Physical Mixing Processes Research Articles

Experimental and numerical investigation of the Advanced Fuel Ignition Delay Analyzer (AFIDA) constant-volume combustion chamber as a research platform for fuel chemical kinetic mechanism validation

Advanced combustion engine strategies that can offer increased efficiency and reduced emissions are enabled by numerical engine combustion simulations, requiring accurate chemical kinetic mechanism input. The Advanced Fuel Ignition Delay Analyzer (AFIDA) device can perform high quality, repeatable measurements of ignition delay (ID) times using small fuel quantities with high throughput. The AFIDA experiments involve liquid fuel injection into the heated and pressurized constant-volume chamber, producing an autoignition delay resulting from a combination of physical mixing and chemical kinetic processes, a complexity which makes the development of complementary numerical models necessary for the development and validation of chemical kinetic mechanisms. Modeling the device based on a homogenous approximation with reduced primary reference fuel (PRF) mechanism shows up to 75% error in the modeled vs. observed autoignition delay data for n-heptane and iso-octane at 10 bar (ɸ = 1.2–0.8) and 20 bar (ɸ = 0.6–0.4) over 973–648 K, whereas the use of a computational fluid dynamics (CFD) model reduces the discrepancy to within 25%. The homogenous approximation error is greatest for conditions where the observed ignition delay is short and the system is not sufficiently mixed (<30 ms), providing guidance to select a homogenous reactor vs. CFD modeling approach based upon desired accuracy. Experimental 20 bar iso-octane ID results show a larger magnitude of negative temperature coefficient chemistry compared to numerical results, indicating possible deficiencies in the PRF chemical kinetic mechanism. This characterization demonstrates the AFIDA as a capable research platform for chemical kinetic model development and validation.

Two-dimensional ultrathin BiOCl nanosheet/graphene heterojunction with enhanced photocatalytic activity

2D semiconductors and their heterostructures promise great potential in solar-driven photocatalysis owing to their unique properties that result from structural planar confinement. Herein, we fabricate the BiOCl nanosheet/graphene hybrid with 2D heterojunction through a hydrothermal and physical mixing two-step process. Studies on the heterostructure reveal the close interfacial contact between the BiOCl nanosheet and graphene through van der Waals interaction rather than chemical bonding. Compared with BiOCl-bulk/graphene hybrid, the BiOCl nanosheet/graphene hybrid showed superior photocatalytic activity towards dye decolorization and decomposition, featuring a remarkable enhancement of a 15-fold higher reaction rate. A series of characterizations reveal that the co-effect of the surface defect of the BiOCl nanosheet and graphene planar structure contributes to an extended light absorption range, better electrical conductivity and larger dye adsorption capacity. Furthermore, the unique van der Waals close contact between graphene and BiOCl promoted the fast and continuous consumption of photogenerated electrons, thereby effectively facilitating the separation of electron–hole pairs. This work underscores the key role of face-to-face heterojunction for the interfacial charge transfer process.

Origin of lunar fragmental matrix breccias—Highly siderophile element constraints

AbstractEjecta at North Ray crater (Apollo 16) sampled a unique section of the lunar highlands not accessible at most other landing sites and provide important constraints on the composition of late accreted materials. New data on multiple aliquots of four fragmental matrix breccias and a fragment‐laden melt breccia from this site display a variety of highly siderophile element patterns which may represent the signatures of volatile element‐depleted carbonaceous chondrite‐like material, primitive achondrite, differentiated metal, and an impactor component that cannot be related to known meteoritic material. The latter component is prevalent in these rocks besides characterized by depletions in Re and Os compared to Ir, Ru and Pt, chondritic Re/Os, and a gradual depletion of Pd and Au. The observed characteristics are more consistent with fractionations by nebular processes, like incomplete condensation or evaporation, than with lunar crustal processes, like partial melting or volatilization. The impactor signature preserved in these breccias may stem from primitive meteorites with a refractory element composition moderately different from known chondrites. The presence of distinct impactor components within the North Ray crater breccias together with observed correlations of characteristic element ratios (e.g., Re/Os, Ru/Pt, Pd/Ir) in different impact lithologies of four Apollo landing sites constrains physical mixing processes ranging from the scale of gram‐sized samples to the area covered by the Apollo missions.

Dissolved organic matter at the fluvial–marine transition in the Laptev Sea using in situ data and ocean colour remote sensing

Abstract. River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle, and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC–aCDOM(λ) model for the fluvial–marine transition zone in the Laptev Sea. The aCDOM(λ) characteristics revealed that the dissolved organic matter (DOM) in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM(443) and its spectral slopes indicate that DOM is modified by microbial and photo-degradation. Ocean colour remote sensing (OCRS) provides the absorption coefficient of coloured dissolved organic matter (aCDOM(λ)sat) at λ=440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The OLCI (Sentinel-3 Ocean and Land Colour Instrument) neural network swarm (ONNS) algorithm showed the best performance compared to in situ aCDOM(440) (r2=0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC–aCDOM(λ) model was applied to ONNS-derived aCDOM(440), and retrieved DOC concentration maps showed moderate agreement to in situ data (r2=0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from Medium Resolution Imaging Spectrometer (MERIS) satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC–aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.

Broadening of Modeled Cloud Droplet Spectra Using Bin Microphysics in an Eulerian Spatial Domain

Abstract This study investigates droplet size distribution (DSD) characteristics from condensational growth and transport in Eulerian dynamical models with bin microphysics. A hierarchy of modeling frameworks is utilized, including parcel, one-dimensional (1D), and three-dimensional large-eddy simulation (LES). The bin DSDs from the 1D model, which includes only vertical advection and condensational growth, are nearly as broad as those from the LES and in line with observed DSD widths for stratocumulus clouds. These DSDs are much broader than those from Lagrangian microphysical calculations within a parcel framework that serve as a numerical benchmark for the 1D tests. In contrast, the bin-modeled DSDs are similar to the Lagrangian microphysical benchmark for a rising parcel in which Eulerian transport is not considered. These results indicate that numerical diffusion associated with vertical advection is a key contributor to broadening DSDs in the 1D model and LES. This DSD broadening from vertical numerical diffusion is unphysical, in contrast to the physical mixing processes that previous studies have indicated broaden DSDs in real clouds. It is proposed that artificial DSD broadening from vertical numerical diffusion compensates for underrepresented horizontal variability and mixing of different droplet populations in typical LES configurations with bin microphysics, or the neglect of other mechanisms that broaden DSDs such as growth of giant cloud condensation nuclei. These results call into question the ability of Eulerian dynamical models with bin microphysics to investigate the physical mechanisms for DSD broadening, even though they may reasonably simulate overall DSD characteristics.

PCO2 Dynamics of Stratified Reservoir in Temperate Zone and CO2 Pulse Emissions During Turnover Events

This study explores the dynamic changes in the partial pressure of CO2 (pCO2) with depth, and the temporal variations of CO2 net atmospheric flux (NAF) in a stratified reservoir. A total of 16 field campaigns were conducted from the summer stratification to fall turnover period in 2017. A random forest (RF) model was developed to estimate the pCO2 using concurrently measured water quality variables. The results showed that the vertical distribution of pCO2 and associated temporal variations of the NAF are closely related to the stratification strength of the reservoir. The reservoir surface pCO2 was supersaturated (1542 µatm) in summer (July 11), but this decreased to undersaturation as algae grew. Meanwhile, dissolved CO2 continuously accumulated below the reservoir mixed-layer due to the thermal stratification barrier and organic-rich floodwater intrusion. Vertical mixing began instantly as the stratification strength began to weaken in mid-October, and the surface pCO2 increased sharply up to 1934 µatm. Consequently, the NAF drastically increased to 3235 mg−CO2 m−2·day−1, which implies that the NAF changes seasonally and large CO2 pulsing occurs during the turnover events. The results provide valuable information about pCO2 variability and physical mixing processes, as well as carbon budget estimation in stratified reservoirs, and offer an improved understanding of these phenomena.

Floating storage and regasification units face specific LNG rollover challenges: Consideration of saturated vapor pressure provides insight and mitigation options

Floating Storage and Regasification Units (FSRU) form a rapidly expanding sector of LNG business. In many cases, FSRU now provide a more cost-effective and very flexible way to deliver natural gas to end users in comparison with shore-based terminals. Due to enhanced operations FSRU are more complex compared to LNG carriers (LNGC). FSRU are essentially merge of the attributes of shore-based terminals and LNGC. The existing FSRU fleet is formed of new-build vessels and converted LNGC. Together with their advantages FSRU come with the inherent problems of handling and storing LNG. Here we focus on the rollover issues that occur on FSRU and suggest ways to improve handling to minimize the impacts of those events. Rollover is a physical mixing process in a single tank with two or more different parcels of LNG of different compositions, temperatures and densities that can manifest in large boil-off rates, beyond handling-equipment capacities, and large tank pressure increases culminating rapidly. If prevention/mitigation actions are not implemented, uncontrolled venting of boil off gas in vapor form to the atmosphere is a likely consequence involving flammability hazards and tank structure over-pressurization with potential damage.This study provides in-depth analysis of FSRU rollovers based on observations of more than twenty rollovers on many different FSRU. The analysis focuses on LNG saturated vapor pressure (SVP) rather than the traditional approach of focusing on boil-off rate (BOG). This approach allows efficient rollover management without any in-built rollover prevention means. Strategies are developed for managing a combination of FSRU tanks utilizing rollover prevention and mitigation actions, as well as efficient pre-planning for LNG stock management. Novel rules of thumb for predicting time to rollover onset, based on many observed FSRU rollovers provide operators with real-time insight to what rollover preventive and mitigating actions are effective in specific circumstances.

Definition and comparison of mixed expansion efficiency for cooled turbine

Over the years, there has been continual increase in the temperature inside a turbine inlet through improvements in the gas turbine efficiency and specific power, and cooling technologies to deal with such temperature increases have been under development for decades. However, the definition of “efficiency” remains ambiguous for cooled turbines, with no consensus achieved on the ideal expansion process. This paper first reviews several proposed definitions, Hartsel, MP (mainstream-pressure), FR (fully reversible), and WP (weighted-pressure) of efficiency and then presents a new one to overcome the existing shortage. The increase in entropy related to mixing is first analysed to demonstrate that FR efficiency consistently provides a significantly lower value than the other definitions, assuming the unavoidable entropy generation to be zero. The flow mixing in a smooth adiabatic channel is then analysed to show that the WP ideal process is not sufficiently “ideal.” A fully mixed (FM) definition is then proposed based on a physical mixing process, followed by isentropic expansion, the value of which does not differ significantly from most of the proposed definitions, and is able to consider the influence of the inlet Mach number on the hypothetical ideal process. Finally, this paper compares several definitions in view of the thermodynamic cycle, and shows that the FM definition can determine the performance potential of an existing turbine better than the other definitions, which means that the FM efficiency can be used as a reliable tool for the performance evaluation and optimization of a cooled turbine.

Using different assumptions of aerosol mixing state and chemical composition to predict CCN concentrations based on field measurements in urban Beijing

Abstract. Understanding the impacts of aerosol chemical composition and mixing state on cloud condensation nuclei (CCN) activity in polluted areas is crucial for accurately predicting CCN number concentrations (NCCN). In this study, we predict NCCN under five assumed schemes of aerosol chemical composition and mixing state based on field measurements in Beijing during the winter of 2016. Our results show that the best closure is achieved with the assumption of size dependent chemical composition for which sulfate, nitrate, secondary organic aerosols, and aged black carbon are internally mixed with each other but externally mixed with primary organic aerosol and fresh black carbon (external–internal size-resolved, abbreviated as EI–SR scheme). The resulting ratios of predicted-to-measured NCCN (RCCN_p∕m) were 0.90 – 0.98 under both clean and polluted conditions. Assumption of an internal mixture and bulk chemical composition (INT–BK scheme) shows good closure with RCCN_p∕m of 1.0 –1.16 under clean conditions, implying that it is adequate for CCN prediction in continental clean regions. On polluted days, assuming the aerosol is internally mixed and has a chemical composition that is size dependent (INT–SR scheme) achieves better closure than the INT–BK scheme due to the heterogeneity and variation in particle composition at different sizes. The improved closure achieved using the EI–SR and INT–SR assumptions highlight the importance of measuring size-resolved chemical composition for CCN predictions in polluted regions. NCCN is significantly underestimated (with RCCN_p∕m of 0.66 – 0.75) when using the schemes of external mixtures with bulk (EXT–BK scheme) or size-resolved composition (EXT–SR scheme), implying that primary particles experience rapid aging and physical mixing processes in urban Beijing. However, our results show that the aerosol mixing state plays a minor role in CCN prediction when the κorg exceeds 0.1.

LNG rollover challenges and their mitigation on Floating Storage and Regasification Units: New perspectives in assessing rollover consequences

Floating Storage and Regasification Units (FSRU) are an expanding fleet (∼22 in service) handling liquefied natural gas (LNG) in a more-complex and dynamic way than LNG carriers and land-based terminals. Rollover is a physical mixing process in a single tank with two or more different parcels of LNG of different compositions, temperatures and densities that can manifest in large boil-off rates, beyond handling-equipment capacities, and large tank pressure increases culminating rapidly. Such tank-pressure rises pose safety, environmental and commercial risks. The consequences of some rollovers, if prevention/mitigation actions are not implemented, are uncontrolled venting of boil off gas in vapor form to the atmosphere, flammability hazards, tank structure over-pressurization with potential damage. Existing industry guidance for handling FSRU rollovers remains limited because: 1) there are a range of vessel designs with different tank pressure ratings; 2) tanks are typically not equipped with specific “anti-rollover “equipment; 3) most FSRUs are not equipped with “densitometers” throughout their tanks; and, 4) FSRU industry procedures are often ill-suited to the operational patterns imposed on the vessels. This study provides in-depth analysis of FSRU rollovers based on observations of more than twenty rollovers on many different FSRU. The analysis leads to a new rollover-magnitude-assessment methodology integrating saturated vapor pressure (SVP) of the LNG versus actual tank pressure and tank strength. This provides operators with a rollover rating that enables them to better prepare and implement efficient and effective prevention and mitigation actions integrating cargo-stock management, internal transfers and standard techniques available on most FSRU (e.g., top spraying). Novel rules of thumb for predicting time to the onset of a rollover, LNG temperature and tank pressure based on many observed FSRU rollovers are developed to provide operators with a better “on the spot” insight to rollovers. This better understanding improves preventive and mitigating actions taken in specific circumstances.

Humidity sensor based on solution processible microporous silica nanoparticles

Composites fabricated by mesoporous silica loading hydrophilic elements have been widely investigated as humidity sensitive materials. The physical mixing process for loading hydrophilic elements is difficult to guarantee the uniformity and structural stability of the composites. Furthermore, the poor dispersibility of the silica skeleton restricts its solution processability. Herein, solution processible organic-inorganic hybrid materials were synthesized via a thiol-ene click reaction between sulfhydryl functionalized microporous silica nanoparticles (MSNs) and hydrophilic alkenyl monomer. The optimal hybrid material could disperse in water stably with a concentration of 50 mg/mL owing to the small particle size (about 105 nm) and the hydrophilic characteristic. Humidity sensors were fabricated by solution process and the humidity sensing properties were investigated. The sensor exhibits high sensitivity (about three orders impedance modulus change), small hysteresis (∼2% RH) and rapid response (the response and recovery time are 5 and 40 s, respectively) in the humidity range of 11%–95% RH.

Facile synthesis of α-Fe2O3/WO3 composite with an enhanced photocatalytic and photo-electrochemical performance

The influence of hematite iron oxide (α-Fe2O3) nanoparticles in tungsten oxide (WO3) nanorods photocatalyst on photodegradation of organic pollutant was investigated in the present work. The spherical-shaped α-Fe2O3 nanoparticles and WO3 nanorods were synthesized from citrate precursor and hydrothermal routes respectively. The different weight percentage (wt%) ratios (1, 2, and 3 wt%) of α-Fe2O3 added heterostructured α-Fe2O3/WO3 composite photocatalysts by a simple physical mixing process. The photocatalytic activities of as-synthesized photocatalysts were evaluated by photodegradation of methylene blue (MB) under visible-light irradiation. It showed that the 2% α-Fe2O3/WO3 composite exhibited excellent photocatalytic activity than the others. This enhancement could be attributed to its strong absorption in the visible region and the low recombination rate of electron-hole pairs. In addition, the photo-electrochemical measurements of the 2% α-Fe2O3/WO3 composite revealed the faster migration of the photo-excited charge-carriers. Hence, this study demonstrates the heterostructured α-Fe2O3/WO3 composite as a promising candidate for environmental remediation.

Amine-functionalized mesoporous ZSM-5 zeolite adsorbents for carbon dioxide capture

ZSM-5 type zeolite with mesoporous structure was prepared and then amine-functionalized with tetraethylenepentamine (TEPA) by wet impregnation method to form a series of CO2 adsorbents (ZTx). The structural properties of ZSM-5 and ZTx were characterized by XRD, FTIR, TGA/DTG, nitrogen adsorption/desorption, SEM and EDX techniques. The adsorption capacity of the adsorbents with different amine loading was measured at a temperature from 40 to 100 °C and the adsorption capacity of ZT7 was 1.80 mmol/g at 100 °C. The adsorption process and mechanism were studied by fitting the experimental data used the three adsorption kinetic models, and a complex physical and chemical mixing process was produced as the amine entered the surface and pore size of the zeolite. The high adsorption selectivity at 10% CO2 concentration and the stability of the five adsorption desorption cycles indicated that ZT7 is a suitable and promising CO2 adsorbent for the purification of industrial flue gas.

The fabrication of porous 4A-zeolite-supported Ag nanoparticles catalysts and its catalytic activity for styrene epoxidation

Binderless hierarchically porous 4A-zeolite has been successful produced through hydrothermal crystallization, in which silicon-aluminum sol binded to the carbon nanofibers (CNFs), that is to say, where the CNFs powder was coated during the crystallization 4A-zeolite. The mixing of silica-alumina sol and CNFs was only a simple physical mixing process. The samples of micropores-macroporous hierarchical 4A-zeolite (P-4A-zeolite) was analyzed by a series of characterization techniques, such as field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), simultaneous thermal analysis (STA) and CO2 adsorption-desorption (BET and BJH), and so on. In addition, the adsorption test of silver nanoparticles was carried out. The characterization results indicated the presence of micropores and the formation of macroporous. At the same time, silver adsorption test proved that the prepared P-4A-zeolite had good adsorption performance and the catalytic performance of Ag/P-4A-zeolite was further investigated through the epoxidation of styrene.

Optimized particle engineering of fluticasone propionate and salmeterol xinafoate by spray drying technique for dry powder inhalation

Asthma is one of the most common respiratory diseases that can be efficiently managed through combined treatment of fluticasone propionate (FP) and salmeterol xinafoate (SX). In this study, we challenged the use of both spray drying and mixing techniques in sequential combination of lactose or mannitol with FP and SX as two steps in development of inhalable powder formulation of the drugs. Leucine was used as a dispersibility enhancer. The formulations were optimized using the Design-Expert software. The effects of three independent variables namely the type of carrier, percentage of spray-dried carrier and the amount of leucine were investigated on in vitro deposition. The results showed that the maximum fine particle fraction (FPF) and the minimum particle size was belonged to formulation in which the percentage of leucine was 20% with respect to the total solid content and 50% of mannitol was used during spray drying, while the remaining 50% of it was applied in the physical mixing process. This study showed that not only the choice of carrier and additives for every drug combination, but also an optimized ratios of them during both spray drying and physical mixing can be crucial in developing suitable inhalable dry powder formulations.

Organic-inorganic hybrid materials based on mesoporous silica derivatives for humidity sensing

Mesoporous silicas loading hydrophilic materials composites were widely used in humidity sensors during the last decade. However, the physical mixing process used for loading the hydrophilic materials in the channel of mesoporous silicas is hard to guarantee their uniform dispersion, and there is no strong force to bind the host and guest materials together. To solve above problems, novel vinyl functionalized mesoporous silicas (SBA-15-vinyl) were chemically modified with hydrophilic sodium p-styrenesulfonate (SSS) with free radical polymerization. The chemical and porous structures of the obtained hybrid materials (SBA-15-PSSx) were characterized by fourier transform infrared spectroscopy (FT-IR), elemental analyses (EA), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and N2 adsorption-desorption. The humidity sensing properties of the sensors based on SBA-15-vinyl and SBA-15-PSS indicate the introduction of PSS could effectively enhance the sensing properties of SBA-15-vinyl. The impedance of the optimized sensor changed by more than three orders of magnitude over the relative humidity (RH) range of 11%–95%, with rapid response to RH change.

Spurious dianeutral mixing in a global ocean model using spherical centroidal voronoi tessellations

In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean (Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z* vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy (RPE), front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter χ, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number (HGRN), ReΔ, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al. (2012), i.e., MITGCM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MITGCM and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexagon cell and the quadrilateral cell with the same resolution. Both the Zalesak (1979) flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.

Importance of microbial iron reduction in deep sediments of river-dominated continental-margins

Remineralization of organic carbon in deep-sea sediments is thought to proceed primarily via aerobic respiration and sulfate reduction because the supply of nitrate and metal oxides is not usually significant in deep-sea sediments. Dissimilatory metal reduction, on the other hand, may represent a dominant pathway in coastal and continental shelf sediments where delivery of terrigenous Fe(III) and Mn(IV/III) oxides is sufficiently high or where physical mixing processes near the sediment–water interface can result in the reoxidation of Fe2+ or Mn2+. Passive continental margin sediments receiving outflow from large rivers are well-known deposition centers for organic carbon and may also be hotspots for metal-reducing microbial activity, considering the simultaneous rapid deposition of unconsolidated metal oxides of terrigenous origin. Despite its potential, only a few studies have examined the role of microbial metal reduction in Corg remineralization in these environments. To investigate carbon remineralization processes in continental margin sediments, shallow cores across channels and levees in the Congo River fan (~5000m) and Louisiana slope (<1800m) were profiled for the main redox species involved in early diagenesis using a combination of voltammetric gold mercury (Au/Hg) microelectrodes and conventional analyses. Interestingly, metal reduction dominated carbon remineralization processes in the top ~20cm of sediment subject to high deposition, while evidence for sulfate reduction was lacking. These findings suggest that dissimilatory Fe(III) reduction may be more significant than previously thought in continental slope sediments, which may have important implications on carbon cycling in marine environments. In addition, these findings may have geological implications in controlling atmospheric oxygen levels over geological time and the evolution of microbial life on Earth.

Morphology Alters Fluid Transport and the Ability of Organisms to Mix Oceanic Waters.

Mixing in the ocean is opposed by the stratification of fluid, such that density of seawater increases with greater depth. The mechanisms by which mixing occurs have been attributed largely to physical processes that include atmospheric forcing, tides, and internal waves. Biogenic mixing, another potential source of mixing in the ocean, may generate significant transport of fluid during diel vertical migrations of organisms. Biogenic mixing is not limited to the near-surface or to regions of rough bottom topography, as are other physical mixing processes, and may contribute significantly to the energy budget of mixing in mid-ocean. "Fluid drift", a mechanism first described by Charles Galton Darwin, has been identified as a mechanism that allows for long-distance, vertical transport of fluid by the smallest of swimming organisms. However, little is known about how fluid drift varies with morphology and behavior of swimming organisms. We conducted numerical simulations of theoretical and experimentally measured flows of swimming medusae (Phyllorhiza sp.), and compared the volume of the drift induced by these flows. Our numerical simulations of fluid drift showed that morphology coupled with swimming behavior alters the transport of fluid both spatially and temporally. Given empirical velocity field data, the methods presented here allow us to systematically compare fluid transport across taxa, and enable us to deduce the potential of swimming organisms to influence fluid transport.

Facile assembling of AgI/Ag3PO4 via dissolution–precipitation mechanism and its excellent photocatalytic activity for contaminant removal

AgI/Ag3PO4 was successfully synthesized via a simple physical mixing process in the medium of water by using AgI microparticles and Ag3PO4 nanospheres as precursors on the basis of a novel dissolution–precipitation strategy. The as-prepared AgI/Ag3PO4 composite exhibited much higher activity than the pure AgI and Ag3PO4 for eliminating methyl orange under visible light (λ>420nm). The pseudo-first-order rate constant of methyl orange degradation over 75% AgI/Ag3PO4 was 0.056min−1, which is 18.6 and 1.36 times higher than those over pure AgI and Ag3PO4. AgI/Ag3PO4 heterostructure interface efficiently separated the photoinduced carriers and acquired excellent photocatalytic activity and stability. It provides a facile, fast and universal tactic to construct inorganic salts semiconductor composite photocatalysts based on the novel dissolution–precipitation strategy.