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The aim of this study is to determine the misconceptions of Greek junior high school students regarding the floating and sinking of a body through the concept of density. Density is included in most international curricula for this age group and is revisited in Greek junior high schools after being introduced in primary school. After interviews with teachers who teach the physics course, in order to discover the students' way of thinking and their common misconceptions, the researchers of this study created targeted questionnaires for students aged 11-12 years old. During the 2022-23 school year, the questionnaires were handed out to 47 first-grade students at a junior high school in Athens, Greece. Before being administered to the students, the questionnaires were subjected to a content validity test by five physics experts according to Aiken's V index. Then, they were completed by the students before the lesson was taught. After the students had completed the initial questionnaire, a teaching proposal focused on the density-based approach was presented to them. Subsequently, the students filled out the same questionnaire again following the instructional session. Statistical analysis demonstrated a notable enhancement in the comprehension of the misconceptions addressed in this study, with the rates of improvement varying between 18.08% and 52.13%. Consequently, the instructional proposal proved to be instrumental in advancing students' conceptual understanding of floating and sinking within the framework of density interpretation. [ABSTRACT FROM AUTHOR]

Kelps are resilient organisms, capable of thriving in high-energy wave environments. However, when hydrodynamic drag forces exerted by the wave environment exceed the kelps' structural limits, individuals become dislodged. Floating kelps generally follow ocean currents, traveling long distances until air-filled structures fail or the epibiont load becomes too great, causing them to sink to the seafloor. The ability of kelp to disperse over vast offshore and nearshore systems makes them important for organic subsidy and as a dispersal vector for marine organisms. Previous research on dislodged macroalgae focused on context-specific rafts, limiting insights into the broader ecological role of floating kelp. This study employed a site-specific Lagrangian trajectory model to describe the spatial distribution of floating Ecklonia maxima along the South African coastline. The model incorporated buoyancy and sinking using site-specific morphological data. Findings revealed that the distribution of floating E. maxima is influenced by oceanographic conditions, and seasonal patterns were also evident. Mesoscale features played a vital role in kelp accumulation on the surface and seafloor and acted as barriers to dispersal. This study offers essential insights into kelp's role as an organic subsidy and provides numerical evidence for kelp's potential as a carbon sink, contributing to a better understanding of kelp ecosystems and their ecological functions. [ABSTRACT FROM AUTHOR]

Sinking accidents can cause catastrophic losses in human, economic resources and environmental damage. Sinking accidents are one of the most common maritime accidents that occur in Indonesia. Therefore, this study aims to analyze the cause-and-effect probability of ship sinkings in Indonesian waters. Bayesian Network method and accident factor level are used to analyze the causal factors of ship sinking accidents. The results found that the Loss of Stability of the vessel is the most sensitive node. An additional take from the investigated sinking is that half of the accidents occurred on passenger vessels, and ships over 25 years old are prone to sinking due to corrosion and lack of proper maintenance. While 70.5% of accident caused by human error that is majorly triggered by unsafe acts. The real-case analysis also performed in this study reveals that eliminating Human Error and ship’s associated factors can reduce the probability of sinking by 17.2%. [ABSTRACT FROM AUTHOR]

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Sinking of microplastics (MPs) after biofouling is considered an important mechanisms responsible for the downward transport/sedimentation of MPs in the ocean and freshwaters. Previous studies demonstrated MP sinking caused by an increase in the composite density of MPs after biofouling, while MPs with smaller size or shapes with higher surface area to volume ratios (SA:V), such as films, are speculated to sink faster. In this study, we designed an in situ microcosm to simulate the ambient environmental conditions experienced by floating MPs to elucidate the biofouling and sinking of polyethylene (PE), polypropylene (PP), and expanded-polystyrene (EPS) MPs of various sizes and shapes. Our results showed smaller PE and PP MP granules sank faster than large ones. Even EPS granules of 100 μm diameter, having a much lower density (0.02 mg/mm3) than water, started to sink after 2 weeks of biofouling. Moreover, PE film and fiber MPs with higher SA:V did not sink faster than PE MP granules of the same mass, implying that mechanisms other than SA:V, such as fouling contact area and drag coefficient, play a role in the regulation of biofouling and sinking of MPs.

The sinking of outfall pipeline is the key link in the process of shipping and installing marine outfall pipelines. A steel pipeline with a length of 500 m and an inner diameter of 1 m is taken as the research object. The critical depth of pipe sinking is determined by numerical analysis and the equivalent stress of S-shaped pipe section is taken as the limiting condition. The buoyancy, number and spacing of the airbag are determined by the buoyancy aid safety factor and negative buoyancy of the pipe section. The sinking of the outfall pipeline is finally realized by means of multiple underwater sinking. The elevation error, axial error and flange joint gap in the engineering example all meet the acceptance requirements, which proves that the sinking technology is reliable and the application effect is good, and can provide reference for the construction of the same type of outfall pipelines. [ABSTRACT FROM AUTHOR]

Phytoplankton sinking is a major component of vertical ocean carbon and nutrient fluxes, and sinking is an integral component of phytoplankton biology and ecology. Much of our understanding of phytoplankton sinking derives from the settling column method (SETCOL) in which sinking speeds are calculated from the proportion of cells reaching the bottom of a water-filled column after a set time. Video-based methods are a recent alternative to SETCOL in which sinking speeds are measured by tracking the movement of individual cells in a salinity-stratified water column. In this study, we present the results of a meta-analysis showing that SETCOL produces significantly and consistently lower sinking speeds than the video method. Next, we perform a particle image velocimetry analysis, which shows that the observed discrepancy in sinking speeds between the two methods can probably be explained by weak convection currents in the SETCOLs. Finally, we discuss the implications of these results for the interpretation of past and future phytoplankton sinking speed measurements and models that rely on those measurements.

Although the Brazilian Amazon is still one of the most well-conserved environments in the world, it contains an extensive network of waterways that are used by a wide range of vessels that transport both people and cargo, as well as undertaking other activities. To plan environmental risk disaster strategies here, the potential effects of technological disasters, including marine accidents, must be taken into consideration. This paper seeks to redress this by providing a review of the possible risks to the Amazon aquatic environment that could result from various types of marine accidents. While the Amazon region has been researched worldwide, both extensively and intensively, regarding land use, climate, and environmental characterization, work in this field is scarce. A review of the main environmental characteristics of the Amazon is provided, including a description of common marine accidents that have occurred in this region. The environmental impacts experienced by the aquatic environment due to marine accidents worldwide were reviewed from the scientific literature to examine potential risks to the Amazon waterways. It was found that marine accidents, such as fire/explosions and the sinking of ships with different types of cargo, can cause the spillage of oil and other hazardous materials, causing catastrophic damage to the aquatic environment. Changes in the hydrological characteristics of rivers, including unexpected changes in the weather, such as heavy rain and winds, may also influence pollutant dispersion. Initiatives to deal with these technological hazards in the Amazon basin should also consider the potential social and environmental impacts in the protected areas of this region. It is hoped that this paper can serve as a starting point toward the governance and planning of risk disaster management actions, which are aimed at reducing the negative environmental impacts caused by marine accidents in the region. [ABSTRACT FROM AUTHOR]

This paper evaluates the susceptibility to subsidence and collapses in karst terrains of Campeche, Mexico, assuming that under a set of conditioning factors these phenomena occur with greater or lesser intensity and may represent a hazard to the population and economic activities. The conceptual model proposes the relative weighting of susceptible areas through multicriteria analysis of analytical hierarchies including lithological, structural, and environmental factors that affect the geomechanics of subsidence and collapse. The conceptual model is translated into a logical one in a Geographic Information System (ArcMap) from which a susceptibility map with four levels is obtained, very high with 13% of the state area, high 25%, medium 30% and low 32%. The susceptibility values correspond to the levels of predisposition of the terrain to hazard. It is concluded that the susceptibility map is a preventive threat cartographic document, useful at the regional level. [ABSTRACT FROM AUTHOR]

In this work, we establish a two-dimensional axisymmetric simulation model to numerically study the impacting behaviors between oil droplets and an immiscible aqueous solution based on the three-phase field method. The numerical model is established by using the commercial software of COMSOL Multiphysics first and then validated by comparing the numerical results with the previous experimental study. The simulation results show that under the impact of oil droplets, a crater will form on the surface of the aqueous solution, which firstly expands and then collapses with the transfer and dissipation of kinetic energy of this three-phase system. As for the droplet, it flattens, spreads, stretches, or immerses on the crater surface and finally achieves an equilibrium state at the gas–liquid interface after experiencing several sinking-bouncing circles. The impacting velocity, fluid density, viscosity, interfacial tension, droplet size, and the property of non-Newtonian fluids all play important roles in the impact between oil droplets and aqueous solution. The conclusions can help to cognize the mechanism of droplet impact on an immiscible fluid and provide useful guidelines for those applications concerning droplet impact. [ABSTRACT FROM AUTHOR]

Diatoms represent the most abundant and diversified class of primary producers in present oceans; their distinctive trait is the ability to incorporate silicic acid in a silica outer shell called frustule. Numerous adaptative functions are ascribed to frustules, including the control of vertical movements through the water column; this indirectly determines cell access to fundamental resources such as light and nutrients, and favors diatom escape from predators. At the same time, light guides phototroph movements in the water column by affecting cell density (e.g., by modulating Si deposition in diatoms, vacuole volume, and/or solution). We investigated how the tremendous diversity in morphology and silicification that characterizes the frustule and the crucial role of light in diatom spatial distribution govern diatom sinking capacity. To test their integrative effects, we acclimated four diatoms distinguished by frustule traits (Chaetoceros muelleri, Conticribra weissflogii, Phaeodactylum tricornutum, and Cylindrotheca fusiformis) to different light conditions and evaluated their physiological performance in terms of growth, elemental composition, morphological changes, and their in vivo sinking capacity. What emerged from this study was that silicification, more than other morphological characteristics, controls species vertical movements, while a higher energy availability enhances cell floating independently from the silica content. [ABSTRACT FROM AUTHOR]

Diatoms represent the most abundant and diversified class of primary producers in present oceans; their distinctive trait is the ability to incorporate silicic acid in a silica outer shell called frustule. Numerous adaptative functions are ascribed to frustules, including the control of vertical movements through the water column; this indirectly determines cell access to fundamental resources such as light and nutrients, and favors diatom escape from predators. At the same time, light guides phototroph movements in the water column by affecting cell density (e.g., by modulating Si deposition in diatoms, vacuole volume, and/or solution). We investigated how the tremendous diversity in morphology and silicification that characterizes the frustule and the crucial role of light in diatom spatial distribution govern diatom sinking capacity. To test their integrative effects, we acclimated four diatoms distinguished by frustule traits (Chaetoceros muelleri, Conticribra weissflogii, Phaeodactylum tricornutum, and Cylindrotheca fusiformis) to different light conditions and evaluated their physiological performance in terms of growth, elemental composition, morphological changes, and their in vivo sinking capacity. What emerged from this study was that silicification, more than other morphological characteristics, controls species vertical movements, while a higher energy availability enhances cell floating independently from the silica content.

Arc machining is suitable for efficiently processing typical difficult-to-cut material Ti6Al4V. Traditional arc sinking machining commonly uses water-based dielectric because of its safety and good cooling capacity. However, water-based dielectric generally has high conductivity that causes frequent short circuits and strong electrolytic reactions during machining, thereby reducing machining stability and deteriorating machining performance. This paper proposes a novel high-efficient compound sinking machining that combines arc machining with electrical discharge machining (EDM). The dielectric is formed by dispersing oxygen into deionized water, thus reducing the shortcomings of traditional water-based dielectric and introducing the advantages of gas-based one. The feasibility of the proposed method is systematically studied compared to the method that uses deionized water. Influences of oxygen pressure, pulse duration, and peak current are investigated. Characteristics of surface topography and recast layer are also studied. Results suggest that the properties of dielectric improve, and the machining stability and machining intensity increase with the assistance of oxygen. Therefore, compared with using deionized water, the proposed method shows better processing characteristics, including larger material removal rate (MRR), smaller relative electrode wear rate (REWR), and thinner recast layers. The proposed method is promising to process Ti6Al4V due to its high efficiency and environment-friendly properties. [ABSTRACT FROM AUTHOR]

The Cheonan, a patrol combat corvette of the South Korean (SK) Navy, sank during a routine patrol mission in the Yellow Sea in March 2010. An SK government report concluded that a North Korean (NK) submarine torpedo attack was responsible for the Cheonan sinking. This report presented a torpedo propulsion section as the conclusive evidence of an NK torpedo attack on the Cheonan. However, a forensic corrosion analysis of this torpedo propulsion section proved it could not have been involved in the Cheonan sinking. Instead, the deformation characteristics of Cheonan's hull plate and main deck are more consistent with damage due to a collision with a submarine than a torpedo explosion. Evidence that led to this conclusion is presented and discussed. [ABSTRACT FROM AUTHOR]

A low-cost methodology is proposed to provide settlement data for solid blocks in order to improve the design of future coastal structures. Two methods were used to determine how far the block was sinking at the sandy bottom: topographically (four field campaigns) and continuously (with two pressure sensors) for 7.5 months. Settlement values obtained were similar in both cases. The difference between both methods at most 2 cm. Half of the sink occurred in the first week. Over the next month, the rate of sinking slowed down until a storm ended it all. Subsequently, the blocks remained stable. A comparison with other researchers' data was performed and significant differences were found. This heterogeneity in behaviour necessitate the use of these types of low-cost tests that would help calibrate both physical and numerical models. • A new affordable way to find out absolute and relative values of concrete block sinking in the sea bottom is shown. • The methodology showed here is a very low cost technique. • Real data of a practical case of great utility for the calibration and validation of physical and mathematical models are also presented. • Amount the results, it is worthy of to highlight that most of the sinking was observed in the first week. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are viewed as a key medium for the transport of land-based plastics into oceans. Microplastic (MP) particles in freshwater environments demonstrate high persistence and an extensive range of size and shape distributions, which make their mobility, distribution, and fate vary distinctly depending on the prevailing environmental conditions. The inherent physical properties of different plastic polymers are constantly evolving at different specific reaction rates due to the complex weathering processes in the environment. This continuously alters the underlying mechanisms governing MP dynamics and further complicates their ultimate fate in natural aquatic systems. This paper conducts a comprehensive review of the dynamic behaviour of MPs in freshwater ecosystems, focusing on investigating the settling, aggregation, retention, and suspension processes governing their transport from the source to the sink. We provide an in-depth overview of the key theoretical foundations of MP behaviour in ambient flows and the key influential factors (i.e. size, density, shape, composition). Our findings highlight intricate interplays between MP dynamic behaviours and local hydrodynamics and water chemistry, which lead to the continuous evolution of MP physicochemical properties (e.g., size, surface charge) through interactions with suspended solids, organic natural matter, and microorganisms under light and wind exposure. This dynamic poses significant challenges in predicting MP transport processes and ultimate fate. Gap analysis highlights the discrepancy between current models based on controlled laboratory conditions and complex natural environments, signifying the need for investigating MP dynamic behaviour across a wide range of environmental conditions (e.g. simulating complex flow patterns and solution chemistries of real water bodies). Further research is needed to expand field studies to correlate environment hydrodynamics with MP abundance and to conduct mesoscale experiments that accurately reflect the effects of weathering and flow hydrodynamics on MP behaviours. Integrating detailed physical experiments with numerical modelling tools is essential for a comprehensive understanding of the interactions among various MPs and their overall impact on the environment. This facilitates robust and reliable environmental risk assessment for MP control and pollution management. Key dynamic process affecting the fate of microplastics in freshwater systems. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we establish a two-dimensional axisymmetric simulation model to numerically study the impacting behaviors between oil droplets and an immiscible aqueous solution based on the three-phase field method. The numerical model is established by using the commercial software of COMSOL Multiphysics first and then validated by comparing the numerical results with the previous experimental study. The simulation results show that under the impact of oil droplets, a crater will form on the surface of the aqueous solution, which firstly expands and then collapses with the transfer and dissipation of kinetic energy of this three-phase system. As for the droplet, it flattens, spreads, stretches, or immerses on the crater surface and finally achieves an equilibrium state at the gas–liquid interface after experiencing several sinking-bouncing circles. The impacting velocity, fluid density, viscosity, interfacial tension, droplet size, and the property of non-Newtonian fluids all play important roles in the impact between oil droplets and aqueous solution. The conclusions can help to cognize the mechanism of droplet impact on an immiscible fluid and provide useful guidelines for those applications concerning droplet impact.

This study aims to explore the pattern of external representation of suspending objects in a static fluid. The study used a qualitative descriptive method involving 57 elementary, junior, senior school, and university students. Data collection implemented a 30-item test covering the dominant context of suspending and partially floating and sinking. Some of phenomenographic steps were adapted in data analysis. Based on the data analysis, it can be concluded that there is a dominant external representation pattern, where there is a simplification of the depiction of suspending objects. Suspending position tends to be locked in a limited area, namely in the middle of the depth of the liquid. In the context of suspending objects' cuts, the cuts were generally represented by an upward shifting pattern. Factors that influence the pattern of representation are the involvement of intuition in conceptualizing the phenomena presented, and the conceptual aspect of density has not been integrated into the reasoning process for compiling external representations, both diagrams, and texts. Research limitation is presented in this article. [ABSTRACT FROM AUTHOR]

This study aims to explore the mental models of students about suspending objects in liquid fluid. The study used a descriptive qualitative method and implemented crosssectional approach. It involved 57 students from grade 5 of elementary school to fourthyear prospective physics teachers. The data collection used a test consisting of twenty-six essay and four multiple-choice items, which covered several contexts and factors. The data were analyzed by adapted phenomenographic procedures and integrated with some stages of thematic analysis. The types of mental models that were successfully explored include the density-, mass-, weight-, volume-, and gravity-based model, leaked boat model, air as a floater model, etc. The predominant students’ mental model was the initial one, followed by the synthetic and scientific level, respectively, and the adopted mental models tended to form a hierarchy based on the grade of students. The results showed that the suspending models tended to be adopted and was influenced by the mental model in the floating and sinking contexts. This result confirms the findings of previous studies, which stated that mental models depend on the context of the phenomenon being presented. The existence of variations in the students' mental models for reasoning about density and depiction of suspending objects revealed gaps in the consolidation of their mental models. In learning activities, it is not enough to teach the concepts of floating and sinking. Hence, an adequate portion for the suspending concept must be provided by depicting various object positions and emphasizing a more conceptual of density-based model. [ABSTRACT FROM AUTHOR]

Spray-dried milk powders are characterized by an underrepresentation of hydrophilic compounds on the particle surface compared to the bulk, which renders reconstitution unfavourable. To overcome this issue, in the present study we instigated the coating of whole milk powder with two types of micronized lactose: crystalline and amorphous. We demonstrate that deposition of micronized lactose on the surface of whole milk powder leads to an increase in the reconstitution rate at 21 °C, correlated with a decrease in the apparent contact angle of the material. We also show that the physical solid state of micronized lactose is an important factor influencing the reconstitution performance of coated whole milk powder; If micronized lactose is amorphous, increasing the coating concentration beyond a certain point has little or no further effect on the reconstitution kinetics, which could be explained by viscosity build-up effects that hamper capillary penetration and sinking. [Display omitted] • Dry coating of whole milk powder with micronized lactose (crystalline/amorphous) • Enhancement of powder wettability and reconstitution at 21 °C • Powder sinking is influenced by the physical solid state of the coating material [ABSTRACT FROM AUTHOR]

Lake transportation by boat in Indonesia is still the favorite transportation mode used by people in the area. Lake transportation is used for various purposes including the distribution of goods and marine tourism activities. These are facilitated by ships that must comply with national/non-convention ship standards (rather than international conventions). The availability of a ferry must be supported by other considerations, such as shipping lanes which are considered safe for navigation in terms of depth, width and other shipping barriers. This article considers the sinking of the Sinar Bangun ship, during which 3 people died, 164 people were missing and the ship destroyed [ABSTRACT FROM AUTHOR]

Sinking and horizontal movements are necessary parameters for assessing the potential impacts of surface subsidence in mining activities. Based on similarity criteria, the surface subsidence mechanism was studied using a physical model composed of similar materials such as sand, cement, and gypsum. With constant field geological parameters maintained in two angles of a coal seam, models of roof subsidence of composite rock were compared for different mining configurations. In accordance with observations from the physical model, it was concluded that subsidence and horizontal movement of strata near to and far from the coal seams were different and divided into five zones. The zone above a mined-out area underwent greater total subsidence compared to unexploited regions on both sides. Correlations between a subsidence curve and the height of a caving zone and the mining dip angle were obtained and verified from numerical model results. According to the roof’s position relative to the goaf, the area above the goaf of the composite rock layer was divided into three regions: a curving zone, a water-conducting fracture zone, and a falling zone, to which the subsidence and movement characteristics of each area could be proposed. Compared with the subsidence and movement characteristics observed from the physical and numerical model, the acquisition of subsidence characteristics and parameters in different areas can provide an idea for improvement, innovation or proposal of a theoretical formula for subsidence prediction of composite rock formations.

The construction period of open caissons is long with the dynamic changes of working conditions, and the influencing factors are complex. Relying on the No.5 open caisson construction of the middle tower of Changzhou -Taixing Yangtze River Bridge, we analyzed its geological conditions and scouring status. Combined with the past engineering experience, by calculating the shaft resistance in the final sinking stage and the tip resistance in construction process, the sinking control depth of excavation was determined, and the control elevations and the digging range of sand and clay layers in different stages of sinking were calculated. For the problem of sinking difficulty of open caisson foundation, the measures of high-pressure rotary jet pre-slackening and air curtain to assist sinking. The research results can guide the actual construction process on site, and provide references for similar projects. [ABSTRACT FROM AUTHOR]

The following paper aims to interrogate the phenomenon of surprise, from the study of the Le volontaire et l'involontaire (1950) of Paul Ricoeur, firstly, in his pendular relationship with attention, and secondly, as a lived resonance and as novelty trial and as body affection. Attention and resonance are revealed as moments of surprise. After such clarifications, it will be possible to recognize in turn that surprise is a phenomenon of sinking and concern: to be surprised by something implies to be sunk in a new situation and to recognize oneself involved in it. [ABSTRACT FROM AUTHOR]

The bucket based structure is sunk and installed by waiting for tide water in the engineering practice, which delays the construction speed, forms no flowing operation, and limits the application scope of the bucket based structure. To this end, the experimental study on the sinking stability of the bucket based structure was carried out. Through the indoor pool test, a test model was made using similar main parameters. The observation model was used to observe the air pressure, water level, and cable tension values in the compartment at different depths. Through comparative analysis, it is concluded that negative buoyancy is the main control factor for the stability of the bucket based structure; the gas in the compartment can provide stable buoyancy and also has the ability to restore balance; using negative buoyancy technology can achieve the bucket based structure that is installed underwater to ensure the safety of the installation process. [ABSTRACT FROM AUTHOR]

• It examines how flooding fits in the concept of water security that is dominated by water scarcity research. • A framework to assess how securitisation of different water-related threats is proposed. • It tests the framework with Jakarta's sinking crisis and its sea wall plan. • It provides insights into a/de/securitisation moves in water policy. • The findings are relevant for evaluating policy process induced by water-related threats. Since first introduced in 2000, 'water security' has grown into a vibrant research area, with the majority of studies examining water supply security. Although protection to water-related hazards is recognised as a dimension in water security, only a few scholars have explicitly put flood-related research under the banner of water security. This paper seeks to theorise the position of flooding in the water security conception using the securitisation lens, which also influenced early works in the water security field. Securitisation is a process of perceiving an issue as a threat, enabling the pursuit of extraordinary measures outside normal politics. I find that water supply security and flood security have the same theoretical root: fear of an unknown future. They are based on the notion that threats to the shortage of water and surplus of water, respectively, create the need for robust policies, which often translate into climate-proofing infrastructures. Here I propose a conceptual tool to assess the likelihood of a threat to undergo a securitisation process and to help answer why a threat was securitised while others not. This tool is deployed to examine the case of flooding and sinking in Jakarta, Indonesia. [ABSTRACT FROM AUTHOR]

Inspired by Nepenthes pitcher plants, lubricating fluid infused slippery (LIS) surfaces have recently gained tremendous attention from various research groups. We, alternatively, present lubricating fluid-coated slippery (LCS) surfaces based on smooth solid surfaces. The biggest advantage of LCS surfaces over LIS surfaces is that solid surfaces need not be rough or porous. We discuss that the surface energy of the underlying solid surfaces plays the most important role in preparing the LCS surfaces. Lubricating fluid-coated hydrophilic surfaces result in sinking aqueous drops due to the instability of the thin lubricating film. Additionally, stable and floating aqueous drops are observed on similar hydrophobic surfaces. We also observed that the presence of surface roughness enhances the stability and performance of LCS surfaces. Later we discuss various characteristics of LCS surfaces and its effects on the static and dynamic behaviour of aqueous drops on LCS surfaces. [ABSTRACT FROM AUTHOR]

Since the first decades of the last century, several hypotheses have been proposed on the role of phytoplankton morphology in maintaining a favorable position in the water column. Here, by an extensive review of literature on sinking rate and cell volume, we firstly attempted to explore the dependency of sinking rate on morphological traits using the allometric scaling approach. We found that sinking rate tends to increase with increasing cell volume showing the allometric scaling exponent of 0.43, which is significantly different than the Stokes' law exponent of 0.66. The violation of the 2/3 power rule clearly indicates that cell shape changes as size increases. Both size and shape affect how phytoplankton sinking drives nutrient acquisition and losses to sinking. Interestingly, from an evolutionary perspective, simple and complex cylindrical shapes can get much larger than spherical and spheroidal shapes and sink at similar rates, but simple and complex cylindrical shapes cannot get small enough to sink slower than small spherical and spheroidal shapes. Cell shape complexity is a morphological attribute resulting from the combination of two or more simple geometric shapes. While the effect of size on sinking rate is well documented, this study deepens the knowledge on how cell shape or geometry affect sinking rates that still needs further consideration. [ABSTRACT FROM AUTHOR]

The main petroleum product transported through pipelines in Canada is diluted bitumen (dilbit), a semiliquid form of heavy crude oil mixed with natural gas condensates to facilitate transport. The weathering, fate, behavior, and environmental effects of dilbit are crucial to consider when responding to a spill; however, few environmental studies on dilbit have been completed. We report on 11‐d‐long experimental spills of dilbit (Cold Lake Winter Blend) in outdoor microcosms meant to simulate a low‐energy aquatic system containing natural lake water and sediments treated with low (1:8000 oil:water) and high (1:800 oil:water) volumes of dilbit. In the first 24 h of the experiment, volatile hydrocarbons quickly evaporated from the dilbit, resulting in increased dilbit density and viscosity. These changes in dilbit's physical and chemical properties ultimately led to its submergence after 8 d. We also detected rapid accumulation of polycyclic aromatic compounds in the water column of the treated microcosms following the spills. The present study provides new information on the environmental fate and behavior of dilbit in a freshwater environment that will be critical to environmental risk assessments of proposed pipeline projects. In particular, the study demonstrates the propensity for dilbit to sink under ambient environmental conditions in freshwaters typical of many boreal lakes. Environ Toxicol Chem 2019;38:2621–2628. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Aggregation between microalgae and microplastics (MPs) significantly influences the MPs distribution in marine environment. We investigated the effects of two diatoms, the planktonic Pseudo-nitzschia pungens and the periphytic Navicula sp., on the formation and sinking of aggregates when they were cultured with four different types of MPs: small and large polyethylene terephthalate (PET) fibers, and low-density and high-density polyethylene (PE) spheres. Navicula sp. formed aggregates with all MPs within one week, but P. pungens only formed aggregates with PE spheres after 9 weeks. The PE- Navicula sp. aggregates settled about 100 times faster than the PE- P. pungens aggregates (12.2 vs. 0.1 mm s−1), and this difference was most likely due to aggregate shape rather than size. Our findings indicate that the periphytic Navicula sp. had a greater effect on the settling of MPs than the planktonic P. pungens. These findings have implications for understanding the behavior of MPs in marine environments. • Periphytic diatom Navicula sp. enhances microplastic (MP) aggregation and sinking more than planktonic diatom P. pungens. • Microalga-MP aggregate shape is crucial for sinking rates, influenced by the physical environment and species specificity. • Understanding MPs dynamics in the marine environment is important, emphasizing aggregation with microalgae and sinking. [ABSTRACT FROM AUTHOR]

The article is an ambitious and complex study of Black response to war trauma, occasioned by the tragedy of the Mendi, a troop transport sunk with great loss of life in 1917. The majority of the victims were South African Blacks on their way to the Western Front. The tragedy inspired a very powerful poetic response, which the author analyses in terms of an indigenous African modernism, and which later on prepared the ground for contemporary nationalist mythopoeia in the Republic of South Africa. Although the country was part of the British Empire in 1917, the position of the Black community was reminiscent of the nations in secondary theatres of war. The recurring presence of the tragic event in South African culture has been analysed in terms of Derrida’s hauntology.

Phytoplankton sinking is a major component of vertical ocean carbon and nutrient fluxes, and sinking is an integral component of phytoplankton biology and ecology. Much of our understanding of phytoplankton sinking derives from the settling column method (SETCOL) in which sinking speeds are calculated from the proportion of cells reaching the bottom of a water-filled column after a set time. Video-based methods are a recent alternative to SETCOL in which sinking speeds are measured by tracking the movement of individual cells in a salinity-stratified water column. In this study, we present the results of a meta-analysis showing that SETCOL produces significantly and consistently lower sinking speeds than the video method. Next, we perform a particle image velocimetry analysis, which shows that the observed discrepancy in sinking speeds between the two methods can probably be explained by weak convection currents in the SETCOLs. Finally, we discuss the implications of these results for the interpretation of past and future phytoplankton sinking speed measurements and models that rely on those measurements., Competing Interests: We declare we have no competing interests., (© 2024 The Authors.)

The accuracy of the proposed criterion (C0) is significantly higher than that of previously reported criteria (C1–C3) comparing with the experimental results, because it considers the fluid force, TPCL movement, and other factors reasonably. • Critical sinking of micron hydrophobic particle is studied by detailed simulation. • Effect of Re , contact angle, and density ratio on critical sinking is revealed. • Both fluid force and surface tension play important roles in critical sinking. • Empirical formulas for accumulated work done by each force are correlated. • A criterion for critical sinking is proposed based on energy conversion analysis. Particle impacting on a liquid surface is frequently observed in natural and industrial processes. This study numerically investigates the critical sinking behaviour after the impact of hydrophobic micron particles on liquid surfaces. The effects of contact angle θ , density ratio D , and the Reynolds number Re on the motions of the particle and TPCL are analyzed. The dimensionless penetration depth of the particle increases with increasing θ and D , whereas the effect of Re is negligible. The relationship between the TPCL position on the particles and the normalised particle displacement is only determined by θ and almost unaffected by Re and D. For the critical sinking of hydrophobic micron particles, both fluid force and surface tension play important roles in the conversion of particle kinetic energy. A dimensionless energy conservation equation is constructed, based on which a simple criterion of critical sinking is proposed. The expression of this criterion is obtained based on the semi-empirical expressions describing the relationships of each dimensionless accumulated work with Re , θ , and D obtained from simulation results. Compared with existing criteria, the proposed criterion is more accurate because it considers the fluid force, TPCL movement, and other factors reasonably. [ABSTRACT FROM AUTHOR]

Microplastics (1 μm–5 mm) are a ubiquitous marine contaminant of global concern, ingested by a wide range of marine taxa. Copepods are a key component of marine food webs, providing a source of food for higher trophic levels, and playing an important role in marine nutrient cycling. Microplastic ingestion has been documented in copepods, but knowledge gaps remain over how this affects feeding preference and faecal density. Here, we use exposure studies incorporating algal prey and microplastics of varying sizes and shapes at a concentration of 100 microplastics mL−1 to show: (1) prey selection by the copepod Calanus helgolandicus was affected by the size and shape of microplastics and algae they were exposed to; Exposure to nylon fibres resulted in a 6% decrease in ingestion of similar shaped chain-forming algae, whilst exposure to nylon fragments led to an 8% decrease in ingestion of a unicellular algae that were similar in shape and size. (2) Ingestion of microplastics with different densities altered the sinking rates of faecal pellets. Faeces containing low-density polyethylene sank significantly more slowly than controls, whilst sinking rates increased when faeces contained high-density polyethylene terephthalate. These results suggest that C. helgolandicus avoid ingesting algae that are similar in size and/or shape to the microplastic particles they are exposed to, potentially in a bid to avoid consuming the plastic. Unlabelled Image • Copepods are an important link in marine food webs and marine nutrient cycling. • Investigated effect of microplastics on Calanus helgolandicus feeding selectivity • Assessed sinking rates of faecal pellets contaminated with different microplastics • C. helgolandicus avoided ingesting algae similar in size and/or shape to the microplastic. • Microplastics with different densities altered the sinking rates of faecal pellets. [ABSTRACT FROM AUTHOR]

Concrete bucket -based structure has been successfully applied in breakwater engineering. Its design and construction methods are basically systematic. In order to explore the feasibility of and construction technology of suction bucket type structure with different materials, different structure forms, expand the application scope of suction barrel type structure, a steel bucket sinking test was carried out. The construction technology of production, transportation, installation, and suction penetration were studied. The sinking resistance and sinking force of the steel composite bucket were also studied, and its sinking feasibility was analyzed. [ABSTRACT FROM AUTHOR]

• Review of surface tension forces to support dense particles at liquid surface. • Experiments show higher surface tension improves powder sinking. • Powders must be thought of as capillary networks and not individual particles. Quick powder reconstitution is generally necessary for consumer acceptance of dehydrated food materials; thus, an improved understanding of the mechanisms preventing complete reconstitution can help aid the discovery of solutions to improve product quality. Among the steps of reconstitution (wetting, sinking, dispersing, and dissolving), the "sinking" step is often described in the literature as being inhibited by a high surface tension, keeping particles afloat, insinuating that a reduced surface tension of the medium would improve sinking and thus overall reconstitution. In the current study, the sinking of food powders maltodextrin and whole milk powder were observed in an axially stirred vessel. Experiments were performed both in demineralized water (surface tension γ = 72 mN m−1) as well as in demineralized water with the surfactant polysorbate 20 added to its critical micelle concentration (CMC), with a surface tension γ = 32 mN m−1. Contrary to the scientific literature, the sinking behavior of the bulk powder was markedly worse when the liquid surface tension was lower. This can be explained due to the reduced capillary penetration into a porous powder bed when the surface tension is reduced. Thus in the scope of the sinking step of powder reconstitution, the powder must not be considered as individual particles, but rather as a porous capillary bed where capillary and resultant waterlogging drive the "sinking" step, particularly when developing physical models to predict the reconstitution behavior of powders. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Slippery behavior of aqueous drops on lubricating oil coated solid surfaces depends strongly on the wettability of the solid substrates. Stable slippery behavior is observed, with floating aqueous drops, if underneath solid substrates are hydrophobic. For hydrophilic surfaces, lubricating oil film underneath an aqueous drop becomes unstable and ruptures due to attractive van der Waals interaction, leading to sinking of the aqueous drop. Here, we report the sinking behavior of aqueous drops on thin lubricating oil coated hydrophobic and hydrophilic surfaces. The sinking behavior of aqueous drops is analyzed in terms of change in the apparent contact angle with time. The sink time of drops depends on both the wettability of the substrate as well as viscosity of the lubricating layer, while the final apparent contact angle depends only on wettability. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is expected to alter plankton community structure in the future ocean. This, in turn, could change the composition of sinking organic matter and the efficiency of the biological carbon pump. So far, most OA experiments involving entire plankton communities have been conducted in meso- to eutrophic environments. However, recent studies suggest that OA effects may be more pronounced during prolonged periods of nutrient limitation. In this study, we investigated how OA-induced changes in low-nutrient adapted plankton communities of the subtropical North Atlantic Ocean may affect particulate organic matter (POM) standing stocks, POM fluxes, and POM stoichiometry. More specifically, we compared the elemental composition of POM suspended in the water column to the corresponding sinking material collected in sediment traps. Three weeks into the experiment, we simulated a natural upwelling event by adding nutrient-rich deep-water to all mesocosms, which induced a diatom-dominated phytoplankton bloom. Our results show that POM was more efficiently retained in the water column in the highest CO2 treatment levels (>800 μatm pCO2) subsequent to this bloom. We further observed significantly lower C:N and C:P ratios in post-bloom sedimented POM in the highest CO2 treatments, suggesting that degradation processes were less pronounced. This trend is most likely explained by differences in micro- and mesozooplankton abundance during the bloom and post-bloom phase. Overall, this study shows that OA can indirectly alter POM fluxes and stoichiometry in subtropical environments through changes in plankton community structure.