2,546 research outputs found
Early-stage aeolian protodunes: bedform development and sand transport dynamics
No full textEarly-stage aeolian bedforms, or protodunes, are elemental in the continuum of dune development and act as essential precursors to mature dunes. Despite this, we know very little about the processes and feedback mechanisms that shape these nascent bedforms. Whilst theory and conceptual models have offered some explanation for protodune existence and development, until now, we have lacked the technical capability to measure such small bedforms in aeolian settings. Here, we employ terrestrial laser scanning to measure morphological change at the high frequency and spatial resolution required to gain new insights into protodune behaviour. On a 0.06 m high protodune, we observe vertical growth of the crest by 0.005 m in two hours. Our direct measurements of sand transport on the protodune account for such growth, with a reduction in time-averaged sediment flux of 18% observed over the crestal region. Detailed measurements of form also establish key points of morphological change on the protodune. The position on the stoss slope where erosion switches to deposition is found at a point 0.07 m upwind of the crest. This finding supports recent models that explain vertical dune growth through an upwind shift of this switching point. Observations also show characteristic changes in the asymmetric cross section of the protodune. Flow-form feedbacks result in a steepening of the lee slope and a decline in lower stoss slope steepness (by 3°), constituting a reshaping of protodune form towards more mature dune morphology. The approaches and findings applied here, a) demonstrate an ability to quantify processes at requisite spatial and temporal scales for monitoring early-stage dune evolution, b) highlight the crucial role of form-flow feedbacks in enabling early-stage bedform growth, alluding to a fluctuation in feedbacks that require better representation in dune models, and c) provide a new stimulus for advancing understanding of aeolian bedforms
An Interview with Matthew Kaiser on Competition and Play
No full textAn Interview with Matthew Kaiser on Competition and Play, by Sean Scanlan. Matthew Kaiser, the author of The World in Play: Portraits of a Victorian Concept (Stanford UP, 2012) says that “[c]ompetition is the disease from which modern life suffers,” and that “[c]ompetition is the only cure” for this suffering. This contradictory pairing seems to get at the heart of his thesis: play, as a totalizing, umbrella-like concept, emanates from a host of philosophical, political, and scientific work produced by Victorians who posed many of their ideas of play in sports metaphors, competitive logics, and narratives of struggle. Kaiser goes beyond the dichotomy of competition and play/competition or play, by stating “I’m interested in the totalizing potential of both concepts, the way that play, or competition for that matter, swallows the world whole, becomes in the minds of so many people, the organizing principle of reality, whether of culture or nature or consciousness, or of all three.
Coupling leeside grainfall to avalanche characteristics in aeolian dune dynamics
No full textAvalanche (grainflow) processes are fundamental drivers of dune morphodynamics and are typically initiated by grainfall accumulations. In sedimentary systems, however, the dynamism between grainfall and grainflow remains unspecified because simple measurements are hampered by the inherent instability of lee slopes. Here, for the first time, terrestrial laser scanning is used to quantify key aspects of the grainfall process on the lee (slip face) of a barchan sand dune. We determine grainfall zone extent and flux and show their variability under differing wind speeds. The increase in the downwind distance from the brink of peak grainfall under stronger winds provides a mechanism that explains the competence of large avalanches to descend the entire lee slope. These findings highlight important interactions between wind speed, grainfall, and subsequent grainflow that influence dune migration rates and are important for correct interpretation of dune stratigraphy
Surface and Meteorological Data at Medano Creek, Great Sand Dunes National Park, Colorado, USA on 15th April 2019
No full textWind and surface morphological data collected at Medano Creek on the 15th April 2019 to investigate protodune initiation. Surface morphological data: This is terrestrial laser scanned (TLS) data collected of the creek sand surface using three different co-located Leica TLS (C10, P20 and P50). The data is raw point cloud format in text columns of x, y and z coordinate data. It has been orientation into the same local coordinate system. Each data set uses the same coordinate system. Data can be viewed in any spatial software. Data is labelled using C10, P20 or P50, followed by the scan number. Scan times are indicated in a separate file. Wind data were collected from a fixed point next to the TLS instruments using a Gill 3D sonic anemometer. The data is in csv file format with column titles and can be viewed in any text or database software.</span
Surface and Meteorological Data of Saltation and Ripple Dynamics at Huab Dune Field, Skeleton Coast National Park, Namibia 2014, 2016 and 2018
No full textThis dataset includes raw point cloud data from repeat terrestrial laser scans (TLS) of rippled surfaces on barchan and dome dunes within the Huab Dune Field, Skeleton Coast National Park, Namibia. This raw data can be used to extract saltation height dynamics as well as 3D ripple data including celerity. As well as the TLS data, additional measurements of the wind speed through a CSAT 3D sonic anemometer or cup anemometer and sediment transport using a Sensit and Wenglor gate sensor.</span
Surface and Meteorological Data at Huab River Valley, Skeleton Coast National Park, Namibia in September 2019
No full textWind, sediment transport and surface/saltation data collected at Huab River Valley during a field campaign in September 2019 to investigate saltation on gravel and sand surfaces. Surface/saltation data: This is terrestrial laser scanned (TLS) data collected over sand and gravel surfaces during multiple days when saltation was active, on a surface approximately 8 m from the TLS, perpendicular to the wind direction. The data is raw point cloud format in text columns of x, y and z coordinate data. Files are named *_^_scan&amp; where * is the date that the data was collected in yymmdd format, ^ is surface type (sand or gravel) and &amp; is the scan number. Each data set uses the same coordinate system. Data can be viewed in any spatial software. Wind and sediment data were collected from a fixed point on each surface, directly downwind of the TLS data. The data is in csv file format with column titles and can be viewed in any text or database software. Data include hot wire measurements at different heights, Wenglor counts, sensit counts and 3D sonic measurements on some days. Sonic data is at 10 Hz, hotwire data at 10 second intervals, transport data is given within both datasets.</span
Artful living and the eradication of worry in Søren Kierkegaard's interpretation of Matthew 6:24-34
No full textDanish thinker Søren Kierkegaard published fourteen discourses, across four collections, on Matthew 6:24-34. The repeated readings of the biblical text, whose themes include the choice between God and mammon, worry, what it means to consider the birds and lilies, and how to seek first the kingdom of God, converge with Kierkegaard’s interest in anxiety, despair, worry, subjectivity, indirect communication, choice, the moment, and life before God. Accordingly, the discourses make connections with his larger works, elucidate frequently explored Kierkegaardian themes in recent scholarship, and contribute to his critique of nineteenth-century Copenhagen. Additionally, the collections present an interpretation of each verse and phrase of Matthew’s text and, held up against modern Matthew scholarship, they correlate with and contribute to Sermon on the Mount and New Testament studies. Kierkegaard’s reading of Matthew also holds implications for the practice of biblical interpretation as it promotes the importance of awareness of sin, interestedness, and appropriation as central to proper reading. His emphasis on Christ as the primary exemplar of Matthew’s text adds an additional Christological element to his hermeneutic. Furthermore, the discourses serve as spiritual treatises which provide the reader with theological terminology to help confront the problem of worry and suffering. In light of a human being’s distinctiveness as imago Dei, Kierkegaard elucidates ways an individual may respond artfully to the ongoing possibility of worry, a possibility which the discourses connect with Christian anthropology and external labels associated with possessions and status. The Matthew 6 discourses intimate Kierkegaard’s sympathy with classic Christian spirituality and, in combination with the cultural-ecclesiastical critique, the creative exegesis, and the in-depth analysis of the cause of and cure for worry, his work emerges as an excellent example of spiritual theology
Topographic perturbation of turbulent boundary layers by low-angle, early-stage aeolian dunes
No full textDecimeter-scale early-stage aeolian bedforms represent topographic features that differ notably from their mature dune counterparts, with nascent forms exhibiting more gently sloping lee sides and a reverse asymmetry in their flow-parallel bed profile compared to mature dunes. Flow associated with the development of these “protodunes,” wherein the crest gradually shifts downstream towards its mature state, was investigated by studying the perturbation of the turbulent boundary layer over a succession of representative bedforms. Rigid, three-dimensional models were studied in a refractive-index-matched experimental flume that enabled near-surface quantification of mean velocities and Reynolds stresses using particle-image velocimetry in wall-normal and wall-parallel measurement planes. Data indicate strong, topographically induced flow perturbations over the protodunes, to a similar relative degree to that found over mature dunes, despite their low-angled slopes. The shape of the crest is found to be an important factor in the development of flow perturbations, and only in the case with the flattest crest was maximal speed-up of flow, and reduction in turbulent stresses, found to occur upstream of the crest. Investigation of the log-linearity of the boundary layer profile over the stoss sides showed that, although the profile is strongly perturbed, a log-linear region exists, but is shifted vertically. A streamwise trend in friction velocity is thus present, showing a behavior similar to the trends in mean velocity. Analysis of the growth of the internal boundary layer on the dune stoss sides, beginning at the toe region, reveals a similar development for all dune shapes, despite clear differences in mean velocity and turbulent stress perturbations in their toe regions. The data presented herein provide the first documentation of flow over morphologies broadly characteristic of subtle, low-angle, aeolian protodunes, and indicate key areas where further study is required to yield a more complete quantitative understanding of flow–form–transport couplings that govern their morphodynamics.</p
Matthew’s Emmanuel Messiah: a paradigm of presence for god's people
No full textThe motif of divine presence is a clear phenomenon within the Gospel of Matthew. The modern critical means for assessing the ancient biblical text have multiplied to the point, some claim, of disparity. This study employs both narrative and redaction criticism in an attempt to respond authentically to the structural, historical and theological dimensions of Matthew's Gospel. This study begins with the presumption of the wholeness and integrity of Matthew's narrative, and assumes the gospel story to have an inherently dramatic structure which invites readers to inhabit imaginatively its narrative world and respond to its call. But since we are concerned with the role of both reader and author, this study also assumes a text with an historical author and context. The introduction focuses on the meta-critical dilemma facing New Testament students - what is the text and how do we read it? - and seeks some balance in terms of Krieger's analogy of the text as both window and mirror. Proposed is a narrative reading of Matthew's presence motif alongside a redaction critical assessment of it. In Chapter 2 the elements of narrative theory are introduced and relevant terms defined: the structure of narrative, the function of the narrator, points of view. Chapter 3 becomes an exercise in narrative reading, with Matthew's presence motif providing the focus, and the implied reader’s interaction with the story being predominant in interpretation. Characters, rhetorical devices, and points of view are discussed, to understand the motif's development throughout the story's progress. The thrust of Chapter 4 is thereafter to examine divine presence as a dominant motif within Matthew's most important literary context: the Jewish scriptures. Here the primary paradigms of divine presence provided by the Patriarchs, the Sinai experience, and the Davidic-Zion traditions are assessed. Chapter 5 follows with a more detailed examination of the OT "I am with you/God is with us" formula and its µeo' vµwv/ηuwv language, so strongly connected to Matthew's presence motif. Chapters 6-8 build on these investigations with a closer analysis of the three critical "presence passages" of Mt 1:23. 18:20 and 28:20. The passages and their contexts are probed from a redaction critical perspective, guided by the narrative investigation of Chapter 3, and the background from Chapters 4 and 5.The three major "presence passages" examined in Chapters 6-8 are also complimented by a number of secondary issues: worship, wisdom, the Spirit and the poor in Matthew, and their relation to Jesus' divine presence. These are discussed in Chapter 9. Chapter 10 summarizes and looks briefly at some implications. Matthew' presence motif proves to be an important element of the Gospel’s rhetorical design, redactional strategy and Christology. The presence of Jesus, the Emmanuel Messiah, exhibited in his risen authority, becomes the focus of his people's hopes and experiences in the post-Easter world. What the presence of Yahweh was to his people. Jesus now provides in a new paradigm for his people - his followers, the little ones, the poor and the marginalized, from all nations
From Philosophy to Flourishing: A Compassionate Case for Going Vegan with Matthew C. Halteman
No full textThere’s a way to talk about going vegan that doesn’t involve shame, blame, or rigid rules. A way that invites people in, instead of pushing them away.
Philosopher and author Matthew C. Halteman, has written one of the most generous, wise, and unexpectedly funny books I’ve read in a long time—Hungry, Beautiful Animals. It’s a love letter to what’s possible when we stop arguing about “being vegan” and start embracing the abundance that can come from going vegan.
Matt is professor of philosophy at Calvin University in Grand Rapids, Michigan, and a fellow at the Oxford Centre for Animal Ethics in the UK.
In this conversation, Matt and I explore the role of family legacy, inner conflict, and philosophy in shaping our choices—and how compassion must be at the heart of advocacy if we want real change.
We speak about what it means to approach others as “vegans in waiting,” the metaphors that make change feel safe rather than threatening, and how joy—not obligation—is the most powerful fuel for transformation
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