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1
Valle, Natalia La. "Temporalités distribuées et partagées. Une approche écologique des activités familiales dans le foyer." Tracés, no. 22 (June 21, 2012): 43–64. http://dx.doi.org/10.4000/traces.5428.
Повний текст джерела
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Clément, Eric, and Michel Dagenais. "Traces Synchronization in Distributed Networks." Journal of Computer Systems, Networks, and Communications 2009 (2009): 1–11. http://dx.doi.org/10.1155/2009/190579.
Повний текст джерелаАнотація:
This article proposes a novel approach to synchronize a posteriori the detailed execution traces from several networked computers. It can be used to debug and investigate complex performance problems in systems where several computers exchange information. When the distributed system is under study, detailed execution traces are generated locally on each system using an efficient and accurate system level tracer, LTTng. When the tracing is finished, the individual traces are collected and analysed together. The messaging events in all the traces are then identified and correlated in order to estimate the time offset over time between each node. The time offset computation imprecision, associated with asymmetric network delays and operating system latency in message sending and receiving, is amortized over a large time interval through a linear least square fit over several messages covering a large time span. The resulting accuracy is such that it is possible to estimate the clock offsets in a distributed system, even with a relatively low volume of messages exchanged, to within the order of a microsecond while having a very low impact on the system execution, which is sufficient to properly order the events traced on the individual computers in the distributed system.
3
Xing, Lida, Martin Lockley, Anthony Romilio, Tao Wang, and Liu Chang. "Dinosaur Tracks from the Lower Jurassic Lufeng Formation of Northern Central Yunnan, China." Biosis: Biological Systems 3, no. 1 (April 1, 2022): e004. http://dx.doi.org/10.37819/biosis.003.01.0169.
Повний текст джерелаАнотація:
An increasing number of theropod-dominated tracksites have been reported from the Jurassic and Cretaceous of China. These include a significant number from the Lower Jurassic of the Lufeng Basin, famous for its Lufengosaurus fauna and known for a typical Lower Jurassic globally-distributed tetrapod footprint biochron. Here we report another localized theropod track occurrence regular of various scattered tracksites from the Lufeng Formation. The tracks are medium-sized tridactyl tracks from the basal member of the Zhangjia'ao Member, Lufeng Formation which shows an unusually wide divarication between the traces of digits III and IV, which suggest several possible interpretations.
4
Mukhutdinova, Alfiya R., Alexander V. Bolotov, Oleg V. Anikin, and Mikhail A. Varfolomeev. "Algorithm for estimating boundary conditions of a distributed tracer for application in a single-well tracer test." Georesursy 24, no. 4 (December 20, 2022): 75–81. http://dx.doi.org/10.18599/grs.2022.4.6.
Повний текст джерелаАнотація:
An important tool in determining residual oil saturation today is the single-well tracer test, as the preferred method for assessing the potential for using enhanced oil recovery methods (EOR) and developing pilot projects. The success of the test performed directly depends on the optimal choice of the tracer composition, which will contribute to the qualitative determination of the parameters required in the calculation of the residual oil saturation of the formation. To assess the boundary conditions for the applicability of the tracer in the field, the kinetic and thermodynamic properties of tracers are considered under various reservoir conditions of the field. Based on the results of this work, an algorithm for assessing the applicability of the tracer for reservoirs in a wide range of salinity and temperatures is presented.
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Carlini, Emanuele, Alessandro Lulli, and Laura Ricci. "Model driven generation of mobility traces for distributed virtual environments with TRACE." Concurrency and Computation: Practice and Experience 30, no. 20 (July 28, 2017): e4235. http://dx.doi.org/10.1002/cpe.4235.
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6
McCarthy, I. D., and S. P. Hughes. "Multiple tracer studies of bone uptake of 99mTc-MDP and 85Sr." American Journal of Physiology-Heart and Circulatory Physiology 256, no. 5 (May 1, 1989): H1261—H1265. http://dx.doi.org/10.1152/ajpheart.1989.256.5.h1261.
Повний текст джерелаАнотація:
Multiple tracer outflow dilution studies were performed on the normal canine tibia. In all cases 125I-labeled albumin was used as a vascular tracer. In one series of experiments 99mTc-labeled methylene diphosphonate and [14C]sucrose were used as test tracers, and in a second series 85Sr and 22Na were used. A bolus of three tracers was injected into the tibial nutrient artery, and fractional concentrations appearing in the ipsilateral femoral vein were measured for a period of 5 min. A distributed model, containing parameters for capillary and bone permeability and apparent volumes of distribution of interstitial fluid, was fitted to these data. It was found that there was no discrimination between movement of 85Sr or 22Na from interstitial fluid space into bone. Transcapillary exchange does not appear to be a significant barrier to exchange between blood and bone surfaces.
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Pemper, Richard R., Michael J. Flecker, Vernie C. McWhirter, and Donald W. Oliver. "Hydraulic fracture evaluation with multiple radioactive tracers." GEOPHYSICS 53, no. 10 (October 1988): 1323–33. http://dx.doi.org/10.1190/1.1442410.
Повний текст джерелаАнотація:
For many years, wireline tracer surveys have been used to determine the height of fractures created during hydraulic stimulation procedures. A recent advancement in fracture evaluation technology has been to tag different stages of a fracture operation with multiple radioactive tracers, providing the capability to discern between created and propped fracture heights in one or more zones of interest. In this research, a wireline instrumentation and data analysis system is implemented to identify and separate the individual yields from multiple radioactive tracers, with an additional feature that determines whether the tracer material is inside of the borehole or distributed throughout the created fracture zone. A single postfracture pass of the logging instrument is used to accumulate gamma ray spectra at each 7.6 cm interval along a borehole. A weighted least‐squares spectrum unfolding algorithm calculates the radioactive intensities as a function of depth, while the peak‐to‐Compton down‐scatter ratio determines the proximity of the tracer material to the wellbore. Field examples illustrate the effectiveness of the system for the evaluation of multistage fracture operations.
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POLATOĞLU, Ahmet, and Cahit YEŞİLYAPRAK. "Using and Testing Camera Sensors with Different Devices at Cosmic Ray Detection." Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi 16, no. 2 (August 24, 2023): 590–97. http://dx.doi.org/10.18185/erzifbed.1167041.
Повний текст джерелаАнотація:
Cosmic Ray (CR) is high-energy charged particles that reach the earth from space. CR detection methods and studies have been progressing rapidly since the beginning of the 20th century. One of these methods is the use of digital cameras with Charge Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) sensors. Mobile phone cameras or webcams offer an easily using and economical measurement system for CR measurement. The sensors are exposed to CR during a long exposure. CRs leave traces in the background. Cosmic particle tracks are then separated from the background noise and can be classified. Making the traces of the particles visible is important for understanding the subject. In this context, traces of particles such as electrons, muons, and alphas can be seen with the cloud chamber experiments. Help of sensor technology and cameras have developed in recent years, CR traces can be easily detected so that it can be seen. There are many software and international projects that detect CR using CMOS sensors in cell phone cameras. In this study, related projects, programs and studies were researched; CR traces that we captured with the help of Cosmic-Ray Extremely Distributed Observatory (CREDO) and Cosmic Ray Finder (CRF) software with web cam and a mobile phone cam CMOS sensor are presented. Links have been made about astrophysical events coinciding with previously detected particle images.
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Nguyen, Tung T., Yashdip S. Pannu, Cynthia Sung, Robert L. Dedrick, Stuart Walbridge, Martin W. Brechbiel, Kayhan Garmestani, Markus Beitzel, Alexander T. Yordanov, and Edward H. Oldfield. "Convective distribution of macromolecules in the primate brain demonstrated using computerized tomography and magnetic resonance imaging." Journal of Neurosurgery 98, no. 3 (March 2003): 584–90. http://dx.doi.org/10.3171/jns.2003.98.3.0584.
Повний текст джерелаАнотація:
Object. Convection-enhanced delivery (CED), the delivery and distribution of drugs by the slow bulk movement of fluid in the extracellular space, allows delivery of therapeutic agents to large volumes of the brain at relatively uniform concentrations. This mode of drug delivery offers great potential for the treatment of many neurological disorders, including brain tumors, neurodegenerative diseases, and seizure disorders. An analysis of the treatment efficacy and toxicity of this approach requires confirmation that the infusion is distributed to the targeted region and that the drug concentrations are in the therapeutic range. Methods. To confirm accurate delivery of therapeutic agents during CED and to monitor the extent of infusion in real time, albumin-linked surrogate tracers that are visible on images obtained using noninvasive techniques (iopanoic acid [IPA] for computerized tomography [CT] and Gd—diethylenetriamine pentaacetic acid for magnetic resonance [MR] imaging) were developed and investigated for their usefulness as surrogate tracers during convective distribution of a macromolecule. The authors infused albumin-linked tracers into the cerebral hemispheres of monkeys and measured the volumes of distribution by using CT and MR imaging. The distribution volumes measured by imaging were compared with tissue volumes measured using quantitative autoradiography with [14C]bovine serum albumin coinfused with the surrogate tracer. For in vivo determination of tracer concentration, the authors examined the correlation between the concentration of the tracer in brain homogenate standards and CT Hounsfield units. They also investigated the long-term effects of the surrogate tracer for CT scanning, IPA-albumin, on animal behavior, the histological characteristics of the tissue, and parenchymal toxicity after cerebral infusion. Conclusions. Distribution of a macromolecule to clinically significant volumes in the brain is possible using convection. The spatial dimensions of the tissue distribution can be accurately defined in vivo during infusion by using surrogate tracers and conventional imaging techniques, and it is expected that it will be possible to determine local concentrations of surrogate tracers in voxels of tissue in vivo by using CT scanning. Use of imaging surrogate tracers is a practical, safe, and essential tool for establishing treatment volumes during high-flow interstitial microinfusion of the central nervous system.
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Ala-aho, Pertti, Doerthe Tetzlaff, James P. McNamara, Hjalmar Laudon, and Chris Soulsby. "Using isotopes to constrain water flux and age estimates in snow-influenced catchments using the STARR (Spatially distributed Tracer-Aided Rainfall–Runoff) model." Hydrology and Earth System Sciences 21, no. 10 (October 9, 2017): 5089–110. http://dx.doi.org/10.5194/hess-21-5089-2017.
Повний текст джерелаАнотація:
Abstract. Tracer-aided hydrological models are increasingly used to reveal fundamentals of runoff generation processes and water travel times in catchments. Modelling studies integrating stable water isotopes as tracers are mostly based in temperate and warm climates, leaving catchments with strong snow influences underrepresented in the literature. Such catchments are challenging, as the isotopic tracer signals in water entering the catchments as snowmelt are typically distorted from incoming precipitation due to fractionation processes in seasonal snowpack. We used the Spatially distributed Tracer-Aided Rainfall–Runoff (STARR) model to simulate fluxes, storage, and mixing of water and tracers, as well as estimating water ages in three long-term experimental catchments with varying degrees of snow influence and contrasting landscape characteristics. In the context of northern catchments the sites have exceptionally long and rich data sets of hydrometric data and – most importantly – stable water isotopes for both rain and snow conditions. To adapt the STARR model for sites with strong snow influence, we used a novel parsimonious calculation scheme that takes into account the isotopic fractionation through snow sublimation and snowmelt. The modified STARR setup simulated the streamflows, isotope ratios, and snow pack dynamics quite well in all three catchments. From this, our simulations indicated contrasting median water ages and water age distributions between catchments brought about mainly by differences in topography and soil characteristics. However, the variable degree of snow influence in catchments also had a major influence on the stream hydrograph, storage dynamics, and water age distributions, which was captured by the model. Our study suggested that snow sublimation fractionation processes can be important to include in tracer-aided modelling for catchments with seasonal snowpack, while the influence of fractionation during snowmelt could not be unequivocally shown. Our work showed the utility of isotopes to provide a proof of concept for our modelling framework in snow-influenced catchments.
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Lewington, Emma L. M., Stephen J. Livingstone, Chris D. Clark, Andrew J. Sole, and Robert D. Storrar. "A model for interaction between conduits and surrounding hydraulically connected distributed drainage based on geomorphological evidence from Keewatin, Canada." Cryosphere 14, no. 9 (September 10, 2020): 2949–76. http://dx.doi.org/10.5194/tc-14-2949-2020.
Повний текст джерелаАнотація:
Abstract. We identify and map visible traces of subglacial meltwater drainage around the former Keewatin Ice Divide, Canada, from high-resolution Arctic Digital Elevation Model (ArcticDEM) data. We find similarities in the characteristics and spatial locations of landforms traditionally treated separately (i.e. meltwater channels, meltwater tracks and eskers) and propose that creating an integrated map of meltwater routes captures a more holistic picture of the large-scale drainage in this area. We propose the grouping of meltwater channels and meltwater tracks under the term meltwater corridor and suggest that these features in the order of 10s–100s m wide, commonly surrounding eskers and transitioning along flow between different types, represent the interaction between a central conduit (the esker) and surrounding hydraulically connected distributed drainage system (the meltwater corridor). Our proposed model is based on contemporary observations and modelling which suggest that connections between conduits and the surrounding distributed drainage system within the ablation zone occur as a result of overpressurisation of the conduit. The widespread aerial coverage of meltwater corridors (5 %–36 % of the bed) provides constraints on the extent of basal uncoupling induced by basal water pressure fluctuations. Geomorphic work resulting from repeated connection to the surrounding hydraulically connected distributed drainage system suggests that basal sediment can be widely accessed and evacuated by meltwater.
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Payment, P., and P. Hartemann. "Les contaminants de l'eau et leurs effets sur la santé." Revue des sciences de l'eau 11 (April 12, 2005): 199–210. http://dx.doi.org/10.7202/705338ar.
Повний текст джерелаАнотація:
La transmission des maladies par la voie hydrique est sous contrôle dans la majorité des pays industrialisés. Malgré tout des maladies épidémiques ou endémiques sont encore observées. Plusieurs microorganismes sont en émergence, et Cryptosporidium a été impliqué dans des épidémies importantes dans plusieurs pays. Le conrôle de ces maladies transmissibles par la voie hydrique requiert des autorités des nouvelles approches qui allient le contrôle des risques de cancer dûs aux sous-produits de la désinfection au contrôle des micro-organismes les plus résistants . Aux Etats-Unis, l'objectif proposé est l'absence de microorganismes dans l'eau potable. Cet objectif ne peut être contrôlé par les indicateurs usuels et l'on recommande donc un niveau de traitement équivalent. Le traitement est alors contrôlé en temps réel par des moyens physico-chimiques tels la turbidité ou la mesure des particules, et un contrôle a posteriori par de nouveaux indicateurs telles les spores des bactéries sporulantes aérobies. Le vieillissement des installations, des populations immunocompromises et une urbanisation grandissante sont autant de causes de l'émergence de nouvelles maladies infectieuses dont certaines transmissibles par la voie hydrique. La proportion des maladies gastro-intestinales qui est attribuable à l'eau de consommation est encore très grande et elle contribue à maintenir ces infections en circulation dans la population. Le dilemme du contrôle des risques de cancer dus aux sous-produits de la désinfection ne doit pas conduire à une réduction de l'efficacité des traitements, car le niveau de risque à partir duquel ont été fixées les concentrations maximales admissibles de ces sous-produits dans l'eau (10-6 cas de cancer par vie entière d'exposition) est bien plus faible que celui de contracter une maladie infectieuse d'origine hydrique en absence de traitement adéquat. La situation en matière de pathologies induites par la consommation d'eau est extrêmement contrastée selon les pays. En effet la transmission de maladies infectieuses par la voie hydrique a été maîtrisée dans la plupart des pays industrialisés par la mise en place d'installations de traitement et d'un contrôle sanitaire s'appuyant sur une réglementation abondante. A l'opposé la situation des pays en voie de développement reste souvent très mauvaise dans ce domaine et l'Organisation Mondiale de Santé estime que 1,5 milliards d'habitants ne disposent pas encore d'eau potable dont cent millions en Europe et que 30 000 morts journalières sont dues à l'absence d'une eau en quantité et qualité satisfaisantes (Ford et Colwell 1996). En revanche les pays développés voient la qualité chimique des eaux distribuées de plus en plus souvent mise en cause par les associations de consommateurs. Outre le progrès très rapide des techniques analytiques qui permet de découvrir la présence de traces dont on ne soupçonnait guère la présence dans l'eau du robinet, la pollution croissante de la ressource, les traitements de désinfection et le contact avec les matériaux des réseaux de distribution apportent des molécules dont la toxicité à moyen et long terme mérite d'être évaluée. La mise en oeuvre de traitements de désinfection dont l'utilité est indiscutable et l'effet sur la morbidité et la mortalité par pathologie infectieuse chez des populations desservies parfaitement significatif, s'accompagne de la formation de sous-produits. Certains de ceux-ci étant cancérigènes et/ou mutagènes en expérimentation de laboratoire et des études épidémiologiques ayant pu montrer une légère augmentation du risque de cancer dans la population, l'impact médiatique de cette information peut conduire à une mauvaise appréciation dans la gestion des risques pour la santé. Ainsi l'arrêt de la chloration pour éviter la formation de sous produits et quelques cas de cancers aurait conduit un pays d'Amérique du Sud a enregistrer une importante épidémie de choléra et des centaines de décès. Il n'est pas facile de gérer ce paradoxe entre sophistication du traitement lié à la pollution de la ressource entraînant la présence de sous produits de désinfection et la persistance d'éléments traces et de divers microorganismes dans une eau de qualité conforme aux critères de potabilité mais que le consommateur ne veut plus consommer. Dans cet article nous tenterons de faire le point sur le risque hydrique pour la santé lié d'une part aux contaminants biologiques et d'autre part aux contaminants chimiques. Sa meilleure connaissance est la clef d'une stratégie de gestion efficace et d'une reconquête du consommateur que la publicité a trop tendance à orienter vers les eaux embouteillées.
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Jaroš, Milan, Lubomír Říha, Petr Strakoš, and Matěj Špeťko. "GPU Accelerated Path Tracing of Massive Scenes." ACM Transactions on Graphics 40, no. 2 (April 27, 2021): 1–17. http://dx.doi.org/10.1145/3447807.
Повний текст джерелаАнотація:
This article presents a solution to path tracing of massive scenes on multiple GPUs. Our approach analyzes the memory access pattern of a path tracer and defines how the scene data should be distributed across up to 16 GPUs with minimal effect on performance. The key concept is that the parts of the scene that have the highest amount of memory accesses are replicated on all GPUs. We propose two methods for maximizing the performance of path tracing when working with partially distributed scene data. Both methods work on the memory management level and therefore path tracer data structures do not have to be redesigned, making our approach applicable to other path tracers with only minor changes in their code. As a proof of concept, we have enhanced the open-source Blender Cycles path tracer. The approach was validated on scenes of sizes up to 169 GB. We show that only 1–5% of the scene data needs to be replicated to all machines for such large scenes. On smaller scenes we have verified that the performance is very close to rendering a fully replicated scene. In terms of scalability we have achieved a parallel efficiency of over 94% using up to 16 GPUs.
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Bingham, Robert G., Peter W. Nienow, Martin J. Sharp, and Sarah Boon. "Subglacial drainage processes at a High Arctic polythermal valley glacier." Journal of Glaciology 51, no. 172 (2005): 15–24. http://dx.doi.org/10.3189/172756505781829520.
Повний текст джерелаАнотація:
AbstractDye-tracer experiments undertaken over two summer melt seasons at polythermal John Evans Glacier, Ellesmere Island, Canada, were designed to investigate the character of the subglacial drainage system and its evolution over a melt season. In both summers, dye injections were conducted at several moulins and traced to a single subglacial outflow. Tracer breakthrough curves suggest that supraglacial meltwater initially encounters a distributed subglacial drainage system in late June. The subsequent development and maintenance of a channelled subglacial network are dependent upon sustained high rates of surface melting maintaining high supraglacial inputs. In a consistently warm summer (2000), subglacial drainage became rapidly and persistently channelled. In a cooler summer (2001), distributed subglacial drainage predominated. These observations confirm that supraglacial meltwater can access the bed of a High Arctic glacier in summer, and induce significant structural evolution of the subglacial drainage system. They do not support the view that subglacial drainage systems beneath polythermal glaciers are always poorly developed. They do suggest that the effects on ice flow of surface water penetration to the bed of predominantly cold glaciers may be short-lived.
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Gisel, A., S. Barella, F. D. Hempel, and P. C. Zambryski. "Temporal and spatial regulation of symplastic trafficking during development in Arabidopsis thaliana apices." Development 126, no. 9 (May 1, 1999): 1879–89. http://dx.doi.org/10.1242/dev.126.9.1879.
Повний текст джерелаАнотація:
Plasmodesmata provide symplastic continuity linking individual plant cells. However, specialized cells may be isolated, either by the absence of plasmodesmata or by down regulation of the cytoplasmic flux through these channels, resulting in the formation of symplastic domains. Maintenance of these domains may be essential for the co-ordination of growth and development. While cells in the center of the meristem divide slowly and remain undifferentiated, cells on the meristem periphery divide more frequently and respond to signals determining organ fate. Such symplastic domains were visualized within shoot apices of Arabidopsis, by monitoring fluorescent symplastic tracers (HPTS: 8-hydroxypyrene 1,3,6 trisulfonic acid and CF: carboxy fluorescein). Tracers were loaded through cut leaves and distributed throughout the whole plant. Confocal laser scanning microscopy on living Arabidopsis plants indicates that HPTS moves via the vascular tissue from leaves to the apex where the tracer exits the phloem and moves symplastically into surrounding cells. The distribution of HPTS was monitored in vegetative apices, and just prior to, during, and after the switch to production of flowers. The apices of vegetative plants loaded with HPTS had detectable amounts of tracer in the tunica layer of the meristem and in very young primordia, whereas the corpus of the meristem excluded tracer uptake. Fluorescence signal intensity decreased prior to the onset of flowering. Moreover, at approximately the time the plants were committed to flowering, HPTS was undetectable in the inflorescence meristem or young primordia. Later in development, after several secondary inflorescences and mature siliques appeared, inflorescence apices again showed tracer loading at levels comparable to that of vegetative apices. Thus, analysis of fluorescent tracer movement via plasmodesmata reveals there is distinct temporal and spatial regulation of symplastic domains at the apex, dependent on the developmental stage of the plant.
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Chalaux-Clergue, Thomas, Rémi Bizeul, Pedro V. G. Batista, Núria Martínez-Carreras, J. Patrick Laceby, and Olivier Evrard. "Sensitivity of source sediment fingerprinting to tracer selection methods." SOIL 10, no. 1 (February 13, 2024): 109–38. http://dx.doi.org/10.5194/soil-10-109-2024.
Повний текст джерелаАнотація:
Abstract. In a context of accelerated soil erosion and sediment supply to water bodies, sediment fingerprinting techniques have received an increasing interest in the last 2 decades. The selection of tracers is a particularly critical step for the subsequent accurate prediction of sediment source contributions. To select tracers, the most conventional approach is the three-step method, although, more recently, the consensus method has also been proposed as an alternative. The outputs of these two approaches were compared in terms of identification of conservative properties, tracer selection, modelled contributions and performance on a single dataset. As for the three-step method, several range test criteria were compared, along with the impact of the discriminant function analysis (DFA). The dataset was composed of tracer properties analysed in soil (three potential sources; n = 56) and sediment core samples (n = 32). Soil and sediment samples were sieved to 63 µm and analysed for organic matter, elemental geochemistry and diffuse visible spectrometry. Virtual mixtures (n = 138) with known source proportions were generated to assess model accuracy of each tracer selection method. The Bayesian un-mixing model MixSIAR was then used to predict source contributions on both virtual mixtures and actual sediments. The different methods tested in the current research can be distributed into three groups according to their sensitivity to the conservative behaviour of properties, which was found to be associated with different predicted source contribution tendencies along the sediment core. The methods selecting the largest number of tracers were associated with a dominant and constant contribution of forests to sediment. In contrast, the methods selecting the lowest number of tracers were associated with a dominant and constant contribution of cropland to sediment. Furthermore, the intermediate selection of tracers led to more balanced contributions of both cropland and forest to sediments. The prediction of the virtual mixtures allowed us to compute several evaluation metrics, which are generally used to support the evaluation of model accuracy for each tracer selection method. However, strong differences or the absence of correspondence were observed between the range of predicted contributions obtained for virtual mixtures and those values obtained for actual sediments. These divergences highlight the fact that evaluation metrics obtained for virtual mixtures may not be directly transferable to models run for actual samples and must be interpreted with caution to avoid over-interpretation or misinterpretation. These divergences may likely be attributed to the occurrence of a not (fully) conservative behaviour of potential tracer properties during erosion, transport and deposition processes, which could not be fully reproduced when generating the virtual mixtures with currently available methods. Future research should develop novel metrics to quantify the conservative behaviour of tracer properties during erosion and transport processes. Furthermore, new methods should be designed to generate virtual mixtures closer to reality and to better evaluate model accuracy. These improvements would contribute to the development of more reliable sediment fingerprinting techniques, which are needed to better support the implementation of effective soil and water conservation measures at the catchment scale.
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Wagner, Isabella C. "The Integration of Distributed Memory Traces." Journal of Neuroscience 36, no. 42 (October 19, 2016): 10723–25. http://dx.doi.org/10.1523/jneurosci.2344-16.2016.
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Thompson, Richard F. "Are memory traces localized or distributed?" Neuropsychologia 29, no. 6 (January 1991): 571–82. http://dx.doi.org/10.1016/0028-3932(91)90011-v.
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Meddah, Ishak H. A., and Nour El Houda REMIL. "Parallel and Distributed Pattern Mining." International Journal of Rough Sets and Data Analysis 6, no. 3 (July 2019): 1–17. http://dx.doi.org/10.4018/ijrsda.2019070101.
Повний текст джерелаАнотація:
The treatment of large data is difficult and it looks like the arrival of the framework MapReduce is a solution of this problem. This framework can be used to analyze and process vast amounts of data. This happens by distributing the computational work across a cluster of virtual servers running in a cloud or a large set of machines. Process mining provides an important bridge between data mining and business process analysis. Its techniques allow for extracting information from event logs. Generally, there are two steps in process mining, correlation definition or discovery and the inference or composition. First of all, their work mines small patterns from log traces. Those patterns are the representation of the traces execution from a log file of a business process. In this step, the authors use existing techniques. The patterns are represented by finite state automaton or their regular expression; and the final model is the combination of only two types of different patterns whom are represented by the regular expressions (ab)* and (ab*c)*. Second, they compute these patterns in parallel, and then combine those small patterns using the Hadoop framework. They have two steps; the first is the Map Step through which they mine patterns from execution traces, and the second one is the combination of these small patterns as a reduce step. The results show that their approach is scalable, general and precise. It minimizes the execution time by the use of the Hadoop framework.
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Quarles, Robert P., Mark A. Mintun, Kenneth B. Larson, Joanne Markham, Ann Mary MacLeod, and Marcus E. Raichle. "Measurement of Regional Cerebral Blood Flow with Positron Emission Tomography: A Comparison of [15O]Water to [11C]Butanol with Distributed-Parameter and Compartmental Models." Journal of Cerebral Blood Flow & Metabolism 13, no. 5 (September 1993): 733–47. http://dx.doi.org/10.1038/jcbfm.1993.94.
Повний текст джерелаАнотація:
To further our understanding of the best way to measure regional CBF with positron emission tomography (PET), we directly compared two candidate tracers ([15O]water and [11C]butanol, administered intravenously) and two popular implementations of the one-compartment (IC) model: the autoradiographic implementation representing a single PET measurement of tissue radioactivity over 1 min and a dynamic implementation representing a sequence of measurements of tissue radioactivity over 200 s. We also examined the feasibility of implementing a more realistic, and thus more complex, distributed-parameter (DP) model by assigning fixed values for all of its parameters other than CBF and tracer volume of distribution ( Vd), a requirement imposed by the low temporal resolution and statistical quality of PET data. The studies were performed in three normal adult human subjects during paired rest and visual stimulation. In each subject seven regions of interest (ROIs) were selected, one of which was the primary visual cortex. The corresponding ROI were anatomically equivalent in the three subjects. Regional CBF, Vd, tracer arrival delay, and dispersion were estimated for the dynamic data curves. A total of 252 parameter sets were estimated. With [11C]butanol both implementations of the IC model provided similar results ( r = 0.97). Flows estimated using the 1C models were lower (p < 0.01) with [15O]water than with [11C]butanol. In comparison with the IC model, the constrained version of the DP used in these studies performed inadequately, overestimating high flow and underestimating low flow with both tracers, possibly as the result of the necessity of assigning fixed values for all of its parameters other than CBF and Vd.
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Stegmayr, Carina, Antje Willuweit, Philipp Lohmann, and Karl-Josef Langen. "O-(2-[18F]-Fluoroethyl)-L-Tyrosine (FET) in Neurooncology: A Review of Experimental Results." Current Radiopharmaceuticals 12, no. 3 (October 1, 2019): 201–10. http://dx.doi.org/10.2174/1874471012666190111111046.
Повний текст джерелаАнотація:
In recent years, PET using radiolabelled amino acids has gained considerable interest as an additional tool besides MRI to improve the diagnosis of cerebral gliomas and brain metastases. A very successful tracer in this field is O-(2-[18F]fluoroethyl)-L-tyrosine (FET) which in recent years has replaced short-lived tracers such as [11C]-methyl-L-methionine in many neuro-oncological centers in Western Europe. FET can be produced with high efficiency and distributed in a satellite concept like 2- [18F]fluoro-2-deoxy-D-glucose. Many clinical studies have demonstrated that FET PET provides important diagnostic information regarding the delineation of cerebral gliomas for therapy planning, an improved differentiation of tumor recurrence from treatment-related changes and sensitive treatment monitoring. In parallel, a considerable number of experimental studies have investigated the uptake mechanisms of FET on the cellular level and the behavior of the tracer in various benign lesions in order to clarify the specificity of FET uptake for tumor tissue. Further studies have explored the effects of treatment related tissue alterations on tracer uptake such as surgery, radiation and drug therapy. Finally, the role of blood-brain barrier integrity for FET uptake which presents an important aspect for PET tracers targeting neoplastic lesions in the brain has been investigated in several studies. Based on a literature research regarding experimental FET studies and corresponding clinical applications this article summarizes the knowledge on the uptake behavior of FET, which has been collected in more than 30 experimental studies during the last two decades and discusses the role of these results in the clinical context.
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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.
Повний текст джерелаАнотація:
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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Wu, Qi Meng, Ke Xie, Ming Fa Zhu, Li Min Xiao, and Li Ruan. "DMFSsim: A Distributed Metadata File System Simulator." Applied Mechanics and Materials 241-244 (December 2012): 1556–61. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.1556.
Повний текст джерелаАнотація:
Parallel file systems deploy multiple metadata servers to distribute heavy metadata workload from clients. With the increasing number of metadata servers, metadata-intensive operations are facing some problems related with collaboration among them, compromising the performance gain. Consequently, a file system simulator is very helpful to try out some optimization ideas to solve these problems. In this paper, we propose DMFSsim to simulate the metadata-intensive operations on large-scale distributed metadata file systems. DMFSsim can flexibly replay traces of multiple metadata operations, support several commonly used metadata distribution algorithms, simulate file system tree hierarchy and underlying disk blocks management mechanism in real systems. Extensive simulations show that DMFSsim is capable of demonstrating the performance of metadata-intensive operations in distributed metadata file system.
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Phillips, C. B., and D. J. Jerolmack. "Dynamics and mechanics of tracer particles." Earth Surface Dynamics Discussions 2, no. 1 (June 11, 2014): 429–76. http://dx.doi.org/10.5194/esurfd-2-429-2014.
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Abstract. Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that: measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement lengths scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modelling framework based on momentum conservation at the grain scale. Tracer displacement shows a weak correlation with particle size at the individual flood scale, however cumulative travel distance begins to show an inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the step-pool and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.
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Phillips, C. B., and D. J. Jerolmack. "Dynamics and mechanics of bed-load tracer particles." Earth Surface Dynamics 2, no. 2 (December 19, 2014): 513–30. http://dx.doi.org/10.5194/esurf-2-513-2014.
Повний текст джерелаАнотація:
Abstract. Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.
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Wagner, I. A., M. Lindenbaum, and A. M. Bruckstein. "Distributed covering by ant-robots using evaporating traces." IEEE Transactions on Robotics and Automation 15, no. 5 (1999): 918–33. http://dx.doi.org/10.1109/70.795795.
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Tretyakov, Evgeniy, Alexey Artamonov, Maria Grigorieva, Alexei Klimentov, Shawn McKee, and Ilija Vukotic. "TRACER (TRACe route ExploRer): A tool to explore OSG/WLCG network route topologies." International Journal of Modern Physics A 36, no. 05 (February 20, 2021): 2130005. http://dx.doi.org/10.1142/s0217751x21300052.
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The experiments at the Large Hadron Collider (LHC) rely upon a complex distributed computing infrastructure (WLCG) consisting of hundreds of individual sites worldwide at universities and national laboratories, providing about half a billion computing job slots and an exabyte of storage interconnected through high speed networks. Wide Area Networking (WAN) is one of the three pillars (together with computational resources and storage) of LHC computing. More than 5 PB/day are transferred between WLCG sites. Monitoring is one of the crucial components of WAN and experiments operations. In the past years all experiments have invested significant effort to improve monitoring and integrate networking information with data management and workload management systems. All WLCG sites are equipped with perfSONAR servers to collect a wide range of network metrics. We will present the latest development to provide the 3D force directed graph visualization for data collected by perfSONAR. The visualization package allows site admins, network engineers, scientists and network researchers to better understand the topology of our Research and Education networks and it provides the ability to identify nonreliable or/and nonoptimal network paths, such as those with routing loops or rapidly changing routes.
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Seo, Woong, Sanghun Park, and Insung Ihm. "Efficient Ray Tracing of Large 3D Scenes for Mobile Distributed Computing Environments." Sensors 22, no. 2 (January 10, 2022): 491. http://dx.doi.org/10.3390/s22020491.
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Cluster computing has attracted much attention as an effective way of solving large-scale problems. However, only a few attempts have been made to explore mobile computing clusters that can be easily built using commodity smartphones and tablets. To investigate the possibility of mobile cluster-based rendering of large datasets, we developed a mobile GPU ray tracer that renders nontrivial 3D scenes with many millions of triangles at an interactive frame rate on a small-scale mobile cluster. To cope with the limited processing power and memory space, we first present an effective 3D scene representation scheme suitable for mobile GPU rendering. Then, to avoid performance impairment caused by the high latency and low bandwidth of mobile networks, we propose using a static load balancing strategy, which we found to be more appropriate for the vulnerable mobile clustering environment than a dynamic strategy. Our mobile distributed rendering system achieved a few frames per second when ray tracing 1024 × 1024 images, using only 16 low-end smartphones, for large 3D scenes, some with more than 10 million triangles. Through a conceptual demonstration, we also show that the presented rendering scheme can be effectively explored for augmenting real scene images, captured or perceived by augmented and mixed reality devices, with high quality ray-traced images.
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Meddah, Ishak H. A., and Khaled Belkadi. "Parallel Distributed Patterns Mining Using Hadoop MapReduce Framework." International Journal of Grid and High Performance Computing 9, no. 2 (April 2017): 70–85. http://dx.doi.org/10.4018/ijghpc.2017040105.
Повний текст джерелаАнотація:
The treatment of large data is proving more difficult in different axes, but the arrival of the framework MapReduce is a solution of this problem. With it we can analyze and process vast amounts of data. It does this by distributing the computational work across a cluster of virtual servers running in a cloud or large set of machines while process mining provides an important bridge between data mining and business process analysis. The process mining techniques allow for extracting information from event logs. In general, there are two steps in process mining: correlation definition or discovery and process inference or composition. Firstly, the authors' work consists to mine small patterns from a log traces. Those patterns are the representation of the traces execution from a log file of a business process. In this step, they use existing techniques. The patterns are represented by finite state automaton or their regular expression. The final model is the combination of only two types of small patterns whom are represented by the regular expressions (ab)* and (ab*c)*. Secondly, the authors compute these patterns in parallel, and then combine those small patterns using the MapReduce framework. They have two parties: the first is the Map Step in which they mine patterns from execution traces; the second is the combination of these small patterns as reduce step. The authors' results are promising in that they show that their approach is scalable, general, and precise. It minimizes the execution time by the use of the MapReduce framework.
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Millán, Saúl. "La domesticación de las almas: El nahualismo y sus variaciones / The domestication of souls: Nahualism and its variations." Revista Trace, no. 82 (July 31, 2022): 12. http://dx.doi.org/10.22134/trace.82.2022.839.
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En Mesoamérica, donde la domesticación de animales se desarrolla tan solo al inicio del periodo colonial, los vínculos entre los hombres y los espíritus han estado sujetos a una trayectoria divergente que supone concepciones opuestas sobre el mundo animal. Aunque estas diferencias son relativas, permiten vislumbrar dos formas alternativas de concebir el nahualismo, cuyas funciones suelen distribuirse entre la depredación de las almas y la protección de los hombres. A través del novedoso mundo de la ganadería, el artículo examina estas variaciones entre diversos pueblos mesoamericanos, a fin de comparar sus diferencias y sus similitudes.Abstract: In Middleamerica, where the domestication of animals takes place only at the beginning of the colonial period, the links between the men and the spirits have been subject to a different process involving opposed conceptions about the animal world. Although these differences are relative, they allow to see two alternative ways of conceiving the nahualismo, whose functions are usually distributed between the depredation of the souls and the protection of men. Through the innovative world of livestock, the article examines these variations between different Mesoamerican peoples, in order to compare their differences and their similarities.Keywords: nahualismo; shamanism; domestication; livestock; predation.Résumé : En Mésoamérique, où la domestication des animaux a lieu uniquement au début de la période coloniale, les liens entre les hommes et les esprits ont été soumis à un procés divergent qui impliques des conceptions opposées sur le monde animal. Bien que ces différences sont relatifs, nous permettent d’apercevoir deux façons de concevoir le nahualismo, dont les fonctions sont généralement distribuées entre la déprédation des âmes et la protection des hommes. À travers le monde innovateur de l’élevage, l’article examine ces variations entre les différents peuples mésoaméricains, afin de comparer leurs différences et leurs similitudes.Mots-clés : nahualisme ; chamanisme ; domestication ; élevage ; prédation.
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Yamba, Zoida Clara, Adel Monette Rivera, Richard Vincent Misa, Benjamin Mahinay, and Iris Mae C. Mendoza. "EMPLOYABILITY INDEX OF COMPUTER SCIENCE GRADUATES." International Journal of Education and Social Science Research 06, no. 05 (2023): 390–97. http://dx.doi.org/10.37500/ijessr.2023.6525.
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The study sought to determine the employability of Computer Sciences graduates from a private school in Davao del Norte Philippines. The researchers utilized a survey questionnaire which were distributed to the graduates. The instrument used for data gathering was based on the Graduate Tracer Study designed by Commission on Higher Education. A total of 82 graduates from year 2015-2019 were identified as participants and 53 (64.63%) were successfully traced. Results show that most graduates were able find a job in less than 6 months. Moreover, the jobs landed by the graduates were diverse wherein graduates opted to work jobs that are not related to Computer Science discipline. Recommendations were drawn from the results which can be used equip graduating students with the necessary skills demanded in the Computer Science industry
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Goresky, C. A., G. G. Bach, and A. J. Schwab. "Distributed-in-space product formation in vivo: linear kinetics." American Journal of Physiology-Heart and Circulatory Physiology 264, no. 6 (June 1, 1993): H2007—H2028. http://dx.doi.org/10.1152/ajpheart.1993.264.6.h2007.
Повний текст джерелаАнотація:
Distributed-in-space conversion of precursor substrate to product within an organ is explored when all formed product is released into the bloodstream. When precursor removal kinetics are linear (conversion occurring proportionately to concentration) and the process is uniformly distributed along the length, exponentially decreasing concentration profiles for precursor result. The vascular profile for product rises in complementary fashion; the sum of precursor and product is constant along the length. Symmetric permeability barriers are found to produce concentration stepdowns of precursor from blood to tissue and, for product, converse stepdowns from tissue to blood. Tracer precursor, introduced as an impulse input, within this steady state, is converted to product, details varying with the number of barriers. Nevertheless, a particular common feature is found in the solutions. The analytic expression for locally generated tracer product is found, in each case, to contain the impulse response to tracer product introduced at the origin. Therefore, to simplify experimental analysis and to superpose a set of constraints on computational approaches to parameter estimation, one should introduce, simultaneously with tracer precursor, tracer product labeled in an identifiably different manner.
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Bai, Hao, Zhengzheng Yang, Jiangfeng Hu, Yang Mu, and Xiaolong Su. "Multi-source Distributed Radar-Infrared Track Association Method Based on Spatial Geometry." Journal of Physics: Conference Series 2558, no. 1 (August 1, 2023): 012004. http://dx.doi.org/10.1088/1742-6596/2558/1/012004.
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Abstract To improve the accuracy of track association between radar and infrared sensors, a multi-source distributed radar infrared track association method based on spatial geometry is proposed. This method uses rough association and fine association to judge the correlation between radar and infrared tracks. Rough correlation calculates the statistical distance through the weighted norm of the redundant information difference between radar and infrared tracks and determines the rough association threshold by hypothesis testing to obtain multiple radar tracks successfully correlated with infrared tracks. Fine association abstracts the radar and infrared tracks in the rough association into points and lines in space respectively. Through the method of spatial analytic geometry, the distance between the spatial points and lines is calculated, and the association results of radar and infrared tracks are obtained based on the spatial distance. The simulation results show that the performance of the track association method based on spatial geometry is better than that of the nearest neighbor method and weighted track association method in the application of distributed multi-source radar and infrared track association.
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Fountain, Andrew G. "Geometry and flow conditions of subglacial water at South Cascade Glacier, Washington State, U.S.A.; an analysis of tracer injections." Journal of Glaciology 39, no. 131 (1993): 143–56. http://dx.doi.org/10.1017/s0022143000015793.
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Abstract Tracers were injected into South Cascade Glacier to determine the flow condition and geometry of the subglacial water system. Results indicate that two distinct drainage basins on the glacier feed the two main streams flowing from the glacier. In the largest basin, two parallel drainage networks exist, one englacial and the other subglacial. The englacial system is an arboresecent network of conduits, whereas the subglacial system is a distributed flow system. Both systems connect to a single subglacial conduit which appears as a stream at the glacier’s terminus. The comparison between the travel time of the tracers and stream discharge indicated that the single conduit was pressurized in July and partly filled in August and September. To estimate the flow geometry (e.g. path length, flow depth and velocity), the advection-diffusion equation was formulated to express the water velocity as a function of water depth. Longitudinal dispersion of the tracer was calculated from the shear in longitudinal water velocity. Results indicate that the flow is very wide compared to its depth and that the path is sinuous. The estimated flow speed in the conduits is an order of magnitude larger than the measured speed through the glacier, indicating that other flow processes, probably englacial, route the water much more slowly. The other, smaller, basin drains the water from the surface to the subglacial distributed flow system. Based on the travel time of the individual concentration peaks, the water could be flowing through a linked-cavity system or interconnected bands of highly permeable debris separated by zones of less permeability.
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Hoffman, K. L. "Coordinated Reactivation of Distributed Memory Traces in Primate Neocortex." Science 297, no. 5589 (September 20, 2002): 2070–73. http://dx.doi.org/10.1126/science.1073538.
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Merz, Stephan. "Validating Traces of Distributed Programs against High-Level Specifications." Electronic Proceedings in Theoretical Computer Science 399 (March 27, 2024): 3. http://dx.doi.org/10.4204/eptcs.399.2.
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Goresky, C. A., G. G. Bach, and A. J. Schwab. "Distributed-in-space product formation in vivo: enzymic kinetics." American Journal of Physiology-Heart and Circulatory Physiology 264, no. 6 (June 1, 1993): H2029—H2050. http://dx.doi.org/10.1152/ajpheart.1993.264.6.h2029.
Повний текст джерелаАнотація:
Distributed-in-space Michaelis-Menten enzymic conversion of precursor substrate to product within an organ is explored when all formed product is released into the bloodstream. In the nonlinear saturating enzymic case, length-wise precursor concentration profiles are found to vary from a falling exponential to a slowly declining linear profile, with rise in input concentration. The vascular profile for product rises in complimentary fashion; the sum of precursor and product is constant along the length. Symmetric permeability barriers produce stepdowns in precursor concentration from blood to tissue and, for product, converse stepdowns from tissue to blood are produced. Tracer precursor, introduced as an impulse input within this steady state, is converted to product with details of its distribution varying with the number of barriers for precursor. During this conversion, reversible tracer precursor association with enzyme leads to an enzymic space effect perceived as a saturating additional compartment, largest at tracer bulk levels, and decreasing with increase in underlying bulk concentration. While tracer product is not delayed by enzyme association, its outflow profile varies with the amount and location of enzyme, the enzymic rate constants, and the barriers for product between enzyme and the blood.
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Pumo, Dario, Francesco Alongi, Giuseppe Ciraolo, and Leonardo Noto. "Optical Methods for River Monitoring: A Simulation-Based Approach to Explore Optimal Experimental Setup for LSPIV." Water 13, no. 3 (January 20, 2021): 247. http://dx.doi.org/10.3390/w13030247.
Повний текст джерелаАнотація:
Recent advances in image-based methods for environmental monitoring are opening new frontiers for remote streamflow measurements in natural environments. Such techniques offer numerous advantages compared to traditional approaches. Despite the wide availability of cost-effective devices and software for image processing, these techniques are still rarely systematically implemented in practical applications, probably due to the lack of consistent operational protocols for both phases of images acquisition and processing. In this work, the optimal experimental setup for LSPIV based flow velocity measurements under different conditions is explored using the software PIVlab, investigating performance and sensitivity to some key factors. Different synthetic image sequences, reproducing a river flow with a realistic velocity profile and uniformly distributed floating tracers, are generated under controlled conditions. Different parametric scenarios are created considering diverse combinations of flow velocity, tracer size, seeding density, and environmental conditions. Multiple replications per scenario are processed, using descriptive statistics to characterize errors in PIVlab estimates. Simulations highlight the crucial role of some parameters (e.g., seeding density) and demonstrate how appropriate video duration, frame-rate and parameters setting in relation to the hydraulic conditions can efficiently counterbalance many of the typical operative issues (i.e., scarce tracer concentration) and improve algorithms performance.
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Obridko, V. N., V. V. Pipin, D. Sokoloff, and A. S. Shibalova. "Solar large-scale magnetic field and cycle patterns in solar dynamo." Monthly Notices of the Royal Astronomical Society 504, no. 4 (April 16, 2021): 4990–5000. http://dx.doi.org/10.1093/mnras/stab1062.
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ABSTRACT We compare spectra of the zonal harmonics of the large-scale magnetic field of the Sun using observation results and solar dynamo models. The main solar activity cycle as recorded in these tracers is a much more complicated phenomenon than the eigen solution of solar dynamo equations with the growth saturated by a back reaction of the dynamo-driven magnetic field on solar hydrodynamics. The nominal 11(22)-yr cycle as recorded in each mode has a specific phase shift varying from cycle to cycle; the actual length of the cycle varies from one cycle to another and from tracer to tracer. Both the observation and the dynamo model show an exceptional role of the axisymmetric ℓ5 mode. Its origin seems to be readily connected with the formation and evolution of sunspots on the solar surface. The results of observations and dynamo models show a good agreement for the low ℓ1 and ℓ3 modes. The results for these modes do not differ significantly for the axisymmetric and non-axisymmetric models. Our findings support the idea that the sources of the solar dynamo arise as a result of both the distributed dynamo processes in the bulk of the convection zone and the surface magnetic activity.
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Lochhead, Jeffrey J., Daniel J. Wolak, Michelle E. Pizzo, and Robert G. Thorne. "Rapid Transport within Cerebral Perivascular Spaces Underlies Widespread Tracer Distribution in the Brain after Intranasal Administration." Journal of Cerebral Blood Flow & Metabolism 35, no. 3 (March 2015): 371–81. http://dx.doi.org/10.1038/jcbfm.2014.215.
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The intranasal administration route is increasingly being used as a noninvasive method to bypass the blood—brain barrier because evidence suggests small fractions of nasally applied macromolecules may reach the brain directly via olfactory and trigeminal nerve components present in the nasal mucosa. Upon reaching the olfactory bulb (olfactory pathway) or brainstem (trigeminal pathway), intranasally delivered macromolecules appear to rapidly distribute within the brains of rodents and primates. The mechanisms responsible for this distribution have yet to be fully characterized. Here, we have used ex vivo fluorescence imaging to show that bulk flow within the perivascular space (PVS) of cerebral blood vessels contributes to the rapid central distribution of fluorescently labeled 3 and 10 kDa dextran tracers after intranasal administration in anesthetized adult rats. Comparison of tracer plasma levels and fluorescent signal distribution associated with the PVS of surface arteries and internal cerebral vessels showed that the intranasal route results in unique central access to the PVS not observed after matched intravascular dosing in separate animals. Intranasal targeting to the PVS was tracer size dependent and could be regulated by modifying nasal epithelial permeability. These results suggest cerebral perivascular convection likely has a key role in intranasal drug delivery to the brain.
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Kutkuhn, B., G. Georgescu, W. Mecklenbeck, A. Suatmadji, H. Vosberg, and Z. Szabö. "Parametrische Darstellung der Nierenfunktion mit 99mTC-Merkaptoazetyltriglyzin (MAG3)." Nuklearmedizin 28, no. 03 (1989): 73–83. http://dx.doi.org/10.1055/s-0038-1629473.
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99mTc-mercaptoacetyltriglycine (MAG3) has recently been introduced for imaging kidney function. Due to the much lower radiation dose per MBq, the total administered activity can be much higher than in the case of 131l-ortho-iodo-hippurate (OIH). The improved counting statistics make this tracer useful for parametric imaging of the kidneys. To investigate this potential of MAG3, its kinetics was compared with that of the reference tracer OIH in 38 patients. Parameters of extrarenal tracer kinetics such as the distribution volumes, the whole-body elimination times and the clearance rates showed a good correlation; however, the clearance rate of MAG3 was always lower than that of OIH. The intrarenal kinetics was investigated using the transfer function which was calculated by deconvolution analysis of the renographic curves. Parameters of the transfer function such as the amplitude, extraction fraction and mean transport time demonstrated a high correlation between the two tracers. Since MAG3 seems to be suitable for parametric imaging of kidney function, parametric images of perfusion, uptake, extraction and transport times were calculated by deconvolution analysis of the MAG3 pixel-renograms in various renal disorders. The parameters were distributed homogenously throughout the parenchyma of normal kidneys. In a kidney with a hemodynamically significant renal artery stenosis the perfusion parameter was decreased and the time parameter was prolonged. Further examples of a renal graft acute tubular necrosis, an obstructive uropathy, an obstructive nephropathy and of a horse-shoe kidney demonstrate that the parametric images are useful for quantitative investigation of regional renal function.
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Paulau, Stanislau, and Thomas F. O'Meara. "A Search for Traces." Philosophy and Theology 32, no. 1 (2020): 283–89. http://dx.doi.org/10.5840/philtheol2021713135.
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This article describes the presence of Karl Rahner in philosophical, theological, and propagandistic works published in the Soviet Union or published outside the USSR and distributed within it. Some references to Rahner appeared in self-published works without the approval of Soviet censors. These included the works of Orthodox theologians such as Sergej Želudkov and Alexander Men’. Other references to Rahner appeared in anti-religious propaganda and in works by Marxist-Leninist philosophers such as Bronislavas Juozas Kuzmickas. By 1992, the year following the collapse of the USSR, Rahner began to receive a more favorable reception in the writing of philosophers such as Elena B. Timerman.
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Kam, Dongjae, and Akhil Datta-Gupta. "Streamline-Based Transport Tomography With Distributed Water Arrival Times." SPE Reservoir Evaluation & Engineering 19, no. 02 (March 6, 2016): 265–77. http://dx.doi.org/10.2118/169105-pa.
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Summary Traditional history matching involves calibration of reservoir models by use of well response such as production or tracer data aggregated during multiple producing intervals. With the advent of novel tracer technologies, we now can obtain distributed water or tracer arrival-time information along the length of horizontal or vertical wellbores. This provides significantly improved flow resolution for detailed reservoir characterization through inversion of distributed water or tracer arrival times in a manner analogous to travel tomography in geophysics. In this paper, we present an efficient approach to incorporate novel tracer-surveillance data and distributed water arrival-time information during history matching of high-resolution reservoir models. Our approach relies on a streamline-based work flow that analytically computes the sensitivity of water-arrival times with respect to reservoir heterogeneity, specifically porosity and permeability variations. The sensitivities relate the changes in arrival time to small perturbations in reservoir properties and can be obtained efficiently with the streamline-based approach with a single flow simulation. This makes the approach particularly well-suited for high-resolution reservoir characterization. Finally, the sensitivities are used in conjunction with an iterative inversion algorithm to update the reservoir models with existing and proven techniques from seismic tomography. The power and utility of our proposed approach are demonstrated with both synthetic and field examples. These include the SPE benchmark Brugge field case and an offshore field in North America. Compared with traditional history-matching techniques, the proposed tomographic approach is shown to result in improved resolution of heterogeneity through matching of water-arrival time at individual completions in addition to the aggregated well-production response. This results in improved performance predictions and better identification of bypassed oil for infill targeting and enhanced-oil-recovery (EOR) applications.
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Croteau, David, Stuart Walbridge, Paul F. Morrison, John A. Butman, Alexander O. Vortmeyer, Dennis Johnson, Edward H. Oldfield, and Russell R. Lonser. "Real-time in vivo imaging of the convective distribution of a low-molecular-weight tracer." Journal of Neurosurgery 102, no. 1 (January 2005): 90–97. http://dx.doi.org/10.3171/jns.2005.102.1.0090.
Повний текст джерелаАнотація:
Object. Convection-enhanced delivery (CED) is increasingly used to distribute therapeutic agents to locations in the central nervous system. The optimal application of convective distribution of various agents requires the development of imaging tracers to monitor CED in vivo in real time. The authors examined the safety and utility of an iodine-based low-molecular-weight surrogate tracer for computerized tomography (CT) scanning during CED. Methods. Various volumes (total volume range 90–150 µ1) of iopamidol (MW 777 D) were delivered to the cerebral white matter of four primates (Macaca mulatta) by using CED. The distribution of this imaging tracer was determined by in vivo real-time and postinfusion CT scanning (≤ 5 days after infusion [one animal]) as well as by quantitative autoradiography (14C-sucrose [all animals] and 14C-dextran [one animal]), and compared with a mathematical model. Clinical observation (≤ 5 months) and histopathological analyses were used to evaluate the safety and toxicity of the tracer delivery. Real-time CT scanning of the tracer during infusion revealed a clearly definable region of perfusion. The volume of distribution (Vd) increased linearly (r2 = 0.97) with an increasing volume of infusion (Vi). The overall Vd/Vi ratio was 4.1 ± 0.7 (mean ± standard deviation) and the distribution of infusate was homogeneous. Quantitative autoradiography confirmed the accuracy of the imaged distribution for a small (sucrose, MW 359 D) and a large (dextran, MW 70 kD) molecule. The distribution of the infusate was identifiable up to 72 hours after infusion. There was no clinical or histopathological evidence of toxicity in any animal. Conclusions. Real-time in vivo CT scanning of CED of iopamidol appears to be safe, feasible, and suitable for monitoring convective delivery of drugs with certain features and low infusion volumes.
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TSAI, JEFFREY J. P., YAO-DONG BI, and STEVE J. H. YANG. "A SYSTEM FOR VISUALIZING AND DEBUGGING DISTRIBUTED REAL-TIME SYSTEMS WITH MONITORING SUPPORT." International Journal of Software Engineering and Knowledge Engineering 06, no. 03 (September 1996): 355–400. http://dx.doi.org/10.1142/s0218194096000168.
Повний текст джерелаАнотація:
Based on system execution traces, this paper presents a dynamic approach for visualizing and debugging timing constraint violations occurring in distributed real-time systems. The system execution traces used for visualization and debugging are collected during the execution of a target program in such a way that its run-time behavior is not interfered with. This is made possible by our non-interference distributed real-time monitoring system which is capable of collecting system’s run-time traces by monitoring and fetching the data passing through the internal buses of a target system. After the run-time data has been collected, the visualization and debugging activities then proceeded. The timing behavior of a target program is visualized as two graphs—the Colored Process Interaction Graph (CPIG) and the Dedicated Colored Process Interaction Graph (DCPIG). The CPIG depicts the timing behavior of a target program by graphically representing interprocess relationships during their communication and synchronization. The DCPIG can reduce visualization and debugging complexity by focusing on the portion of a target program which has direct or indirect correspondence with an imposed timing constraint. With the help of the CPIG and the DCPIG, a timing analysis method is used for computing the system-related timing statistics and analyzing the causes of timing constraint violations. A visualization and debugging system, called VDS, has been implemented using OpenWindows on Sun-4’s/UNIX workstations.
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Abbes, Samy, and Vincent Jugé. "Uniform generation of infinite traces." Pure Mathematics and Applications 30, no. 1 (June 1, 2022): 1–7. http://dx.doi.org/10.2478/puma-2022-0002.
Повний текст джерелаАнотація:
Abstract We introduce an algorithm for the uniform generation of infinite traces, i.e., infinite words up to commutation of some letters. The algorithm outputs on-the-fly approximations of a theoretical infinite trace, the latter being distributed according to the exact uniform probability measure. The average size of the approximation grows linearly with the time of execution of the algorithm, provided that some–costly–precomputations have been done.
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Sun, Yeran, Yinming Ren, and Xuan Sun. "Uber Movement Data: A Proxy for Average One-way Commuting Times by Car." ISPRS International Journal of Geo-Information 9, no. 3 (March 24, 2020): 184. http://dx.doi.org/10.3390/ijgi9030184.
Повний текст джерелаАнотація:
Recently, Uber released datasets named Uber Movement to the public in support of urban planning and transportation planning. To prevent user privacy issues, Uber aggregates car GPS traces into small areas. After aggregating car GPS traces into small areas, Uber releases free data products that indicate the average travel times of Uber cars between two small areas. The average travel times of Uber cars in the morning peak time periods on weekdays could be used as a proxy for average one-way car-based commuting times. In this study, to demonstrate usefulness of Uber Movement data, we use Uber Movement data as a proxy for commuting time data by which commuters’ average one-way commuting time across Greater Boston can be figured out. We propose a new approach to estimate the average car-based commuting times through combining commuting times from Uber Movement data and commuting flows from travel survey data. To further demonstrate the applicability of the commuting times estimated by Uber movement data, this study further measures the spatial accessibility of jobs by car by aggregating place-to-place commuting times to census tracts. The empirical results further uncover that 1) commuters’ average one-way commuting time is around 20 min across Greater Boston; 2) more than 75% of car-based commuters are likely to have a one-way commuting time of less than 30 min; 3) less than 1% of car-based commuters are likely to have a one-way commuting time of more than 60 min; and 4) the areas suffering a lower level of spatial accessibility of jobs by car are likely to be evenly distributed across Greater Boston.
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Li, Song, Yongmei Cheng, Huibin Wang, and Shibo Gao. "Distributed Multisensor Multitarget Tracking Algorithm with Time-Offset Registration." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 38, no. 4 (August 2020): 797–805. http://dx.doi.org/10.1051/jnwpu/20203840797.
Повний текст джерелаАнотація:
In multisensor systems, the signal processing delay, measurement acquisition delay, and other factors will lead to imprecisely time-stamped measurements, namely, the problem of time-offset. To deal with the measurement time offsets in distributed multisensor systems, a distributed multisensor multitarget tracking algorithm with time-offset registration is proposed. The local processors track multiple targets in the presence of false alarms and missed detections based on the joint probabilistic data association (JPDA) algorithm and the extended Kalman filter (EKF), providing the time-biased local tracks. In the global processor, in allusion to the global track accuracy degradation introduced by the time offsets of local tracks, the equivalent measurements are firstly constructed based on local tracks by using the inverse Kalman filter. The pseudo-measurement equation of time offset for constant velocity targets is derived and the pseudo-measurement calculation method is presented. Then, the pseudo-measurement based relative time-offset estimation algorithm is presented, by using the recursive least squares estimation (RLSE) and the Kalman filter (KF) to jointly estimate the state in space and time domains, respectively. Finally, a framework of distributed multisensor multitarget tracking with time-offset registration is presented, where the time-varying relative time-offset estimation and compensation, 'equivalent measurement to global track' association, and global track update are included. Simulations for multisensor multitarget tracking in the presence of false alarms and missed detections are conducted, demonstrating that the present algorithm effectively improves the accuracy of fused global tracks.
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Lamarche-Perrin, Robin, Lucas M. Schnorr, Jean-Marc Vincent, and Yves Demazeau. "Agrégation de traces d’exécution pour la visualisation de grands systèmes distribués." Techniques et sciences informatiques 33, no. 5-6 (August 30, 2014): 465–98. http://dx.doi.org/10.3166/tsi.33.465-498.
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Naldrett, Dana L. "Locomotion and feeding traces in Champlain Sea subaqueous outwash deposits near Ottawa, Canada." Canadian Journal of Earth Sciences 27, no. 11 (November 1, 1990): 1495–503. http://dx.doi.org/10.1139/e90-159.
Повний текст джерелаАнотація:
Locomotion and feeding traces (repichnia and fodichnia) observed on bedding planes of rhythmically bedded subaqueous outwash deposits in the Brazeau sand pit, Nepean, Ontario, Canada, are the first bedding-plane traces described in detail from the western Champlain Sea. The Planolites–Palaeophycus-like and Taenidium-like traces are cylindrical with circular cross section, smooth sided, unlined, sinuous, sometimes branching, and sometimes meniscate. Organisms producing the traces are tentatively identified as errant polychaetes or nemerteans. The enclosing sediments are rhythmic couplets of alternating fine sand and silt layers overlain by silty clay and fine–medium silt layers. The occurrence of traces within the uppermost portion of the coarse unit, and within the coarser, upper portion of the overlying fine unit, and the rhythmic alternation of coarse and fine layers suggest these deposits may be varves. The traces formed during the more biologically suitable summer months but were preserved only during the latter portion of the summer. Traces are distributed on bedding planes in close association with bedforms and show a high correlation with the substrate and possibly the hydrodynamic regime. This is interpreted as indicating a strong preference in feeding behaviour. The presence of traces in the subaqueous outwash environment necessitates rethinking of the depositional environment to include the presence of errant polychaetes, nemerteans or similar organisms, and the lower life-forms such as epontic algae and bacteria on which they live.