Journal articles on the topic 'Time-space pathways'
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Saltiel, Alan R., and Jeffrey E. Pessin. "Insulin signaling pathways in time and space." Trends in Cell Biology 12, no. 2 (February 2002): 65–71. http://dx.doi.org/10.1016/s0962-8924(01)02207-3.
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Smith, C. A. B., and V. V. Nalimov. "Space, Time and Life: The Probabilistic Pathways of Evolution." Biometrics 43, no. 1 (March 1987): 255. http://dx.doi.org/10.2307/2531973.
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Lukas, Jiri, Claudia Lukas, and Jiri Bartek. "Mammalian cell cycle checkpoints: signalling pathways and their organization in space and time." DNA Repair 3, no. 8-9 (August 2004): 997–1007. http://dx.doi.org/10.1016/j.dnarep.2004.03.006.
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Wang, Siqin, Yan Liu, Thomas Sigler, and Jonathan Corcoran. "3D space–time visualization of individual settlement pathways of Mainland China-born migrants in Queensland, Australia." Environment and Planning A: Economy and Space 51, no. 2 (October 4, 2018): 275–78. http://dx.doi.org/10.1177/0308518x18805752.
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The number of migrants from Mainland China (MC) to Australia have been sharply increasing since 2000 and MC became the largest non-Commonwealth source country in 2011. The integration process of migrants to the host society involves the exposure and movement of migrants to the majority, which is reflected by the settlement pathways of migrants moving from ethnic to non-ethnic communities over time. Most of the existing research regarding migrants’ pathways is constrained by the limitations of cross-sectional data, which are usually available at the community or above levels. Little is known about the individual-level settlement pathways of migrants due to lack of data availability. In order to address this deficit, a 3D visualization is used to express the individual pathways of MC-born migrants based on primary survey data. This enables a more detailed, spatio-temporal picture of how long migrants live at each address and how they move across neighbourhoods.
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Mills, Denise A., and Shelagh Ferguson-Miller. "Proton uptake and release in cytochrome c oxidase: separate pathways in time and space?" Biochimica et Biophysica Acta (BBA) - Bioenergetics 1365, no. 1-2 (June 1998): 46–52. http://dx.doi.org/10.1016/s0005-2728(98)00040-1.
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Pérez, María Lucía, and José Luis Peña. "Comparison of Midbrain and Thalamic Space-Specific Neurons in Barn Owls." Journal of Neurophysiology 95, no. 2 (February 2006): 783–90. http://dx.doi.org/10.1152/jn.00833.2005.
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Spatial receptive fields of neurons in the auditory pathway of the barn owl result from the sensitivity to combinations of interaural time (ITD) and level differences across stimulus frequency. Both the forebrain and tectum of the owl contain such neurons. The neural pathways, which lead to the forebrain and tectal representations of auditory space, separate before the midbrain map of auditory space is synthesized. The first nuclei that belong exclusively to either the forebrain or the tectal pathways are the nucleus ovoidalis (Ov) and the external nucleus of the inferior colliculus (ICx), respectively. Both receive projections from the lateral shell subdivision of the inferior colliculus but are not interconnected. Previous studies indicate that the owl's tectal representation of auditory space is different from those found in the owl's forebrain and the mammalian brain. We addressed the question of whether the computation of spatial cues in both pathways is the same by comparing the ITD tuning of Ov and ICx neurons. Unlike in ICx, the relationship between frequency and ITD tuning had not been studied in single Ov units. In contrast to the conspicuous frequency independent ITD tuning of space-specific neurons of ICx, ITD selectivity varied with frequency in Ov. We also observed that the spatially tuned neurons of Ov respond to lower frequencies and are more broadly tuned to ITD than in ICx. Thus there are differences in the integration of frequency and ITD in the two sound-localization pathways. Thalamic neurons integrate spatial information not only within a broader frequency band but also across ITD channels.
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King, Wayne E., Michael Armstrong, Victor Malka, Bryan W. Reed, and Antoine Rousse. "Ultrafast Imaging of Materials: Exploring the Gap of Space and Time." MRS Bulletin 31, no. 8 (August 2006): 614–19. http://dx.doi.org/10.1557/mrs2006.158.
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AbstractThe materials science community is poised to take advantage of new technologies that add unprecedented time resolution to already existing spatial-resolution capabilities. In the same way that chemists and biologists are using ultrafast optical, photon, and particle techniques to reveal transition pathways, materials scientists can expect to use variations of these methods to probe the most fundamental aspects of complex transient phenomena in materials. The combination of high-spatial-resolution imaging with high time resolution is critical because it enables the observation of specific phenomena that are important to developing fundamental understanding. Such a capability is also important because it enables experiments that are on the same time and length scales as recent high-performance computer simulations. This article describes several new techniques that have great potential for broader application in materials science, including electron, x-ray, and γ-ray imaging.
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Pidoux, Guillaume, and Kjetil Taskén. "Specificity and spatial dynamics of protein kinase A signaling organized by A-kinase-anchoring proteins." Journal of Molecular Endocrinology 44, no. 5 (February 11, 2010): 271–84. http://dx.doi.org/10.1677/jme-10-0010.
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Protein phosphorylation is the most common post-translational modification observed in cell signaling and is controlled by the balance between protein kinase and phosphatase activities. The cAMP–protein kinase A (PKA) pathway is one of the most studied and well-known signal pathways. To maintain a high level of specificity, the cAMP–PKA pathway is tightly regulated in space and time. A-kinase-anchoring proteins (AKAPs) target PKA to specific substrates and distinct subcellular compartments providing spatial and temporal specificity in the mediation of biological effects controlled by the cAMP–PKA pathway. AKAPs also serve as scaffolding proteins that assemble PKA together with signal terminators such as phosphoprotein phosphatases and cAMP-specific phosphodiesterases as well as components of other signaling pathways into multiprotein-signaling complexes.
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Saul, Alan B., Peter L. Carras, and Allen L. Humphrey. "Temporal Properties of Inputs to Direction-Selective Neurons in Monkey V1." Journal of Neurophysiology 94, no. 1 (July 2005): 282–94. http://dx.doi.org/10.1152/jn.00868.2004.
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Motion in the visual scene is processed by direction-selective neurons in primary visual cortex. These cells receive inputs that differ in space and time. What are these inputs? A previous single-unit recording study in anesthetized monkey V1 proposed that the two major streams arising in the primate retina, the M and P pathways, differed in space and time as required to create direction selectivity. We confirmed that cortical cells driven by P inputs tend to have sustained responses. The M pathway, however, as assessed by recordings in layer 4Cα and from cells with high contrast sensitivity, is not purely transient. The diversity of timing in the M stream suggests that combinations of M inputs, as well as of M and P inputs, create direction selectivity.
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Denil, Misha, Loris Bazzani, Hugo Larochelle, and Nando de Freitas. "Learning Where to Attend with Deep Architectures for Image Tracking." Neural Computation 24, no. 8 (August 2012): 2151–84. http://dx.doi.org/10.1162/neco_a_00312.
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We discuss an attentional model for simultaneous object tracking and recognition that is driven by gaze data. Motivated by theories of perception, the model consists of two interacting pathways, identity and control, intended to mirror the what and where pathways in neuroscience models. The identity pathway models object appearance and performs classification using deep (factored)-restricted Boltzmann machines. At each point in time, the observations consist of foveated images, with decaying resolution toward the periphery of the gaze. The control pathway models the location, orientation, scale, and speed of the attended object. The posterior distribution of these states is estimated with particle filtering. Deeper in the control pathway, we encounter an attentional mechanism that learns to select gazes so as to minimize tracking uncertainty. Unlike in our previous work, we introduce gaze selection strategies that operate in the presence of partial information and on a continuous action space. We show that a straightforward extension of the existing approach to the partial information setting results in poor performance, and we propose an alternative method based on modeling the reward surface as a gaussian process. This approach gives good performance in the presence of partial information and allows us to expand the action space from a small, discrete set of fixation points to a continuous domain.
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Guegueniat, P., J. C. Salomon, M. Wartel, L. Cabioch, and A. Fraizier. "Transfer Pathways and Transit Time of Dissolved Matter in the Eastern English Channel Indicated by Space-Time Radiotracers Measurement and Hydrodynamic Modelling." Estuarine, Coastal and Shelf Science 36, no. 5 (May 1993): 477–94. http://dx.doi.org/10.1006/ecss.1993.1029.
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Takahashi, T. T. "The neural coding of auditory space." Journal of Experimental Biology 146, no. 1 (September 1, 1989): 307–22. http://dx.doi.org/10.1242/jeb.146.1.307.
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The barn owl's auditory system computes interaural differences in time and amplitude and derives from them the horizontal and vertical coordinates of the sound source, respectively. Within the external nucleus of its inferior colliculus are auditory neurones, called ‘space-specific neurones’, that have spatial receptive fields. To activate a space-specific neurone, a sound must originate from a circumscribed region of space, or, if the sounds are delivered to each ear separately, using earphones, the stimuli must have the combination of interaural time and amplitude difference that simulates a sound broadcast from their receptive field. The sound-localization cues are processed in parallel, non-overlapping pathways extending from the cochlear nuclei to the subdivision of the inferior colliculus that innervates the space-specific neurones. Processing in the time pathway involves the coding of monaural phase angle, the derivation of sensitivity for interaural phase difference, and the calculation of interaural time difference (ITD) from interaural phase difference. The last process involves groups of neurones in the inferior colliculus whose collective firing signals a unique ITD, even though the activity of each constituent neurone signals multiple ITDs. The projections of these ensembles to the space-specific neurone endow the latter with a selectivity for ITD. Processing in the amplitude channel, about which less is known, initially involves an inhibitory process that sharpens the directional sensitivity of neurones in a lateral lemniscal nucleus. The inhibition is mediated by a commissural projection from the same lemniscal nucleus of the opposite side. At higher levels of the auditory system, neurones that are tuned to a limited range of interaural amplitude differences are found. It is proposed that at these higher stages, interaural amplitude difference, like ITD, is coded amidst an ensemble of neurones.
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Fu, B. M., F. E. Curry, and S. Weinbaum. "A diffusion wake model for tracer ultrastructure-permeability studies in microvessels." American Journal of Physiology-Heart and Circulatory Physiology 269, no. 6 (December 1, 1995): H2124—H2140. http://dx.doi.org/10.1152/ajpheart.1995.269.6.h2124.
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We developed a time-dependent diffusion model for analyzing the concentration profiles of low-molecular-weight tracers in the interendothelial clefts of the capillary wall that takes into account the three-dimensional time-dependent filling of the surrounding tissue space. The model provides a connecting link between two methods to investigate transvascular exchange: electron-microscopic experiments to study the time-dependent wake formed by low-molecular-weight tracers (such as lanthanum nitrate) on the tissue side of the junction strand discontinuities in the interendothelial cleft of frog mesentery capillaries (R. H. Adamson and C. C. Michel. J. Physiol. Lond. 466: 303-327, 1993) and confocal-microscopic experiments to measure the spread of low-molecular-weight fluorescent tracers in the tissue space surrounding these microvessels (R. H. Adamson, J. F. Lenz, and F. E. Curry, Microcirculation 1: 251-265, 1994). We show that the interpretation of the presence of tracer as an all-or-none indication of a pathway across the junctional strand is likely to be incorrect for small solutes. Large-pore pathways, in which the local tracer flux densities are high, reach a threshold concentration for detection and are likely to be detected after relatively short perfusion times, whereas distributed small-pore pathways may not be detected until the tissue concentrations surrounding the entire vessel approach threshold concentrations. The analysis using this approach supports the hypothesis advanced by Fu et al. (J. Biomech. Eng. 116: 502-513, 1994) that the principal pathways for water and solutes of < 1.0 nm diameter across the interendothelial cleft may be different and suggests new experiments to test this hypothesis.
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ZHAO, Shuang, and Chenshu WANG. "Deep sequencing and transcriptome analyses to identify genes involved in iridoid biosynthesis in the medicinal plant Valeriana jatamansi Jones." Notulae Botanicae Horti Agrobotanici Cluj-Napoca 48, no. 1 (March 31, 2020): 189–99. http://dx.doi.org/10.15835/nbha48111759.
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Valeriana jatamansi Jones is utilized for medicinal purposes in China, and is also an important substitute for European Valeriana officinalis. The major active principles are generally called valepotriates, which belong to iridoids compounds. To better understand the iridoid biosynthesis pathway in V. jatamansi, we generated transcriptome sequences from the leaf and root tissues, and performed de novo sequence assembly, a total of 183,524,060 transcripts and 61,876 unigenes for V. jatamansi were obtained from 13.28 Gb clean reads. 56,641 unigenes were annotated by public databases, while 5,235 unigenes remained unannotated. Different unigenes in V. jatamansi were identified by MISA analysis, and 5,195 unigenes containing Simple Sequence Repeat (SSR) were identified. When examining the annotation of transcriptome contigs against the KEGG database, we identified 24 unigenes that could be classified into 24 enzyme categories associated with three metabolic pathways leading to iridoid biosynthesis, 6 genes of MVA pathways, 9 genes of MEP pathways and 9 genes of iridoids pathways. We selected 9 genes encoding key enzymes in the iridoid pathway of V. jatamansi to examine their organ specificity of expression using quantitative real-time PCR (qPCR). In conclusion, we generated a comprehensive transcriptome assembly representing the gene space in V. jatamansi, and the genomic dataset and analyses presented here lay the foundation for further research on this important medicinal plant.
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Múnera-Roldán, Claudia, Dirk Roux, Matthew Colloff, and Lorrae van Kerkhoff. "Beyond Calendars and Maps: Rethinking Time and Space for Effective Knowledge Governance in Protected Areas." Land 9, no. 9 (August 25, 2020): 293. http://dx.doi.org/10.3390/land9090293.
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Protected area managers rely on relevant, credible, and legitimate knowledge. However, an increase in the rate, extent, severity, and magnitude of the impacts of drivers of change (e.g., climate change, altered land use, and demand for natural resources) is affecting the response capacity of managers and their agencies. We address temporal aspects of knowledge governance by exploring time-related characteristics of information and decision-making processes in protected areas. These areas represent artefacts where the past (e.g., geological periods and evolutionary processes), the present (e.g., biodiversity richness), and the future (e.g., protection of ecosystem services for future generations) are intimately connected and integrated. However, temporal horizons linked with spatial scales are often neglected or misinterpreted in environmental management plans and monitoring programs. In this paper, we present a framework to address multi-dimensional understandings of knowledge-based processes for managing protected areas to guide researchers, managers, and practitioners to consider temporal horizons, spatial scales, different knowledge systems, and future decisions. We propose that dealing with uncertain futures starts with understanding the knowledge governance context that shapes decision-making processes, explicitly embracing temporal dimensions of information in decision-making at different scales. We present examples from South Africa and Colombia to illustrate the concepts. This framework can help to enable a reflexive practice, identify pathways or transitions to enable actions and connect knowledge for effective conservation of protected areas.
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Roth, Silke, Clare Saunders, and Cristiana Olcese. "Occupy as a Free Space - Mobilization Processes and Outcomes." Sociological Research Online 19, no. 1 (February 2014): 95–100. http://dx.doi.org/10.5153/sro.3201.
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Although Occupy has received extensive media and scholarly attention, there has not yet been systematic research on its activists’ recruitment pathways and modes of participation. In this article, we focus on the mobilization success ( Staggenborg 1995 ) of Occupy and adopt the concepts of ‘free space’ and ‘modes of association’ ( Polletta 1999 ) to understand how individuals came to participate in Occupy. We consider biographical and structural availability and make distinctions between those more or less involved. By drawing on qualitative and quantitative data gathered in November and December 2011 in London we find that Occupy activists take a range of pathways into differential forms of involvement (more or less visible or time-consuming, offline and on-line). Some participants had previously been involved in social movement and ‘indigenous’ organisations, like the church. Yet at the same time Occupy attracted novices lacking prior engagement in indigenous or social movement organisations. But what Occupy activists shared was an interest in creating inclusive prefigurative structures where the ‘path was the destination’. In contrast to the mass media's scepticism of the success of Occupy, our focus on mobilization processes and outcomes shows Occupy to be successful in this regard.
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Goodman, Paul J., Wilco Hazeleger, Pedro de Vries, and Mark Cane. "Pathways into the Pacific Equatorial Undercurrent: A Trajectory Analysis*." Journal of Physical Oceanography 35, no. 11 (November 1, 2005): 2134–51. http://dx.doi.org/10.1175/jpo2825.1.
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Abstract A time-dependent trajectory algorithm is used to determine the sources of the Pacific Ocean Equatorial Undercurrent (EUC) in a global climate model with ¼° (eddy permitting) resolution and forced with realistic winds. The primary sources and pathways are identified, and the transformation of properties in temperature/salinity space is explored. An estimate for the quantity of recirculation, a notoriously difficult property to estimate from observational data, is given. Over two-thirds of the water in the Pacific EUC at 140°W originates south of the equator; 70% of the EUC is ventilated outside of the Tropics (poleward of 13°S or 10°N): three-quarters of these extratropical trajectories travel through the western boundary currents between their subduction and incorporation into the EUC, and one-fifth of the extratropical trajectories enter and leave the tropical band at least once before entering the EUC.
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Plak, Katarzyna, Ineke Keizer-Gunnink, Peter J. M. van Haastert, and Arjan Kortholt. "Rap1-dependent pathways coordinate cytokinesis in Dictyostelium." Molecular Biology of the Cell 25, no. 25 (December 15, 2014): 4195–204. http://dx.doi.org/10.1091/mbc.e14-08-1285.
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Cytokinesis is the final step of mitosis when a mother cell is separated into two daughter cells. Major cytoskeletal changes are essential for cytokinesis; it is, however, not well understood how the microtubules and actomyosin cytoskeleton are exactly regulated in time and space. In this paper, we show that during the early stages of cytokinesis, in rounded-up Dictyostelium discoideum cells, the small G-protein Rap1 is activated uniformly at the cell cortex. When cells begin to elongate, active Rap1 becomes restricted from the furrow region, where the myosin contractile ring is subsequently formed. In the final stages of cytokinesis, active Rap1 is only present at the cell poles. Mutant cells with decreased Rap1 activation at the poles showed strongly decreased growth rates. Hyperactivation of Rap1 results in severe growth delays and defective spindle formation in adherent cells and cell death in suspension. Furthermore, Rap mutants show aberrant regulation of the actomyosin cytoskeleton, resulting in extended furrow ingression times and asymmetrical cell division. We propose that Rap1 drives cytokinesis progression by coordinating the three major cytoskeletal components: microtubules, actin, and myosin II. Importantly, mutated forms of Rap also affect cytokinesis in other organisms, suggesting a conserved role for Rap in cell division.
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Tanggaard, Lene, and Ronald A. Beghetto. "Ideational Pathways: Toward a New Approach for Studying the Life of Ideas." Creativity. Theories – Research - Applications 2, no. 2 (November 1, 2015): 129–44. http://dx.doi.org/10.1515/ctra-2015-0017.
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Abstract What is the life of an idea? How do some ideas result in creative outcomes? People interested in creativity often want to know the answers to these questions. Although there are numerous methods and measures for assessing creative persons and products, there is little by way of methods for documenting and analysing the trajectories of ideas. The purpose of this paper is to address this need by introducing a new approach for tracing and analysing ideational pathways. Ideational pathways refer to the trajectory of ideas in temporal and spatial dimensions. That is, how ideas travel through time and space and whether those ideas end up resulting in creative outcomes. We open the paper by providing a theoretical and conceptual background for ideational pathways. We then introduce an emerging approach for tracing these pathways and apply it to two examples. We close by discussing implications and directions for future research.
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Byrne, C. M., E. R. Stanway, and J. J. Eldridge. "Binary evolution pathways of blue large-amplitude pulsators." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 24, 2021): 621–31. http://dx.doi.org/10.1093/mnras/stab2115.
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ABSTRACT Blue large-amplitude pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or through Roche lobe overflow, with a main-sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12 000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.
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Rodríguez, José-Luis, Ramiro Velázquez, Carolina Del-Valle-Soto, Sebastián Gutiérrez, Jorge Varona, and Josué Enríquez-Zarate. "Active and Passive Haptic Perception of Shape: Passive Haptics Can Support Navigation." Electronics 8, no. 3 (March 23, 2019): 355. http://dx.doi.org/10.3390/electronics8030355.
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Real-time haptic interactions occur under two exploration modes: active and passive. In this paper, we present a series of experiments that evaluate the main perceptual characteristics of both exploration modes. In particular, we focus on haptic shape recognition as it represents a fundamental task in many applications using haptic environments. The results of four experiments conducted with a group of 10 voluntary subjects show that the differences in motor activity between active and passive haptics ease the perception of surfaces for the first case and the perception of pathways for the latter. In addition, the guidance nature of passive haptics makes the pathway direction easy to recognize. This work shows that this last observation could find application in more challenging tasks such as navigation in space.
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Kwate, Naa Oyo A. "THE RACE AGAINST TIME." Du Bois Review: Social Science Research on Race 14, no. 2 (2017): 497–514. http://dx.doi.org/10.1017/s1742058x17000145.
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AbstractIn this paper I argue that time is a social determinant of health, and one that perpetuates racial health inequalities. Specifically, Black people in the United States experience time losses across numerous domains throughout the life course, putting them at risk of disproportionate morbidity and mortality. Fundamental cause theory holds that social conditions structure health through pathways to resources including money, knowledge, power, prestige, freedom, and social networks. Racialized time indirectly harms health by disrupting or denying access to these flexible resources and by undoing utility among those that are obtained. Racialized time harms health directly when it produces stress and exacerbates conditions of racial subordination. I examine racialized time in three categories: 1) Black people spending too much time to meet basic needs; 2) Black people having less time spent on them than is required; and 3) lost years of (good quality of) life. Linkages between time and health disadvantage exist in material resources, interactions with the state, intimate lives, public space, and cognitive processes.
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Cook, Gericke, Catherine Jarnevich, Melissa Warden, Marla Downing, John Withrow, and Ian Leinwand. "Iterative Models for Early Detection of Invasive Species across Spread Pathways." Forests 10, no. 2 (January 29, 2019): 108. http://dx.doi.org/10.3390/f10020108.
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Species distribution models can be used to direct early detection of invasive species, if they include proxies for invasion pathways. Due to the dynamic nature of invasion, these models violate assumptions of stationarity across space and time. To compensate for issues of stationarity, we iteratively update regionalized species distribution models annually for European gypsy moth (Lymantria dispar dispar) to target early detection surveys for the USDA APHIS gypsy moth program. We defined regions based on the distances from the invasion spread front where shifts in variable importance occurred and included models for the non-quarantine portion of the state of Maine, a short-range region, an intermediate region, and a long-range region. We considered variables that represented potential gypsy moth movement pathways within each region, including transportation networks, recreational activities, urban characteristics, and household movement data originating from gypsy moth infested areas (U.S. Postal Service address forwarding data). We updated the models annually, linked the models to an early detection survey design, and validated the models for the following year using predicted risk at new positive detection locations. Human-assisted pathways data, such as address forwarding, became increasingly important predictors of gypsy moth detection in the intermediate-range geographic model as more predictor data accumulated over time (relative importance = 5.9%, 17.36%, and 35.76% for 2015, 2016, and 2018, respectively). Receiver operating curves showed increasing performance for iterative annual models (area under the curve (AUC) = 0.63, 0.76, and 0.84 for 2014, 2015, and 2016 models, respectively), and boxplots of predicted risk each year showed increasing accuracy and precision of following year positive detection locations. The inclusion of human-assisted pathway predictors combined with the strategy of iterative modeling brings significant advantages to targeting early detection of invasive species. We present the first published example of iterative species distribution modeling for invasive species in an operational context.
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Kranaster, Petra, Christiaan Karreman, Jeremias E. G. A. Dold, Alice Krebs, Melina Funke, Anna-Katharina Holzer, Stefanie Klima, et al. "Time and space-resolved quantification of plasma membrane sialylation for measurements of cell function and neurotoxicity." Archives of Toxicology 94, no. 2 (December 11, 2019): 449–67. http://dx.doi.org/10.1007/s00204-019-02642-z.
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AbstractWhile there are many methods to quantify the synthesis, localization, and pool sizes of proteins and DNA during physiological responses and toxicological stress, only few approaches allow following the fate of carbohydrates. One of them is metabolic glycoengineering (MGE), which makes use of chemically modified sugars (CMS) that enter the cellular biosynthesis pathways leading to glycoproteins and glycolipids. The CMS can subsequently be coupled (via bio-orthogonal chemical reactions) to tags that are quantifiable by microscopic imaging. We asked here, whether MGE can be used in a quantitative and time-resolved way to study neuronal glycoprotein synthesis and its impairment. We focused on the detection of sialic acid (Sia), by feeding human neurons the biosynthetic precursor N-acetyl-mannosamine, modified by an azide tag. Using this system, we identified non-toxic conditions that allowed live cell labeling with high spatial and temporal resolution, as well as the quantification of cell surface Sia. Using combinations of immunostaining, chromatography, and western blotting, we quantified the percentage of cellular label incorporation and effects on glycoproteins such as polysialylated neural cell adhesion molecule. A specific imaging algorithm was used to quantify Sia incorporation into neuronal projections, as potential measure of complex cell function in toxicological studies. When various toxicants were studied, we identified a subgroup (mitochondrial respiration inhibitors) that affected neurite glycan levels several hours before any other viability parameter was affected. The MGE-based neurotoxicity assay, thus allowed the identification of subtle impairments of neurochemical function with very high sensitivity.
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Yancey, Nan Russell. "Technology and Teaching-Learning: Opportunities and Restrictions." Nursing Science Quarterly 31, no. 4 (September 17, 2018): 333–34. http://dx.doi.org/10.1177/0894318418792880.
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The author introduces a discussion by a nurse faculty of a teaching-learning strategy based on King’s theory of goal attainment. Considering technology merely as a tool to be used in extending the traditional time-space boundaries of the classroom, the author challenges faculty to seek innovative ways of honoring the unique person of the student and illuminating pathways of discovery in the teaching-learning journey.
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Pronovost, Gilles. "On Constructing Typologies of Young People’s Cosmopolitanism." Youth and Globalization 2, no. 1 (July 7, 2020): 1–17. http://dx.doi.org/10.1163/25895745-bja10001.
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This paper addresses a number of fundamental epistemological obstacles faced by researchers interested in studying young people’s cosmopolitanism, more specifically, the normative temptation and “first experience” obstacles. It goes on to tackle the inherent temporality of cosmopolitan behaviour, seeing how it is a fundamentally dynamic phenomenon that entails itineraries, trajectories and pathways through young people’s life cycles. As such, the text proposes six typical trajectories. In terms of temporalities: “the confirmed cosmopolitan,” “late starters,” “cosmopolitan and uncosmopolitan at the same time,” and “disengagement from cosmopolitanism”; in terms of moving through social space: “focusing on social space close to home,” “the ordinary tourist.”
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Beheshti, Afshin, J. McDonald, Jack Miller, Peter Grabham, and Sylvain Costes. "GeneLab Database Analyses Suggest Long-Term Impact of Space Radiation on the Cardiovascular System by the Activation of FYN Through Reactive Oxygen Species." International Journal of Molecular Sciences 20, no. 3 (February 3, 2019): 661. http://dx.doi.org/10.3390/ijms20030661.
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Space radiation has recently been considered a risk factor for astronauts’ cardiac health. As an example, for the case of how to query and identify datasets within NASA’s GeneLab database and demonstrate the database utility, we used an unbiased systems biology method for identifying key genes/drivers for the contribution of space radiation on the cardiovascular system. This knowledge can contribute to designing appropriate experiments targeting these specific pathways. Microarray data from cardiomyocytes of male C57BL/6 mice followed-up for 28 days after exposure to 900 mGy of 1 GeV proton or 150 mGy of 1 GeV/n 56Fe were compared to human endothelial cells (HUVECs) cultured for 7 days on the International Space Station (ISS). We observed common molecular pathways between simulated space radiation and HUVECs flown on the ISS. The analysis suggests FYN is the central driver/hub for the cardiovascular response to space radiation: the known oxidative stress induced immediately following radiation would only be transient and would upregulate FYN, which in turn would reduce reactive oxygen species (ROS) levels, protecting the cardiovascular system. The transcriptomic signature of exposure to protons was also much closer to the spaceflight signature than 56Fe’s signature. To our knowledge, this is the first time GeneLab datasets were utilized to provide potential biological indications that the majority of ions on the ISS are protons, clearly illustrating the power of omics analysis. More generally, this work also demonstrates how to combine animal radiation studies done on the ground and spaceflight studies to evaluate human risk in space.
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Yuan, Yuan, Hongbo Li, Xiaolin Zhang, Xiaoliang Hu, and Yahua Wang. "Emerging Location-Based Service Data on Perceiving and Measuring Multifunctionality of Rural Space: A Study of Suzhou, China." Sustainability 11, no. 20 (October 22, 2019): 5862. http://dx.doi.org/10.3390/su11205862.
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Understanding how human mobilities reconstruct contemporary rural space is of great significance to multifunctional rural transition. However, conventional approaches adopted by social surveys have a technological restriction on collecting data of individual behavior, such as limited samples, subjective self-reported data, and time-consuming investigation. This study proposes a data-driven methodology to explore multifunctionality of rural space by employing the real-time Tencent user quantity (RTUQ) data to analyze the quantity and distribution of observables in rural space. Based on over 250,000 records of hourly RTUQ data during a one-week research period, we perceive spatiotemporal variation of human mobilities in three differentiated villages in Suzhou, China, as well as measure function of residence, employment and consumption on holidays, weekdays and weekends using original equations of function index. Results show that the RTUQ data is valid and reliable for perceiving dynamic patterns of human mobilities at village level, as well as offering new implication for transitional pathways of decision-making. The proposed method is proved to be suitable for distinguishing and comparing multifunctionality of rural space in various times and places, future research on exploring contemporary rural space towards multifunctionality with more geospatial big data is put forward.
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RUSHTON, S. P., M. D. F. SHIRLEY, E. A. SHERIDAN, C. V. LANYON, and A. G. O'DONNELL. "The transmission of nosocomial pathogens in an intensive care unit: a space–time clustering and structural equation modelling approach." Epidemiology and Infection 138, no. 6 (October 9, 2009): 915–26. http://dx.doi.org/10.1017/s095026880999094x.
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SUMMARYWe investigated the incidence of cases of nosocomial pathogens and risk factors in an intensive treatment unit ward to determine if the number of cases is dependent on location of patients and the colonization/infection history of the ward. A clustering approach method was developed to investigate the patterns of spread of cases through time for five microorganisms [methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter spp., Klebsiella spp., Candida spp., and Pseudomonas aeruginosa] using hospital microbiological monitoring data and ward records of patient-bed use. Cases of colonization/infection by MRSA, Candida and Pseudomonas were clustered in beds and through time while cases of Klebsiella and Acinetobacter were not. We used structural equation modelling to analyse interacting risk factors and the potential pathways of transmission in the ward. Prior nurse contact with colonized/infected patients, mediated by the number of patient-bed movements, were important predictors for all cases, except for those of Pseudomonas. General health and invasive surgery were significant predictors of cases of Candida and Klebsiella. We suggest that isolation and bed movement as a strategy to manage MRSA infections is likely to impact upon the incidence of cases of other opportunist pathogens.
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Rudgers, Jennifer A., Michelle E. Afkhami, Lukas Bell-Dereske, Y. Anny Chung, Kerri M. Crawford, Stephanie N. Kivlin, Michael A. Mann, and Martin A. Nuñez. "Climate Disruption of Plant-Microbe Interactions." Annual Review of Ecology, Evolution, and Systematics 51, no. 1 (November 2, 2020): 561–86. http://dx.doi.org/10.1146/annurev-ecolsys-011720-090819.
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Interactions between plants and microbes have important influences on evolutionary processes, population dynamics, community structure, and ecosystem function. We review the literature to document how climate change may disrupt these ecological interactions and develop a conceptual framework to integrate the pathways of plant-microbe responses to climate over different scales in space and time. We then create a blueprint to aid generalization that categorizes climate effects into changes in the context dependency of plant-microbe pairs, temporal mismatches and altered feedbacks over time, or spatial mismatches that accompany species range shifts. We pair a new graphical model of how plant-microbe interactions influence resistance to climate change with a statistical approach to predictthe consequences of increasing variability in climate. Finally, we suggest pathways through which plant-microbe interactions can affect resilience during recovery from climate disruption. Throughout, we take a forward-looking perspective, highlighting knowledge gaps and directions for future research.
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Schroeder, Gabrielle M., Beate Diehl, Fahmida A. Chowdhury, John S. Duncan, Jane de Tisi, Andrew J. Trevelyan, Rob Forsyth, Andrew Jackson, Peter N. Taylor, and Yujiang Wang. "Seizure pathways change on circadian and slower timescales in individual patients with focal epilepsy." Proceedings of the National Academy of Sciences 117, no. 20 (May 4, 2020): 11048–58. http://dx.doi.org/10.1073/pnas.1922084117.
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Personalized medicine requires that treatments adapt to not only the patient but also changing factors within each individual. Although epilepsy is a dynamic disorder characterized by pathological fluctuations in brain state, surprisingly little is known about whether and how seizures vary in the same patient. We quantitatively compared within-patient seizure network evolutions using intracranial electroencephalographic (iEEG) recordings of over 500 seizures from 31 patients with focal epilepsy (mean 16.5 seizures per patient). In all patients, we found variability in seizure paths through the space of possible network dynamics. Seizures with similar pathways tended to occur closer together in time, and a simple model suggested that seizure pathways change on circadian and/or slower timescales in the majority of patients. These temporal relationships occurred independent of whether the patient underwent antiepileptic medication reduction. Our results suggest that various modulatory processes, operating at different timescales, shape within-patient seizure evolutions, leading to variable seizure pathways that may require tailored treatment approaches.
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Chapagain, Prem Sagar, Mohan Kumar Rai, and Basanta Paudel. "Land Use Land Cover Change and its Pathways in Sidin VDC, Panchthar District, Nepal." Geographical Journal of Nepal 11 (April 3, 2018): 77–94. http://dx.doi.org/10.3126/gjn.v11i0.19550.
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Land use/land cover situation is an important indicator of human interaction with environment. It reflects both environmental situation and the livelihood strategies of the people in space over time. This paper has attempted to study the land use/ land cover change of Sidin VDC, in the Koshi River basin in Nepal, based on maps and Remote sensing imageries (RS) data and household survey using structured questionnaires, focus group discussion and key informant interview. The study has focused on analysis the trend and pathways of land use change by dividing the study area into three elevation zones – upper, middle and lower. The time series data analysis from 1994-2004-2014 show major changes in forest and agricultural land. The dominant pathways of change is from forest to agriculture and forest to shrub during 1994-2004 and agriculture to forest during 2004-2014. The development of community forest, labor migration and labor shortage are found the major causes of land use change.The Geographical Journal of NepalVol. 11: 77-94, 2018
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Rinaldo, A., G. Botter, E. Bertuzzo, A. Uccelli, T. Settin, and M. Marani. "Transport at basin scales: 2. Applications." Hydrology and Earth System Sciences 10, no. 1 (February 8, 2006): 31–48. http://dx.doi.org/10.5194/hess-10-31-2006.
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Abstract. In this paper, the second of a series, we apply the models discussed in Part 1 to a significant case study. The nature of the catchment under study, the transport phenomena investigated (i.e. nitrates moving as solutes within runoff waters) and the scales involved in space and time, provide an elaborate test for theory and applications. Comparison of modeling predictions with field data (i.e. fluxes of carrier flow and solute nitrates) suggests that the framework proposed for geomorphic transport models is capable to describe well large-scale transport phenomena driven and/or controlled by spatially distributed hydrologic fields (e.g. rainfall patterns in space and time, drainage pathways, soil coverage and type, matter stored in immobile phases). A sample MonteCarlo mode of application of the model is also discussed where hydrologic forcings and external nitrate applications (through fertilization) are treated as random processes.
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Rinaldo, A., G. Botter, E. Bertuzzo, A. Uccelli, T. Settin, and M. Marani. "Transport at basin scales: 2. Applications." Hydrology and Earth System Sciences Discussions 2, no. 4 (August 23, 2005): 1641–81. http://dx.doi.org/10.5194/hessd-2-1641-2005.
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Abstract. In this paper, the second of a series, we apply the models discussed in Part 1 to a significant case study. The nature of the catchment under study, the transport phenomena investigated (i.e. nitrates moving as solutes within runoff waters) and the scales involved in space and time, provide an elaborate test for theory and applications. Comparison of modeling predictions with field data (i.e. fluxes of carrier flow and solute nitrates) suggests that the framework proposed for geomorphic transport models is capable to describe well large-scale transport phenomena driven and/or controlled by spatially distributed hydrologic fields (e.g. rainfall patterns in space and time, drainage pathways, soil coverage and type, matter stored in immobile phases). A sample MonteCarlo mode of application of the model is also discussed where hydrologic forcings and external nitrate applications (through fertilization) are treated as random processes.
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Cernicharo, J., N. Marcelino, M. Agúndez, C. Bermúdez, C. Cabezas, B. Tercero, and J. R. Pardo. "Discovery of HC4NC in TMC-1: A study of the isomers of HC3N, HC5N, and HC7N." Astronomy & Astrophysics 642 (October 2020): L8. http://dx.doi.org/10.1051/0004-6361/202039274.
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We present a study of the isocyano isomers of the cyanopolyynes HC3N, HC5N, and HC7N in TMC-1 and IRC+10216 carried out with the Yebes 40m radio telescope. This study has enabled us to report the detection, for the first time in space, of HCCCCNC in TMC-1 and to give upper limits for HC6NC in the same source. In addition, the deuterated isotopologues of HCCNC and HNCCC were detected, along with all 13C substitutions of HCCNC, also for the first time in space. The abundance ratios of HC3N and HC5N, with their isomers, are very different in TMC-1 and IRC+10216, namely, N(HC5N)/N(HC4NC) is ∼300 and ≥2100, respectively. We discuss the chemistry of the metastable isomers of cyanopolyynes in terms of the most likely formation pathways and by comparing observational abundance ratios between different sources.
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Zhang, Jiaming, Maik Lang, Rodney C. Ewing, Ram Devanathan, William J. Weber, and Marcel Toulemonde. "Nanoscale phase transitions under extreme conditions within an ion track." Journal of Materials Research 25, no. 7 (July 2010): 1344–51. http://dx.doi.org/10.1557/jmr.2010.0180.
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The dynamics of track development due to the passage of relativistic heavy ions through solids is a long-standing issue relevant to nuclear materials, age dating of minerals, space exploration, and nanoscale fabrication of novel devices. We have integrated experimental and simulation approaches to investigate nanoscale phase transitions under the extreme conditions created within single tracks of relativistic ions in Gd2O3(TiO2)x and Gd2Zr2–xTixO7. Track size and internal structure depend on energy density deposition, irradiation temperature, and material composition. Based on the inelastic thermal spike model, molecular dynamics simulations follow the time evolution of individual tracks and reveal the phase transition pathways to the concentric track structures observed experimentally. Individual ion tracks have nanoscale core-shell structures that provide a unique record of the phase transition pathways under extreme conditions.
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Zarnack, Kathi, Sureshkumar Balasubramanian, Michael P. Gantier, Vladislav Kunetsky, Michael Kracht, M. Lienhard Schmitz, and Katja Sträßer. "Dynamic mRNP Remodeling in Response to Internal and External Stimuli." Biomolecules 10, no. 9 (September 11, 2020): 1310. http://dx.doi.org/10.3390/biom10091310.
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Signal transduction and the regulation of gene expression are fundamental processes in every cell. RNA-binding proteins (RBPs) play a key role in the post-transcriptional modulation of gene expression in response to both internal and external stimuli. However, how signaling pathways regulate the assembly of RBPs with mRNAs remains largely unknown. Here, we summarize observations showing that the formation and composition of messenger ribonucleoprotein particles (mRNPs) is dynamically remodeled in space and time by specific signaling cascades and the resulting post-translational modifications. The integration of signaling events with gene expression is key to the rapid adaptation of cells to environmental changes and stress. Only a combined approach analyzing the signal transduction pathways and the changes in post-transcriptional gene expression they cause will unravel the mechanisms coordinating these important cellular processes.
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Chamberlain, Elizabeth L., and Jakob Wallinga. "Seeking enlightenment of fluvial sediment pathways by optically stimulated luminescence signal bleaching of river sediments and deltaic deposits." Earth Surface Dynamics 7, no. 3 (August 9, 2019): 723–36. http://dx.doi.org/10.5194/esurf-7-723-2019.
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Abstract. Reconstructing sediment pathways in fluvial and deltaic systems beyond instrumental records is challenging due to a lack of suitable methods. Here we explore the potential of luminescence methods for such purposes, focusing on bleaching of the optically stimulated luminescence (OSL) signal of quartz sediments in a large fluviodeltaic system across time and space. We approach this by comparing residual doses of sand and silt from the modern Mississippi River channel with estimated residual doses of sand isolated from Late Holocene Mississippi Delta mouth bar and overbank deposits. Further insight is obtained from a comparison of burial ages of paired quartz sand and silt of Mississippi Delta overbank deposits. In contrast to some previous investigations, we find that the bleaching of the OSL signal is at least as likely for finer sediment as for coarser sediment of the meandering Mississippi River and its delta. We attribute this to the differences in light exposure related to transport mode (bedload vs. suspended load). In addition, we find an unexpected spatiotemporal pattern in OSL bleaching of mouth bar sand deposits. We suggest this may be caused by changes in upstream pathways of the meandering channel belt(s) within the alluvial valley or by distributary channel and coastal dynamics within the delta. Our study demonstrates that the degree of OSL signal bleaching of sand in a large delta can be highly time- and/or space-dependent. Silt is shown to be generally sufficiently bleached in both the modern Mississippi River and associated paleo-deposits regardless of age, and silt may therefore provide a viable option for obtaining OSL chronologies in megadeltas. Our work contributes to initiatives to use luminescence signals to fingerprint sediment pathways within river channel networks and their deltas and also helps inform luminescence dating approaches in fluviodeltaic environments.
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Sabharwal, J., R. L. Seilheimer, X. Tao, C. S. Cowan, B. J. Frankfort, and S. M. Wu. "Elevated IOP alters the space–time profiles in the center and surround of both ON and OFF RGCs in mouse." Proceedings of the National Academy of Sciences 114, no. 33 (July 31, 2017): 8859–64. http://dx.doi.org/10.1073/pnas.1706994114.
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Glaucoma is a leading cause of blindness worldwide, and is characterized by progressive retinal ganglion cell (RGC) death. An experimental model of glaucoma has been established by elevating the intraocular pressure (IOP) via microbead occlusion of ocular fluid outflow in mice. Studies in this model have found visual dysfunction that varied with adaptational state, occurred before anatomical changes, and affected OFF RGCs more than ON RGCs. These results indicate subtle alterations in the underlying retinal circuitry that could help identify disease before irreversible RGC changes. Therefore, we looked at how RGC function was altered with elevated IOP under both photopic and scotopic conditions. We first found that responses to light offset are diminished with IOP elevation along with a concomitant decrease in receptive field center size for OFF RGCs. In addition, the antagonistic surround strength and size was reduced in ON RGCs. Furthermore, elevation of IOP significantly accelerated the photopic temporal tuning of RGC center responses in both ON and OFF RGCs. We found that some of the IOP-induced functional changes to OFF RGCs relied on ON cross-over pathways, indicating dysfunction in inner retinal circuitry. Overall, these results suggest that IOP alters multiple functions in the retina depending on the adaptational state. They provide a basis for designing multiple functional tests for early detection of glaucoma and for circuit-specific therapeutic targets in treatment of this blinding disease.
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Lecarpentier, Yves, Victor Claes, and Jean-Louis Hébert. "PPARs, Cardiovascular Metabolism, and Function: Near- or Far-from-Equilibrium Pathways." PPAR Research 2010 (2010): 1–10. http://dx.doi.org/10.1155/2010/783273.
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Peroxisome proliferator-activated receptors (PPAR α, β/δ and γ) play a key role in metabolic regulatory processes and gene regulation of cellular metabolism, particularly in the cardiovascular system. Moreover, PPARs have various extra metabolic roles, in circadian rhythms, inflammation and oxidative stress. In this review, we focus mainly on the effects of PPARs on some thermodynamic processes, which can behave either near equilibrium, or far-from-equilibrium. New functions of PPARs are reported in the arrhythmogenic right ventricular cardiomyopathy, a human genetic heart disease. It is now possible to link the genetic desmosomal abnormalitiy to the presence of fat in the right ventricle, partly due to an overexpression of PPARγ. Moreover, PPARs are directly or indirectly involved in cellular oscillatory processes such as the Wnt-b-catenin pathway, circadian rhythms of arterial blood pressure and cardiac frequency and glycolysis metabolic pathway. Dysfunction of clock genes and PPARγ may lead to hyperphagia, obesity, metabolic syndrome, myocardial infarction and sudden cardiac death, In pathological conditions, regulatory processes of the cardiovascular system may bifurcate towards new states, such as those encountered in hypertension, type 2 diabetes, and heart failure. Numerous of these oscillatory mechanisms, organized in time and space, behave far from equilibrium and are “dissipative structures”.
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Tajbakhsh, S., U. Borello, E. Vivarelli, R. Kelly, J. Papkoff, D. Duprez, M. Buckingham, and G. Cossu. "Differential activation of Myf5 and MyoD by different Wnts in explants of mouse paraxial mesoderm and the later activation of myogenesis in the absence of Myf5." Development 125, no. 21 (November 1, 1998): 4155–62. http://dx.doi.org/10.1242/dev.125.21.4155.
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Activation of myogenesis in newly formed somites is dependent upon signals derived from neighboring tissues, namely axial structures (neural tube and notochord) and dorsal ectoderm. In explants of paraxial mesoderm from mouse embryos, axial structures preferentially activate myogenesis through a Myf5-dependent pathway and dorsal ectoderm preferentially through a MyoD-dependent pathway. Here we report that cells expressing Wnt1 will preferentially activate Myf5 while cells expressing Wnt7a will preferentially activate MyoD. Wnt1 is expressed in the dorsal neural tube and Wnt7a in dorsal ectoderm in the early embryo, therefore both can potentially act in vivo to activate Myf5 and MyoD, respectively. Wnt4, Wnt5a and Wnt6 exert an intermediate effect activating both Myf5 and MyoD equivalently in paraxial mesoderm. Sonic Hedgehog synergises with both Wnt1 and Wnt7a in explants from E8.5 paraxial mesoderm but not in explants from E9.5 embryos. Signaling through different myogenic pathways may explain the rescue of muscle formation in Myf5 null embryos, which do not form an early myotome but later develop both epaxial and hypaxial musculature. Explants of unsegmented paraxial mesoderm contain myogenic precursors capable of expressing MyoD in response to signaling from a neural tube isolated from E10.5 embryos, the developmental stage when MyoD is present throughout the embryo. Myogenic cells cannot activate MyoD in response to signaling from a less mature neural tube. Together these data suggest that different Wnt molecules can activate myogenesis through different pathways such that commitment of myogenic precursors is precisely regulated in space and time to achieve the correct pattern of skeletal muscle development.
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Zika, Jan D., Matthew H. England, and Willem P. Sijp. "The Ocean Circulation in Thermohaline Coordinates." Journal of Physical Oceanography 42, no. 5 (May 1, 2012): 708–24. http://dx.doi.org/10.1175/jpo-d-11-0139.1.
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Abstract The thermohaline streamfunction is presented. The thermohaline streamfunction is the integral of transport in temperature–salinity space and represents the net pathway of oceanic water parcels in that space. The thermohaline streamfunction is proposed as a diagnostic to understand the global oceanic circulation and its role in the global movement of heat and freshwater. The coordinate system used filters out adiabatic fluctuations. Physical pathways and ventilation time scales are naturally diagnosed, as are the roles of the mean flow and turbulent fluctuations. Because potential density is a function of temperature and salinity, the framework is naturally isopycnal and is ideal for the diagnosis of water-mass transformations and advective diapycnal heat and freshwater transports. Crucially, the thermohaline streamfunction is computationally and practically trivial to implement as a diagnostic for ocean models. Here, the thermohaline streamfunction is computed using the output of an equilibrated intermediate complexity climate model. It describes a global cell, a warm tropical cell, and a bottom water cell. The streamfunction computed from eddy-induced advection is equivalent in magnitude to that from the total advection, demonstrating the leading-order importance of parameterized eddy fluxes in oceanic heat and freshwater transports. The global cell, being clockwise in thermohaline space, tends to advect both heat and salt toward denser (poleward) water masses in symmetry with the atmosphere’s poleward transport of moisture. A reprojection of the global cell from thermohaline to geographical coordinates reveals a thermohaline circulation reminiscent of the schematized “global conveyor.”
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Pérez, M. Lucía, Sharad J. Shanbhag, and José Luis Peña. "Auditory Spatial Tuning at the Crossroads of the Midbrain and Forebrain." Journal of Neurophysiology 102, no. 3 (September 2009): 1472–82. http://dx.doi.org/10.1152/jn.00400.2009.
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The barn owl's midbrain and forebrain contain neurons tuned to sound direction. The spatial receptive fields of these neurons result from sensitivity to combinations of interaural time (ITD) and level (ILD) differences over a broad frequency range. While a map of auditory space has been described in the midbrain, no similar topographic representation has been found in the forebrain. The first nuclei that belong exclusively to the forebrain and midbrain pathways are the thalamic nucleus ovoidalis (Ov) and the external nucleus of the inferior colliculus (ICx), respectively. The midbrain projects to the auditory thalamus before sharp spatial receptive fields emerge; although Ov and ICx receive projections from the same midbrain nuclei, they are not directly connected. We compared the spatial tuning in Ov and ICx. Thalamic neurons respond to a broader frequency range and their ITD and ILD tuning varied more across frequency. However, neurons in Ov showed spatial receptive fields as selective as neurons in ICx. Thalamic spatial receptive fields were tuned to frontal and contralateral space and correlated with their tuning to ITD and ILD. Our results indicate that spatial tuning emerges in both pathways by similar combination selectivity to ITD and ILD. However, the midbrain and the thalamus do not appear to repeat exactly the same processing, as indicated by the difference in frequency range and the broader tuning to binaural cues. The differences observed at the initial stages of these sound-localization pathways may reflect diverse functions and coding schemes of midbrain and forebrain.
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Vallino, Joseph J. "Ecosystem biogeochemistry considered as a distributed metabolic network ordered by maximum entropy production." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1545 (May 12, 2010): 1417–27. http://dx.doi.org/10.1098/rstb.2009.0272.
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We examine the application of the maximum entropy production principle for describing ecosystem biogeochemistry. Since ecosystems can be functionally stable despite changes in species composition, we use a distributed metabolic network for describing biogeochemistry, which synthesizes generic biological structures that catalyse reaction pathways, but is otherwise organism independent. Allocation of biological structure and regulation of biogeochemical reactions is determined via solution of an optimal control problem in which entropy production is maximized. However, because synthesis of biological structures cannot occur if entropy production is maximized instantaneously, we propose that information stored within the metagenome allows biological systems to maximize entropy production when averaged over time. This differs from abiotic systems that maximize entropy production at a point in space–time, which we refer to as the steepest descent pathway. It is the spatio-temporal averaging that allows biological systems to outperform abiotic processes in entropy production, at least in many situations. A simulation of a methanotrophic system is used to demonstrate the approach. We conclude with a brief discussion on the implications of viewing ecosystems as self-organizing molecular machines that function to maximize entropy production at the ecosystem level of organization.
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Chaulagain, Diptee, and Julia Frugoli. "The Regulation of Nodule Number in Legumes Is a Balance of Three Signal Transduction Pathways." International Journal of Molecular Sciences 22, no. 3 (January 23, 2021): 1117. http://dx.doi.org/10.3390/ijms22031117.
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Nitrogen is a major determinant of plant growth and productivity and the ability of legumes to form a symbiotic relationship with nitrogen-fixing rhizobia bacteria allows legumes to exploit nitrogen-poor niches in the biosphere. But hosting nitrogen-fixing bacteria comes with a metabolic cost, and the process requires regulation. The symbiosis is regulated through three signal transduction pathways: in response to available nitrogen, at the initiation of contact between the organisms, and during the development of the nodules that will host the rhizobia. Here we provide an overview of our knowledge of how the three signaling pathways operate in space and time, and what we know about the cross-talk between symbiotic signaling for nodule initiation and organogenesis, nitrate dependent signaling, and autoregulation of nodulation. Identification of common components and points of intersection suggest directions for research on the fine-tuning of the plant’s response to rhizobia.
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WILSON, CHRIS. "PETITIONS AND PATHWAYS TO THE ASYLUM IN BRITISH MANDATE PALESTINE, 1930–1948." Historical Journal 62, no. 2 (July 20, 2018): 451–71. http://dx.doi.org/10.1017/s0018246x18000092.
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AbstractThis article draws on a collection of petitions by Palestinian Arabs and Jews to explore how families negotiated the admission of mentally ill relatives into government mental institutions under the British mandate between 1930 and 1948. In contrast to the conclusions of the existing literature, which focuses largely on the development of parallel Jewish institutions as establishing the foundations of the Israeli health system, these petitions reveal that the trajectories of both Arab and Jewish mentally ill were complex, traversing domestic, private, and government contexts in highly contingent ways. The second part of this article examines the petitions themselves as dense moments of engagement by Palestinian Arabs and Jews with the British mandate, in which the anxieties and priorities of the mandate were strategically re-deployed in order to secure admission into chronically underfunded and overcrowded institutions. Petitioners also sought to mobilize other actors, often within the state itself, as intercessors, a strategy which attempted to thread together state and society in a meaningful and advantageous way at a time when both seemed to be unravelling. Taken together, these pathways and petitions foreground the space of interaction between the British mandate and its subjects, thereby offering new perspectives on both.
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Bell, V. A., and R. J. Moore. "A grid-based distributed flood forecasting model for use with weather radar data: Part 1. Formulation." Hydrology and Earth System Sciences 2, no. 2/3 (September 30, 1998): 265–81. http://dx.doi.org/10.5194/hess-2-265-1998.
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Abstract. A practical methodology for distributed rainfall-runoff modelling using grid square weather radar data is developed for use in real-time flood forecasting. The model, called the Grid Model, is configured so as to share the same grid as used by the weather radar, thereby exploiting the distributed rainfall estimates to the full. Each grid square in the catchment is conceptualised as a storage which receives water as precipitation and generates water by overflow and drainage. This water is routed across the catchment using isochrone pathways. These are derived from a digital terrain model assuming two fixed velocities of travel for land and river pathways which are regarded as model parameters to be optimised. Translation of water between isochrones is achieved using a discrete kinematic routing procedure, parameterised through a single dimensionless wave speed parameter, which advects the water and incorporates diffusion effects through the discrete space-time formulation. The basic model routes overflow and drainage separately through a parallel system of kinematic routing reaches, characterised by different wave speeds but using the same isochrone-based space discretisation; these represent fast and slow pathways to the basin outlet, respectively. A variant allows the slow pathway to have separate isochrones calculated using Darcy velocities controlled by the hydraulic gradient as estimated by the local gradient of the terrain. Runoff production within a grid square is controlled by its absorption capacity which is parameterised through a simple linkage function to the mean gradient in the square, as calculated from digital terrain data. This allows absorption capacity to be specified differently for every grid square in the catchment through the use of only two regional parameters and a DTM measurement of mean gradient for each square. An extension of this basic idea to consider the distribution of gradient within the square leads analytically to a Pareto distribution of absorption capacity, given a power distribution of gradient within the square. The probability-distributed model theory (Moore, 1985) can then be used directly to obtain the integrated runoff production for the square for routing to the catchment outlet. justification for the simple linkage function is in part sought through consideration of variants on the basic model where (i) runoff production is based on a topographic index control on saturation and (ii) absorption capacity is related to the Integrated Air Capacity of the soil, as obtained from soil survey. An impervious area fraction is also introduced based on the use of Landsat classified urban areas. The Grid Model and its variants are assessed in Part 2 (Bell and Moore, 1998), first as simulation models and then as forecasting models, following the development of updating procedures to accommodate recent observations of flow so as to improve forecast performance in a real-time context.
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Boyce, F. M., W. M. Schertzer, P. F. Hamblin, and C. R. Murthy. "Physical Behaviour of Lake Ontario with Reference to Contaminant Pathways and Climate Change." Canadian Journal of Fisheries and Aquatic Sciences 48, no. 8 (August 1, 1991): 1517–28. http://dx.doi.org/10.1139/f91-180.
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Current understanding of the physical behaviour of Lake Ontario is assessed. In particular, the role of water movements in the distribution and fate of contaminants is described, and our ability to anticipate the results of global climate warming on the Great Lakes is surveyed. In the past two decades, the general features of large-lake circulation and mixing have been successfully delineated, although detailed climatological studies will be required for particular sites of interest or concern. More sophisticated models of thermal structure will be needed to assess the potential consequences of climate warming, particularly in the matter of convective overturning. The process of "sediment focusing," so strongly linked to the fate of many organic contaminants, is only recently amenable to study with instruments that respect the time and space scales of resuspension and settling. The rates of transfer of gases and contaminants across the air–water interface are known to depend on wind and wave conditions; this dependence is being explored. Experience over the past 20 yr has consistently shown that large-lake studies of chemical and biological processes are difficult if not impossible to interpret in the absence of an adequate base of concurrent physical measurements.
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LEMON, MARK, PAUL JEFFREY, BRIAN S. MCINTOSH, and TIM OXLEY. "UNDERSTANDING PERCEPTIONS OF CHANGE: A PATHWAYS CONTRIBUTION TO COMMUNITY CONSULTATION AND ENVIRONMENTAL DECISION-MAKING." Journal of Environmental Assessment Policy and Management 06, no. 02 (June 2004): 189–211. http://dx.doi.org/10.1142/s146433320400164x.
Full textAbstract:
Participation has become part of the language of environmental management. While this move is positive there remains a danger that overly formalised and restricted participatory procedures, in terms of the information sought, may constrain and hinder dialogue and learning between the public and management agencies. Responses to specific issues are often sought from members of the public without a clear understanding about whether those issues are salient to them, where they are salient or how they fit into multiple and dynamic interpretations of environmental change. This paper uses case study material from the UK to demonstrate a novel Pathways Approach to the recording and analysis of individual perceptions about environmental change. The approach seeks to concentrate on experience and interpretation and is based on the conceptualisation of perceived cause–effect relationships and the pathways that support them. The links between time, space and community are considered within this analysis, as is the potential for improved participation through the provision of policy relevant information to planners and environmental managers operating in complex, multi-perspective situations.
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Afrasiabi, Fatemeh, Ramin Dehghanpoor, and Nurit Haspel. "Integrating Rigidity Analysis into the Exploration of Protein Conformational Pathways Using RRT* and MC." Molecules 26, no. 8 (April 16, 2021): 2329. http://dx.doi.org/10.3390/molecules26082329.
Full textAbstract:
To understand how proteins function on a cellular level, it is of paramount importance to understand their structures and dynamics, including the conformational changes they undergo to carry out their function. For the aforementioned reasons, the study of large conformational changes in proteins has been an interest to researchers for years. However, since some proteins experience rapid and transient conformational changes, it is hard to experimentally capture the intermediate structures. Additionally, computational brute force methods are computationally intractable, which makes it impossible to find these pathways which require a search in a high-dimensional, complex space. In our previous work, we implemented a hybrid algorithm that combines Monte-Carlo (MC) sampling and RRT*, a version of the Rapidly Exploring Random Trees (RRT) robotics-based method, to make the conformational exploration more accurate and efficient, and produce smooth conformational pathways. In this work, we integrated the rigidity analysis of proteins into our algorithm to guide the search to explore flexible regions. We demonstrate that rigidity analysis dramatically reduces the run time and accelerates convergence.