Observation of nano-indent induced strain fields and dislocation generation in silicon wafers using micro-raman spectroscopy and white beam x-ray topography

In the semiconductor manufacturing industry, wafer handling introduces micro-cracks at the wafer edge. During heat treatment these can produce larger, long-range cracks in the wafer which can cause wafer breakage during manufacture. Two complimentary techniques, micro-Raman spectroscopy (μRS) and White Beam Synchrotron X-ray Topography (WBSXRT) were employed to study both the micro-cracks and the associated strain fields produced by nano-indentations in Si wafers, which were used as a means of introducing controlled strain in the wafers. It is shown that both the spatial lateral and depth distribution of these long range strain fields are relatively isotropic in nature. The Raman spectra suggest the presence of a region under tensile strain beneath the indents, which can indicate a crack beneath the indent and the data strongly suggests that there exists a minimum critical applied load below which cracking will not initiate

Determining patterns in the composition of dissolved organic matter in fresh waters according to land use and management

In fresh waters, the origins of dissolved organic matter (DOM) have been found to exert a fundamental control on its reactivity, and ultimately, its ecosystem functional role. A detailed understanding of landscape scale factors that control the export of DOM to aquatic ecosystems is, therefore, pivotal if the effects of DOM flux to fresh waters are to be fully understood. In this study we present data from a national sampling campaign across the United Kingdom in which we explore the variability in DOM composition in three broad landscape types defined by similar precipitation, geology, land use and management, hydrology, and nutrient enrichment status. We characterised samples from fifty-one sites, grouping them into one of three major underlying classifications: circumneutral streams underlain by clay and mudstone (referred to as ‘clay’), alkaline streams underlain by Cretaceous Chalk or by Carboniferous or Jurassic Limestone (‘limestone’), and acidic streams in peatland catchments underlain by a range of low permeability lithologies (‘peat’). DOM composition was assessed through organic matter stoichiometry (organic carbon: organic nitrogen; organic carbon: organic phosphorus; C/N(P)DOM) and metrics derived from ultra-violet (UV)/visible spectroscopic analysis of DOM such as specific UV absorption (a254 nm; SUVA254). We found similar SUVA254, C/NDOM and DOM/a254 relationships within classifications, demonstrating that despite a large degree of heterogeneity within environments, catchments with shared environmental character and anthropogenic disturbance export DOM with a similar composition and character. Improving our understanding of DOM characterisation is important to help predict shifts in stream ecosystem function, and ecological responses to enrichment or mitigation efforts and how these may result in species composition shifts and biodiversity loss in freshwater ecosystems

Nitrous oxide and methane fluxes from plasma-treated pig slurry applied to winter wheat

The use of livestock waste as an organic fertiliser releases significant greenhouse gas emissions, exacerbating climate change. Innovative fertiliser management practices, such as treating slurry with plasma induction, have the potential to reduce losses of carbon and nitrogen to the environment. The existing research on the effectiveness of plasma-treated slurry at reducing nitrous oxide (N2O) and methane (CH4) emissions, however, is not comprehensive, although must be understood if this technology is to be utilised on a large scale. A randomised block experiment was conducted to measure soil fluxes of N2O and CH4 from winter wheat every two hours over an 83-day period using automated chambers. Three treatments receiving a similar amount of plant-available N were used: (1) inorganic fertiliser (IF); (2) pig slurry combined with inorganic fertiliser (PS); (3) plasma-treated pig slurry combined with inorganic fertiliser (TPS). Cumulative N2O fluxes from TPS (1.14 g N m−2) were greater than those from PS (0.32 g N m−2) and IF (0.13 g N m−2). A diurnal pattern in N2O fluxes was observed towards the end of the experiment for all treatments, and was driven by increases in water-filled pore space and photosynthetically active radiation and decreases in air temperature. Cumulative CH4 fluxes from PS (3.2 g C m−2) were considerably greater than those from IF (− 1.4 g C m−2) and TPS (− 1.4 g C m−2). The greenhouse gas intensity of TPS (0.2 g CO2-eq kg grain−1) was over twice that of PS (0.07 g CO2-eq kg grain−1) and around six times that of IF (0.03 g CO2-eq kg grain−1). Although treating pig slurry with plasma induction considerably reduced CH4 fluxes from soil, it increased N2O emissions, resulting in higher non-CO2 emissions from this treatment. Life-cycle analysis will be required to evaluate whether the upstream manufacturing and transport emissions associated with inorganic fertiliser usage are outweighed by the emissions observed following the application of treated pig slurry to soil

Characterisation of riverine dissolved organic matter using a complementary suite of chromatographic and mass spectrometric methods

Dissolved organic matter (DOM) plays a fundamental role in nutrient cycling dynamics in riverine systems. Recent research has confirmed that the concentration of riverine DOM is not the only factor regulating its functional significance; the need to define the chemical composition of DOM is a priority. Past studies of riverine DOM rested on bulk quantification, however technological advancements have meant there has been a shift towards analytical methods which allow the characterisation of DOM either at compound class or more recently molecular level. However, it is important to consider that all analytical methods only consider a defined analytical window. Thus, herein, we explore the use of a hierarchy of methods which can be used in combination for the investigation of a wide range of DOM chemistries. By using these methods to investigate the DOM composition of a range of streams draining catchments of contrasting environmental character, a wide range of compounds were identified across a range of polarities and molecular weight, thereby extending the analytical window. Through the elucidation of the DOM character in stream samples, information can be collected about likely the sources of DOM. The identification of individual key compounds within the DOM pool is a key step in the design of robust and informative bioassay experiments, used to understand in-stream ecosystem responses. This is critical if we are to assess the role of DOM as a bioavailable nutrient resource and/or ecotoxicological factor in freshwater

Darkness visible: reflections on underground ecology

1 Soil science and ecology have developed independently, making it difficult for ecologists to contribute to urgent current debates on the destruction of the global soil resource and its key role in the global carbon cycle. Soils are believed to be exceptionally biodiverse parts of ecosystems, a view confirmed by recent data from the UK Soil Biodiversity Programme at Sourhope, Scotland, where high diversity was a characteristic of small organisms, but not of larger ones. Explaining this difference requires knowledge that we currently lack about the basic biology and biogeography of micro-organisms. 2 It seems inherently plausible that the high levels of biological diversity in soil play some part in determining the ability of soils to undertake ecosystem-level processes, such as carbon and mineral cycling. However, we lack conceptual models to address this issue, and debate about the role of biodiversity in ecosystem processes has centred around the concept of functional redundancy, and has consequently been largely semantic. More precise construction of our experimental questions is needed to advance understanding. 3 These issues are well illustrated by the fungi that form arbuscular mycorrhizas, the Glomeromycota. This ancient symbiosis of plants and fungi is responsible for phosphate uptake in most land plants, and the phylum is generally held to be species-poor and non-specific, with most members readily colonizing any plant species. Molecular techniques have shown both those assumptions to be unsafe, raising questions about what factors have promoted diversification in these fungi. One source of this genetic diversity may be functional diversity. 4 Specificity of the mycorrhizal interaction between plants and fungi would have important ecosystem consequences. One example would be in the control of invasiveness in introduced plant species: surprisingly, naturalized plant species in Britain are disproportionately from mycorrhizal families, suggesting that these fungi may play a role in assisting invasion. 5 What emerges from an attempt to relate biodiversity and ecosystem processes in soil is our extraordinary ignorance about the organisms involved. There are fundamental questions that are now answerable with new techniques and sufficient will, such as how biodiverse are natural soils? Do microbes have biogeography? Are there rare or even endangered microbes

Electromigration-Induced Flow of Islands and Voids on the Cu(001) Surface

Electromigration-induced flow of islands and voids on the Cu(001) surface is studied at the atomic scale. The basic drift mechanisms are identified using a complete set of energy barriers for adatom hopping on the Cu(001) surface, combined with kinetic Monte Carlo simulations. The energy barriers are calculated by the embedded atom method, and parameterized using a simple model. The dependence of the flow on the temperature, the size of the clusters, and the strength of the applied field is obtained. For both islands and voids it is found that edge diffusion is the dominant mass-transport mechanism. The rate limiting steps are identified. For both islands and voids they involve detachment of atoms from corners into the adjacent edge. The energy barriers for these moves are found to be in good agreement with the activation energy for island/void drift obtained from Arrhenius analysis of the simulation results. The relevance of the results to other FCC(001) metal surfaces and their experimental implications are discussed.Comment: 9 pages, 13 ps figure

Measuring and modelling the impact of outdoor pigs on soil carbon and nutrient dynamics under a changing climate and different management scenarios

A mixed agricultural system that integrates livestock and cropping is essential to organic, agroecological, and regenerative farming. The demand for improved welfare systems has made the practice of outdoor rearing of pigs very popular; it currently makes up 40% of the UK pig industry and has also been integrated into arable rotations. Besides the benefits of outdoor production systems, they also potentially pose environmental risks to farmlands, such as accumulation of nitrogen and phosphorus in the soil, soil erosion and compaction and carbon loss. Despite this, the impact of outdoor pigs and arable crop rotations on soil health has been under-researched relative to other livestock species. This study was conducted at the University of Leeds Research Farm from 2018 to 2020 using a combined experimental and modelling approach to understand the impact of outdoor pigs on soil carbon and nutrient dynamics. The physio-chemical properties of arable soil were measured prior to the introduction of the pigs and after introducing the pigs at the end of first and second years, consecutively. There was assessment of control sites (without pigs, mowing once a year) and pig pens (pigs in a rotation with arable crops). The soil was sampled at two different depths, 0–10 cm and 10–20 cm. It was observed that measured soil organic carbon (SOC) stocks in the soil depths of 0–10 cm and 10–20 cm layer were decreased by 7% and 3%, respectively, in the pig pens from 2019 to 2020, and total available nitrogen and phosphorus were significantly higher in pig pens than the control sites. Hence, at a depth between 0 and 20 cm, the average total available nitrogen was 2.51 and 2.68 mg kg−1 in the control sites and 21.76 and 20.45 mg kg−1 in the pig pens in 2019 and 2020, respectively. The average total available phosphorus at 0–20 cm was 26.54 and 37.02 mg kg−1 in control sites and 48.15 and 63.58 mg kg−1 in pig pens during 2019 and 2020, respectively. A process-based model (DayCent) was used to simulate soil carbon and nitrogen dynamics in the arable rotation with outdoor pigs and showed SOC stock losses of – 0.09 ± 0.23 T C ha−1 year−1 using the future climate CMIP5 RCP 8.5 scenario for 2020 to 2048. To reduce this loss, we modelled the impact of changing the management of the pig rotation and found that the loss of SOC stock could be decreased by shortening the period of pig retention in the field, growing grass in the field, and leguminous crops in the crop rotation

Slater-Pauling Behavior of the Half-Ferromagnetic Full-Heusler Alloys

Using the full-potential screened Korringa-Kohn-Rostoker method we study the full-Heusler alloys based on Co, Fe, Rh and Ru. We show that many of these compounds show a half-metallic behavior, however in contrast to the half-Heusler alloys the energy gap in the minority band is extremely small. These full-Heusler compounds show a Slater-Pauling behavior and the total spin-magnetic moment per unit cell (M_t) scales with the total number of valence electrons (Z_t) following the rule: M_t=Z_t-24. We explain why the spin-down band contains exactly 12 electrons using arguments based on the group theory and show that this rule holds also for compounds with less than 24 valence electrons. Finally we discuss the deviations from this rule and the differences compared to the half-Heusler alloys.Comment: 10 pages, 8 figures, revised figure 3, new text adde

Density-related reproductive costs and natal conditions predict male life history in a highly polygynous mammal

DATA AVAILABILITY: Data to reproduce manuscript analyses are available on figshare: https://doi.org/10.6084/m9.figshare.21790016 (Lloyd et al., 2022).Polygynous males allocate substantial resources to sexual traits and behaviours to improve their chances of winning competitions for mates often at the cost of body maintenance. However, the degree to which males experience these trade-offs can be influenced by external conditions. Studies are needed that assess whether polygynous male resource allocation decisions about life history traits are density dependent. We tested for an influence of density on age-specific life history traits in male southern elephant seals, Mirounga leonina, using a 34-year data set collected at Marion Island. Specifically, we determine whether life history varied with density-related factors for survival, improved breeding success (measured as social status) and recruitment age. This was done by selecting linear models that tested biological hypotheses about density-dependent covariates related to competition intensity during breeding and natal conditions, while accounting for known intrinsic effects such as age and social status. Baseline mortalities were higher for males that had accumulated above average reproductive costs for their age than males with below average costs. This reproductive cost was determined by the number of females per harem relative to the population average. Thus, males likely allocated more resources to reproduction and less to body maintenance at all ages when defending and servicing relatively large harems, and this cost was compounding for males that dominated large harems at a young age. Males born in years with few pups were more likely to be dominant breeders and recruit at an earlier age than males born in years with many pups. Thus, breeding success and recruitment age likely depended on the population density experienced during early life, suggesting lasting effects of natal conditions in a long-lived animal. We show how density-dependent factors interact with intrinsic determinants of resource allocation to determine variation in polygynous male life history with long-term consequences.The National Research Foundation (South African Department of Science and Innovation), FILAMO Mobility Grant (University of Bergen) and Postgraduate Study Abroad Bursary Programme (University of Pretoria).http://www.elsevier.com/locate/anbehavMammal Research InstituteZoology and Entomolog

Maize grown for bioenergy on peat emits twice as much carbon as when grown on mineral soil

The area of land dedicated to growing maize for bioenergy in the United Kingdom is rapidly expanding. To understand how maize production influences soil carbon (C) dynamics, and whether this is influenced by soil type, we measured net ecosystem exchange (NEE) using the eddy covariance technique over the 2021 growing season. We combined the NEE data with C imports and exports to calculate the net ecosystem productivity (NEP) of two maize crops grown for bioenergy in the United Kingdom, one site on mineral soil and the other on lowland agricultural peat. Maize was similarly productive at both sites—gross primary productivity was 1107 g C m−2 at the site with mineral soil and 1407 g C m−2 at the peat site. However, total ecosystem respiration was considerably higher from the peat site (1198 g C m−2) compared with the mineral soil site (678 g C m−2). After accounting for the removal of C in harvested biomass, both sites were net C sources, but C losses were over two times greater from the peat site (NEP = 290 g C m−2) than the mineral site (NEP = 136 g C m−2). While annual crops may be needed to produce bioenergy in the short term, growing maize for bioenergy in the United Kingdom does not appear to be a viable option for C sequestration over the long term, as it leads to high carbon losses from agroecosystems, especially those on organic soils. Instead, growing perennial bioenergy crops on mineral soils with a low organic C content is a more appropriate option