Flux Of Matter Research Articles

Verbs and Adjectives to Nouns: The Evolution of Headwords in Encyclopedias from the Late Seventeenth to the Late Nineteenth Century

Abstract This article examines the changing forms of headwords in the partial differentiation of encyclopedias away from dictionaries from the late seventeenth century to the late nineteenth century. In the past, this differentiation has mostly been studied as a process of reducing lexical content in encyclopedias and reducing encyclopedic content in dictionaries, but it also manifested itself in the grammatical forms of allowable headwords. Specifically, proto-encyclopedias of the seventeenth and eighteenth centuries tended to accept verbs and adjectives as headwords, whereas many general encyclopedias from the mid-nineteenth century onward virtually eliminated any headwords except nouns. Here I point to three causes for this development in encyclopedias’ headwords: an influx of historical material as general encyclopedias acquired their modern scope, a de-emphasis on terminology and technolects in favor of coverage of concepts, and a rising concern for standardization and making it easier for readers to find what they wanted.

The importance of acid-processed meteoric smoke relative to meteoric fragments for crystal nucleation in polar stratospheric clouds

Abstract. The crystal formation of nitric acid trihydrate (NAT) in the absence of water ice is important for a subset of polar stratospheric clouds (PSCs) and thereby ozone depletion. It has been suggested that either fragmented meteoroids or meteoric smoke particles (MSPs), or possibly both, are important as heterogeneous nuclei of these crystals. Previous work has focused on the nucleating ability of meteoric material in nitric acid in the absence of sulfuric acid. However, it is known that when immersed in stratospheric sulfuric acid droplets, metal-containing meteoric material particles partially dissolve and components can reprecipitate as silica and alumina that have different morphologies to the original meteoric material. Hence, in this study, we experimentally and theoretically explore the relative role that sulfuric acid-processed MSPs and meteoric fragments may play in NAT nucleation in PSCs. We compared meteoric fragments that had recently been prepared (by milling a meteorite sample) to a sample annealed under conditions designed to simulate heating during entry into the Earth's atmosphere. Whilst the addition of sulfuric acid decreased the nucleating ability of the recently milled meteoric material relative to nucleation in binary nitric acid-water solutions (at similar NAT saturation ratio), the annealed meteoric fragments nucleated NAT with a similar effectiveness in both solutions. However, combining our results with measured fluxes of meteoric material to the Earth, sedimentation modelling and recent experiments on fragmentation of incoming meteoroids suggests that it is unlikely for there to be sufficient fragments to contribute to the nucleation of crystalline NAT particles. We then considered silica formed from sulfuric acid-processed MSPs. Our previous work showed that nanoparticulate silica (radius ∼6 nm) is a relatively poor promoter of nucleation compared with micron-scaled silica particles, which were more effective. Both materials have similar chemical and structural (crystallographically amorphous) properties, indicating that size is critical. Here, we account for surface curvature of primary grains using the Classical Nucleation Theory (CNT) to explore this size dependence. This model is able to explain the discrepancy in nucleation effectiveness of fumed silica and fused quartz by treating their nucleating activity (contact angle) as equal but with differing particle size (or surface curvature), assuming interfacial energies that are physically reasonable. Here, we use this CNT model to present evidence that nucleation of NAT on acid-processed MSPs, where the primary grain size is tens of nanometres, is also effective enough to contribute to NAT crystals in early season PSCs where there is an absence of ice. This study demonstrates that the modelling of crystal nucleation in PSCs and resulting ozone depletion relies on an accurate understanding of the transport and chemical processing of MSPs. This will affect estimated sensitivity of stratospheric chemistry to rare events such as large volcanic eruptions and long-term forecasting of ozone recovery in a changing climate.

Rational Design of High-Flux, Eco-Friendly, and Versatile Superhydrophobic/Superoleophilic PDMS@ZIF-7/Cu3(PO4)2 Mesh with Self-Cleaning Property for Oil-Water Mixture and Emulsion Separation.

In recent years, efficient oil-water separation has gradually become an indispensable part of environmental treatment. Superhydrophobic/superoleophilic materials with excellent self-cleaning performance are urgently required and remain challenging in the investigation of practical, rapid, and efficient separation of oil-water mixture and emulsion, especially those with robust surfaces that can be used in harsh conditions. In this work, a novel superhydrophobic/superoleophilic material was first fabricated by in situ constructing PDMS@ZIF-7/Cu3(PO4)2 hierarchical architectures on a copper mesh, which was adopted as a high flux and efficient separation material for gravity-driven separation of oil-water mixture as well as emulsion. The introduction of crucial Cu3(PO4)2 nanosheet interlayers created the ideal hierarchical structures and serve as partial templates for the subsequent in situ growth of hydrophobic ZIF-7 nanosheets. An improved superhydrophobicity (CA = 155°), permeation flux (102,000 L m-2 h-1), and preferred self-cleaning property were thus achieved by such manipulation of the copper mesh. The PDMS@ZIF-7/Cu3(PO4)2 mesh exhibited exceptional separation efficiency for diverse oil-water mixtures and emulsions attributed to the superhydrophobicity and the demulsification ability and considerable stability to cope with extreme environments including sunlight resistance, low temperature, and corrosion resistance, which prompted its promising applicability in cleaning emulsified wastewater.

Dark matter from Monogem

As a supernova shock expands into space, it may collide with dark matter particles, scattering them up to velocities more than an order of magnitude larger than typical dark matter velocities in the Milky Way. If a supernova remnant is close enough to Earth, and the appropriate age, this flux of high-velocity dark matter could be detectable in direct detection experiments, particularly if the dark matter interacts via a velocity-dependent operator. This could make it easier to detect light dark matter that would otherwise have too little energy to be detected. We show that the Monogem Ring supernova remnant is both close enough and the correct age to produce such a flux, and thus we produce novel direct detection constraints and sensitivities for future experiments.

Interface resistance of biomolecular condensates.

A hallmark of biomolecular condensates formed via liquid-liquid phase separation is the dynamic exchange of condensate components with the surroundings. Such material exchange can be key to condensate function, as the rate of component exchange can impact biochemical reaction rates in the condensates, the speed of response of condensates to a changing environment, and their number and sizes. How is this exchange rate controlled? Intuitively, this rate can be limited by the flux of materials from the dilute phase or by the speed of mixing inside the dense phase. Surprisingly, recent experiments suggest that this rate can also be limited by the dynamics of molecules at the droplet interface, implying the existence of an “interface resistance”. Here, we combined theory and simulation to show that an interface resistance can arise when incident molecules contact the interface without entering the dense phase. We find that such “bouncing” occurs for incident molecules that are capable of self-collapse into a non-sticking conformation. Our work highlights the underappreciated role of interface resistance in condensate exchange dynamics, with implications for natural and synthetic systems.

Active sinking particles: sessile suspension feeders significantly alter the flow and transport to sinking aggregates.

Sinking or sedimentation of biological aggregates plays a critical role in carbon sequestration in the ocean and in vertical material fluxes in wastewater treatment plants. In both these contexts, the sinking aggregates are 'active', since they are biological hot-spots and are densely colonized by microorganisms including bacteria and sessile protists, some of which generate feeding currents. However, the effect of these feeding currents on the sinking rates, trajectories and mass transfer to these 'active sinking particles' has not previously been studied. Here, we use a novel scale-free vertical tracking microscope (a.k.a. gravity machine; Krishnamurthy et al. 2020 Nat. Methods 17, 1040-1051 (doi:10.1038/s41592-020-0924-7)) to follow model sinking aggregates (agar spheres) with attached protists (Vorticella convallaria), sinking over long distances while simultaneously measuring local flows. We find that activity due to attached V. convallaria causes significant changes to the flow around aggregates in a dynamic manner and reshapes mass transport boundary layers. Further, we find that activity-mediated local flows along with sinking modify the encounter and plume cross-sections of the aggregate and induce sustained aggregate rotations. Overall, our work shows the important role of biological activity in shaping the near-field flows around aggregates with potentially important effects on aggregate fate and material fluxes.

Spatial and seasonal variations in the particulate sinking flux in the Bay of Bengal

Sediment traps have been widely used to study particles sinking through the oceanic water column. As part of the SIBER-INDIA program, sediment traps were deployed at three depths − 430 m (shallow), 1020 m (middle), and 1555 m (deep) on a mooring line in the northern BoB (Bay of Bengal Sediment Trap, BoBST). We present here data on fluxes, concentrations, and isotopic composition of carbon and nitrogen, for the period 2011–2012 for all three traps, and the shallow (505 m) and middle (1035 m) traps for 2019–2020. The mooring site was largely influenced by riverine water in 2011–2012 and the increase in flux during the southwest monsoon was attributed to both autochthonous production and a high influx of river-supplied material. On the other hand, the contribution of the lithogenic matter was less in 2019–2020. The weak sea level anomaly (SLA) signal showed that the influence of cyclonic eddies at the mooring location was minimal during the deployment period in 2011, whereas a cyclonic eddy seems to have contributed to the higher flux seen in May-June 2019. To delineate the long-term changes in the component fluxes, data collected during 2011–2012 and 2019–2020 were compared with earlier available data from the Northern Bay of Bengal Traps (NBBT-N). The annual carbonate fluxes in the present study (9.3 and 7.1 g m−2 y-1 in 2011 and 2019, respectively in the ∼ 1000 m trap, and 7.7 g m−2 y-1 in the deep trap in 2011) were low compared to earlier (1987–1997) data of NBBT-N (10.9–14.7 g m−2 y-1; avg. 13.1 ± 1.4 g m−2 y-1 for ∼ 1000 m traps and 12.0–16.1 g m−2 y-1; avg. 13.3 ± 1.3 g m−2 y-1 for deep traps). On the other hand, the opal fluxes were higher in 2011 as compared to earlier (1987–1997) and 2019 data. This is also reflected in the abundance of silicifiers, which was much higher in 2011 mainly supported by significant dissolved silica in the river runoff and from the lithogenic material dissolved in the seawater. The present study highlights the seasonal and inter-annual variations in riverine suspended particulate material in the BoB and warrants the continuation of time-series studies to infer long-term changes in the component fluxes.

Partitioning free energies and induced dipole response of small molecules across a POPC membrane using polarizable molecular dynamics.

The cell membrane is the semi-permeable barrier that regulates flux of materials in and out of the cell. The membrane has a characteristic dielectric gradient due to the amphiphilic nature of its constituent lipids, which have polar head groups and hydrophobic tails. This gradient plays governs many aspects of small-molecule partitioning and membrane protein folding and function. Atomistic details of small-molecule partitioning related to hydration and electronic polarization are still largely unknown. Here, we used polarizable molecular dynamics simulations to understand how the electronic environment influences the process of partitioning. We performed a series of unbiased and umbrella sampling (US) simulations using the Drude polarizable force field (FF) for six different amino-acid sidechain analogs in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer. Using a polarizable FF such as Drude allows for the investigation of explicit dipole responses as a function of local electric fields along the membrane normal. We assessed molecular dipole moments, which vary as a function of localization within the membrane, and compared outcomes of the Drude FF simulations to those of the nonpolarizable CHARMM36 FF to investigate the differences in the free energy surfaces of partitioning for our different amino-acid analogs. In doing so, we sought to quantify the effects of using the fixed-charge convention of nonpolarizable FFs, which may average out the influence of the membrane dielectric gradient. We show how polarity of small molecules influences their partitioning and describe key differences in the free energy surfaces between polarizable and nonpolarizable systems in these contexts. This work serves as a foundation for future investigations into polarizable simulations of drug partitioning, as well as simulations of membrane proteins.

Exergy Analysis

This paper argues for a continuing exploration of Nature’s organizing principles that sustain prolonged homeostasis of the earth’s ecosystems punctuated by forceful transitions to new emergent states. Ecosystems develop and maintain a dynamically stable state by transacting energy and materials with the surrounding flows to keep reversing their continual fall to the ground state. Conversely, the elevation of any component of the ecosystem above the ground level may be regarded as a measure of its functional efficiency. This measure, called exergy, can be calculated for an eco-subsystem based on knowledge of the energy and material fluxes that thread it and, most importantly, of where the ground level happens to be. Admittedly, it is not straightforward to quantify these figures, and the departure of assumptions from reality will inevitably translate into errors in the calculated exergy figures. However, the variance may be estimated by analysing the results of an ensemble...

Boundary exchange completes the marine Pb cycle jigsaw

Material fluxes at the land-ocean interface impact seawater composition and global cycling of elements. However, most attention has been focused on the fluvial dissolved fluxes. For elements like lead (Pb), whose fluvial particulate flux into the ocean is two orders of magnitude higher than the dissolved counterpart, the role of particulates in elemental cycling is potentially important but currently less appreciated. Using both chemical analyses on samples collected from around equatorial Southeast Asia and model simulations, we show that particulate-dissolved exchange is an important mechanism controlling the concentration and isotopic composition of dissolved Pb in the ocean. Our model indicates that Pb contributed from particulate-dissolved exchange at ocean boundaries is larger than, or at least comparable to, other major Pb sources to the seawater before the Anthropocene, when the anthropogenic Pb was absent. Our work highlights the importance of boundary exchange in understanding marine element cycling and weathering-climate feedback.

Sediment provenances shift driven by sea level and Indian monsoon in the southern Bay of Bengal since the last glacial maximum

The Tibetan Plateau uplift has induced the formation of the largest sediment source-sink system in the northeast Indian Ocean, which has become an ideal region for investigating land-sea interaction processes. However, many questions regarding sediment transport patterns and their controlling factors at different time scales remain unanswered. Therefore, in the present study, a gravity core named BoB-79, based on the southern Bay of Bengal (BoB) was selected to investigate sediment provenance shift and its corresponding mechanism to sedimentary environment change since the last glacial maximum (LGM). The clay mineral compositions are analyzed and the whole core sediments reveal a feature dominated by illite (~55%), followed by chlorite (~24%) and kaolinite (~17%), and the content of smectite (~4%) is the lowest. A trigonometric analysis of provenance discrimination of clay minerals showed that the Himalayas, together with the Indian Peninsula, represent the main sources of southern BoB sediments, and the last glacial period might have been controlled by the dominant Himalayan provenance, with an average contribution of approximately 90%. However, as a secondary source, the influence of the Indian Peninsula increased significantly during the Holocene, and its mean contribution was 24%, thus, indicating that it had a crucial effect on the evolution process of BoB. The sediment transportation pattern changed significantly from the LGM to the Holocene: in the last glacial period, the low sea level exposed the shelf area that caused the Ganges River connected with the largest submarine canyon in BoB named Swatch of No Ground (SoNG), and the Himalayan materials could be transported to the BoB directly under a strong turbidity current, thereby forming the deep sea deposition center with a sedimentation rate of 4.5 cm/kyr. Following Holocene, the sea level increased significantly, and the materials from multiple rivers around the BoB were directly imported into the continental shelf area. The intensive Indian summer monsoon dominated the transportation process of the terrestrial materials, thereby forming a deposition center in the shallow water area of the continental shelf northeast Indian Ocean; subsequently, the material flux relative to the input to the deep sea area decreased significantly, and the sedimentation rate in the southern BoB decreased to 1.7 cm/kyr.

Climate fluctuations during the Ordovician-Silurian transition period in South China: Implications for paleoenvironmental evolution and organic matter enrichment

The Ordovician-Silurian (OS) transition witnessed dramatic tectonic, climatic, marine, and biological coevolution, during which organic-rich black shale was widely deposited and is considered an important source rock. However, the potential links between the differential enrichment pattern of organic matter and climate fluctuations and paleoenvironmental evolution during this period are still unclear. In this paper, the Late Ordovician-early Silurian black shale in a JieLong (JL) section in South China was identified by graptolitic fossils, total organic carbon (TOC) content, X-ray diffraction (XRD), scanning electron microscopy (SEM) and geochemical analysis. The results show that the provenances of sedimentary rocks are all granodiorite-like. According to the variations in the TOC content and geochemical indicators, four layers are delineated. Under warm and humid climatic conditions, sea level rise and unstable seasonal upwelling led to Unit 1 organic matter enrichment controlled by high primary productivity, anoxic conditions and effective smectite production. Unit 2 organic matter burial was controlled by cold, arid and oxic environmental conditions, but primary productivity was still relatively high. After the end of the glacial period, warm and humid climatic conditions and rapid transgression were the main factors affecting the burial of organic matter in Unit 3. Under hot and humid climate conditions, higher terrigenous detrital inputs and unfavourable preservation environments, the dilution of organic matter in Unit 4 was accelerated. The corrected chemical index of alteration (CIAcorr) values show that the study area experienced a climate change of alternating cold and warm conditions in response to the climate fluctuation during the glacial-interglacial period. The CIAcorr value is negatively correlated with the TOC content, while the generation of available clay minerals (smectite) in warm and humid climates is usually consistent with the enhanced burial flux of organic matter, supporting the important role of climate fluctuations in the accumulation of organic matter. Finally, a comparison of the data from the present study with geochemical data from different profiles in South China reveals the role of climatic fluctuations during the OS transition in controlling paleoenvironmental evolution and organic matter enrichment, while such a heterogeneous factor is usually associated with global or regional geological events. Our study highlights this differential enrichment mechanism as a combined response of multiple factors and provides important implications for glacial-interglacial organic matter enrichment mechanisms.

Malformation in coccolithophores in low pH waters: evidences from the eastern Arabian Sea.

Oceanic calcifying plankton such as coccolithophores is expected to exhibit sensitivity to climate change stressors such as warming and acidification. Observational studies on coccolithophore communities along with carbonate chemistry provide important perceptions of possible adaptations of these organisms to ocean acidification. However, this phytoplankton group remains one of the least studied in the northern Indian Ocean. In 2017, the biogeochemistry group at the Council for Scientific and Industrial Research-National Institute of Oceanography (CSIR-NIO) initiated a coccolithophore monitoring study in the eastern Arabian Sea (EAS). Here, we document for the first time a detailed spatial and seasonal distribution of coccolithophores and their controlling factors from the EAS, which is a well-known source of CO2 to the atmosphere. To infer the seasonality, data collected at three transects (Goa, Mangalore, and Kochi) during the Southwest Monsoon (SWM) of 2018 was compared with that of the late SWM of 2017. Apart from this, the abundance of coccolithophores was studied at the Candolim Time Series (CaTS) transect, off Goa during the Northeast Monsoon (NEM). The most abundant coccolithophore species found in the study region was Gephyrocapsa oceanica. A high abundance of G. oceanica (1800 × 103cells L-1) was observed at the Mangalore transect during the late SWM despite experiencing low pH and can be linked to nitrogen availability. The high abundance of G. oceanica at Mangalore was associated with high dimethylsulphide (DMS). Particulate inorganic carbon (PIC) and scattering coefficient retrieved from satellites also indicated a high abundance of coccolithophores off Mangalore during the late SWM of 2017. Interestingly, G. oceanica showed malformation during the late SWM in low pH waters. Malformation in coccolithophores could have a far-reaching impact on the settling fluxes of organic matter and also on the emissions of climatically important gases such as DMS and CO2, thus influencing atmospheric chemistry. The satellite data for PIC in the EAS indicates a high abundance of coccolithophore in recent years, especially during the warm El Nino years (2015 and 2018). This warrants the need for a better assessment of the fate of coccolithophores in high-CO2 and warmer oceans.

Porous functional materials with excellent solar-thermal and electro-thermal properties for desalination of saline water

Desalination of saline water is a key technology to produce safe drinking water. Here, we report a novel type of reduced graphene oxide (GO) nanosheets modified porous functional materials (rGS) with both excellent solar-thermal and electro-thermal properties for efficient, portable, and continuous desalination of saline water. The rGS porous materials are prepared by modifying porous melamine sponges with GO nanosheets, and then reducing GO nanosheets into reduced GO (rGO) nanosheets. With sufficient rGO nanosheets coated on rGS porous materials, water evaporation fluxes of rGS-5 porous materials are > 1100 g m-2h−1 in solar-thermal desalination under 1000 W m−2 and > 3600 g m-2h−1 in electro-thermal desalination under direct voltage of 20 V due to the excellent solar-thermal property and Joule effect of rGS. The salt rejection values are always higher than 99.95% towards different saline waters including hypersaline water, and the salinities of distilled waters are always far lower than the WHO standard for safe drinking water. The strategy and results in this work provide valuable guidance for designing portable desalination systems to produce safe drinking water by simply using solar energy and/or direct-current power supply in certain applications with special needs such as remote regions and disaster situations.

Dynamical origin of Dimorphos from fast spinning Didymos

Didymos is a binary near-Earth asteroid. It is the target of the DART and HERA space missions. The primary body, Didymos, rotates close to the spin at which it is expected to shed mass. The secondary body, Dimorphos, is a 140 meters moon that orbits the primary body in about 12 h. Here we investigate the possible origin of Dimorphos. Using 1D models of ring/satellite interactions, we study the evolution of material lost from Didymos’ surface and deposited as a ring at its equator. We find that due to viscous spreading, the ring spreads outside the Didymos’ Roche limit forming moonlets. A fraction of the mass will form Dimorphos and a set of objects near the Roche limit, while most of the ring’s mass falls back on Didymos. To match the properties of today’s Dimorphos, the total mass that must be deposited in the ring is about 25% of Didymos’ mass. It is possible that a fraction of the material travelled several times between the ring and the surface of Didymos. The models produce an orbit similar to that observed for a Didymos tidal parameter k2/Q≤10−5. If the ring deposition timescale is long (≥102 yr) (so the material flux is small) Dimorphos could be irregularly shaped as it forms from the collision of similar-sized satellitesimals. However, the top-shape of Didymos is expected to be achieved due to a fast spin-up of the asteroid, which would result in a short deposition timescale (≲yr). In that case, the satellite would form from progressively accreting material at the Roche Limit, resulting in an ellipsoidal Dimorphos constructed of small pieces with sizes of the order of meters, which is apparently in agreement with the recent images of Dimorphos obtained by DART mission.

Biogeochemical controls on climatically active gases and atmospheric sulfate aerosols in the western Pacific

The Pacific Ocean plays an important role in regulating the budget of climatically active gases and the burden of sulfate aerosols. Here, a field investigation was conducted to clarify the key processes and factors controlling climatically active gases, including dimethyl sulfide (DMS), carbonyl sulfide (OCS), carbon disulfide (CS2), and carbon dioxide (CO2), in both surface seawater and the lower atmosphere of the western Pacific. In addition, the relative contributions of different sources to atmospheric sulfate aerosols were quantitatively estimated, and their causes were explored. The maximum concentrations of DMS, OCS and CS2 and the minimum partial pressure of CO2 (pCO2) were observed in the Kuroshio-Oyashio Extension. Kuroshio-induced mesoscale eddies brought abundant nutrients and organic matter from the subsurface layer of Oyashio into the euphotic layer, thus enhancing primary productivity and accelerating the photoreaction of organic matter. These processes led to higher concentrations of DMS, OCS and CS2 and lower pCO2. However, the oligotrophic subsurface layer in the subtropical gyre and the strong barrier layer in the equatorial waters suppressed the upward fluxes of nutrients and organic matter, resulting in lower surface concentrations of DMS, OCS, and CS2 in these areas. Being far from the continents, atmospheric concentrations of DMS, OCS and CS2 and pCO2 in the western Pacific generally were observed to depend on the local sea-to-air exchange and may be regulated by atmospheric oxidation and mixing of air masses. In general, oceanic DMS emissions played an important role in the formation of sulfate aerosols in the western Pacific (accounting for ∼19.5% of total sulfate aerosols), especially in the Kuroshio-Oyashio Extension (∼32.3%). These processes in seawater may also determine the variations and emissions of other climatically active gases from biogenic and photochemical sources.

Green Ironmaking Industry: Production of Iron Pellets Using Lime Sludge

The use of alternative raw materials is essential for establishing a circular economy in the mineral and ironmaking sectors. Therefore, this study investigates the potential of lime sludge as fluxing material during pelletization and proposes an alternative route for the usage of waste. The pellets were manufactured with different binary basicity values (CaO/SiO2) (0.15-0.45) and bentonite (0.5-0.7 wt%) and fixed carbon (0.5-1.1 wt%) contents. The results demonstrated that lime sludge has significant potential for application in pelletization. Pellet quality was evaluated using drop number, mechanical strength, tumble index, porosity, and kinetic analyses. Pellets with the optimal composition using lime sludge withstood 3.6 drops/pellet, a tumble test of 1.57 wt.%, and a mechanical strength test of 214.83 kgf/pellet and exhibited a porosity of 31.28%. Lime sludge did not influence the reducibility of the iron-ore pellets. In the temperature range of 800-900 °C, the reaction was controlled by diffusion, with Ea between 179.89 and 233.10 kJ/mol.

Sediment Traps: A Renowned Tool in Oceanography Applied to New Marine Pollutants

Particles afloat in the ocean are important components of marine element cycles. Most of this particulate matter is suspended in the sunlit surface layer and is mainly composed of microscopic living and dead organisms and fecal pellets. Aggregation of small, suspended particles into large, rapidly sinking aggregates can transport surface-​derived material to the deep ocean and the seafloor, contributing to the so-called biological pump. The comprehensive analysis of these sinking particles has increased our understanding of important biogeochemical ocean processes, such as the relationship between the rate of primary production and downward flux of particulate organic matter, the biological control of the removal of abiogenic particles from the surface ocean, and seasonal or inter­annual variations in downward particle fluxes. Sediment traps have been widely used since the late 1970s to capture the downward flux of particles for study (e.g., Staresinic et al., 1978; Knauer et al., 1979).

Thermal heat storage and convective melting dynamics of phase change materials in inclined square enclosures: Effect of the Prandtl number

We study numerically the effect of the Prandtl number on the thermal heat storage, heat flux, and melting dynamics in phase change materials enclosed in square geometries inclined from 0° (bottom horizontal heating) to 180° (top horizontal heating) at increments of at least 5°. Chosen phase change materials are representative of very low, moderate, and high Prandtl numbers: gallium ( P r = 0 . 021 ), water ( P r = 13 . 5 ), and erythritol ( P r = 201 ). The Stefan number is fixed to 0.5, and the Rayleigh number to R a ∼ 1 0 8 . Water and erythritol exhibit a global bifurcation angle at θ c = 3 0 ∘ , separating the liquid phase dynamics from turbulent to laminar. Gallium exhibits stages of turbulent behavior up to 165°. The optimum tilt for harvested thermal energy corresponds to 95° for water and erythritol, and 100° for gallium. The maximum energy efficiency in harvesting thermal energy corresponds to small inclinations within the turbulent region, and 50° for water and erythritol, and the region about 45° for gallium. The maxima at 50° and 95° are very close to those values of the most frequent inclinations 45° and 90° investigated in the experimental literature. There is a power-law dependence between the Nusselt and Rayleigh number N u ∼ R a α for all the Prandtl numbers. Power-law exponents for water and erythritol exhibit a global upward trend with the inclination and undefined for gallium. • Simulations on erythritol (Pr=201), water (Pr=13.5), gallium (Pr=0.021) for Rã10̂8. • Power-law with inclination between Nusselt and Rayleigh numbers for all the Prandtl. • Similar melting time, energy storage and efficiency curves for all Prandtl. • Exists a critical inclination splitting laminar from turbulent flow for all Prandtl. • Optimal inclination for energy storage: 95° water and erythritol, 100° for gallium.

Black Ecologies (Humanity, Animality, Property)

Black Ecologies (Humanity, Animality, Property)