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1
Hawley, Robert L., Zoe R. Courville, Laura M. Kehrl, Eric R. Lutz, Erich C. Osterberg, Thomas B. Overly, and Gifford J. Wong. "Recent accumulation variability in northwest Greenland from ground-penetrating radar and shallow cores along the Greenland Inland Traverse." Journal of Glaciology 60, no. 220 (2014): 375–82. http://dx.doi.org/10.3189/2014jog13j141.
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AbstractAccumulation is a key parameter governing the mass balance of the Greenland ice sheet. Several studies have documented the spatial variability of accumulation over wide spatial scales, primarily using point data, remote sensing or modeling. Direct measurements of spatially extensive, detailed profiles of accumulation in Greenland, however, are rare. We used 400 MHz ground-penetrating radar along the 1009 km route of the Greenland Inland Traverse from Thule to Summit during April and May of 2011, to image continuous internal reflecting horizons. We dated these horizons using ice-core chemistry at each end of the traverse. Using density profiles measured along the traverse, we determined the depth to the horizons and the corresponding water-equivalent accumulation rates. The measured accumulation rates vary from ~0.1 m w.e. a–1 in the interior to ~0.7 m w.e. a–1 near the coast, and correspond broadly with existing published model results, though there are some excursions. Comparison of our recent accumulation rates with those collected along a similar route in the 1950s shows a ~10% increase in accumulation rates over the past 52 years along most of the traverse route. This implies that the increased water vapor capacity of warmer air is increasing accumulation in the interior of Greenland.
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Guest, M., J. Bliss, and J. Lohmeier. "Landmark Enhancement and Strategic Processing: An Evaluation of Strategies for Spatial Navigation Training." Perceptual and Motor Skills 85, no. 3 (December 1997): 1123–35. http://dx.doi.org/10.2466/pms.1997.85.3.1123.
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Viewing a filmed route offers an alternative to more expensive and rigid methods of learning navigation skills. One advantage of film is the ability to enhance important landmarks or focus on particularly relevant information. The current research used a videotape of a spatial route to assess the usefulness of participants' interaction with landmarks and enhancement of landmarks for training spatial navigation. 48 participants were exposed to one of four videotaped route conditions: Landmark-enhanced, Question-based Interaction, Landmark-enhanced Plus Question-based Interaction, or Control (Nonenhanced without Question-based Interaction). Following the spatial navigation training with videotape, participants were asked to traverse the route in the actual building. Analyses of variance indicated that the Question-based Interaction group made significantly fewer wrong turns during traversal of the route than did the Control group. Also, enhancement of the landmarks did not significantly reduce wrong turns; in fact, it may have hindered the benefit of question-based interaction in reducing wrong turns.
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Legrand, Michel, and Robert J. Delmas. "Spatial and Temporal Variations of Snow Chemistry in Terre Adélie (East Antarctica)." Annals of Glaciology 7 (1985): 20–25. http://dx.doi.org/10.1017/s0260305500005851.
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The chemistry of recently deposited snow sampled in 1982–83 along a 430 km coast-interior traverse in Terre Adelie, East Antarctica, is reported. In addition, three firn samples, covering the same time period (1959 to 1969) and collected on the traverse at D 55, D 80 and Dome C stations, respectively at 200, 430 and 1070 km from the sea, are also studied. Concentrations of major soluble impurities (H+, , Na+, K+, Cl−, and ) were determined by ion chromatography (except H+ which was titrated) on more than 200 samples. Conditions of sampling and analysis were carefully controlled in order to avoid contamination problems. A balanced ionic budget was generally obtained for each of the samples. For stations occupying an intermediary position between the coastal areas and the central Antarctic plateau, our results demonstrate that the two major impurities are H2SO4 and HNO3. HCl is also present, but at a lower level of concentration; the sea-salt contribution is dominant only at the most coastal sites (within 40 km) of the sea. The degree of neutralization of the snow acidity by NH3 is always very low as indicated by the values of content. The mean concentrations of H2SO4 along the traverse are relatively constant whereas an increase of the HNO3 concentrations is observed when going inland. It decreases, however, in most central areas. These results are discussed in relation to the glaciochemical data published for other locations on the Antarctic plateau, in particular the sulphate concentrations which depend strongly on explosive volcanic activity.
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Legrand, Michel, and Robert J. Delmas. "Spatial and Temporal Variations of Snow Chemistry in Terre Adélie (East Antarctica)." Annals of Glaciology 7 (1985): 20–25. http://dx.doi.org/10.3189/s0260305500005851.
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The chemistry of recently deposited snow sampled in 1982–83 along a 430 km coast-interior traverse in Terre Adelie, East Antarctica, is reported. In addition, three firn samples, covering the same time period (1959 to 1969) and collected on the traverse at D 55, D 80 and Dome C stations, respectively at 200, 430 and 1070 km from the sea, are also studied. Concentrations of major soluble impurities (H+, , Na+, K+, Cl−, and ) were determined by ion chromatography (except H+ which was titrated) on more than 200 samples. Conditions of sampling and analysis were carefully controlled in order to avoid contamination problems. A balanced ionic budget was generally obtained for each of the samples. For stations occupying an intermediary position between the coastal areas and the central Antarctic plateau, our results demonstrate that the two major impurities are H2SO4 and HNO3. HCl is also present, but at a lower level of concentration; the sea-salt contribution is dominant only at the most coastal sites (within 40 km) of the sea. The degree of neutralization of the snow acidity by NH3 is always very low as indicated by the values of content. The mean concentrations of H2SO4 along the traverse are relatively constant whereas an increase of the HNO3 concentrations is observed when going inland. It decreases, however, in most central areas. These results are discussed in relation to the glaciochemical data published for other locations on the Antarctic plateau, in particular the sulphate concentrations which depend strongly on explosive volcanic activity.
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Khodzher, T. V., L. P. Golobokova, E. Yu Osipov, Yu A. Shibaev, V. Ya Lipenkov, O. P. Osipova, and J. R. Petit. "Spatial–temporal dynamics of chemical composition of surface snow in East Antarctica along the Progress station–Vostok station transect." Cryosphere 8, no. 3 (May 19, 2014): 931–39. http://dx.doi.org/10.5194/tc-8-931-2014.
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Abstract. In January of 2008, during the 53rd Russian Antarctic Expedition, surface snow samples were taken from 13 shallow (0.7 to 1.5 m depth) snow pits along the first tractor traverse from Progress to Vostok stations, East Antarctica. Sub-surface snow/firn layers are dated from 2.1 to 18 yr. The total length of the coast to inland traverse is more than 1280 km. Here we analysed spatial variability of concentrations of sulphate ions and elements and their fluxes in the snow deposited within the 2006–2008 time interval. Anions were analysed by high-performance liquid chromatography (HPLC), and the determination of selected metals, including Na, K, Mg, Ca and Al, was carried out by mass spectroscopy with atomization by induced coupled plasma (ICP-MS). Surface snow concentration records were examined for trends versus distance inland, elevation, accumulation rate and slope gradient. Na shows a significant positive correlation with accumulation rate, which decreases as distance from the sea and altitude increase. K, Ca and Mg concentrations do not show any significant relationship either with distance inland or with elevation. Maximal concentrations of these elements with a prominent Al peak are revealed in the middle part of the traverse (500–600 km from the coast). Analysis of element correlations and atmospheric circulation patterns allow us to suggest their terrestrial origin (e.g. aluminosilicates carried as a continental dust) from the Antarctic nunatak areas. Sulphate concentrations show no significant relationship with distance inland, elevation, slope gradient and accumulation rate. Non-sea salt secondary sulphate is the most important contribution to the total sulphate budget along the traverse. Sulphate of volcanic origin attributed to the Pinatubo eruption (1991) was revealed in the snow pit at 1276 km (depth 120–130 cm).
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DOLADOV, Yury I., Marina A. ZORINA, Irina V. KHABUR, Ekaterina N. BOKAREVA, and Daria A. DODONOVA. "INSTALLATION FEATURES OF SPATIAL LATTICE METAL COVERING OF A PRODUCTION BUILDING IN LIMITED SPACE CONDITIONS." Urban construction and architecture 9, no. 4 (December 15, 2019): 74–81. http://dx.doi.org/10.17673/vestnik.2019.04.12.
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A version of the project for the installation of the spatial structure of the coating of an industrial building was developed. The technological feature of the project was the presence of cramped working conditions. The feasibility study of the methods of assembly and installation of the coating, taking into account the peculiarities of the construction of the coating, the features of the construction site and the needs for lifting machines, showed the eff ectiveness of the installation of the coating with enlarged blocks assembled on the ground. Mounting the unit using a traverse allowed to reduce the estimated height of the hook and select a crane that does not diff er in the high cost of rent. It became possible to apply the adopted installation scheme provided that an individual design of the beam was developed. The calculation and design of the traverse itself was performed, as well as the calculation of the enlarged unit for the installation situation.
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Frezzotti, Massimo, Michel Pourchet, Onelio Flora, Stefano Gandolfi, Michel Gay, Stefano Urbini, Christian Vincent, et al. "Spatial and temporal variability of snow accumulation in East Antarctica from traverse data." Journal of Glaciology 51, no. 172 (2005): 113–24. http://dx.doi.org/10.3189/172756505781829502.
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AbstractRecent snow accumulation rate is a key quantity for ice-core and mass-balance studies. Several accumulation measurement methods (stake farm, fin core, snow-radar profiling, surface morphology, remote sensing) were used, compared and integrated at eight sites along a transect from Terra Nova Bay to Dome C, East Antarctica, to provide information about the spatial and temporal variability of snow accumulation. Thirty-nine cores were dated by identifying tritium/b marker levels (1965_66) and non-sea-salt (nss) SO42_ spikes of the Tambora (Indonesia) volcanic event (1816) in order to provide information on temporal variability. Cores were linked by snow radar and global positioning system surveys to provide detailed information on spatial variability in snow accumulation. Stake-farm and ice-core accumulation rates are observed to differ significantly, but isochrones (snow radar) correlate well with ice-core derived accumulation. The accumulation/ablation pattern from stake measurements suggests that the annual local noise (metre scale) in snow accumulation can approach 2 years of ablation and more than four times the average annual accumulation, with no accumulation or ablation for a 5 year period in up to 40% of cases. The spatial variability of snow accumulation at the kilometre scale is one order of magnitude higher than temporal variability at the multi-decadal/secular scale. Stake measurements and firn cores at Dome C confirm an approximate 30% increase in accumulation over the last two centuries, with respect to the average over the last 5000 years
8
Dixon, D. A., P. A. Mayewski, E. Korotkikh, S. B. Sneed, M. J. Handley, D. S. Introne, and T. A. Scambos. "A spatial framework for assessing current conditions and monitoring future change in the chemistry of the Antarctic atmosphere." Cryosphere Discussions 5, no. 2 (March 16, 2011): 885–950. http://dx.doi.org/10.5194/tcd-5-885-2011.
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Abstract. This is the first study to measure more than 25 chemical constituents in the surface snow and firn across extensive regions of Antarctica. It is also the first to report total-Cs concentrations. We present major ion, trace element, heavy metal, rare earth element and oxygen isotope data from a series of surface snow samples and shallow firn sections collected along four US ITASE traverses across East and West Antarctica. In each sample we measure dissolved concentrations of Na+, K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and MS− using ion chromatography and total concentrations of Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co, Na, Mg, Li, and K using inductively coupled plasma sector field mass spectrometry. We also measure δ18O by isotope ratio mass spectrometry. The 2002/2003 traverse began at Byrd Surface Camp, West Antarctica, and ended close to South Pole, East Antarctica. The 2003/2004 traverse began at South Pole, passed through AGO4 in central East Antarctica before turning north and finishing at Taylor Dome. The combined 2006/2007 and 2007/2008 traverses started out at Taylor Dome and headed south, passing through the Byrd Glacier drainage basin and ending at South Pole. In this study, we utilize satellite remote sensing measurements of microwave backscatter and grain size to assist in the identification of glaze/dune areas across Antarctica and show how chemical concentrations are higher in these areas, precluding them from containing useful high-resolution chemical climate records. The majority of the non-glaze/dune samples in this study exhibit similar, or lower, concentrations to those from previous studies. Consequently, the results presented here comprise a conservative baseline for Antarctic surface snow chemical concentrations. The elements Cd, Pb, Bi, As, and Li are enriched across Antarctica relative to both ocean and upper crust elemental ratios. Global volcanic outgassing accounts for the majority of the Bi measured in East and West Antarctica and for a significant fraction of the Cd in East Antarctica. Nonetheless, global volcanic outgassing cannot account for the enriched values of Pb or As. Local volcanic outgassing from Mount Erebus may account for a significant fraction of the As and Cd in West Antarctica and for a significant fraction in East Antarctic glaze/dune areas. However, despite potential contributions from local and global volcanic sources, significant concentrations of Pb, Cd, and As remain across much of Antarctica. Most importantly, this study provides a baseline from which changes in the chemistry of the atmosphere over Antarctica can be monitored under expected warming scenarios and continued intensification of industrial activities in the Southern Hemisphere.
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Richardson, Cecilia, and Per Holmlund. "Spatial variability at shallow snow-layer depths in central Dronning Maud Land, East Antarctica." Annals of Glaciology 29 (1999): 10–16. http://dx.doi.org/10.3189/172756499781820905.
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AbstractThe spatial variability in snow accumulation varies between different regions in Dronning Maud Land, East Antarctica. This pattern cannot easily be explained by the single action of parameters such as distance to open sea, surface elevation or slope. In 1996-97 we mapped snow-layer depths within the top 11 m of the snowpack with a ground-based radar along a 500 km traverse on the polar plateau in central Dronning Maud Land. The results showed that the general accumulation pattern could be described by three major characteristic sections: a pronounced trend of decreasing net accumulation with increasing altitude from 2400 to 2840 m a.s.l.; relatively high erosion rates and occurrence of areas with net erosion at 2840-3140 m a.s.l.; and a slight trend of decreasing net accumulation with increasing altitude from 3140 to 3450 m a.s.l. The spatial variability in snow-layer depths showed a marked change around 3080 m a.s.l., with high variability at lower elevations and low variability at higher elevations. We also determined the spatial representativeness of 11 firn cores drilled along the traverse. In general, the representativeness of the cores was high. However, the core with the lowest representativeness underestimated the mean accumulation rate around the coring site by 22%. This shows that snow-radar data on spatial snow distribution are important for the interpretation of accumulation rates obtained from firn and ice cores.
10
Bleichmar, Daniela, and Vanessa R. Schwartz. "Visual History: The Past in Pictures." Representations 145, no. 1 (2019): 1–31. http://dx.doi.org/10.1525/rep.2019.145.1.1.
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This essay defines the category of “visual history” and introduces its operations across the essays included in this special issue. It proposes that such narratives accelerated time in cultures where it became increasingly common to traverse spatial distances. In this way, visual histories are not simply guides to the times, but guides to time itself.
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Wahid, Arif Rahman, Kristanti Dewi Paramita, and Yandi Andri Yatmo. "Inscriptions: Narrating the Spatial Dynamics of the Immaterial Interior." Interiority 4, no. 1 (January 29, 2021): 43–62. http://dx.doi.org/10.7454/in.v4i1.87.
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This paper explores inscription as a projection of the spatial dynamics of a setting, beyond a historical or cultural symbol in a context, and highlights that inscription—a written or carved message on a surface—is an element that immaterially demonstrates a more in-depth narrative of an interior. This paper focuses on exploring inscriptions embedded in various production settings in Jakarta and Central Java, collecting individual and observational accounts on the production of such inscriptions and their meanings. The study suggests that inscriptions demonstrate various roles, from providing information, mediating different spaces and performing as tools to assist activities. Inscriptions may traverse the trajectories of different spaces and exist in different layers of time, creating an interior connection across space and time. These layers and trajectories project the dynamics of material and bodily processes, assembling the immaterial interior.
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Nguyen, H., P. Dayan, and G. J. Goodhill. "How receptor diffusion influences gradient sensing." Journal of The Royal Society Interface 12, no. 102 (January 2015): 20141097. http://dx.doi.org/10.1098/rsif.2014.1097.
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Chemotaxis, or directed motion in chemical gradients, is critical for various biological processes. Many eukaryotic cells perform spatial sensing, i.e. they detect gradients by comparing spatial differences in binding occupancy of chemosensory receptors across their membrane. In many theoretical models of spatial sensing, it is assumed, for the sake of simplicity, that the receptors concerned do not move. However, in reality, receptors undergo diverse modes of diffusion, and can traverse considerable distances in the time it takes such cells to turn in an external gradient. This sets a physical limit on the accuracy of spatial sensing, which we explore using a model in which receptors diffuse freely over the membrane. We find that the Fisher information carried in binding and unbinding events decreases monotonically with the diffusion constant of the receptors.
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van den Broeke, Michiel R., Jan-Gunnar Winther, Elisabeth Isaksson, Jean Francis Pinglot, Lars Karlöf, Trond Eiken, and Louk Conrads. "Climate variables along a traverse line in Dronning Maud Land, East Antarctica." Journal of Glaciology 45, no. 150 (1999): 295–302. http://dx.doi.org/10.3189/s0022143000001799.
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AbstractTemperature, density and accumulation data were obtained from shallow firn cores, drilled during an overland traverse through a previously unknown part of Dronning Maud Land, East Antarctica. The traverse area is characterised by high mountains that obstruct the ice flow, resulting in a sudden transition from the polar plateau to the coastal region. The spatial variations of potential temperature, near-surface firn density and accumulation suggest that katabatic winds are active in this region. Proxy wind data derived from firn-density profiles confirm that annual mean wind speed is strongly related to the magnitude of the surface slope. The high elevation of the ice sheet south of the mountains makes for a dry, cold climate, in which mass loss owing to sublimation is small and erosion of snow by the wind has a potentially large impact on the surface mass balance. A simple katabatic-wind model is used to explain the variations of accumulation along the traverse line in terms of divergence/convergence of the local transport of drifting snow. The resulting wind- and snowdrift patterns are closely connected to the topography of the ice sheet: ridges are especially sensitive to erosion, while ice streams and other depressions act as collectors of drifting snow.
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van den Broeke, Michiel R., Jan-Gunnar Winther, Elisabeth Isaksson, Jean Francis Pinglot, Lars Karlöf, Trond Eiken, and Louk Conrads. "Climate variables along a traverse line in Dronning Maud Land, East Antarctica." Journal of Glaciology 45, no. 150 (1999): 295–302. http://dx.doi.org/10.1017/s0022143000001799.
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AbstractTemperature, density and accumulation data were obtained from shallow firn cores, drilled during an overland traverse through a previously unknown part of Dronning Maud Land, East Antarctica. The traverse area is characterised by high mountains that obstruct the ice flow, resulting in a sudden transition from the polar plateau to the coastal region. The spatial variations of potential temperature, near-surface firn density and accumulation suggest that katabatic winds are active in this region. Proxy wind data derived from firn-density profiles confirm that annual mean wind speed is strongly related to the magnitude of the surface slope. The high elevation of the ice sheet south of the mountains makes for a dry, cold climate, in which mass loss owing to sublimation is small and erosion of snow by the wind has a potentially large impact on the surface mass balance. A simple katabatic-wind model is used to explain the variations of accumulation along the traverse line in terms of divergence/convergence of the local transport of drifting snow. The resulting wind- and snowdrift patterns are closely connected to the topography of the ice sheet: ridges are especially sensitive to erosion, while ice streams and other depressions act as collectors of drifting snow.
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Luo, Kun, Sixin Liu, Jingxue Guo, Tiantian Wang, Lin Li, Xiangbin Cui, Bo Sun, and Xueyuan Tang. "Radar-Derived Internal Structure and Basal Roughness Characterization along a Traverse from Zhongshan Station to Dome A, East Antarctica." Remote Sensing 12, no. 7 (March 27, 2020): 1079. http://dx.doi.org/10.3390/rs12071079.
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The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice sheet (EAIS) from Zhongshan Station to Dome A. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS were collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). In this study, the Internal Layering Continuity Index (ILCI) and basal roughness were taken as indicators to provide an opportunity to evaluate the past internal environment and dynamics of the ice sheet. Except for the upstream of Lambert Glacier, the fold patterns of internal layers are basically similar to that of the bed topography. The relatively flat basal topography and the decrease of ILCI with increasing depth provide evidence for identifying previous rapid ice flow areas that are unavailable to satellites, especially in the upstream of Lambert Glacier. Continuous internal layers of Dome A, recording the spatial change of past ice accumulation and ice-flow history over 160 ka, almost extend to the bed, with high ILCI and high basal roughness of the corresponding bed topography. There are three kinds of basal roughness patterns along the traverse, that is, “low ξt low η”, “low ξt high η”, and “high ξt high η”, where ξt represents the amplitude of the undulations, and quantifies the vertical variation of the bedrock, and η measures the frequency variation of fluctuations and the horizontal irregularity of the profile. The characteristics of internal layers and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.
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Turcotte, Joseph F., and M. Len Ball. ""All Transportation Is Local"." Transfers 3, no. 1 (March 1, 2013): 119–39. http://dx.doi.org/10.3167/trans.2013.030109.
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In an increasingly mediated situation, mobile, digital, and networked technologies (MDNTs) prompt individuals to orient themselves in new ways to the spaces they traverse. How users and communities experience these technologies in relation to the environments around them subsequently affects mentalities, including perceptions of space and mobility. The mediating presence of digital technology interconnects internal and external factors through diverse social and technological networks. This paper uses interdisciplinary theoretical perspectives to argue that ubiquitous MDNTs alter the ways that individuals orient themselves in relation to the spaces, both on- and offline, that they traverse. By mediating various visual, audible, and informational aspects of daily life while remaining implicated within external networks of related experiences, individuals move through on- and offline spaces in ways that allow the subject to negotiate her local environment(s). Experiences of mobility and space become more fluid as spatial subjectivities and mobility become integrated.
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Brewster, Jeffrey D., and James L. Anderson. "On Absorbance Measurements in Spatially Inhomogeneous Fields." Applied Spectroscopy 43, no. 4 (May 1989): 710–14. http://dx.doi.org/10.1366/0003702894202427.
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The measured absorbance of a spatially inhomogeneous sample may be strongly affected by the relative spatial distribution of the absorbing medium and the optical beam. The measured absorbance is, in general, not the average of local absorbances across the beam, except when the maximum range of local absorbance values across the entire field is small (<0.1 AU). The measured transmittance of an optically inhomogeneous field is equal to the average transmittance only if incident intensity is everywhere uniform. The general problem is outlined and is illustrated by examples of transient spectroelectrochemical experiments monitoring the time course of reactant consumption or product generation as they traverse a thin optical beam parallel to the electrode.
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Karlsson, Nanna B., Sebastian Razik, Maria Hörhold, Anna Winter, Daniel Steinhage, Tobias Binder, and Olaf Eisen. "Surface accumulation in Northern Central Greenland during the last 300 years." Annals of Glaciology 61, no. 81 (April 2020): 214–24. http://dx.doi.org/10.1017/aog.2020.30.
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AbstractThe internal stratigraphy of snow and ice as imaged by ground-penetrating radar may serve as a source of information on past accumulation. This study presents results from two ground-based radar surveys conducted in Greenland in 2007 and 2015, respectively. The first survey was conducted during the traverse from the ice-core station NGRIP (North Greenland Ice Core Project) to the ice-core station NEEM (North Greenland Eemian Ice Drilling). The second survey was carried out during the traverse from NEEM to the ice-core station EGRIP (East Greenland Ice Core Project) and then onwards to Summit Station. The total length of the radar profiles is 1427 km. From the radar data, we retrieve the large-scale spatial variation of the accumulation rates in the interior of the ice sheet. The accumulation rates range from 0.11 to 0.26 m a−1 ice equivalent with the lowest values found in the northeastern sector towards EGRIP. We find no evidence of temporal or spatial changes in accumulation rates when comparing the 150-year average accumulation rates with the 321-year average accumulation rates. Comparisons with regional climate models reveal that the models underestimate accumulation rates by up to 35% in northeastern Greenland. Our results serve as a robust baseline to detect present changes in either surface accumulation rates or patterns.
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Hynd, D., S. C. Hughes, and D. J. Ewins. "The development of a long, dual-platform triaxial walkway for the measurement of forces and temporal-spatial data in the clinical assessment of gait." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 214, no. 2 (February 1, 2000): 193–201. http://dx.doi.org/10.1243/0954411001535354.
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Force-plate measurement of the ground reaction force (GRF) has, for many years, been considered a vital component of the comprehensive assessment of human gait in the clinical context. For example, the data can be used in the adjustment of prostheses and orthoses and in identifying the mechanisms underlying a gait dysfunction. However, commercial force plates are usually only capable of measuring GRF data from one step in a single traverse. That can lead to problems of ‘targeting’ and, with less able subjects, fatigue before the necessary data have been collected. Previous work at the University of Surrey resulted in a prototype dual-platform force walkway capable of measuring the vertical component of the GRF and estimating the position of application of that force for multiple foot contacts in a single traverse. In addition, temporal-spatial information, e.g. speed and step length, could also be determined. This paper describes the development of a longer walkway that can measure the three orthogonal components of the GRF and provide a more accurate estimate of the position of application of that force. Software to allow the rapid reduction of gait data to useful clinical information has also been developed.
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Ayiter, Elif. "Spatial poetics, place, non-place and storyworlds: Intimate spaces for metaverse avatars." Technoetic Arts 17, no. 1 (June 1, 2019): 155–69. http://dx.doi.org/10.1386/tear_00013_1.
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Abstract This article will ask questions that connect the conceptions of Marc Augé's 'place/non-place' and Gaston Bachelard's 'poetic space' to the avatar of real-time, perpetual, online, three-dimensional virtual builder's worlds, also known as the metaverse. Are metaverses 'places' or 'non-places'? Do we actually live in the metaverse or do we just traverse these worlds very much in the sense that Marc Augé defines them as transitional loci that are assigned only to circumscribed and specific positions? The question following from this is whether there are nevertheless three-dimensionally embodied virtual spaces that go beyond being transitional 'non-places' to locations in which an imaginative relationship to architecture in the sense in which Bachelard describes them in his seminal work The Poetics of Space (1958) or that correspond to Marc Augé's definition of 'place' exist.
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Tang, X., K. Luo, and J. Guo. "RADAR-DERIVED INTERNAL LAYERING AND BASAL ROUGHNESS CHARACTERIZATION ALONG A TRAVERSE FROM ZHONGSHAN STATION TO DOME A, EAST ANTARCTICA." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2020 (August 21, 2020): 905–10. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2020-905-2020.
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Abstract. The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the englacial conditions and ice-flow field. This paper presents a new detailed analysis of the spatial distribution characteristics of internal layers and subglacial topography of East Antarctic ice sheet (EAIS) from Zhongshan station to Dome A. Taking the internal layering continuity index (ILCI) and basal roughness as indicators, it provides an opportunity to evaluate the past internal environment and dynamics of ice sheet. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS was collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). Except for the upstream of Lambert Glacier, the patterns of the folds in the internal layers are basically similar to the bed topography. The relatively flat basal topography and the decrease of ILCI with the deepening of the depth provide evidence for identifying previous rapid ice flow areas that the satellite cannot obtain, especially in the upstream of Lambert Glacier. Well continuous internal layers of Dome A almost extend to the bed, with high ILCI and high roughness characteristics. There are three kinds of basal roughness patterns in the whole traverse. The characteristics of the internal layer and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.
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Minghu, Ding, Xiao Cunde, Li Yuansheng, Ren Jiawen, Hou Shugui, Jin Bo, and Sun Bo. "Spatial variability of surface mass balance along a traverse route from Zhongshan station to Dome A, Antarctica." Journal of Glaciology 57, no. 204 (2011): 658–66. http://dx.doi.org/10.3189/002214311797409820.
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AbstractStakes at 2 km intervals were installed in January 1997 and remeasured in February 1998, January 1999, January 2005 and during the 2007/08 austral summer along a 1248 km traverse route from Zhongshan station to Dome A, East Antarctica. Based on topographical parameters, meteorological features and the records of ∼650 stakes and six stake arrays, the route is divided into five zones. We find that the snow accumulation rate decreases with increasing altitude as one progresses inland, except in the zone 800–1128 km from the coast, where the average annual accumulation rate is higher than in the zone 524–800 km from the coast. The Dome A zone (1128–1248 km) has the lowest accumulation rate (35 kg m−2 a−1, 2005–08) due to having the highest elevation and being furthest from the coast. The surface mass balance in the region 202–1128 km from the coast exhibits no temporal change from 1999–2005 to 2005–08, but there is a change in the accumulation distribution. The zone from 202 to 524 km shows a decrease in surface mass balance from 84 kg m−2 a−1 in 1999–2005 to 67 kg m−2 a−1 in 2005–08, while the zone between 800 and 1128 km shows an increase from 67 kg m−2 a−1 in 1999–2005 to 75 kg m−2 a−1 in 2005–08.
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Liu, Xiang, Yuchun Guo, Xiaoying Tan, and Yishuai Chen. "Differentially Private Web Browsing Trajectory over Infinite Streams." Security and Communication Networks 2021 (August 4, 2021): 1–14. http://dx.doi.org/10.1155/2021/9968905.
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Nowadays, a lot of data mining applications, such as web traffic analysis and content popularity prediction, leverage users’ web browsing trajectories to improve their performance. However, the disclosure of web browsing trajectory is the most prominent issue. A novel privacy model, named Differential Privacy, is used to rigorously protect user’s privacy. Some works have applied this privacy model to spatial-temporal streams. However, these works either protect the users’ activities in different places separately or protect their activities in all places jointly. The former one cannot protect trajectories that traverse multiple places; while the latter ignores the differences among places and suffers the degradation of data utility (i.e., data accuracy). In this paper, we propose a w , n -differential privacy to protect any spatial-temporal sequence occurring in w successive timestamps and n -range places. To achieve better data utility, we propose two implementation algorithms, named Spatial-Temporal Budget Distribution (STBD) and Spatial-Temporal RescueDP (STR). Theoretical analysis and experimental results show that these two algorithms can achieve a balance between data utility and trajectory privacy guarantee.
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Le Meur, Emmanuel, Olivier Magand, Laurent Arnaud, Michel Fily, Massimo Frezzotti, Marie Cavitte, Robert Mulvaney, and Stefano Urbini. "Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis." Cryosphere 12, no. 5 (May 31, 2018): 1831–50. http://dx.doi.org/10.5194/tc-12-1831-2018.
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Abstract. Results from ground-penetrating radar (GPR) measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC) and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last 600 years. Accurate dating of these internal reflection horizons (IRHs) is obtained from a depth–age relationship derived from volcanic horizons and bomb testing fallouts on a DC ice core and shows a very good consistency when tested against extra ice cores drilled along the radar profile. Accumulation rates are then inferred by accounting for density profiles down to each IRH. For the latter purpose, a careful error analysis showed that using a single and more accurate density profile along a DC core provided more reliable results than trying to include the potential spatial variability in density from extra (but less accurate) ice cores distributed along the profile. The most striking feature is an accumulation pattern that remains constant through time with persistent gradients such as a marked decrease from 26 mm w.e. yr−1 at DC to 20 mm w.e. yr−1 at the south-west end of the profile over the last 234 years on average (with a similar decrease from 25 to 19 mm w.e. yr−1 over the last 592 years). As for the time dependency, despite an overall consistency with similar measurements carried out along the main East Antarctic divides, interpreting possible trends remains difficult. Indeed, error bars in our measurements are still too large to unambiguously infer an apparent time increase in accumulation rate. For the proposed absolute values, maximum margins of error are in the range 4 mm w.e. yr−1 (last 234 years) to 2 mm w.e. yr−1 (last 592 years), a decrease with depth mainly resulting from the time-averaging when computing accumulation rates.
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Farr, Anna Charisse, Tristan Kleinschmidt, Sandra Johnson, Prasad K. D. V. Yarlagadda, and Kerrie Mengersen. "INVESTIGATING EFFECTIVE WAYFINDING IN AIRPORTS: A BAYESIAN NETWORK APPROACH." TRANSPORT 29, no. 1 (March 25, 2014): 90–99. http://dx.doi.org/10.3846/16484142.2014.898695.
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Effective wayfinding is the successful interplay of human and environmental factors resulting in a person successfully moving from their current position to a desired location in a timely manner. To date this process has not been modelled to reflect this interplay. This paper proposes a complex modelling system approach of wayfinding by using Bayesian Networks to model this process, and applies the model to airports. The model suggests that human factors have a greater impact on effective wayfinding in airports than environmental factors. The greatest influences on human factors are found to be the level of spatial anxiety experienced by travellers and their cognitive and spatial skills. The model also predicted that the navigation pathway that a traveller must traverse has a larger impact on the effectiveness of an airport’s environment in promoting effective wayfinding than the terminal design.
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Cagney, Kathleen A., Erin York Cornwell, Alyssa W. Goldman, and Liang Cai. "Urban Mobility and Activity Space." Annual Review of Sociology 46, no. 1 (July 30, 2020): 623–48. http://dx.doi.org/10.1146/annurev-soc-121919-054848.
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Recent theoretical and methodological advances in urban sociology, including spatially located data, provide new opportunities to consider the joint influence of mobility and place in urban social life. This review defines the concept of activity space, describes its origins in urban sociology, and examines the extent to which activity space approaches advance sociological research in four substantive domains—spatial inequality and segregation, social connectedness and engagement, crime and offending patterns, and health and health-related behavior. It next describes the evolution of methods for location tracking and new approaches that hold promise for maximizing urban mobility and activity space contributions. It then discusses how location data may be augmented to enhance our sociological understanding of the structure, meaning, and implications of the places people visit or traverse in daily life. We close with new directions for activity space research, emphasizing how such work could enable comparative contextual research.
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Marinic, Gregory, Rebekah Radtke, and Gregory Luhan. "Critical Spatial Practices: A Trans-scalar Study of Chinese Hutongs and American Alleyways." Interiority 4, no. 1 (January 29, 2021): 27–42. http://dx.doi.org/10.7454/in.v4i1.79.
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Across time and cultures, the built environment has been fundamentally shaped by forces of occupancy, obsolescence, and change. In an era of increasing political uncertainty and ecological decline, contemporary design practices must respond with critical actions that envision more collaborative and sustainable futures. The concept of critical spatial practice, introduced by architectural historian Jane Rendell, builds on Walter Benjamin and the late 20th century theories of Henri Lefebvre and Michel de Certeau to propose multi-disciplinary design practices that more effectively address contemporary spatial complexities. These theoretical frameworks operate through trans-scalar means to resituate the built environment as a nexus of flows, atmospheres, and narratives (Rendell, 2010). Assuming an analogous relationship to the contemporary city, critical spatial practices traverse space and time to engage issues of migration, informality, globalisation, heterotopia, and ecology. This essay documents an interdisciplinary academic design studio that employed critical spatial practices to study correspondences between Chinese and American cities. Here, the notions of urban and interior are relational. Urbanism and interior spaces are viewed as intertwined aspects in the historical development of Beijing hutongs and Cincinnati alleyways. These hybrid exterior-interior civic spaces create sheltered public worlds and socio-spatial conditions that nurture people and culture.
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Larson-Praplan, S., M. R. George, J. C. Buckhouse, and E. A. Laca. "Spatial and temporal domains of scale of grazing cattle." Animal Production Science 55, no. 3 (2015): 284. http://dx.doi.org/10.1071/an14641.
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Spatio-temporal patterns of cattle grazing were studied in four annual grassland pastures in California, differing mainly in tree canopy cover. Cows were equipped with global positioning collars that recorded position, temperature and head movements at 5-min intervals during 6 days in each of four seasons repeated during 2 years. The time animals took to traverse areas of varying diameter revealed patches of 6–9-m diameter in the pastures with low, and 18–21-m diameter in the pastures with high tree canopy cover. In agreement with the current model, crookedness of cow paths had two distinct domains. Within distances of 0–40 m, paths were relatively straight and similar, but from 40 to 200 m, they became increasingly tortuous. Correlation of sequential turning angles identified patches of movement with diameters between 40 and 100 m, which correspond to the ‘patch’ level of grazing within grazing sites. Seasonal changes in meal patterns were consistent with changes in temperature and forage quality and interacted with the distribution of shade. Thus, spatial distribution of grazing and temporal distribution of meals were inextricably linked. Low forage quality and high temperatures in summer resulted in highly concentrated grazing around trees. Conversely, winter and early spring forages of very high quality and low availability motivated more widely distributed grazing, with low proportion of areas being re-grazed. Resting sites acted as beginning and end of grazing bouts. We conclude that shade distribution can modulate meal start and duration.
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Neylon, C. B., J. Hoyland, W. T. Mason, and R. F. Irvine. "Spatial dynamics of intracellular calcium in agonist-stimulated vascular smooth muscle cells." American Journal of Physiology-Cell Physiology 259, no. 4 (October 1, 1990): C675—C686. http://dx.doi.org/10.1152/ajpcell.1990.259.4.c675.
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Vasoconstrictor agonists stimulate smooth muscle contraction by inducing a rise in intracellular free Ca2+. Digital-imaging microscopy of fura-2 fluorescence from single vascular smooth muscle cells cultured from the human internal mammary artery has allowed us to record the subcellular alterations in Ca2+ that occur immediately after stimulation by receptor agonists. The thrombin-induced rise in cytoplasmic free Ca2+ begins in a discrete region typically located close to the end of the cell. Subsequently, this region of elevated Ca2+ expands until Ca2+ is elevated throughout the cell cytoplasm. The rate of spreading in the region of elevated Ca2+ in a linear direction averaged 10.1 microns/s, enabling it to traverse the length of most cells within approximately 5 s, and involved rises in Ca2+ of between 200 and 500 nM. In some cells, the Ca2+ rise began at both ends and collided midway. Similar dynamic changes in the spatial distribution of Ca2+ were recorded in cells stimulated by acetylcholine. The novel observation that vasoconstrictor agonists induce an elevation of Ca2+ in a localized region which subsequently expands throughout the cytoplasm of single smooth muscle cells may provide new insight into the nature of Ca2+ signaling in vascular tissue.
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Stenbrrg, Malin, Elisabeth Isaksson, Margareta Hansson, WibjöRn Karlen, Paul A. Mayewski, Mark S. Twickler, Sallie I. Whitlow, and Niels Gundestrup. "Spatial variability of snow chemistry in western Dronning Maud Land, Antarctica." Annals of Glaciology 27 (1998): 378–84. http://dx.doi.org/10.3189/1998aog27-1-378-384.
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During the austral summer of 1993-94 a number of 1-2 m deep snow pits were sampled in connection with firn-coring in western Dronning Maud Land, Antarctica. The traverse went from 800 to about 3000 m a.s.l. upon the high-altitude plateau. Profiles of cations (Na+, K+, Mg2+, Ca2+), anions (Cl−, NO3-, SO4 2- , CH3SO3 −) and stable oxygen isotopes (δ18O) from 11 snow pils are presented here. Close to the coast 2 m of snow accumulates in about 2-3 years, whilst at sites on the high-altitude plateau 2 m of snow accumulates in 10—14 years. The spatial variation in ion concentrations shows that the ions can be divided into two groups, one with sea-salt elements and methane sulfonate and the other with nitrate and sulfate. For the sca-salt elements and methane sulfonate the concentrations decrease with increasing altitude and increasing distance from the coast, as well as with decreasing temperature and decreasing accumulation rate. For nitrate and sulfate the concentrations are constant or increase with respect to these parameters. This pattern suggests that the sources for sca-salt elements and methane sulfonate are local, whereas the sources for nitrate and sulfate are a mixture of local and long-range transport.
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Magand, Olivier, Massimo Frezzotti, Michel Pourchet, Barbara Stenni, Laura Genoni, and Michel Fily. "Climate variability along latitudinal and longitudinal transects in East Antarctica." Annals of Glaciology 39 (2004): 351–58. http://dx.doi.org/10.3189/172756404781813961.
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AbstractIn the framework of the International Trans-Antarctic Scientific Expedition (ITASE) programme, France and Italy carried out a traverse along one west–east and two north–south transects in East Antarctica from November 2001 to January 2002. Eighteen shallow snow–firn cores were drilled, and surface snow samples were collected every 5km along the traverse. Firn temperatures were measured in boreholes down to 30 m. The cores were analyzed for β radioactivity to obtain snow accumulation-rate data. The surface snow samples were analyzed for δ18O to correlate isotopic values with borehole temperatures. Multiple regression analysis shows a global near-dry-adiabatic lapse rate and a latitudinal lapse rate of 1.05˚C(˚ lat. S)–1, in the Dome C drainage area. Analysis of firn temperatures reveals a super-adiabatic lapse rate along the ice divide between Talos Dome and the Southern Ocean coast, and in some sectors along the ice divide between the Astrolabe Basin and D59. Snow accumulation rates and firn temperatures show warmer temperatures and higher accumulation values close to the ice divides extending from Talos Dome and Dome C to the Southern Ocean. The spatial pattern of data is linked with a katabatic-wind-source basin and moisture-source region.
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Veenstra, Frank, Pablo González de Prado Salas, Kasper Stoy, Josh Bongard, and Sebastian Risi. "Death and Progress: How Evolvability is Influenced by Intrinsic Mortality." Artificial Life 26, no. 1 (April 2020): 90–111. http://dx.doi.org/10.1162/artl_a_00311.
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Many factors influence the evolvability of populations, and this article illustrates how intrinsic mortality (death induced through internal factors) in an evolving population contributes favorably to evolvability on a fixed deceptive fitness landscape. We test for evolvability using the hierarchical if-and-only-if (h-iff) function as a deceptive fitness landscape together with a steady state genetic algorithm (SSGA) with a variable mutation rate and indiscriminate intrinsic mortality rate. The mutation rate and the intrinsic mortality rate display a relationship for finding the global maximum. This relationship was also found when implementing the same deceptive fitness landscape in a spatial model consisting of an evolving population. We also compared the performance of the optimal mutation and mortality rate with a state-of-the-art evolutionary algorithm called age-fitness Pareto optimization (AFPO) and show how the two approaches traverse the h-iff landscape differently. Our results indicate that the intrinsic mortality rate and mutation rate induce random genetic drift that allows a population to efficiently traverse a deceptive fitness landscape. This article gives an overview of how intrinsic mortality influences the evolvability of a population. It thereby supports the premise that programmed death of individuals could have a beneficial effect on the evolvability of the entire population.
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Jiang, Haoyu. "Spatially Tracking Wave Events in Partitioned Numerical Wave Model Outputs." Journal of Atmospheric and Oceanic Technology 36, no. 10 (October 2019): 1933–44. http://dx.doi.org/10.1175/jtech-d-18-0228.1.
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AbstractNumerical wave models can output partitioned wave parameters at each grid point using a spectral partitioning technique. Because these wave partitions are usually organized according to the magnitude of their wave energy without considering the coherence of wave parameters in space, it can be difficult to observe the spatial distributions of wave field features from these outputs. In this study, an approach for spatially tracking coherent wave events (which means a cluster of partitions originating from the same meteorological event) from partitioned numerical wave model outputs is presented to solve this problem. First, an efficient traverse algorithm applicable for different types of grids, termed breadth-first search, is employed to track wave events using the continuity of wave parameters. Second, to reduce the impact of the garden sprinkler effect on tracking, tracked wave events are merged if their boundary outlines and wave parameters on these boundaries are both in good agreement. Partitioned wave information from the Integrated Ocean Waves for Geophysical and other Applications dataset is used to test the performance of this spatial tracking approach. The test results indicate that this approach is able to capture the primary features of partitioned wave fields, demonstrating its potential for wave data analysis, model verification, and data assimilation.
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Ram, Abhay K., Kyriakos Hizanidis, and Richard J. Temkin. "Current drive by high intensity, pulsed, electron cyclotron wave packets." EPJ Web of Conferences 203 (2019): 01009. http://dx.doi.org/10.1051/epjconf/201920301009.
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The nonlinear interaction of electrons with a high intensity, spatially localized, Gaussian, electro-magnetic wave packet, or beam, in the electron cyclotron range of frequencies is described by the relativistic Lorentz equation. There are two distinct sets of electrons that result from wave-particle interactions. One set of electrons is reflected by the ponderomotive force due to the spatial variation of the wave packet. The second set of electrons are energetic enough to traverse across the wave packet. Both sets of electrons can exchange energy and momentum with the wave packet. The trapping of electrons in plane waves, which are constituents of the Gaussian beam, leads to dynamics that is distinctly different from quasilinear modeling of wave-particle interactions. This paper illustrates the changes that occur in the electron motion as a result of the nonlinear interaction. The dynamical differences between electrons interacting with a wave packet composed of ordinary electromagnetic waves and electrons interacting with a wave packet composed of extraordinary waves are exemplified.
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Li, Chuanjin, Jiawen Ren, Guitao Shi, Hongxi Pang, Yetang Wang, Shugui Hou, Zhongqin Li, et al. "Spatial and temporal variations of fractionation of stable isotopes in East-Antarctic snow." Journal of Glaciology 67, no. 263 (March 1, 2021): 523–32. http://dx.doi.org/10.1017/jog.2021.5.
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AbstractStable isotope ratios (δ18O and δD) in Antarctic snow and ice are basic proxy indices of climate in ice core studies. The relation between the ratios has important indicative significance for moisture sources. In general, the fractionation characteristics of the two isotopes vary with different meteorological and topographical conditions. This paper presents the spatial and temporal distribution of meteoric water line (MWL) slopes along a traverse from the Zhongshan Station (ZSS) to Dome A in East Antarctica. It is found that the slopes decrease with the increasing distance inland from the coast and the lowest slope occurred at Dome A, where the long-range transported moisture dominates and clear sky snowing have an influence. The slopes in different layers of the snowpack showed a decreasing trend with depth and this is attributed to the fractionation during the interstitial sublimation and re-condensation processes of the water vapor. Frost flower development on the interior plateau surface can greatly alter the depth evolution of the MWL slope. The coastal snow pits also go through the post-depositional smoothing effect, but their influences are not so significant as the inland regions.
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Hayek, Lee-Ann C., Martin A. Buzas, Pamela Buzas-Stephens, and Jeffrey S. Buzas. "On Replicates for Comparing Species Densities in Space and Time." Journal of Foraminiferal Research 51, no. 2 (April 1, 2021): 92–97. http://dx.doi.org/10.2113/gsjfr.51.2.92.
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ABSTRACT Because benthic foraminifera exhibit spatial heterogeneity, a number of replicates or multiple biological samples are necessary to estimate population densities. In this study, we empirically examine the efficacy of taking four or fewer replicates to differentiate among mean densities in location and time using p-values as a metric for strength of evidence against the null hypothesis of no difference in taxon density. For spatial analyses, four stations along a traverse with four replicates per station were compared with ANOVA within Mission Bay, Texas, using the four most abundant taxa. The p-values for comparing mean densities among stations increased markedly for all taxa, as the number of samples per station decreased from four to two. Using a test level of 0.05, four replicates per station resulted, on average, in significant differences for three of four taxa, three replicates distinguished two of four taxa, and two replicates detected only one difference. For temporal analyses, a single station was sampled in the Indian River Lagoon, Florida, seasonally over four years. Again, p-values increased markedly as the number of samples per station decreased. Using a test level of 0.05, both four- and three-replicate groups were found to separate mean densities among the four years for three of four taxa, two replicates distinguished one taxon, and use of only one replicate could not detect any difference in mean densities among the four years. Based on these and previous field results, we recommend at least four replicates per station for environmental monitoring. However, when examining mean densities within larger ecological entities such as biofacies, just one sample at each station along a single traverse containing four stations in each bay could delineate Mission, Copano, and Mesquite bays in Texas.
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Shi, Guitao, Hongmei Ma, Zhengyi Hu, Zhenlou Chen, Chunlei An, Su Jiang, Yuansheng Li, et al. "Brief communication: Spatial and temporal variations in surface snow chemistry along a traverse from coastal East Antarctica to the ice sheet summit (Dome A)." Cryosphere 15, no. 2 (March 1, 2021): 1087–95. http://dx.doi.org/10.5194/tc-15-1087-2021.
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Abstract. To better understand snow chemistry in different environments across the Antarctic ice sheet, we investigated snow ions on a traverse from the coast to Dome A. Results show that the non-sea-salt (nss) fractions of K+, Mg2+, and Ca2+ are mainly from terrestrial particle mass and nssCl− is associated with HCl. Spatially, the non-sea-salt fractions of ions to the totals are higher in the interior areas than on the coast, and seasonally, the proportions are higher in summer than in winter. Negative nssSO42- on the coast indicates sea salts from the sea ice, and marine biogenic emissions dominate snow SO42- in interior areas throughout the year.
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Pang, Hongxi, Shugui Hou, Amaelle Landais, Valérie Masson-Delmotte, Frederic Prie, Hans Christian Steen-Larsen, Camille Risi, et al. "Spatial distribution of 17O-excess in surface snow along a traverse from Zhongshan station to Dome A, East Antarctica." Earth and Planetary Science Letters 414 (March 2015): 126–33. http://dx.doi.org/10.1016/j.epsl.2015.01.014.
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MUROTANI, Takuma, Shin-ichi IGARASHI, and Yusuke TERASAWA. "COMPARISON OF CHARACTERISTIC DISTANCES BETWEEN AIR VOIDS EVALUATED BY THE LINEAR TRAVERSE PROCEDURE AND THE SPATIAL POINT PROCESS METHOD." Cement Science and Concrete Technology 72, no. 1 (March 29, 2019): 158–65. http://dx.doi.org/10.14250/cement.72.158.
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Hirata, Masahiko, Chihiro Tomita, and Karin Yamada. "Use of a maze test to assess spatial learning and memory in cattle: Can cattle traverse a complex maze?" Applied Animal Behaviour Science 180 (July 2016): 18–25. http://dx.doi.org/10.1016/j.applanim.2016.04.004.
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Skaff, Nicholas K., Qu Cheng, Rachel E. S. Clemesha, Philip A. Collender, Alexander Gershunov, Jennifer R. Head, Christopher M. Hoover, et al. "Thermal thresholds heighten sensitivity of West Nile virus transmission to changing temperatures in coastal California." Proceedings of the Royal Society B: Biological Sciences 287, no. 1932 (August 5, 2020): 20201065. http://dx.doi.org/10.1098/rspb.2020.1065.
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Temperature is widely known to influence the spatio-temporal dynamics of vector-borne disease transmission, particularly as temperatures vary across critical thermal thresholds. When temperature conditions exhibit such ‘transcritical variation’, abrupt spatial or temporal discontinuities may result, generating sharp geographical or seasonal boundaries in transmission. Here, we develop a spatio-temporal machine learning algorithm to examine the implications of transcritical variation for West Nile virus (WNV) transmission in the Los Angeles metropolitan area (LA). Analysing a large vector and WNV surveillance dataset spanning 2006–2016, we found that mean temperatures in the previous month strongly predicted the probability of WNV presence in pools of Culex quinquefasciatus mosquitoes, forming distinctive inhibitory (10.0–21.0°C) and favourable (22.7–30.2°C) mean temperature ranges that bound a narrow 1.7°C transitional zone (21–22.7°C). Temperatures during the most intense months of WNV transmission (August/September) were more strongly associated with infection probability in Cx. quinquefasciatus pools in coastal LA, where temperature variation more frequently traversed the narrow transitional temperature range compared to warmer inland locations. This contributed to a pronounced expansion in the geographical distribution of human cases near the coast during warmer-than-average periods. Our findings suggest that transcritical variation may influence the sensitivity of transmission to climate warming, and that especially vulnerable locations may occur where present climatic fluctuations traverse critical temperature thresholds.
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Cortezzi, Francisco Martins. "Au-delà de la forêt : la géo-dynamique de l’açaí brésilien dans la ville de Paris." Caderno de Geografia 31, no. 65 (April 22, 2021): 318. http://dx.doi.org/10.5752/p.2318-2962.2021v31n65p318.
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Originaire du palmier Euterpe oleracea, l'açaí est un fruit endémique de la forêt amazonienne, dont la consommation s’est fortement développée au Brésil depuis les années 1990 et est émergente dans d'autres régions du monde. Consommé surtout sous forme de pulpe et érigé en « superfruit » par des acteurs du marketing pour son potentiel antioxydant et nutritionnel, la baie d'açaí traverse un processus dynamique englobant à la fois son circuit spatial de production et de distribution internationale ainsi que sa composition de produits dérivés. Dans le cas de Paris, des entretiens et des travaux de terrain ont été menés afin de mieux comprendre la dynamique commerciale et les principales relations spatiales établies par les produits dérivés du fruit dans la capitale française. Ces analyses nous montrent qu’il existe un « axe de l’açaí » à Paris dû à la forte concentration de points de vente sur la rive-droite de la ville. Les résultats montrent l’importance d’une consommation urbaine relevant de classes sociales aisées de la population. Paris illustre un phénomène de consommation de l’açaí dans les métropoles mondiales.
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ARISTARCO, Guido. "La ville, les possibilités du cinéma et les films." Sociologie et sociétés 8, no. 1 (September 30, 2002): 91–116. http://dx.doi.org/10.7202/001013ar.
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Résumé " Le film est essentiellement différent des autres arts parce que, dans sa vision du monde, espace et temps se confondent : le premier en revêtant un caractère presque temporel, le second, jusqu'à un certain degré, un caractère spatial ". Aristarco après avoir analysé les spécificités du cinéma fait appel à cet art pour chercher " une solution aux problèmes culturels d'existence et de notre situation dans la crise que traverse la ville. L'auteur s'interroge sur les films dits " populaires " qu'il voit comme " le pendant de la spéculation immobilière du cinéma ". Aristarco conclut : " Dans sa forme " épique ", le cinéma peut collaborer (...) au problème de l'urbanisme, à l'explication la plus approfondie possible de la crise qui envahit l'espace de la ville, l'homme et son habitat (...) ".
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Birdsall, Carolyn, Anastasiya Halauniova, and Linda van de Kamp. "Sensing Urban Values: Reassessing Urban Cultures and Histories Amidst Redevelopment Agendas." Space and Culture 24, no. 3 (April 15, 2021): 348–58. http://dx.doi.org/10.1177/12063312211000654.
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Introduction to Sensing Urban Values. This special issue assembles a set of papers that respond to a neglected, undertheorized yet crucial question relating to spatial politics and urban renewal: How do economic and non-economic values depend on and co-constitute each other in different urban contexts? In response, the contributors to this special issue build on recent critical reassessments of value; they explore how the spatial and cultural politics of value unfolds in contemporary urban environments globally. They examine cases that traverse Poland, South Africa, Malaysia, Germany, and The Netherlands. The papers demonstrate a theoretical and empirically engaged concern with themes such as the cultural dimensions of place-making processes in contemporary cities; how identity, memory, heritage, and value-making processes may matter for the production of urban spaces today through sensing; aesthetic reorganizations of places, movements, and interactions with urban matters; and through storytelling. Taking up the theme of urban valuation with a multisensory approach has prompted the contributors to explore the multiple and translocal ways through which urban valuations unfold, are performed, and are experienced. This approach reveals the multiple valuations of spaces—not only economic but also symbolic—that inform the struggles for social and spatial justice in cities across the world as well as their scholarly examinations.
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Hamilton, Gordon S., V. Blue spikes, and Leigh A. Stearns. "Spatial patterns in mass balance of the Siple Coast and Amundsen Sea sectors, West Antarctica." Annals of Glaciology 41 (2005): 105–10. http://dx.doi.org/10.3189/172756405781813195.
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AbstractLocal rates of change in ice-sheet thickness were calculated at 15 sites in West Antarctica using the submergence velocity technique. This method entails a comparison of the vertical velocity of the ice sheet, measured using repeat global positioning system surveys of markers, and local long-term rates of snow accumulation obtained using firn-core stratigraphy. Any significant difference between these two quantities represents a thickness change with time. Measurements were conducted at sites located ~100–200km apart along US ITASE traverse routes, and at several isolated locations. All but one of the sites are distributed in the Siple Coast and the Amundsen Sea basin along contours of constant elevation, along flowlines, across ice divides and close to regions of enhanced flow. Calculated rates of thickness change are different from site to site. Most of the large rates of change in ice thickness (~10cm a–1 or larger) are observed in or close to regions of rapid flow, and are probably related to ice-dynamics effects. Near-steady-state conditions are calculated mostly at sites in the slow-moving ice-sheet interior and near the mainWest Antarctic ice divide. These results are consistent with regional estimates of ice-sheet change derived from remote-sensing measurements at similar locations in West Antarctica
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Bristow, T. F., J. P. Grotzinger, E. B. Rampe, J. Cuadros, S. J. Chipera, G. W. Downs, C. M. Fedo, et al. "Brine-driven destruction of clay minerals in Gale crater, Mars." Science 373, no. 6551 (July 8, 2021): 198–204. http://dx.doi.org/10.1126/science.abg5449.
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Mars’ sedimentary rock record preserves information on geological (and potential astrobiological) processes that occurred on the planet billions of years ago. The Curiosity rover is exploring the lower reaches of Mount Sharp, in Gale crater on Mars. A traverse from Vera Rubin ridge to Glen Torridon has allowed Curiosity to examine a lateral transect of rock strata laid down in a martian lake ~3.5 billion years ago. We report spatial differences in the mineralogy of time-equivalent sedimentary rocks <400 meters apart. These differences indicate localized infiltration of silica-poor brines, generated during deposition of overlying magnesium sulfate–bearing strata. We propose that destabilization of silicate minerals driven by silica-poor brines (rarely observed on Earth) was widespread on ancient Mars, because sulfate deposits are globally distributed.
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Zápražný, Zdenko, Dušan Korytár, Petr Mikulík, and Vladimír Áč. "Processing of projections containing phase contrast in laboratory micro-computerized tomography imaging." Journal of Applied Crystallography 46, no. 4 (June 7, 2013): 933–38. http://dx.doi.org/10.1107/s002188981300558x.
Full textAbstract:
Free-space-propagation-based imaging belongs to several techniques for achieving phase contrast in the hard X-ray range. The basic precondition is to use an X-ray beam with a high degree of coherence. Although the best sources of coherent X-rays are synchrotrons, spatially coherent X-rays emitted from a sufficiently small spot of laboratory microfocus or sub-microfocus sources allow the transfer of some of the modern imaging techniques from synchrotrons to laboratories. Spatially coherent X-rays traverse a sample leading to a phase shift. Beam deflection induced by the local change of refractive index may be expressed as a dark–bright contrast on the edges of the object in an X-ray projection. This phenomenon of edge enhancement leads to an increase in spatial resolution of X-ray projections but may also lead to unpleasant artefacts in computerized tomography unless phase and absorption contributions are separated. The possibilities of processing X-ray images of lightweight objects containing phase contrast using phase-retrieval methods in laboratory conditions are tested and the results obtained are presented. For this purpose, simulated and recorded X-ray projections taken from a laboratory imaging system with a microfocus X-ray source and a high-resolution CCD camera were processed and a qualitative comparison of results was made.
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Becagli, Silvia, Marco Proposito, Silvia Benassai, Onelio Flora, Laura Genoni, Roberto Gragnani, Ombretta Largiuni, et al. "Chemical and isotopic snow variability in East Antarctica along the 2001/02 ITASE traverse." Annals of Glaciology 39 (2004): 473–82. http://dx.doi.org/10.3189/172756404781814636.
Full textAbstract:
AbstractAs part of the International Trans-Antarctic Scientific Expedition (ITASE) project, a traverse was carried out from November 2001 to January 2002 through Terre Adélie, George V Land, Oates Land and northern Victoria Land, for a total length of about 1875 km. The research goal is to determine the latitudinal and longitudinal variability of physical, chemical and isotopic parameters along three transects: one west–east transect (WE), following the 2150m contour line (about 400 km inland of the Adélie, George V and Oates coasts), and two north–south transects (inland Terre Adélie and Oates Coast–Talos Dome–Victoria Land). The intersection between the WE and Oates Coast–Victoria Land transects is in the Talos Dome area. Along the traverse, eight 2 m deep snow pits were dug and sampled with a 2.5 cm depth resolution. For spatial variability, 1 m deep integrated samples were collected every 5 km (363 sampling sites). In the snow-pit stratigraphy, pronounced annual cycles, with summer maxima, were observed for nssSO42–, MSA, NO3– and H2O2. The seasonality of these chemical trace species was used in combination with stable-isotope stratigraphy to derive reliable and temporally representative snow-accumulation rates. The study of chemical, isotopic and accumulation-rate variability allowed the identification of a distribution pattern which is controlled not only by altitude and distance from the sea, but also by the complex circulation of air masses in the study area. In particular, although the Talos Dome area is almost equidistant from the Southern Ocean and the Ross Sea, local atmospheric circulation is such that the area is strongly affected only by the Ross Sea. Moreover, we observed a decrease in concentration of aerosol components in the central portion of the WE transect and in the southern portion of the Talos Dome transect; this decrease was linked to the higher stability of atmospheric pressure due to the channelling of katabatic winds.
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Khodzher, T. V., L. P. Golobokova, Y. A. Shibaev, V. Y. Lipenkov, and J. R. Petit. "Spatial-temporal dynamics of chemical composition of surface snow in East Antarctic along the transect Station Progress-Station Vostok." Cryosphere Discussions 7, no. 3 (May 15, 2013): 2007–28. http://dx.doi.org/10.5194/tcd-7-2007-2013.
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Abstract. This paper presents data on chemical composition of the Antarctic snow sampled during the 53rd Russian Antarctic Expedition (RAE, 2008) along the first tractor traverse (TT) from Station Progress to Station Vostok (East Antarctica). Snow samples were obtained from the cores drilled at 55.3, 253, 337, 369, 403, 441, 480, 519, 560, 618, 819, and 1276 km from Station Progress. Data on horizontal and deep distribution of chemical components in the snow provide evidence of spatial and temporal variations of conditions for the snow cover formation along the transect under study. Sea salt was the main source for chemical composition of snow cover near the ice edge. Concentrations of marine-derived components decreased further inland. A hypothesis was put forward that some ions in the snow cover of the central part of East Antarctica were likely to be of continental origin. Elevated concentrations of sulphate ions of continental origin were recorded in some profiles of the transect at a depth of 130–150 cm which was attributed to buried signals of the Pinatubo volcano eruption (1991).
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XIE, HUAN, RONGXING LI, XIAOHUA TONG, XIAOLEI JU, JUN LIU, YUNZHONG SHEN, LEI CHEN, et al. "A comparative study of changes in the Lambert Glacier/Amery Ice Shelf system, East Antarctica, during 2004–2008 using gravity and surface elevation observations." Journal of Glaciology 62, no. 235 (June 16, 2016): 888–904. http://dx.doi.org/10.1017/jog.2016.76.
Full textAbstract:
ABSTRACTWe present results of a regional comparative study of surface mass changes from 2004 to 2008 based on Gravity Recovery and Climate Experiment (GRACE), The Ice, Cloud and Land Elevation Satellite (ICESat) and CHINARE observations over the Lambert Glacier/Amery Ice Shelf system (LAS). Estimation of the ICESat mass change rates benefitted from the density measurements along the CHINARE traverse and a spatial density adjustment method for reducing the effect of spatial density variations. In the high-elevation inland region, a positive trend was estimated from both ICESat and GRACE data, which is in line with the CHINARE accumulation measurements. In the coastal region, there were areas with high level accumulations in both ICESat and GRACE trend maps. In many high flow-speed glacier areas, negative mass change rates may be caused by dynamic ice flow discharges that have surpassed the snow accumulation. Overall, the mass change rate estimate in the LAS of 2004–2008 from the GRACE, ICESat and CHINARE data is 5.41 ± 4.59 Gt a−1, indicating a balanced to slightly positive mass trend. Along with other published results, this suggests that a longer-term positive mass trend in the LAS may have slowed in recent years.