1,721,177 research outputs found
Dynamic Magma Evolution
No full textUnderstanding the magmatic processes responsible for the chemical and textural signatures of volcanic products and igneous rocks is crucial for monitoring, forecasting, and mitigating the impacts of volcanic activity.
Dynamic Magma Evolution is a compilation of recent geochemical, petrological, physical, and thermodynamic studies. It combines field research, experimental results, theoretical approaches, unconventional and novel techniques, and computational modeling to present the latest developments in the field
Rheological behavior of partly crystallized silicate melts under variable shear rate
No full textHigh‐temperature experiments were performed in order to shed new light on the shear‐rate controls on magma viscosity. We compare viscosity data from three different compositions: an andesite from the Calbuco volcano, a basalt from the Etna 122 BCE Plinian eruption and a synthetic pyroxenite with a composition similar to the Canadian Theo’s Flow. In addition to the determination of melt viscosity (at 1545–1715 K), we performed viscosity determinations at subliquidus conditions in partially crystallized materials, under controlled shear rates of 0.1 and 1 s−1 and at temperatures of 1483, 1493, and 1503 K for the Calbuco andesite, Etna basalt, and synthetic pyroxenite, respectively. The two different shear rates allow us to retrieve information about shear‐rate influences on viscosity of partly crystallized systems. A decrease in viscosity is observed with increase in shear rate. This behavior is known in the literature as the “shear thinning effect.” Our data show that changes of shear rates from 0.1 to 1 s−1 may cause a viscosity difference of 0.5 to one order of magnitude. This effect should be taken into account when considering magmatic processes occurring in volcanic conduits. The rheological properties of partly crystallized systems could drastically change depending on the dynamics of the magmatic system. © 2021 American Geophysical Union
The Technology Explorers: Partnering with Older Adults to Engage with Virtual Reality and Virtual Avatars
Full text linkParticipatory research methods are increasingly being adopted when designing and evaluating emerging technologies for older adults. This chapter details our approach to applying participatory methods to our work with a group of older adults during series of workshops. The workshops involved working with 25 adults from both regional and metropolitan areas, who were over the age of 70. We referred to these participants as the Technology Explorers. The Technology Explorers partnered with us to explore how Virtual Reality (VR) technology could be harnessed to provide older adults with opportunities to participate in meaningful social activities. This chapter focusses on the initial engagement phase of the project that involved introducing the Technology Explorers to a range of VR systems and interaction techniques, co-designing 3D Avatars, and interacting with each other in two social VR technology probes. We describe the participatory methods that helped us to build a strong collaborative partnership with the Technology Explorers, before detailing the techniques used to engage with group members who had vastly different levels on technical knowledge. As none of the Technology Explorers had any experience with VR or virtual avatars, in a final section we describe three techniques we employed to develop this capacity in the group, with a particular focus on the deployment of two technology probes that marked the end of the workshop series
Building Social Connections: A Framework for Enriching Older Adults’ Social Connectedness Through Information and Communication Technologies
No full textAged care providers and researchers are increasingly exploring the use of communication technologies to help older people remain connected to the world as they age. These initiatives often aim to counteract the negative effects of social isolation, thereby aiming to compensate for deficiencies associated with old age, rather than aiming to build on and enrich the social connections that people find valuable in later life. In this chapter, we present a framework that aims to inform the design of technologies for enriching older people’s social lives. Drawing on research from the field of social gerontology that provides insight into the multiple ways older adults experience social connection and isolation, the framework describes three interrelated dimensions that characterise the experience of social connection in later life: (i) personal relationships, (ii) community connections, and (iii) societal engagement. A person may experience inadequacies in one or more of these dimensions, to varying degrees and intensity. However, enrichment in one dimension could potentially compensate for a sense of disconnection in other dimensions. We argue that this conceptualisation of social connection in later life is useful for informing the design of technology-based interventions. We illustrate how information and communication technologies (ICTs) can be designed and used to enrich the three different kinds of social connections by drawing on examples from the human–computer interaction literature that have demonstrated the value of new technologies for enriching different dimensions of social connectedness in later life
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Rheological changes in melts and magmas induced by crystallization and strain rate
Full text linkThis review highlights the rheological and phase proportions variation induced by cooling events from superliquidus temperature (melt) to subliquidus temperatures. It provides a comprehensive view of the rheological response of magmatic systems undergoing dynamic cooling and shear deformation. The two main parameters which are of importance to model the rheological properties of such crystallizing systems and which are simultaneously poorly investigated so far are crystallization and strain rates. The response to relatively high deformation rates results in shear thinning behavior in partly crystallized systems under variable shear rate and it should be considered in magmatic processes. Due to the sluggish crystallization of SiO2-rich melts, data are mainly available for mafic systems, which does not allow a general reappraisal. An attempt to model available literature data for less evolved systems in dynamic scenarios and a comparison with MELTS algorithm approach (thermodynamic equilibrium conditions) is provided. Since there are difficulties in comparing experimental data gained using different methodologies, we focus mainly on data obtained with the concentric cylinder technique. This highlights the fact that a general experimental protocol is needed in order to compare and model viscosity data to predict the dynamic rheological evolution for volcanic rocks
Extending the Rock Cycle to a Cosmic Scale
Full text linkThe rock cycle, a cornerstone of geosciences, describes rock formation and transformation on Earth. However, this Earth-centric view overlooks the broader history of rock evolution across the cosmos, with two fundamental limitations: (i) Earth-centric paradigms that ignore extraterrestrial lithogenesis, excluding cosmically significant rocks and processes, and (ii) disciplinary fragmentation between geological and astrophysical sciences, from the micro- to the macroscale. This review proposes an extension of the rock cycle concept to a cosmic scale, exploring the origin of rocks and their evolution from interstellar space, through the aggregation of solid materials in protoplanetary disks, and their subsequent evolution on planetary bodies. Through systematic analysis of igneous, metamorphic, and sedimentary processes occurring beyond Earth, we identify four major domains in which distinct dynamics govern the rock cycle, each reworking rocks with domain-specific characteristics: (1) stellar and nebular dynamics, (2) protoplanetary disk dynamics, (3) asteroidal dynamics, and (4) planetary dynamics. Here we propose the cosmic rock cycle as a new epistemic tool that could transform interdisciplinary research and geoscience education. This perspective reveals Earth's rock cycle as a rare and invaluable subset of rock genesis in the cosmos
Viscosity behaviour of silicate melts during cooling under variable shear rates
No full textThe viscosity of a crystal-bearing shoshonite from Vulcanello (Aeolian Archipelago, Italy) was measured using the concentric cylinder method. Experiments were performed in the temperature interval from superliquidus (1573 K) to 1373 K with the aim to investigate the rheological response of the magma during variable cooling rate (i.e. 1000, 100 and 10 K/h) and shear rate (0.01, 0.1 and 1 s−1). In one experiment, with a cooling rate of 10 K/h and shear rate of 1 s−1, clinopyroxenes (ca. 11 vol.%) with hopper texture crystallized. One further experiment was performed for a longer time with a cooling rate of 100 K/h and shear rate of 1 s−1 to the final temperature of 1323 K. In this case, the final product showed skeletal crystals of pyroxenes (ca. 17 vol.%) and an apparent viscosity of 1.10 × 104 Pa s, which was very close to the experiment performed at 10 K/h and shear rate of 1 s−1 to 1373 K (1.18 × 104 Pa s). The comparison between experiments performed at cooling rate of 100 K/h, and finally quenched at to 1373 and 1323 K, respectively, showed that a temperature decrease of 50 K produces an increase in the apparent viscosity of ca. 1 log unit due to the transition from crystal-free to crystal-bearing melts. This study provides new data on apparent viscosity variation as cooling and shear rates vary in a crystallizing magmatic system. Results show that, on average, the viscosity of a shoshonitic system can increase by about two orders of magnitude due to temperature decrease from 1573 to 1373 K and the incipient crystallization occurring at the lowest temperatures. Finally, the results confirm that crystal nucleation and growth kinetics, as well as magma viscosity, are controlled by the dynamic state of the system. © 2020 Elsevier B.V
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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