the speed of the cloud and the radiative cooling rate. In order to shock-heat environmental gas to temperatures of > or = 10^6 K, cloud speeds of > or = 300 km/s are required. If cooling is quenched, then the shock-heated ambient gas is X-ray emissive, producing bright X-rays in the 1/4 keV band and some X-rays in the 3/4 keV band due to O VII and other ions. If, in contrast, the radiative cooling rate is similar to that of collisional ionizational equilibrium plasma with solar abundances, then the shocked gas is only mildly bright and for only about 1 Myr. The predicted count rates for the non-radiative case are bright enough to explain the count rate observed with XMM-Newton toward a Magellanic Stream cloud and some enhancement in the ROSAT 1/4 keV count rate toward Complex C, while the predicted count rates for the fully radiative case are not. In the second scenario, the clouds travel through and mix with hot ambient gas. The mixed zone can contain hot gas, but the hot portion of the mixed gas is not as bright as those from the shock-heating scenario.

Phytoplankton and Physicochemical Analysis on the Water System of the Temperate Estuary in South America:Bahía Blanca Estuary, Argentina

Under the contemporary scenario of global climate change and increasing coastal eutrophication, baseline studies of phytoplankton diversity and distribution in relation to habitat conditions constitute the first approach to evaluate potential shifts at the base of the food webs. Here we present data of phytoplankton species composition and environmental variables in winter 2006 in a temperate estuary in South America, Argentina. The results showed that the Bahia Blanca Estuary is markedly turbid (particulate suspended matter up to 60 mg L-1) with high nutrient concentrations. Apparently, besides high light attenuation coefficients (k up to 2.7 m-1), the combination of a shallow (~7 m depth) and well mix water column in the innermost zone of the estuary allows light penetration (mean light intensity in the mixed zone Im 57.8 μEm-2s-1 and euphotic zone to mixed zone ratio Zeu:Zm over 0.2), intensive nutrient regeneration and eventually phytoplankton massive growth (up to 1.8 x 106 cells L-1). Moreover, the relatively low residence time and the low river runoff seem to promote the accumulation of nutrients and phytoplankton biomass in the head of the estuary. Anthropogenic activities and autochthonous production are responsible of high particulate organic matter loads (8.3 ± 1.5 mg L-1). Diatoms appeared as the dominant group in winter with the emergence of Cyclotella aff. choctawatcheena (5-15 μm) as the dominant species (up to 82 % of the total phytoplankton abundance). The distribution and habitat preferences of this diatom are briefly discussed in relation to the pelagic environment in the Bahia Blanca Estuary.

새만금 신간척지 토양의 염농도별 식생특성

간척지를 농업용지로 개발하는데 간척지에 자생하는 식생의 이용가능성에 관한 기초 자료를 얻고자 새만금 간척지 내 계화지구에서 식생군락에 따라 식물종을 분류하고 토양 화학성과의 관계를 분석한 결과는 다음과 같다. 담수면 토양을 기점으로 조사된 위치별 토양염농도는 담수면 인접부가 22.3dS <TEX>$m^{-1}$</TEX> 로 가장 높았고 육지쪽으로 진행될수록 낮아져 해수면에서 2km이상 되는 지점에서는 1.1~3.44dS <TEX>$m^{-1}$</TEX>를 나타냈다. 자생하는 식물은 6과 26종이 조사되었으며, 식물종별 발생빈도는 갯개미취, 비짜루국화가 61.5로 가장 높은 빈도를 나타냈고, 이어 갈대와 갯꾸러미풀이 53.8이었다. 식생의 발생은 토양 염농도 14dS <TEX>$m^{-1}$</TEX> 지점에서 시작되었고 주로 명아주과 염생식물들인 퉁퉁마디, 나문재, 칠면초, 해홍나물 등이 나타났다. 이후 6.7dS <TEX>$m^{-1}$</TEX> 지점에서부터 화본과 식물인 갈대, 갯꾸러미풀 등이 나타났고, 5dS <TEX>$m^{-1}$</TEX> 에서 사초과 식물이 나타났다. 3dS <TEX>$m^{-1}$</TEX>이하에서는 비짜루국화, 갈대, 피, 갯잔디, 망초 등 중성식물들이 나타났다. 식생 종수는 염생식물과 중생식물이 동시에 나타나는 5dS <TEX>$m^{-1}$</TEX> 지점에서 많았고, Biomass는 갈대가 우점한 식생구가 가장 많았으며, 다음으로는 갈대+자귀풀이 우점한 식생에서 많았다. 식생의 생장량은 토양 염농도와는 부의상관을 나타냈고, 유기물함량과는 정의상관을 나타냈으며, pH와 식생의 우점도간에는 부의 상관을 나타냈다. This study was conducted to survey vegetation changes and soil characteristics in Saemangeum new reclaimed tidal land. Soil salinity in border area to tidal land was 22.3 dS <TEX>$m^{-1}$</TEX> but showed 1.1~3.44 dS <TEX>$m^{-1}$</TEX> over the distance of 2 km from border line. The vascular plants in survey sites were recorded as total 26 taxa in 6 families. The frequency of species appearance of Aster tripolium, A. subulatus var. sandwicensis were highest by 61.5 and that of Phragmites communis, Puccinellia nipponica were 53.8. The almost vegetations occurred in the patch which range of soil salinity 14 dS <TEX>$m^{-1}$</TEX> were halophytes as Salicornia europaea, Suaeda asparagoides, S. japonica. As lowed soil salinity as 6.7 dS <TEX>$m^{-1}$</TEX>, mixed vegetation of halophytes with P. communis, P. nipponica, Carex pumila were occurred. Dominant species in the range of 3.0 dS <TEX>$m^{-1}$</TEX> area were A. subulatus var. sandwicensis, P. communis, Echinochloa spp., Zoysia sinica and Conyza canadensis. Biomass production was the highest in the area of dominant vegetation with P. communis, and mixed zone with P. communis and Aeschynomene indica are followed. The correlation between vegetation biomass and soil salinity, soil pH and dominance index of vegetation were negative. But that of vegetation biomass and soil organic content were positive.

Horizontal liquid–liquid flow characteristics at low superficial velocities using laser-induced fluorescence

Horizontal flows of two immiscible liquids with the same refractive index, a kerosene-like hydrocarbon and a glycerol–water solution, have been instigated with planar laser-induced fluorescence in a square duct. Four flow regime categories were observed, these being: (1) stratified flow; (2) mixed flow (i.e., two distinct continuous phase regions with droplets in each); (3) two-layer flow, comprised of a dispersed region and a continuous, unmixed region (i.e., oil-dispersed flow over glycerol solution flow and, oil flow over a glycerol solution dispersion); and (4) dispersed flows (i.e., continuous oil phase dispersion and continuous glycerol solution dispersion. The flow can be described as occupying three zones; an oil phase at the top, a glycerol–water phase at the bottom, with a mixed zone between them. The vertical height covered by the mixed zone increased for increasing superficial mixture velocity, and the vertical height of the glycerol–water phase decreased for increasing input oil fraction. At low oil fractions the interface level separating the two phases was not affected by changes to the superficial mixture velocity. However, at higher oil fractions the interface height from the bottom of the channel decreased progressively as the superficial velocity was increased. Higher velocities also gave rise to increasingly fluctuating interface level heights. The mean droplet size increased initially, reached a maximum and then decreased as the oil fraction was increased, and was largest at intermediate and smallest at high superficial velocities.

On stress and strain in a continuous-discontinuous shear zone undergoing simple shear and volume loss

I summarise observations within a continuous-discontinuous shear zone to discuss the local stress and strain conditions experienced within a mixed rheology shear zone undergoing volume loss and deformation approximating simple shear. The Chrystalls Beach Complex, New Zealand, comprises phacoids formed from dismembered beds by layer-parallel extension, enclosed within a relatively incompetent matrix. Local extension is generally subparallel to the regional direction of shortening, and overall it appears that layer-parallel extension is a geometrical necessity in low angle shear zones where significant flattening occurs in response to simple shear accompanied by volume loss.Preferential stress loading of phacoids is predicted by fibre-loading theory, and the failure of phacoids by brittle fracture is thereby governed by fibre stresses transferred from the matrix. The principal stress orientations in a phacoid are likely rotated relative to the matrix, and either parallel or perpendicular to the phacoid-matrix interface. As preferential loading of phacoids decreases the stress level in the matrix, an increased volume fraction of phacoids increases the strength of the shear zone as a whole. However, only small matrix volume fractions are required for the composite to act nearly as weak as the matrix.

Spiders in Bangtaesan Mountain in Gangwon-do, Korea

In order to qualitatively examine the spider fauna of Bangtaesan (Mt.) of Inje-gun, Gangwon-do, 4 collection sessions were conducted between May and October of 2010. A total of 479 spiders were collected in Bangtaesan (Mt.), at 128 species of 86 genera in 27 families, and coniferous forest zone or mixed tree forest zone, characterized by the dominance of conifers, displayed higher number of species than decideous forest zone. In terms of family, Linyphiidae included the highest number of species (18 species, 14.1%), followed by Theridiidae (16 species, 12.5%), Araneidae (14 species, 11.0%), Salticidae (13 species, 10.2%) and Tetragnathidae (9 species, 7.0%). Four species, Nesticella mogera of family Nesticidae, Clubiona lena of Clubionidae, Phrurolithus sinicus of Corinnidae and Synagelides zhilcovae of Salticidae, were discovered for the first time in Korean mountains. Zoogeographically, spiders in Bangtaesan (Mt.) displayed 1 cosmopolitan species, with holarctic region and palearctic region species making up 14.1% and endemic species making up 7.8% of the species observed during the study. This shows that spider fauna of Bangtaesan (Mt.) experience northern influence. The result of this study provides an inventory of mountain spiders and information regarding the region's biodiversity, and the results will not only become useful for the effective management and long-term use of national biological resources, but will also become a highly important data for the preservation of biodiversity based on changes in distribution, time and space.

Microstructural and mechanical characteristics of laser welding of Ti6Al4V and lead metal

Titanium alloy Ti6Al4V and lead metal were welded using a continuous wave Nd:YAG laser. The influences of laser power, scanning velocity, and laser beam offset on weld morphology were investigated. Microstructure, chemical composition and mechanical properties of the joints were evaluated. Experimental results showed that fusion weld formed at the upper part of the weld and brazing weld with solder of Pb formed at the lower part of the weld under appropriate process condition. Interfaces were formed between mixed fusion zone and liquid lead zone in molten pool during laser welding of Ti6Al4V and lead. Reasons for interface formation may be different driving force of various regions in molten pool, and the miscibility gap of Ti and Pb binary system. Ti-Pb intermetallic compound Ti4Pb was detected at the fusion weld zone, which made the microhardness of the weld seam was higher than that of the base materials. The strength of the joint was at least equal to or larger than that of lead base material.

Basement types of the Thrace Basin and a new approach to the pre-Eocene tectonic evolution of the northeastern Aegean and northwestern Anatolia: a review of data and concepts

In northwestern Turkey, the pre-Eocene basement of the Thrace Basin consists of the Strandja-Rhodope metamorphics in the north/northwest, the Istanbul-Zonguldak Paleozoic sequence in the northeast, a tectonic mixture of the fragments from the Sakarya Continent and pre-Upper Cretaceous ophiolites in the southeast, and the uppermost Cretaceous–Paleocene transgressive sediments. The ophiolites belong to a Dogger-Early Cretaceous oceanic basin (the Northeastern Vardar Ocean) between the Rhodope and Sakarya Continents. The NE-trending oceanic branch closed diachronously during the early Late Malm to the northeast but during latest Early Cretaceous to Late Cretaceous time toward the main Vardar Ocean in the southwest. During the final closure, the suture zone acted as a strike-slip fault zone. The latest Cretaceous–Paleocene transpressional to transtensional activities caused the juxtaposition of different basement types and the development of a tectonic mixed zone (the Biga–Armutlu–Ovacik Zone) between the Rhodope and Sakarya Continents. Under the regional N–S compression, on the plate overlying the north/northeastward-dipping Vardar subduction zone, the southwestward escape of an area of crust bounding by the WNW-trending Balkan-Thrace Dextral Fault Zone to the north and the NE-trending Biga–Armutlu–Ovacik Sinistral Zone to the southeast caused a triangular-shaped and isolated depression area for the deposition of the uppermost Cretaceous–Paleocene transgressive sediments in a transtensional setting. The tectonically bounded depression area constitutes also a necessary accommodation space for the deposition of the initial deposits of Early Eocene age in the Thrace Basin.

An additional challenge of Lake Kivu in Central Africa - upward movement of the chemoclines

In Lake Kivu, gases accumulate, exposing the riparian population to the perils of a limnic eruption. This primary challenge has been known for years. Measurements have now established that the chemoclines in Lake Kivu are moving upward at the following total vertical flow rates (in km3 y-1): ~0.05 below 390 m, ~0.12 below 313 m, ~0.13 below 257 m, ~0.25 below 191 m, and ~1.39 below ~140 m depth. The upward movement is caused by inflows to the deeper parts of the lake from water sources with different salinities and thus of different densities. As a result, they stratify at their different isopycnal levels (especially at 350 m and at 220 to 245 m depth) and mix into the waters at those levels, thus pushing up all water above, chemoclines and mixed zones alike. Water from rivers in the catchment area remains in the mixolimnion and when cold, some may sink down to the uppermost mixolimnion. Depending on the wind direction, it is suggested that alternating outflows from Kabuno Bay with variable density ends up either in the mixolimnion or at 245 m depth. In Lake Kivu, only the uppermost chemocline remains at the same level; in this case the upward movement results in transport of mass across the chemocline. In the uppermost mixed zone of the monimolimnion, from 130 to 180 m depth, the natural dilution might suffice to outbalance methane accumulation and thus to prevent any future limnic eruption from this zone. In the next mixed zone below (at 200 to 250 m depth), the upward displacement of dissolved gases to higher levels increases the risk of future limnic eruption. In fact, over time this risk is changed to certainty, even if gas is removed from the deeper (commercially attractive) layers. The limited dilution in this zone probably does not suffice to outbalance methane accumulation. Furthermore, if this upward movement is not prevented, probably within a decade or two a point of no return is likely to be passed, leaving us with no reliable means of responding to this challenge. It is therefore necessary to stop the upward movement by disposing ~0.25 km3 y-1 of degassed water into the mixolimnion. It is what gas extraction plants do to the lake in the next decades that determines whether realistically a future limnic eruption from this layer may be prevented.

Influence of physical forcing on mesozooplankton communities at the Ushant tidal front

The pelagic ecosystem around Ushant tidal front was studied over a spring–neap tidal cycle in September 2009. The system was divided in a mixed coastal zone, the frontal zone and a stratified oceanic zone, which remained stable from spring to neap tide. Standing stock, size structure and composition of the phytoplankton and mesozooplankton communities varied more intensely between zones than with the tidal cycle. Localized changes in chlorophyll a occurred due to forcing by wind and tides. At the front, a diatom bloom intensified from spring to neap tide, but generally phytoplankton communities maintained stable proportions and were numerically dominated by pico- and nanophytoplankton. Highest mesozooplankton diversity was encountered in the frontal zone where organisms from both sides are blended; yet highest biomass was found in the stratified zone 30nm west of the front. Temporal changes in the abundance of several zooplankton groups occurred and mirror trophic dynamics, physical processes and phytoplankton production. Differences between normalized biomass spectra from LOPC and image analysis were strongest during spring tide. The spectral slope steepened from a theoretical equilibrium value in the stratified zone to <−1 in the mixed zone reflecting the greater importance of small sized mesozooplankton in coastal marine ecosystems.

Moisture and dynamical interactions maintaining decoupled Arctic mixed-phase stratocumulus in the presence of a humidity inversion

Abstract. Observations suggest that processes maintaining subtropical and Arctic stratocumulus differ, due to the different environments in which they occur. For example, specific humidity inversions (specific humidity increasing with height) are frequently observed to occur near cloud top coincident with temperature inversions in the Arctic, while they do not occur in the subtropics. In this study we use nested LES simulations of decoupled Arctic Mixed-Phase Stratocumulus (AMPS) clouds observed during the DOE Atmospheric Radiation Measurement Program's Indirect and SemiDirect Aerosol Campaign (ISDAC) to analyze budgets of water components, potential temperature, and turbulent kinetic energy. These analyses quantify the processes that maintain decoupled AMPS, including the role of humidity inversions. Key structural features include a shallow upper entrainment zone at cloud top that is located within the temperature and humidity inversions, a mixed layer driven by cloud-top cooling that extends from the base of the upper entrainment zone to below cloud base, and a lower entrainment zone at the base of the mixed layer. The surface layer below the lower entrainment zone is decoupled from the cloud mixed-layer system. Budget results show that cloud liquid water is maintained in the upper entrainment zone near cloud top (within a temperature and humidity inversion) due to a down gradient transport of water vapor by turbulent fluxes into the cloud layer from above and direct condensation forced by radiative cooling. Liquid water is generated in the updraft portions of the mixed-layer eddies below cloud top by buoyant destabilization. These processes cause at least 20% of the cloud liquid water to extend into the inversion. The redistribution of water vapor from the top of the humidity inversion to its base maintains the cloud layer, while the mixed layer-entrainment zone system is continually losing total water. In this decoupled system, the humidity inversion is the only source of water vapor for the cloud system, since water vapor from the surface layer is not efficiently transported into the mixed layer. Sedimentation of ice is the dominant sink of moisture from the mixed layer.

Fault architecture and deformation processes within poorly lithified rift sediments, Central Greece

Deformation mechanisms and resultant fault architecture are primary controls on the permeability of faults in poorly lithified sediments. We characterise fault architecture using outcrop studies, hand samples, thin sections and grain-size data from a minor (1–10 m displacement) normal-fault array exposed within Gulf of Corinth rift sediments, Central Greece. These faults are dominated by mixed zones with poorly developed fault cores and damage zones. In poorly lithified sediment deformation is distributed across the mixed zone as beds are entrained and smeared. We find particulate flow aided by limited distributed cataclasis to be the primary deformation mechanism. Deformation may be localised in more competent sediments. Stratigraphic variations in sediment competency, and the subsequent alternating distributed and localised strain causes complexities within the mixed zone such as undeformed blocks or lenses of cohesive sediment, or asperities at the mixed zone/protolith boundary. Fault tip bifurcation and asperity removal are important processes in the evolution of these fault zones. Our results indicate that fault zone architecture and thus permeability is controlled by a range of factors including lithology, stratigraphy, cementation history and fault evolution, and that minor faults in poorly lithified sediment may significantly impact subsurface fluid flow.

Sirius A: turbulence or mass loss?

Context. Abundance anomalies observed in a fraction of A and B stars of both Pop I and II are apparently related to internal particle transport. Aims. Using available constraints from Sirius A, we wish to determine how well evolutionary models including atomic diffusion can explain observed abundance anomalies when either turbulence or mass loss is used as the main competitor to atomic diffusion. Methods. Complete stellar evolution models, including the effects of atomic diffusion and radiative accelerations, have been computed from the zero age main-sequence of 2.1M\odot stars for metallicities of Z0 = 0.01 \pm 0.001 and shown to agree with the observed parameters of Sirius A. Surface abundances were predicted for three values of the mass loss rate and for four values of the mixed surface zone. Results. A mixed mass of ~ 10^-6 M\odot or a mass loss rate of 10^-13 M\odot/yr were determined through comparison with observations. Of the 17 abundances determined observationally which are included in our calculations, up to 15 can be predicted within 2 sigmas and 3 of the 4 determined upper limits are compatible. Conclusions. While the abundance anomalies can be reproduced slightly better using turbulence as the process competing with atomic diffusion, mass loss probably ought to be preferred since the mass loss rate required to fit abundance anomalies is compatible with the observationally determined rate. A mass loss rate within a factor of 2 of 10^-13 M\odot/yr is preferred. This restricts the range of the directly observed mass loss rate.