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Microplastics in freshwater systems : dynamic behaviour and transport processes
Get PDFFreshwater 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
Dynamics of a bubble-pair between two parallel rigid walls
No full textThe dynamics of two gas bubbles placed side-by-side in liquid between parallel rigid plates is studied numerically using the multiphase volume of fluid (VOF) model in OpenFOAM. This model solves a single set of Navier–Stokes equations for both the gas in the bubbles and the surrounding liquid. Being initially stationary, the bubbles first expand to their maximum volume due to the high gas pressure inside them and then collapse. Both phases are treated as viscous and immiscible without any phase change. The model is validated against available experimental data of a single bubble oscillation between parallel plates and a bubble-pair oscillation near a single rigid wall. Parametric studies are then performed, with the main variables being the initial sizes of the bubbles and their standoff distances from the rigid plates. The bubbles exhibit symmetric or asymmetric behavior depending on these two variables. Three distinct scenarios are identified in the symmetric case based on the relative influence of bubble-bubble and bubble-wall interactions. The jet strength and direction, bubble oscillation period, coalescence, and early asymmetric bubble collapse are characterized by initial distances and radii. This study provides valuable insights into intricate hydrodynamic interactions and behaviors of bubble pairs bounded by rigid surfaces
Voters' expectations in constituency elections without local polls
No full textHow do voters form accurate expectations about the strength of political candidates in constituency elections if there are no reliable constituency polls available? We argue that voters can use national election polls and past election results to increase the accuracy of their expectations. A survey experiment during the German federal election of 2021 confirms that the provision of national election polls and past results increases the accuracy of voters’ expectations. The analysis further shows that voters leverage the information to update their beliefs. The results have relevant implications for debates about belief formation in low-information environments
Coherent model for cross-polarization coupling from a single point-like perturbation in optical fibers
Get PDFThe transfer matrix is proposed to describe the coherent cross-polarization coupling (CPC) induced by a single point-like perturbation (PLP) in optical fibers. This matrix remains independent of the fiber length, making it suitable for characterizing the PLP that have a zero-dimensional impact on fiber length. Consequently, the fiber can be fully characterized by a matrix combining the transfer matrix of CPC and the Jones matrix of the fiber birefringence. The polarization performance of fibers exhibiting both CPC and birefringence is analyzed using the developed combined model
A comprehensive literature review of biomass characterisation and application for iron and steelmaking processes
No full textThis study provides a fundamental literature review of biomass characterisation and application for utilisation as a reducing agent and fuel in an integrated steelmaking process. This review contains and evaluates the existing literature concerning the properties of different biomass sources and available pre-treatment technologies for upgrading biomasses to have similar characteristics to fossil coal. The suitability of biofuels in different operating units including Brazilian mini blast furnaces, cokemaking, larger blast furnace injection, sintering and production of carbon composite agglomerates are analysed. There is a considerable opportunity to reduce CO2 emissions in the integrated steelmaking process by using biomass-based reducing agents. The literature reports that charcoal optimisation in the integrated steel plant can achieve reduction in net CO2 emissions of 31-57%, depending on the substitution rate. Although, some level of pre-treatment is also necessary for efficient use of biomass, the pre-treatment requirement will depend on the unit operation where the biomass material is added. Solid biofuels are considered the most suitable form of biomass-based reducing agents due to similarities in the physical properties with the injected coals; this will make coal replacement more straightforward and lower the costs required for plant modifications
Population reduction in salt intake for the prevention of cardiovascular disease: the 'Four Imperatives'
Get PDFSalt consumption is now much greater than needed for survival. High salt intake increases blood pressure in both animals and humans. Conversely, a reduction in salt intake causes a dose-dependent reduction in blood pressure in men and women of all ages and ethnic groups, and in patients already on medication. The risk of strokes and heart attacks rises with increasing blood pressure, and a reduction of blood pressure with drugs reduces the risk. However, most events occur in individuals with ‘normal’ blood pressure levels. Non-pharmacological prevention is therefore the only option to reduce such events in the population at large. Reduction in population salt intake reduces the number of vascular events. It is one of the most important public health measures to reduce the global cardiovascular burden. Salt reduction policies are feasible and effective (preventive imperative), cost-saving (economic imperative), powerful, rapid, equitable (political imperative) and life-saving (moral imperative). The World Health Organization recommends reducing salt consumption by 30% globally by 2025, aiming to reduce salt consumption to less than 5g per day, eventually
Effect of plasma transferred arc current on the carbide formation and mechanical properties in additively manufactured metal matrix composite coating
No full textMC-type carbide-reinforced metal matrix composites (MMCs) coatings are additively manufactured by plasma transferred arc (PTA) on Q235 steel under different arc currents ranging from 120 A to 160 A. The microstructure, elemental distribution, hardness, and wear resistance of MMCs coatings are studied. The results show that the MMCs coating possesses a high hardness up to 1112.1 HV1.0, 30.3 % volume fraction of carbides, and excellent wear resistance when PTA main arc current is 140 A. The mechanical performance improvement is in that the MMCs coatings manufactured at 140 A have the highest density of finer fishbone-shaped carbides and favorable size uniformity, compared with other main arc currents
Analysis of music-exposure interventions for impacting prosocial behaviour via behaviour change techniques and mechanisms of action : a rapid review
Get PDFThe aim of the study is to evaluate the interventions examining music exposure’s effects on prosocial behaviour, to identify the behaviour change techniques (BCTs) through which they change it, and to examine the mechanisms of action (MoAs) that mediate the relationship between music exposure and prosocial behaviour. The review identified 15 research articles, comprising 19 relevant studies. The results revealed that, though many of the included studies did not provide enough information to code them adequately, the BCTs “Instruction on how to perform a behaviour”, “Salience of consequences”, “Reduce negative emotions” and “Identification of self as role model” were the most commonly utilized techniques. Additionally, “Emotion” was the most significant MoA in the intervention-behaviour relationship in this context, but too few BCTs were able to be coded to make conclusions about any BCT-MoA relationships
Gender, sexuality, and constitutionalism in Nepal
No full textThis chapter analyses the complex way in which Nepal’s constitutional system frames sex, gender, and sexuality. It adopts an inclusive, non-binary definition of gender that overlaps with sex on the basis that both sexual and gender identities are socially constructed in culturally contingent terms,1 and that perceptions of the body are shaped by society. 2 Nepal’s 2015 constitution, and a number of recent, highly publicised decisions from the Supreme Court of Nepal, have recognised the rights of both women and sexual- and gender-diverse people (SGDP). However, the enforcement of these measures remains uneven and often problematic