Net Deposition Rate Research Articles

Electrode-selective deposition/etching processes using an SiF4/H2/Ar plasma chemistry excited by sawtooth tailored voltage waveforms

We report on the electrode-selective deposition and etching of hydrogenated silicon thin films using a plasma enhanced chemical vapour deposition process excited by sawtooth-shaped tailored voltage waveforms (TVWs). The slope asymmetry of such waveforms leads to a different rate of sheath expansion and contraction at each electrode, and therefore different electron power absorption near each electrode. This effect was employed with an SiF4/H2/Ar plasma chemistry, as the surface processes that result from this gas mixture depend strongly on the local balance between multiple precursors. For a specific gas flow ratio, a deposition rate of 0.82 Å s−1 on one electrode and an etching rate of 1.2 Å s−1 on the other were achieved. Moreover, this deposition/etching balance is controlled by the H2 flow rate, which limits the deposition rate at low flows. When the H2 injection is sufficiently high, the processes are then limited by the dissociation of SiF4, and the relative rate of the surface processes on the two electrodes are reversed, i.e. a higher net deposition rate is observed on the electrode where the fast sheath contraction occurs due to the electronegative character of the plasma.

Measuring the ‘Great Unconformity’ on the North China Craton using new detrital zircon age data

Abstract New detrital zircon ages confirm that the Neoproterozoic strata of the southeastern North China Craton (NCC) are mostly of early Tonian age, but that the Gouhou Formation, previously assigned to the Tonian, is Cambrian in age. A discordant hiatus of >150–300 myr occurs across the NCC, spanning most of the late Tonian, Cryogenian, Ediacaran and early Cambrian periods. This widespread unconformable surface is akin to the Great Unconformity seen elsewhere in the world and highlights a major shift in depositional style from largely erosional, marked by low rates of net deposition, during the mid- to late Neoproterozoic to high rates of transgressive deposition during the mid- to late Cambrian. The age spectra for the southeastern NCC and northern India are consistent with a provenance affinity linking the NCC and East Gondwana by c. 510 Ma. Supplementary material: Sample descriptions, sampling GPS locations and a compiled dataset of detrital zircon U–Pb LA-ICP-MS dating results are available at https://doi.org/10.6084/m9.figshare.c.3571119

Potentials and problems of building detailed dust records using peat archives: An example from Store Mosse (the “Great Bog”), Sweden

Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the “Great Bog”), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385–5300calyr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE-rich phosphate minerals over time. These clays are likely transported from a long-distance source (<100km). While dust deposition was reduced during the second event (5300–4370calyr BP), this is the most distinct in terms of its source character with [Eu/Eu∗]UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380–2200calyr BP) and fourth (1275–1080calyr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere.

First mirror deposition/erosion experiment by using multi-purpose manipulators in KSTAR

First mirrors are essential plasma-facing components (PFCs) for fusion devices. Erosion and redeposition on first mirrors are of interest, since they cause degradation of signal intensity. In order to trace deposition/erosion characteristics of amorphous hydrogenated carbon (a-C:H) films on first mirrors, two manipulators attached at midplane and divertor regions of KSTAR vacuum vessel are utilized. A net deposition rate of 0.3–0.5nm/s during a discharge and an erosion rates of 0.1nm/s during He ion cyclotron wall conditioning (ICWC) are obtained. Property of redeposited layers are different depending on the location, varying from soft polymer-like to hard diamond-like a-C:H layers. For the deposition and erosion of metal layers, a plan for a dedicated experimental session has been set at KSTAR.

Sediment transport dynamics near a river inflow in a large alpine lake

AbstractSediment dynamics were investigated in Lake Maggiore, Italy, with field observations from October to mid‐December 2012. Three moorings were deployed in Pallanza Bay, a small embayment on the western side of the lake near the Toce River inflow, to measure temperature and currents throughout the water column and suspended sediment concentration (SSC) was estimated with acoustic instrumentation. River intrusions are shown to dominate observed SSC, although a small amount of sediment resuspension was observed at the site of the shallowest mooring during a large wind event that produced strong upwelling of the thermocline followed by downwelling. Although vertical turbulent sediment flux is typically assumed to indicate resuspension and the upward transport of sediment ( ), downward turbulent sediment flux was observed ( ) near the bed during the largest observed intrusion event. The downward turbulent sediment flux significantly contributes to net deposition rates, which are one order of magnitude larger than rates of erosion measured during the two major events observed. Horizontal transport of sediment occurs in vertically confined layers due to buoyancy‐driven intrusions. Beneath the intrusions, sediment settles out of the water column at settling rates that appear to be constant with depth based on acoustic Doppler current profiler backscatter measurements. The effective settling velocities needed to produce the observed vertical transport of SSC during an inflow intrusion are one order of magnitude larger than those due to the Stokes settling velocity ( ) alone. Particle flocculation and possible convective instabilities may play a role in generating the large observed effective settling rates.

Nitrate postdeposition processes in Svalbard surface snow

AbstractThe snowpack acts as a sink for atmospheric reactive nitrogen, but several postdeposition pathways have been reported to alter the concentration and isotopic composition of snow nitrate with implications for atmospheric boundary layer chemistry, ice core records, and terrestrial ecology following snow melt. Careful daily sampling of surface snow during winter (11–15 February 2010) and springtime (9 April to 5 May 2010) near Ny‐Ålesund, Svalbard reveals a complex pattern of processes within the snowpack. Dry deposition was found to dominate over postdeposition losses, with a net nitrate deposition rate of (0.6 ± 0.2) µmol m−2 d−1 to homogeneous surface snow. At Ny‐Ålesund, such surface dry deposition can either solely result from long‐range atmospheric transport of oxidized nitrogen or include the redeposition of photolytic/bacterial emission originating from deeper snow layers. Our data further confirm that polar basin air masses bring 15N‐depleted nitrate to Svalbard, while high nitrate δ(18O) values only occur in connection with ozone‐depleted air, and show that these signatures are reflected in the deposited nitrate. Such ozone‐depleted air is attributed to active halogen chemistry in the air masses advected to the site. However, here the Ny‐Ålesund surface snow was shown to have an active role in the halogen dynamics for this region, as indicated by declining bromide concentrations and increasing nitrate δ(18O), during high BrO (low‐ozone) events. The data also indicate that the snowpack BrO‐NOx cycling continued in postevent periods, when ambient ozone and BrO levels recovered.

Seasonal sedimentary processes of the macrotidal flat in Gomso Bay, Korea

ABSTRACT Kang, J., Woo, H.J., Lee, Y.-K., Son, Y.B., 2014. Seasonal sedimentary processes of the macrotidal flat in Gomso Bay, Korea. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 157–163, ISSN 0749-0208. To understand seasonal sedimentary processes, we analyzed sediment grain size, short-term sedimentation rates, and chemical tracers to determine sediment provenance in the Gomso tidal flat, which is located on the western coast of Korea. It is a funnel-shaped embayment with a mean tidal range of 4.3 m. Calculating the elevation from a digital elevation model (DEM), the landward inner bay was relatively higher than that of the outer bay. Sandy sediments generally dominated the outer bay, whereas sandy mud sediments were distributed in the inner bay. The middle bay consisted of muddy sand sediments. From February 2011 to February 2012, the net deposition rate in the inner tidal flat ...

Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness

AbstractStratigraphy contains the most complete record of information necessary to quantitatively reconstruct paleolandscape dynamics, but this record contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and erosional events that remove previously deposited sediment. Building on earlier statistical studies, we examine stratigraphic completeness in three laboratory experiments where the topography of aggrading deltas was monitored at high temporal and spatial scales. The three experiments cover unique combinations in the absolute magnitudes of sediment and water discharge in addition to generation of accommodation space through base‐level rise. This analysis centers on three time scales: (1) the time at which a record is discretized (t), (2) the time necessary to build a deposit with mean thickness equivalent to the maximum roughness on a surface (Tc), and (3) the time necessary for channelized flow to migrate over all locations in a basin (Tch). These time scales incorporate information pertaining to the time‐variant topography of actively changing surfaces, kinematics by which the surfaces are changing, and net deposition rate. We find that stratigraphic completeness increases as a function of t/Tc but decreases as a function of Tc/Tch over the parameter space covered in the experiments. Our results suggest that environmental signals disconnected from a sediment routing system are best preserved in systems with low Tc values. Nondimensionalizing t by Tc, however, shows that preservation of information characterizing system morphodynamics is best preserved in stratigraphy constructed by systems with low water to sediment flux ratios.

DIRECT NUMERICAL SIMULATION OF RADIATION PRESSURE-DRIVEN TURBULENCE AND WINDS IN STAR CLUSTERS AND GALACTIC DISKS

[abridged] The pressure exerted by the radiation of young stars may be an important feedback mechanism in forming star clusters and the disks of starburst galaxies. However, there is great uncertainty in how efficiently radiation couples to matter in these high optical depth environments. In particular, it is unclear what levels of turbulence the radiation can produce, and whether the infrared radiation trapped by the dust opacity can give rise to heavily mass-loaded winds. In this paper we report a series of two-dimensional flux-limited diffusion radiation-hydrodynamics calculations performed with the code ORION in which we drive strong radiation fluxes through columns of dusty matter confined by gravity. We consider both systems where the radiation flux is sub-Eddington throughout the gas column, and where it is super-Eddington at the midplane but sub-Eddington in the atmosphere. In the latter, we find that the radiation-matter interaction gives rise to radiation-driven Rayleigh-Taylor instability, which drives supersonic turbulence at a level sufficient to fully explain the turbulence seen in Galactic protocluster gas clouds, and to make a non-trivial contribution to the turbulence observed in starburst galaxy disks. However, the instability also produces a channel structure in which the radiation-matter interaction is reduced because the radiation field is not fully trapped. For astrophysical parameters relevant to forming star clusters and starburst galaxies, we find that this effect reduces the net momentum deposition rate in the dusty gas by a factor of ~2-6 compared to simple analytic estimates, and that in steady state the Eddington ratio reaches unity and there are no strong winds. We provide an approximation formula, appropriate for implementation in analytic models and non-radiative simulations, for the force exerted by the infrared radiation field in this regime.

Reading the climate record of the martian polar layered deposits

The martian polar regions have layered deposits of ice and dust. The stratigraphy of these deposits is exposed within scarps and trough walls and is thought to have formed due to climate variations in the past. Insolation has varied significantly over time and caused dramatic changes in climate, but it has remained unclear whether insolation variations could be linked to the stratigraphic record. We present a model of layer formation based on physical processes that expresses polar deposition rates of ice and dust in terms of insolation. In this model, layer formation is controlled by the insolation record, and dust-rich layers form by two mechanisms: (1) increased summer sublimation during high obliquity, and (2) variations in the polar deposition of dust modulated by obliquity variations. The model is simple, yet physically plausible, and allows for investigations of the climate control of the polar layered deposits (PLD). We compare the model to a stratigraphic column obtained from the north polar layered deposits (NPLD) (Fishbaugh, K.E., Hvidberg, C.S., Byrne, S., Russel, P.S., Herkenhoff, K.E., Winstrup, M., Kirk, R. [2010a]. Geophys. Res. Lett., 37, L07201) and show that the model can be tuned to reproduce complex layer sequences. The comparison with observations cannot uniquely constrain the PLD chronology, and it is limited by our interpretation of the observed stratigraphic column as a proxy for NPLD composition. We identified, however, a set of parameters that provides a chronology of the NPLD tied to the insolation record and consistently explains layer formation in accordance with observations of NPLD stratigraphy. This model dates the top 500m of the NPLD back to ∼1millionyears with an average net deposition rate of ice and dust of 0.55mma−1. The model stratigraphy contains a quasi-periodic ∼30m cycle, similar to a previously suggested cycle in brightness profiles from the NPLD (Laskar, J., Levrard, B., Mustard, F. [2002]. Nature, 419, 375–377; Milkovich, S., Head, J.W. [2005]. J. Geophys. Res. 110), but here related to half of the obliquity cycles of 120 and 99kyr and resulting from a combination of the two layer formation mechanisms. Further investigations of the non-linear insolation control of PLD formation should consider data from other geographical locations and include radar data and other stratigraphic datasets that can constrain the composition and stratigraphy of the NPLD layers.

Application of 210Pbex inventories to measure net hillslope erosion at burned sites

ABSTRACTFallout radionuclides, including lead‐210 excess (210Pbex), have been broadly and successfully used to quantify net hillslope sediment transport in agricultural, pastoral and forested landscapes but have only recently been applied in burned terrain. Quantifying post‐fire erosion is important because fires can amplify hillslope erosion, impacting terrestrial and aquatic habitat and water quality. However, we lack a basic understanding of the fate of 210Pbex in fires. To address this knowledge gap, we collected over 400 soil samples from unburned, moderately and severely burned forested sites in central Idaho. We measured soil 210Pbex content at stable reference and eroding sites and in mineral and organic soil components. At all sites, organic matter had the highest concentration of 210Pbex, representing 30% to 73% of the total activity. At the severely and moderately burned sites, 210Pbex reference inventories were lower by 58% and 41%, with about 40% less organic mass, relative to the unburned site. These results indicate that most 210Pbex in our semi‐arid, forested sites was bound to organic matter, and that a substantial portion of this lead was lost due to forest fires. These losses likely occurred through volatilization and wind transport of smoke and ash. In the moderately burned site, 210Pbex losses were more spatially variable, potentially due to spatially uneven fire intensity and effects. Despite equal percent losses of 210Pbex, lower inventories at the burned sites produced lower calculated net erosion rates relative to the unburned site. Thus, given methodological uncertainties, 210Pbex losses due to fire, and the subsequent sensitivity of calculated net erosion rates to these lower 210Pbex inventories, we suggest this method should not be used in burned terrain to calculate absolute net erosion and deposition rates. However, within a given burned site, 210Pbex inventories still provide useful information describing relative soil losses and storage across the landscape. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Deposition of ammonium and nitrate in the roots of maize seedlings supplied with different nitrogen salts

This study measured total osmolarity and concentrations of NH4+, NO3–, K+, soluble carbohydrates, and organic acids in maize seminal roots as a function of distance from the apex, and NH4+ and NO3– in xylem sap for plants receiving NH4+ or NO3– as a sole N-source, NH4+ plus NO3–, or no nitrogen at all. The disparity between net deposition rates and net exogenous influx of NH4+ indicated that growing cells imported NH4+ from more mature tissue, whereas more mature root tissues assimilated or translocated a portion of the NH4+ absorbed. Net root NO3– influx under Ca(NO3)2 nutrition was adequate to account for pools found in the growth zone and provided twice as much as was deposited locally throughout the non-growing tissue. In contrast, net root NO3– influx under NH4NO3 was less than the local deposition rate in the growth zone, indicating that additional NO3– was imported or metabolically produced. The profile of NO3– deposition rate in the growth zone, however, was similar for the plants receiving Ca(NO3)2 or NH4NO3. These results suggest that NO3– may serve a major role as an osmoticant for supporting root elongation in the basal part of the growth zone and maintaining root function in the young mature tissues.

Kinetics of SiHCl&lt;SUB&gt;3&lt;/SUB&gt; Chemical Vapor Deposition and Fluid Dynamic Simulations

Though most of the current silicon photovoltaic technology relies on trichlorosilane (SiHCl3) as a precursor gas to deposit Si, only a few studies have been devoted to the investigation of its gas phase and surface kinetics. In the present work we propose a new kinetic mechanism apt to describe the gas phase and surface chemistry active during the deposition of Si from SiHCl3. Kinetic constants of key reactions were either taken from the literature or determined through ab initio calculations. The capability of the mechanism to reproduce experimental data was tested through the implementation of the kinetic scheme in a fluid dynamic model and in the simulation of both deposition and etching of Si in horizontal reactors. The results of the simulations show that the reactivity of HCl is of key importance in order to control the Si deposition rate. When HCl reaches a critical concentration in the gas phase it starts etching the Si surface, so that the net deposition rate is the net sum of the adsorption rate of the gas phase precursors and the etching rate due to HCl. In these conditions the possibility to further deposit Si is directly related to the rate of consumption of HCl through its reaction with SiHCl3 to give SiCl4. The proposed reaction mechanism was implemented in a 3D fluid dynamic model of a simple Siemens reactor. The simulation results indicate that the proposed interpretation of the growth process applies also to this class of reactors, which operate in what can be defined as a mixed kinetic-transport controlled regime.

A GENERAL RELATIVISTIC RAY-TRACING METHOD FOR ESTIMATING THE ENERGY AND MOMENTUM DEPOSITION BY NEUTRINO PAIR ANNIHILATION IN COLLAPSARS

Bearing in mind the application to the collapsar models of gamma-ray bursts (GRBs), we develop a numerical scheme and code for estimating the deposition of energy and momentum due to the neutrino pair annihilation ($\nu + {\bar \nu} \rightarrow e^{-} + e^{+}$) in the vicinity of accretion tori around a Kerr black hole. Our code is designed to solve the general relativistic neutrino transfer by a ray-tracing method. To solve the collisional Boltzmann equation in curved spacetime, we numerically integrate the so-called rendering equation along the null geodesics. For the neutrino opacity, the charged-current $\beta$-processes are taken into account, which are dominant in the vicinity of the accretion tori. The numerical accuracy of the developed code is certificated by several tests, in which we show comparisons with the corresponding analytic solutions. Based on the hydrodynamical data in our collapsar simulation, we estimate the annihilation rates in a post-processing manner. Increasing the Kerr parameter from 0 to 1, it is found that the general relativistic effect can increase the local energy deposition rate by about one order of magnitude, and the net energy deposition rate by several tens of percents. After the accretion disk settles into a stationary state (typically later than $\sim 9$ s from the onset of gravitational collapse), we point out that the neutrino-heating timescale in the vicinity of the polar funnel region can be shorter than the dynamical timescale. Our results suggest the neutrino pair annihilation has a potential importance equal to the conventional magnetohydrodynamic mechanism for igniting the GRB fireballs.

Soil redistribution rate and its relationship with soil organic carbon and total nitrogen using 137Cs technique in a cultivated complex hillslope in western Iran

The spatial pattern of soil redistribution rate was investigated using cesium-137 ( 137Cs) within a cultivated complex hillslope in western Iran. The relationship between soil redistribution rate and soil organic carbon and total nitrogen pattern were studied using co-regionalization analysis. Ninety-one soil cores were sampled for 137Cs, total nitrogen, and soil organic carbon measurements. The simplified mass balance model estimated a gross erosion rate of 29.8 t ha −1 yr −1 and a net soil deposition rate of 21.8 t ha −1 yr −1; hence, a net soil loss rate of 8 t ha −1 yr −1. This magnitude of soil erosion rate is higher than the acceptable rate in semiarid regions. Co-regionalization analysis and co-dispersive coefficients among the selected variables showed that only a small fraction of the variability in total nitrogen and soil organic carbon could be explained by soil redistribution and that the remaining might be the result of different management practices by local farmers.

Beneficial Effects of Insulin on Cell Proliferation and Protein Metabolism in Skin Donor Site Wound

Insulin has been demonstrated to accelerate skin wound healing; however, its effects on wound metabolism have not been adequately studied. Adult rabbits were prepared by creation of skin donor site wound on the back, catheterization of the carotid artery and jugular vein, and placement of a nasogastric feeding tube under general anesthesia. The rabbits were given total enteral nutrition thereafter. On day 5 stable isotope tracers were infused to measure the kinetics of protein (reflecting tissue repair) and DNA (reflecting cell proliferation) in the wound. During the isotope tracer infusion, regular human insulin was infused at 2.5 mU/kg per min with concomitant glucose infusion for euglycemia in an insulin group but not in a control group. Plasma insulin concentration was 140±26 μU/mL in the insulin group (n=8), greater (P<0.001) than that of 16±3 μU/mL in the control group (N=8). In the insulin group the fractional synthetic rates of wound protein and DNA were 9.0±1.2 and 5.4±0.5%/day, greater (P < or=0.05) than those of 6.4±0.5 and 4.0±0.6%/day in the control group, respectively. Wound protein fractional breakdown rates were not significantly (P =0.2) different; net protein deposition rate was ~50% greater in the insulin than in the control group, although the difference was not statistically different (P=0.2). Insulin infusion increased wound protein and DNA synthesis, which are anticipated to promote tissue repair and reepithelialization.

Sediment management and the renewability of floodplain clay for structural ceramics

Background, aim, and scope: The Netherlands has vast resources of clay that are exploited for the fabrication of structural ceramic products such as bricks and roof tiles. Most clay is extracted from the so-called embanked floodplains along the rivers Rhine and Meuse, areas that are flooded during high-discharge conditions. Riverside clay extraction is-at least in theory-compensated by deposition. Based on a sediment balance (deposition versus extraction), we explore the extent to which clay can be regarded as a renewable resource, with potential for sustainable use. Beyond that, we discuss the implications for river and sediment management, especially for the large engineering works that are to be undertaken to increase the discharge capacities of the Rhine and Meuse. Materials and methods: Extraction rates are based on production statistics for clay, as well as those for fired end-products. Deposition rates are estimated from published and unpublished geological data (clay volumes and thicknesses, datings, etc.) and from morphological modeling studies. Comparisons between extraction and deposition are made at three different time-space scales: (1) long term (post-1850)/large scale (all Dutch floodplains), (2) present/large scale, and (3) present/site scale. The year 1850 is relevant because it approximately marks the beginning of the current, fully engineered river systems, in which depositional processes are constrained by dikes and groynes. As the Industrial Revolution began in the same period, post-1850 sediments can be identified by their pollution with heavy metals. Results: (1) We estimate the post-1850 clay volume in situ at about 0.20 km3, and the total extracted volume in the same period at about 0.17 km3. This puts the net long-term average deposition rate of clay at ∼1.3 million m3/year and the corresponding extraction rate at ∼1.1 million m3/year. (2) Current accumulation is approximately 0.4 million m3/year and expected to increase, and current extraction is about 0.7 million m3/year and expected to decrease. (3) Clay extraction creates a depression that has an increased sediment-trapping efficiency. This local effect is not considered explicitly in large-scale morphological modeling. Based on maximum observed sedimentation rates, we estimate that replenishment of a clay site takes in the order of 150 years. As clay extraction lowers some 0.5 km2 of floodplain yearly, a surface area of approximately 75 km2 would be required for sustainable clay extraction. This is about 1/6 of the total surface area of the embanked floodplains. Discussion: On the long term, clay extraction from the embanked floodplain depositional environment has been sustainable. At strongly decreasing deposition rates, the ratio between extraction and replenishment seems to have shifted towards unsustainable. However, current sedimentation is estimated conservatively. The site-scale approach suggests that, even if extraction would currently exceed deposition, this could be resolved with sediment management, that is, with site restoration measures aimed at higher sediment-trapping efficiency. Our results have implications for river engineering, especially where substantial digging is involved (floodplain lowering, high-discharge bypass channels, obstacle removal). First, this inevitably affects the clay resources that we studied, while resource sterilization should be avoided. Secondly, the effect that any form of digging has on subsequent sedimentation-increased rates-relates to long-term river maintenance. Conclusions, recommendations, and perspectives: We conclude that floodplain clay is a renewable resource, especially if managed accordingly. Beyond that, we established that clay extraction is a significant, lasting factor in floodplain evolution along the Rhine and Meuse Rivers. The interests of the extractive industry and river managers could be served jointly with sediment management plans that are based on sediment-budget analyses. © 2009 The Author(s).

Self-limiting deposition of semiconducting ZnO by pulsed plasma-enhanced chemical vapor deposition

Self-limiting growth of zinc oxide was accomplished over a temperature range from 25to155°C by pulsed plasma-enhanced chemical vapor deposition using dimethyl zinc [Zn(CH3)2] as the metal precursor. The deposition rate was independent of plasma exposure (1–5s) but was found to increase from 1.4to6.0Å∕cycle as a function of temperature. Over the narrow range explored, substrate temperature had a dramatic impact on the film structure and properties. Amorphous films were obtained at room temperature, while a polycrystalline morphology with a preferred (100) orientation developed as the temperature increased. The electrical resistivity decreased linearly with temperature from 45to∼2Ωcm. Spectroscopic characterization showed that films deposited at room temperature were contaminated by carbon and hydroxyl impurities; however, these defects were attenuated with temperature and were not detected in films deposited above 64°C. Room temperature photoluminescence was dominated by defect emission in most films; however, this signal was attenuated, and a strong band edge emission was observed for films deposited at temperatures &amp;gt;135°C. Film quality was comparable to material grown by plasma-enhanced atomic layer deposition in the same reactor; however, precursor requirements and net deposition rates were improved by an order of magnitude.

Numerical modelling of steady-state fluxes at the ITER first wall

Plasma parameters in the vicinity of the ITER upper and equatorial ports have been modeled with B2-EIRENE code (SOLPS4.3). Erosion rates of Mo and W due to charge-exchange neutrals and deposition rates of C and Be have been estimated. The modelling results can be used for estimating the lifetime of the first mirrors of optical diagnostics and, to some extent, for evaluating the lifetime of metallic wall. Maximum calculated sputtering rate of Mo at the outer mid-plane is ≈0.005 nm/s, maximum calculated net deposition rate of Be is ≈0.01 nm/s. The modelling shows that gas puff can lead to significant local increase of erosion and decrease of deposition, ensuring the net erosion conditions for C and Be.

Modeling the preservation potential of tidal flat sedimentary records, Jiangsu coast, eastern China

A forward modeling approach is proposed to simulate the preservation potential of tidal flat deposits. The preservation potential is expressed as a function of net deposition rate and a factor that represents the vertical flux of suspended load, or seabed lowering during erosion periods associated with bedload transport. The model takes into account a number of geometric parameters of a tidal flat sediment system and sediment dynamic processes. The former includes high water level, total sediment supply, the annual rate of the supply, the ratio of mud to bilk sediment in the supply, the bed slope of the tidal flat profile, as well as the slope of the stratigraphic boundary; the latter includes spring-neap cycles of tidal water level changes, boundary layer processes, resuspension of fine-grained sediments, bedload transport due to tidal currents, and bed elevation changes in response to sediment movement. Using this model, numerical experiments are carried out for a tidal flat system on the Jiangsu coast, eastern China, with the input data being derived from literature and from a series of sediment cores collected along an onshore–offshore transect. The results show that the preservation potential is highest over the upper part of the inter-tidal zone and in the lower part of the sub-tidal zone, and lowest near mean sea level and at low water on springs. The preservation potential tends to decrease with the advancement of the shoreline. The bed slope, tidal current direction and resuspension intensity influence the spatial distributions of the preservation potential. An implication of these results is that the temporal resolution of the tidal flat record depends upon the location and depth within the deposit; this should be taken into account in the interpretation of sedimentary records. Further studies are required to improve the model, on the hydrodynamic processes associated with extremely shallow water depths, sediment dynamic modeling of bed slope and profile shape, and the combined action of tides and waves for sediment transport on tidal flats.