18 research outputs found

    Reinterpreting turbidity: new methodologies for suspended-sediment research

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    Existing instruments for turbidity measurement vary considerably in terms of the principles of operation, the physical design, and the cost to the researcher. The operational methodologies of late twentieth century turbidity instruments have led to the development of new turbidity measurement standards, and the invention of new turbidity measurement units. These measurement units are invalid and do not have a sound footing with regard to the underlying physics of the scattering and absorption of light by suspended particles. A review of the turbidity literature has shown that the proliferation of these incommensurate units of measurement throughout the physical sciences has caused extensive misinterpretation of turbidity data, particularly concerning its use as a surrogate for suspended sediment concentration (SSC). Turbidity is a complex phenomenon, and its measurement reported in terms of a single numeric quantity in some physically indeterminate units of measurement. It is not necessarily useful to reduce complex data to a single value, since this approach does not permit the researcher any a posteriori opportunity to reinterpret existing data in light of innovations in analysis methodology. This thesis proposes a new way to present turbidity data that will facilitate the cross-comparison of turbidity measurements made by different instruments on any type of suspended sediment. The creation of a new turbidity research instrument that illustrates the application of the new method for reporting turbidity data as a ratio of light attenuation values in decibels, promotes a positive change in direction away from the traditional measurement units. The design process focusses on the instrument calibration procedure. With a simple reinterpretation of the phase-function description of light scattering from suspended particles, measurements of light attenuation made at multiple angles with respect to the axis of the incident light beam, compare easily with the same measurements made using different wavelengths of incident light. This work goes on to introduce new nomenclature that requires the citing of measurement angle and wavelength of light to be an integral part of any recorded turbidity measurement. A modelling approach is used in the evaluation of the new turbidity instrument. This modelling is important for three reasons. First, it identifies which instrument parameters affect the result of a turbidity measurement – the key parameter being the mathematical function that describes the spatial divergence of the incident light beam, which is important to measurement systems that employ incoherent light sources such as LEDs, rather than to laser-based systems. Secondly, the modelling reveals two fundamental theories of light scattering due to suspended particles, both of which are required to describe adequately the turbidity of sediment-laden water. These two theories are Mie scattering and geometric optics. Mie scattering is well accounted for by the developed model - geometric optics, less so. The extent to which the model predictions diverge from the empirical data is characterised by a metric related to the backscatter fraction, and the consistency and linearity of the model is established. Ideas for the improvement of the geometric optics feature of the model are discussed, as is the third reason for the importance of numerical modelling. This third reason relates to the use of multi-parameter turbidity measurements as a means to characterise the properties of a suspended sediment. By simulating precisely the measurement response of the turbidity instrument, then it is notionally possible to infer the properties of an unknown sediment by tuning the model parameters to match the empirical response of the unknown sediment. This tuning process could reveal information pertaining to particle size and shape. Finally, potential applications for the new research instrument focus on improvements to the instrument itself and the methodology, and the further development of the turbidity data reporting nomenclature. Prototype methodologies that relate turbidity to suspended sediment concentration are suggested, which also consider ways in which the optical measurements can potentially classify the physical properties of a sediment

    Experimental investigation into the impact of a liquid droplet onto a granular bed using three-dimensional, time-resolved, particle tracking

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    This article was published in the journal, Physical Review E [ © American Physical Society] and the definitive version is available at: http://dx.doi.org/10.1103/PhysRevE.89.032201An experimental investigation into the interaction that occurs between an impacting water droplet and a granular bed of loose graded sand has been carried out. High-speed imaging, three-dimensional time-resolved particle tracking, and photogrammetric surface proïŹling have been used to examine individual impact events. The focus of the study is the quantiïŹcation and trajectory analysis of the particles ejected from the sand bed, along with measurement of the change in bed morphology. The results from the experiments have detailed two distinct mechanisms of particle ejection: the ejection of water-encapsulated particles from the edge of the wetted region and the ejection of dry sand from the periphery of the impact crater. That the process occurs by these two distinct mechanisms has hitherto been unobserved. Presented in the paper are distributions of the particle ejection velocities, angles, and transport distances for both mechanisms. The ejected water-encapsulated particles, which are few in number, are characterized by low ejection angles and high ejection velocities, leading to large transport distances; the ejected dry particles, which are much greater in number, are characterized by high ejection angles and low velocities, leading to lower transport distances. From the particle ejection data, the momentum of the individual ballistic sand particles has been calculated; it was found that only 2% of the water-droplet momentum at impact is transferred to the ballistic sand particles. In addition to the particle tracking, surface proïŹling of the granular bed postimpact has provided detailed information on its morphology; these data have demonstrated the consistent nature of the craters produced by the impact and suggest that particle agglomerations released from their edges make up about twice the number of particles involved in ballistic ejection. It is estimated that, overall, about 4% of the water-droplet momentum is taken up in particle movement

    The dynamics and prognostic potential of DNA methylation changes at stem cell gene loci in women's cancer.

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    Aberrant DNA methylation is an important cancer hallmark, yet the dynamics of DNA methylation changes in human carcinogenesis remain largely unexplored. Moreover, the role of DNA methylation for prediction of clinical outcome is still uncertain and confined to specific cancers. Here we perform the most comprehensive study of DNA methylation changes throughout human carcinogenesis, analysing 27,578 CpGs in each of 1,475 samples, ranging from normal cells in advance of non-invasive neoplastic transformation to non-invasive and invasive cancers and metastatic tissue. We demonstrate that hypermethylation at stem cell PolyComb Group Target genes (PCGTs) occurs in cytologically normal cells three years in advance of the first morphological neoplastic changes, while hypomethylation occurs preferentially at CpGs which are heavily Methylated in Embryonic Stem Cells (MESCs) and increases significantly with cancer invasion in both the epithelial and stromal tumour compartments. In contrast to PCGT hypermethylation, MESC hypomethylation progresses significantly from primary to metastatic cancer and defines a poor prognostic signature in four different gynaecological cancers. Finally, we associate expression of TET enzymes, which are involved in active DNA demethylation, to MESC hypomethylation in cancer. These findings have major implications for cancer and embryonic stem cell biology and establish the importance of systemic DNA hypomethylation for predicting prognosis in a wide range of different cancers

    Data from: Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events

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    The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back 40 Myr ago. Recent studies, however, suggest that much of Sulawesi’s fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification, and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric data sets derived from Sulawesi’s three largest mammals: the Babirusa, Anoa, and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Myr ago to 2-3 Myr ago), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (~1–2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years

    Reflective Personality: Identifying Cognitive Style and Cognitive Complexity

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    Categorized among learning practices, reflection involves cognitive processing. Some people say they reflect often, whereas others claim they are less inclined to reflect on a regular basis. The present study examines reflection in an academic learning setting. In contrast with previous studies testing reflective task accomplishment, we are interested in personality traits that can predict reflection or a reflective outcome. By means of a survey university students are questioned about their learning practices when working on their final thesis. To test whether certain traits influence reflection and whether reflection produces cognitive outcomes at the individual level, we performed hierarchical regression analysis. In addition, structural equation modeling is used to test for the mediation effects of reflection. The data stress a mediating role of reflection in the relationship between particular personality traits and cognitive complexity

    Materials and Methods, Supplementary Tables and Supplementary Figures from Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events

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    The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back 40 Ma. Recent studies, however, suggest that much of Sulawesi's fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric datasets derived from Sulawesi's three largest mammals: the Babirusa, Anoa and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Ma to 2–3 Ma), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (approx. 1–2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years

    AusTraits: a curated plant trait database for the Australian flora

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    INTRODUCTION AusTraits is a transformative database, containing measurements on the traits of Australia’s plant taxa, standardised from hundreds of disconnected primary sources. So far, data have been assembled from > 250 distinct sources, describing > 400 plant traits and > 26,000 taxa. To handle the harmonising of diverse data sources, we use a reproducible workflow to implement the various changes required for each source to reformat it suitable for incorporation in AusTraits. Such changes include restructuring datasets, renaming variables, changing variable units, changing taxon names. While this repository contains the harmonised data, the raw data and code used to build the resource are also available on the project’s GitHub repository, http://traitecoevo.github.io/austraits.build/. Further information on the project is available in the associated publication and at the project website austraits.org. Falster, Gallagher et al (2021) AusTraits, a curated plant trait database for the Australian flora. Scientific Data 8: 254, https://doi.org/10.1038/s41597-021-01006-6 CONTRIBUTORS The project is jointly led by Dr Daniel Falster (UNSW Sydney), Dr Rachael Gallagher (Western Sydney University), Dr Elizabeth Wenk (UNSW Sydney), and Dr HervĂ© Sauquet (Royal Botanic Gardens and Domain Trust Sydney), with input from > 300 contributors from over > 100 institutions (see full list above). The project was initiated by Dr Rachael Gallagher and Prof Ian Wright while at Macquarie University. We are grateful to the following institutions for contributing data Australian National Botanic Garden, Brisbane Rainforest Action and Information Network, Kew Botanic Gardens, National Herbarium of NSW, Northern Territory Herbarium, Queensland Herbarium, Western Australian Herbarium, South Australian Herbarium, State Herbarium of South Australia, Tasmanian Herbarium, Department of Environment, Land, Water and Planning, Victoria. AusTraits has been supported by investment from the Australian Research Data Commons (ARDC), via their “Transformative data collections” (https://doi.org/10.47486/TD044) and “Data Partnerships” (https://doi.org/10.47486/DP720) programs; fellowship grants from Australian Research Council to Falster (FT160100113), Gallagher (DE170100208) and Wright (FT100100910), a grant from Macquarie University to Gallagher. The ARDC is enabled by National Collaborative Research Investment Strategy (NCRIS). ACCESSING AND USE OF DATA The compiled AusTraits database is released under an open source licence (CC-BY), enabling re-use by the community. A requirement of use is that users cite the AusTraits resource paper, which includes all contributors as co-authors: Falster, Gallagher et al (2021) AusTraits, a curated plant trait database for the Australian flora. Scientific Data 8: 254, https://doi.org/10.1038/s41597-021-01006-6 In addition, we encourage users you to cite the original data sources, wherever possible. Note that under the license data may be redistributed, provided the attribution is maintained. The downloads below provide the data in two formats: austraits-3.0.2.zip: data in plain text format (.csv, .bib, .yml files). Suitable for anyone, including those using Python. austraits-3.0.2.rds: data as compressed R object. Suitable for users of R (see below). Both objects contain all the data and relevant meta-data. AUSTRAITS R PACKAGE For R users, access and manipulation of data is assisted with the austraits R package. The package can both download data and provides examples and functions for running queries. STRUCTURE OF AUSTRAITS The compiled AusTraits database has the following main components: austraits ├── traits ├── sites ├── contexts ├── methods ├── excluded_data ├── taxanomic_updates ├── taxa ├── definitions ├── contributors ├── sources └── build_info These elements include all the data and contextual information submitted with each contributed datasets. A schema and definitions for the database are given in the file/component definitions, available within the download. The file dictionary.html provides the same information in textual format. Full details on each of these components and columns are contained within the definition. Similar information is available at http://traitecoevo.github.io/austraits.build/articles/Trait_definitions.html and http://traitecoevo.github.io/austraits.build/articles/austraits_database_structure.html. CONTRIBUTING We envision AusTraits as an on-going collaborative community resource that: Increases our collective understanding the Australian flora; and Facilitates accumulation and sharing of trait data; Builds a sense of community among contributors and users; and Aspires to fully transparent and reproducible research of the highest standard. As a community resource, we are very keen for people to contribute. Assembly of the database is managed on GitHub at traitecoevo/austraits.build. Here are some of the ways you can contribute: Reporting Errors: If you notice a possible error in AusTraits, please post an issue on GitHub. Refining documentation: We welcome additions and edits that make using the existing data or adding new data easier for the community. Contributing new data: We gladly accept new data contributions to AusTraits. See full instructions on how to contribute at http://traitecoevo.github.io/austraits.build/articles/contributing_data.html

    Contentious Issues: Copyright Reform in the Age of Digital Technologies

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