Sparse Population Research Articles

Building a phenomenological chain-level understanding of mechanics of semicrystalline polymers: 2. Conceptual

To rationalize the comprehensive phenomenology in Paper 1 (this volume, p. 125878), we present a qualitative description for the mechanical behavior of semicrystalline polymers (SCPs) through a synthesis of prior understandings about the mechanical characteristics of glassy and semicrystalline polymers. Based on the central idea to regard an SCP as a crystalline chain network (CCN), in which a test chain can have crystalline and amorphous strands, we emphasize several key concepts: (a) crystallization determines the structure of the CCN, which is generally weaker than the pre-crystallization chain network in the molten state formed by interchain uncrossability, (b) ductility in SCPs is afforded by a sufficiently robust CCN, and (c) yielding and plastic deformation of SCPs require a successful structural transformation involving shape-change of crystalline phases through appreciable chain pull-out from the crystalline phases without breakdown of the CCN. In other words, it is the CCN that drives ductile SCPs to undergo yielding and subsequent large deformation through massive pull-out of load bearing strands (LBSs), which are the tie and entangling strands. Brittle fracture and lack of drawability occur in those SCPs where the CCN is too weak (due to a sparse population of LBSs) to cause sufficient meltdown of crystalline phases: There are not enough LBSs to undergo pull-out that is necessary for yielding and crystal transformation. Based on these concepts we can explore the processing-structure-property (P–S–P) relationship by demonstrating how pre-deformation in either crystalline or molten state produces more favorable structures for stronger mechanical characteristics.

Exploring extreme conditions for star formation: A deep search for molecular gas in the Leo ring

Aims. We carried out sensitive searches for the 12CO J = 1–0 and J = 2–1 lines in the giant extragalactic HI ring in Leo to investigate the star formation process within environments where gas metallicities are close to solar, but physical conditions are different than those typical of bright galaxy disks. Our aim is to check the range of validity of known scaling relations. Methods. We used the IRAM-30 m telescope to observe 11 regions close to HI gas peaks or where sparse young massive stars have been found. For all pointed observations we reached spectral noise between 1 and 5 mK for at least one of the observed frequencies at 2 km s−1 spectral resolution. Results. We marginally detect two 12CO J = 1–0 lines in the star-forming region Clump 1 of the Leo ring, whose radial velocities are consistent with those of Hα lines, but whose line widths are much smaller than observed for virialized molecular clouds of similar mass in galaxies. The low signal-to-noise ratio, the small line widths, and the extremely low number densities inferred by virialized cloud models suggest that a more standard population of molecular clouds, still undetected, might be in place. Using upper limits to the CO lines, the most sensitive pointed observations show that the molecular gas mass surface density is lower than expected from the extrapolation of the molecular Kennicutt–Schmidt relation established in the disk of galaxies. The sparse stellar population in the ring, possibly forming ultra diffuse dwarf galaxies, might then be the result of a short molecular gas depletion time in this extreme environment.

Critical review of household water treatment in Southeast Asian countries

AbstractWorldwide, an average gap of 32% was observed between urban and rural populations in terms of access to safe drinking water. Worryingly, 50% of the Southeast Asia population resides in rural areas, making the region highly vulnerable to threats from not having access to safe drinking water. The sparse population density and infrastructural complexities in rural areas have made centralized water treatment systems very challenging in terms of implementation and significantly increased cost. Hence, adopting a household water treatment (HWT) system would be a more suitable co‐existing water provision solution. However, data on the sustainability of HWT in Southeast Asia is still lacking. Therefore, this review aims to provide a critical overview of water poverty and current HWT implemented in Southeast Asian countries. The factors associated with feasibility and potentially sustained implementation of the HWT in Southeast Asian countries covering user preferences, user perception towards water safety, education and training, economic feasibility, collaborations, and supportive policy environment were also discussed. In a nutshell, there is a need for co‐designing the HWT with the targeted community before its implementation for better sustainability.This article is categorized under: Human Water > Rights to Water Science of Water > Water Quality Human Water > Methods

Estimating County Level Health Indicators Using Spatial Microsimulation.

Given the importance of understanding health outcomes at fine spatial scales, iterative proportional fitting (IPF), a form of small area estimation, was applied to a fixed number of health-related variables (obesity, overweight, diabetes) taken from regionalized 2019 survey responses (n = 5474) from the Idaho Behavioral Risk Factor Surveillance System (BRFSS). Using associated county-level American Community Survey (ACS) census data, a set of constraints, which included age categorization, race, sex, and education level, were used to create county-level weighting matrices for each variable, for each of the seven (7) Idaho public health districts. Using an optimized modeling construction technique, we identified significant constraints and grouping splits for each variable/region, resulting in estimates that were internally and externally validated. Externally validated model results for the most populated counties showed correlations ranging from .79 to .85, with p values all below .05. Estimates indicated higher levels of obesity and overweight individuals for midsouth and southwestern Idaho counties, with a cluster of higher diabetes estimates in the center of the state (Gooding, Lincoln, Minidoka, and Jerome counties). Alternative external sources for health outcomes aligned extremely well with our estimates, with wider confidence intervals in more rural counties with sparse populations.

Multiple meanings and boundaries of growth in shrinking regions in East and North Finland

Growth stands out as a key development object in contemporary green economy policies. It is particularly interesting in the Nordic context such as in East and North Finland, where many regions are rich in natural resources, but also shrinking and lagging. Therefore, their regional development is simultaneously framed by an expected sustainability transition that alternates between green growth and degrowth agendas, and the socio-economic phenomenon of shrinkage. This article examines how growth is understood and framed among regional development actors, with special interest placed on different meanings, possible critics, and the boundaries of growth. The interviewed actors are positioned as intermediaries who possess special knowledge regarding regional development. The interviews show that the understanding of growth in this context requires various framings that combine global, regional, and local perspectives on sustainable development, as well as the burdens of shrinking and lagging regions balanced against cohesive and inclusive promises of green growth. The hegemonic frame is approached through a lens of green growth, yet the shrinking population remains in the background. Growth appears as a favoured means to tackle societal problems, which reflects a mission-oriented goal setting. Critical statements are directed at growth policies and funding instruments that do not seem to promote cohesive and inclusive growth. The clearest boundary for growth relates to nature, but it is far too early to make interpretations on an intentional degrowth agenda. From the regional actors’ perspective, setting boundaries for growth in a context of long-term shrinkage, sparse population, and extensive natural surroundings seems trivial. Handling the peripheries’ societal problems related to shrinkage and their struggle for resources appears as the more relevant mission that also requires growth in various forms.

Influence of nucleation on cavitation inception in tip leakage flows

Cavitation in a tip leakage flow is experimentally investigated in a cavitation tunnel using a stationary hydrofoil analogy. The experiments were performed for different tip clearances (τ=gap height/maximum profile thickness) and hydrofoil incidences (α). The chord-based Reynolds number remained fixed at Re=3×106. The influence of nucleation on both inception and developed cavitation is evaluated by performing tests with two populations of freestream nuclei: a low concentration with strong critical tensions for activation and a high concentration with weak critical tensions. These populations represent the extremes that would be expected in practical tip leakage flows. Cavitation was characterized using high-speed imaging and acoustic measurements. Following a survey of developed cavitation topology for a range τ and α values, α=6° was selected for further investigation of cavitation inception as it demonstrated a rich variety of physical processes. From the acoustic measurements, the worst performance in terms of cavitation inception was observed at an intermediate gap height of around τ=0.6–0.8 for the “strong water” case. Broadly, cavitation and inception is intermittent when nuclei are sparse, becoming continuous as additional nuclei are introduced. While a continuous cavity in the seeded flow resulted in a higher baseline acoustic signature, sparse populations allow the leakage vortex to sustain tension, which can result in extremely loud incipient events. Optimization of gap height will, therefore, depend on the expected nuclei population during operation.

Camera trapping ekes out some improvement for surveying sparse mammal populations in northern Queensland

Monitoring is a critical component of conservation land management and the choice of methods can influence the final inventory of species recorded. The use of camera trapping has increased in recent years as a cost-effective method to record more species and to identify more cryptic and rare species. In this study we first examined data from detailed field surveys (which did not employ camera trapping) in northern Queensland to examine the abundance and frequency of mammals detected by cage, box and pitfall traps, and spotlighting. We then used data from an additional set of sites that compared these methods with camera trapping. Twenty-five species were recorded in the first data set and 26 species were recorded in the second. Overall, mammals were recorded in exceedingly low numbers, and camera trapping only improved the detection of some species such as larger species that could not be trapped (i.e. dingo Canis familiaris and pig Sus scrofa) or were uncommon (i.e. northern quoll Dasyurus hallucatus and northern brown bandicoot Isoodon macrourus). Our results suggest that survey effort should be substantial and use the most suitable methods to identify management, threat and habitat relationships for potentially precarious wildlife communities.

The Principle of Common Heritage of Mankind in the Law of Outer Space

Nomadic primitive men were in constant quest for food and water. With sparse population, they rarely encountered other humans. Chance meetings were greeted with confrontations over food and water, the basic essentials for survival. With the passage of time, life became easier when humans transited from hunting to farming. No longer in perpetual pursuit of food and water, civilization and property ownership commenced. Prior to the advent of international law, conquering land seemed simple: the fittest survived and won the land. The victor’s flag flapped majestically in the air above the conquered territory as a symbol of acquisition. No rules existed to ensure fairness. Superior armies seized land or those skilled in the exploration declared new unoccupied areas for their kingdoms. For a millennium, homo sapiens followed this savagery and barbaric “first in time, first in right” rule of property ownership. Haven conquered the earth, the inordinate expansionist tendencies of man have shifted his attention to the outer space, an area devoid of the obnoxious “first in time, first in right rule”. Rather, the order of the day in this sphere is the doctrine of “common heritage and province of mankind”. What is it all about? What is the genesis of the doctrine? Is it absolute and sacrosanct? Or is it a case of all animals are equal, but some are more equal than others”. All these will be unraveled as we explore the topic in this exercise.

«Устная история» в дневниках Ц. Дамдинсурэна

Introduction. The oral tradition has figured largely in the literature of Mongols since ancient times. This is due to the nomadic way of life resulting in that sparse population gets scattered across vast territories forced to exchange news and knowledge by word of mouth. Such intensive functioning of the oral text transmission form can be witnessed even nowadays. Goals. The paper aims at introducing some data on ‘oral histories’ contained in Ts. Damdinsüren’s diaries into scientific circulation. Results. The tradition of using oral narratives in the functional sphere, in particular, to preserve and transmit historical facts — i.e. to somewhat ‘document’ the past — has given rise to such genres as ‘oral history’ (aman tuuh), ‘oral memoires’ (huuch yaria), and ‘folkloric accounts’ (yaria) that have become very popular in recent decades. And it is Academician Ts. Damdinsüren that can be viewed as initiator of this genre in Mongolian literature. The diaries of Ts. Damdinsüren dated from 1956 to 1986 contain materials used by him in his publications of ‘oral histories’. The latter can be somewhat provisionally classified into a few categories. First of all, it is evident enough that Ts. Damdinsüren was interested in funny stories, amusements, and anecdotes. Furthermore, he had been collecting narratives about supernatural entities for many years. The theme aroused the academician’s interest as manifested mythopoeia of the Mongols and as embodied living mythology of the people rather than as some mere object of curiosity, neither was he ever that enthusiastic about insights into esoteric practices of Mongolian Buddhist priests. The notebooks also contain quite a number of texts dealing with the Mongolian Revolution and the dramatic 1930s to have witnessed harsh repressions. The latter coupled with arrangements directed against the old culture did capture the scholar’s attention. The recorded ‘oral histories’ were articulating inconvenient and sometimes even hostile data for authorities on topics that remained banned up to the 1990s. So, the ‘oral histories’ not only introduce new historical and cultural facts, opinions of commoners on certain events, but also narrate about Mongolian household life of the past, peculiarities of ethnic worldviews and attitudes.

Ex Situ Conservation of Atriplex taltalensis I.M. Johnst. via In Vitro Culturing of Its Axillary Shoots

Atriplex taltalensis is an endangered shrub endemic to northern Chile. Sparse populations of this species can be found in areas with extreme edaphoclimatic conditions in the Atacama desert, and its seeds have a poor germination rate. Consequently, mass-cultivating it can be challenging. In this study, the vegetative propagation mechanisms of A. taltalensis were evaluated using an in vitro culture to aid in their conservation. A. taltalensis shoot explants were treated with two phytoregulators, indole-3-butyric acid (IBA) and 6-benzylaminopurine (BAP), to assess the morphogenic responses and their effects on the propagation of the species, based on shoot multiplication, elongation, and rooting, through subculturing. During multiplication, the treatment with IBA alone efficiently promoted explant elongation, lateral root formation, and axillary shoot proliferation, allowing for the rapid development of shoots into whole plants. Alternatively, treatment with IBA and BAP in combination stimulated the proliferation of basal shoots with little elongation and rooting and promoted shoot hyperhydricity at 0.25–1 mg L−1 BAP concentrations. Thus, we conclude that A. taltalensis propagation is viable through in vitro plant tissue culture using a rapid axillary shoot multiplication system, and this method could aid in the conservation of this species through in vitro propagation and rescue programs.

Pandemic-influenced human mobility on tribal lands in California: Data sparsity and analytical precision.

Human mobility datasets collected from personal mobile device locations are integral to understanding how states, counties, and cities have collectively adapted to pervasive social disruption stemming from the COVID-19 pandemic. However, while indigenous tribal communities in the United States have been disproportionately devastated by the pandemic, the relatively sparse populations and data available in these hard-hit tribal areas often exclude them from mobility studies. We explore the effects of sparse mobility data in untangling the often inter-correlated relationship between human mobility, distancing orders, and case growth throughout 2020 in tribal and rural areas of California. Our findings account for data sparsity imprecision to show: 1) Mobility through legal tribal boundaries was unusually low but still correlated highly with case growth; 2) Case growth correlated less strongly with mobility later in the the year in all areas; and 3) State-mandated distancing orders later in the year did not necessarily precede lower mobility medians, especially in tribal areas. It is our hope that with more timely feedback offered by mobile device datasets even in sparse areas, health policy makers can better plan health emergency responses that still keep the economy vibrant across all sectors.

Multi-Scale Spatiotemporal Pattern Analysis and Simulation (MSPAS) Model with Driving Factors for Land Cover Change and Sustainable Development Goals: A Case Study of Nepal

In pursuit of Sustainable Development Goals (SDGs), land cover change (LCC) has been utilized to explore different dynamic processes such as farmland abandonment and urban expansion. The study proposed a multi-scale spatiotemporal pattern analysis and simulation (MSPAS) model with driving factors for SDGs. With population information from the census, multi-scale analysis criteria were designed using the combination of administrative and regional divisions, i.e., district, province, nation and ecological region. Contribution and correlation of LCC or population were quantified between multiple scales. Different kinds of driving factors were explored in the pattern analysis and then utilized for the definition of adaptive land suitability rules using the Cellular Automata-Markov (CA-Markov) simulation. As a case study of the MSPAS model, Nepal entered into a new era by the establishment of a Federal Republic in 2015. The model focused on four specific land cover classes of urban, farmland, forest and grassland to explore the pattern of Nepal’s LCC from 2016 to 2019. The result demonstrated the performance of the MSPAS model. The spatiotemporal pattern had consistency, and characteristics between multiple scales and population were related to LCC. Urban area nearly doubled while farmland decreased by 3% in these years. Urban areas expanded at the expense of farmland, especially in Kathmandu and some districts of the Terai region, which tended to occur on flat areas near the existing urban centers or along the roads. Farmland abandonment was relatively intense with scattered abandoned areas widely distributed in the Hill region under conditions of steep topography and sparse population. The MSPAS model can provide references for the development of sustainable urbanization and agriculture in SDGs.

Television White Space Based Broadband Network’s Coverage and CAPEX Performance for Rural Areas Connectivity in Tanzania

This study compared the CAPEX requirements for a television white space (TVWS) based broadband network and that of deploying the UMTS based mobile broadband networks to deliver broadband connectivity in areas with sparse population which characterize most of Tanzania rural. Like many developing countries, Tanzania has low Internet penetration, with penetration of just over 46% when multiple subscriptions are taken into account. The affected communities are mostly rural due to low population densities which make deployment of the mobile broadband to be much expensive in terms of costs. This limits the economic development potential in these areas given that the broadband connectivity and services is a key driver for the Fourth Industrial Revolution (4IR or Industry 4.0) and modern digital economy. Comparative between the coverage capability of the TVWS and UMTS family of standards by considering the number of base transceiver stations (BTS) is conducted to cover a specific geographic area for three different radio operating environments namely hilly, undulating and flat terrain landscapes. The broadband connectivity data rate is defined at the receiver rate of 2 Mbps or above, and used to determine the number of BTS required for the two technologies. Results show that introducing the TVWS as a middle mile solution, cuts the number of UMTS BTS required to serve the same population by 68%, 66.7%, and 75% for the three canonical environments respectively.

High‐throughput morphometric and transcriptomic profiling uncovers composition of naïve and sensory‐deprived cortical cholinergic VIP/CHAT neurons

Cortical neuronal networks control cognitive output, but their composition and modulation remain elusive. Here, we studied the morphological and transcriptional diversity of cortical cholinergic VIP/ChAT interneurons (VChIs), a sparse population with a largely unknown function. We focused on VChIs from the whole barrel cortex and developed a high‐throughput automated reconstruction framework, termed PopRec, to characterize hundreds of VChIs from each mouse in an unbiased manner, while preserving 3D cortical coordinates in multiple cleared mouse brains, accumulating thousands of cells. We identified two fundamentally distinct morphological types of VChIs, bipolar and multipolar that differ in their cortical distribution and general morphological features. Following mild unilateral whisker deprivation on postnatal day seven, we found after three weeks both ipsi‐ and contralateral dendritic arborization differences and modified cortical depth and distribution patterns in the barrel fields alone. To seek the transcriptomic drivers, we developed NuNeX, a method for isolating nuclei from fixed tissues, to explore sorted VChIs. This highlighted differentially expressed neuronal structural transcripts, altered exitatory innervation pathways and established Elmo1 as a key regulator of morphology following deprivation.

Japanese Encephalitis Virus: The Emergence of Genotype IV in Australia and Its Potential Endemicity.

A fatal case of Japanese encephalitis (JE) occurred in northern Australia in early 2021. Sequence studies showed that the virus belonged to genotype IV (GIV), a genotype previously believed to be restricted to the Indonesian archipelago. This was the first locally acquired case of Japanese encephalitis virus (JEV) GIV to occur outside Indonesia, and the second confirmed fatal human case caused by a GIV virus. A closely related GIV JEV strain subsequently caused a widespread outbreak in eastern Australia in 2022 that was first detected by fetal death and abnormalities in commercial piggeries. Forty-two human cases also occurred with seven fatalities. This has been the first major outbreak of JEV in mainland Australia, and geographically the largest virgin soil outbreak recorded for JEV. This outbreak provides an opportunity to discuss and document the factors involved in the virus' spread and its ecology in a novel ecological milieu in which other flaviviruses, including members of the JE serological complex, also occur. The probable vertebrate hosts and mosquito vectors are discussed with respect to virus spread and its possible endemicity in Australia, and the need to develop a One Health approach to develop improved surveillance methods to rapidly detect future outbreak activity across a large geographical area containing a sparse human population. Understanding the spread of JEV in a novel ecological environment is relevant to the possible threat that JEV may pose in the future to other receptive geographic areas, such as the west coast of the United States, southern Europe or Africa.

Permafrost degradation increases risk and large future costs of infrastructure on the Third Pole

The damage to infrastructure caused by near-surface permafrost degradation is directly related to the well-being of 10 million people and the sustainable development on the Qinghai-Tibet Plateau, the Third Pole of the Earth. Here we identify the economic damage caused by permafrost degradation to infrastructure on the Qinghai-Tibet Plateau by integrating data-driven projection, multihazard index, and lifespan replacement model. We found that additional cost of approximately $6.31 billion will be needed to maintain the service function of current infrastructure under the historical scenario (SSP245) by 2090. While 20.9% of these potential costs can be saved with strategic adaptations. Controlling global warming to below 1.5 °C will reduce the costs by $1.32 billion relative to the 2 °C target of Paris Agreement. These findings highlight the importance of mitigating global warming and of investment in the adaptation and maintenance of infrastructure on the Qinghai-Tibet Plateau, which has a sparse population but is a climate hotspot.

Unveiling deep-sea habitats of the Southern Ocean-facing submarine canyons of southwestern Australia

Here we present the outcomes of the first deep-sea remotely operated vehicle study of previously unexplored submarine canyon systems along the southwest Australian continental margin. This was conducted around: (1) the Bremer Marine Park; (2) the Mount Gabi seamount and nearby slope-shelf margin at the interface of the Southern and Indian oceans; with new information from (3) the Perth Canyon Marine Park located in the SE Indian Ocean. These canyons differ from many explored around the world in having no connectivity to continental river systems, thus little detrital input, with the Bremer systems and Mount Gabi facing the Southern Ocean which plays a key role in the global ocean circulation and climate systems. Such studies in the vast deep waters around the Australian continent are rare given the lack of local ROV capability available for research, thus little is known about these environments.Using the resources of the Schmidt Ocean Institute, we characterised the submarine topography from high-resolution bathymetric mapping, geology, physical and chemical oceanography, and provide an overview of these environments including the fauna observed and collected. We show that these Southern Ocean-influenced environments incorporate South Indian Central Water, Subantarctic Mode Water, Antarctic Intermediate Water, and Upper and Lower Circumpolar Deep Water, with Antarctic Bottom Water present in deep water just south of the Bremer canyon systems. The richness in megabenthos, especially along the steep, rocky substrates of the canyon heads and walls around the Bremer canyon systems, contrasts to the comparatively depauperate fauna of the more northerly Perth Canyon. Various corals serve as important substrates for a range of other species and often exhibit particular faunal associations. Especially notable are distinct ecological zones including a bryozoan and sponge-dominated (animal) forest on the shelf edge, spectacular coral gardens along canyon margins, and the occurrence of solitary scleractinians well below the aragonite saturation horizon. Subfossil coral deposits were discovered across all three study areas, reflecting periodic waxing and waning of deep-water Scleractinia throughout this southwest region. Extensive pre-modern assemblages at Mount Gabi contrast markedly with the sparse populations of living species and suggest that it might have once been a major coral hotspot, or whether they reflect long-term coral aggregations is yet to be determined. Nevertheless, stark differences in both living and past coral distribution patterns across our study sites point to at least localised fluctuations in Southern Ocean-derived nutrient and/or oxygen supplies to these deep-sea communities.

Low-Altitude Remote Sensing Inversion of River Flow in Ungauged Basins

Runoff is closely related to human production, the regional environment, and hydrological characteristics. It is also an important basis for water cycle research and regional water resource development and management. However, obtaining hydrological information for uninformed river sections is complicated by harsh environments, limited transportation, sparse populations, and a low density of hydrological observation stations in the inland arid zone. Here, low-altitude remote sensing technology was introduced to combine riverbed characteristics through unmanned aerial vehicle (UAV) inversion with classical hydraulic equations for ungauged basins in the middle and lower reaches of the Keriya River, northwest China, and investigate the applicability of this method on wide and shallow riverbeds of inland rivers. The results indicated that the estimated average error of the low-altitude remote sensing flow was 8.49% (ranging 3.26–17.00%), with a root mean square error (RMSE) of 0.59 m3·s−1 across the six selected river sections, suggesting that this method has some applicability in the study area. Simultaneously, a method for estimating river flow based on the water surface width– and water depth–flow relationship curves for each section was proposed whereas the precise relationships were selected based on actual section attributes to provide a new method for obtaining runoff data in small- and medium-scale river areas where information is lacking.

Simulating the distribution of beached litter on the northwest coast of Scotland

Various field methods have been used globally in an attempt to understand and quantify plastic pollution. However, in regions, such as the west coast of Scotland, sparse populations, combined with complex coastlines of numerous islands, sea lochs and headlands, has resulted in limited field data. The Clyde Sea is the most populated and industrialised region on the west coast of Scotland and therefore a potential source of land-based plastic litter to the less populated coast to the north. This study first presents an analysis of Marine Conservation Society (MCS) citizen-science beach-clean data, from 1994 to 2019, revealing spatial patterns between beach-clean sites. Plastic litter was categorised into land, marine and unknown sources, with the most common items in these three categories being crisp packets, fishing rope and fragments, respectively. On the west coast of Scotland there is on average 380.3 ± 419.9 plastic items per 100 m of coast, with the site average number of items recovered ranging from 1–2,355 per 100 m of coast. To simulate marine plastic litter movement from the Clyde Sea to a defined northwest model sub-area, an unstructured-grid hydrodynamic model was coupled with a particle tracking model subject to currents, diffusion, and wind. Three coastal boundary conditions were used to compare transport paths with or without particle beach resuspension, and for the resuspending cases, with or without a distinction between coastal type (retentive beaches versus reflective rocky coasts). Of the total released particles, the percentage that beached within the model sub-area, after a 1-year model run, ranged between 45.7% and 88.3% depending on the coastal boundary condition. The Clyde Sea was found to be a potential source of beached land-based plastic litter to the north, as on average, 6.8% (range: 2.9%–11.7%) of particles exited the Clyde Sea, crossed a defined northern boundary, and beached on the northwest coast. Both hydrodynamic and particle tracking models were tested, and the varying boundary conditions were compared to investigate holistic methodologies to better understand plastic pollution.

Electromagnetic solitons and their stability in relativistic degenerate dense plasmas with two electron species

The evolution of electromagnetic (EM) solitons due to nonlinear coupling of circularly polarized intense laser pulses with low-frequency electron-acoustic perturbations is studied in relativistic degenerate dense astrophysical plasmas with two groups of electrons: a sparse population of classical relativistic electrons and a dense population of relativistic degenerate electron gas. Different forms of localized stationary solutions are obtained and their properties are analyzed. Using the Vakhitov-Kolokolov stability criterion, the conditions for the existence and stability of a moving EM soliton are also studied. It is noted that the stable and unstable regions shift around the plane of soliton eigenfrequency and the soliton velocity due to the effects of relativistic degeneracy, the fraction of classical to degenerate electrons and the EM wave frequency. Furthermore, while the standing solitons exhibit stable profiles for a longer time, the moving solitons, however, can be stable or unstable depending on the degree of electron degeneracy, the soliton eigenfrequency and the soliton velocity. The latter with an enhanced value can eventually lead to a soliton collapse. The results should be useful for understanding the formation of solitons in the coupling of highly intense laser pulses with slow response of degenerate dense plasmas in the next generation laser-plasma interaction experiments as well as the novel features of x-ray and γ-ray pulses that originate from compact astrophysical objects.