569 research outputs found

    Distortion-Memory Tradeoffs in Cache-Aided Wireless Video Delivery

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    Mobile network operators are considering caching as one of the strategies to keep up with the increasing demand for high-definition wireless video streaming. By prefetching popular content into memory at wireless access points or end user devices, requests can be served locally, relieving strain on expensive backhaul. In addition, using network coding allows the simultaneous serving of distinct cache misses via common coded multicast transmissions, resulting in significantly larger load reductions compared to those achieved with conventional delivery schemes. However, prior work does not exploit the properties of video and simply treats content as fixed-size files that users would like to fully download. Our work is motivated by the fact that video can be coded in a scalable fashion and that the decoded video quality depends on the number of layers a user is able to receive. Using a Gaussian source model, caching and coded delivery methods are designed to minimize the squared error distortion at end user devices. Our work is general enough to consider heterogeneous cache sizes and video popularity distributions.Comment: To appear in Allerton 2015 Proceedings of the 53rd annual Allerton conference on Communication, control, and computin

    The Neotethyan Sanandaj-Sirjan zone of Iran as an archetype for passive margin-arc transitions

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    The Sanandaj-Sirjan zone of Iran is a northwest trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. The zone contains the most extensive, best preserved record of key events in the formation and evolution of the Neotethys, from its birth in Late Paleozoic time through its demise during the mid-Tertiary collision of Arabia with Eurasia. The record includes rifting of continental fragments off of the northern margin of Gondwanaland, formation of facing passive continental margins, initiation of subduction along the northern margin, and progressive development of a continental magmatic arc. The latter two of these events are critical phases of the Wilson Cycle that, elsewhere in the world, are poorly preserved in the geologic record because of superimposed events. Our new synthesis reaffirms the similarity between this zone and various terranes to the north in Central Iran. Late Paleozoic rifting, preserved as A-type granites and accelerated subsidence, was followed by a phase of pronounced subsidence and shallow marine sedimentation in Permian through Triassic time, marking the formation and evolution of passive margins on both sides of the suture. Subduction and arc magmatism began in latest Triassic/Early Jurassic time, culminating at ~170 Ma. The extinction of arc magmatism in this zone, and its shift northeastward to form the subparallel Urumieh-Dokhtar arc, occurred diachronously along strike, in Late Cretaceous or Paleogene time. Post-Cretaceous uplift transformed the zone from a primarily marine borderland into a marine archipelago that persisted until mid-Tertiary time

    Comment on "Neotethyan subduction ignited the Iran arc and back-arc differently" by Shafaii Moghadam et al. (2020)

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    Shafaii Moghadam et al. (2020) contribute important new data on Late Cretaceous-Tertiary subduction- related magmatism in Iran, but their plate convergence model, wherein Neotethyan subduction begins in mid-Cretaceous time (c. 100 Ma), overlooks well established facts relating to the tectonic history of Neotethys, in regard to global plate reconstructions, paleolatitude data, the regional stratigraphy, geochronology and geochemistry, and metamorphic history. Based on their model, Neotethys subduction beneath Eurasia began at ~100 Ma, meaning that the Neotethys was spreading and bounded by opposing passive margins during Jurassic and Early Cretaceous time, for ~100 Ma prior to their proposed onset of Neotethyan convergence. Consequently, their subduction model contradicts (1) the Indian Ocean spreading history derived from magnetic anomalies; (2) continental paleolatitude data from paleomagnetism; (3) sedimentary and igneous evolution of the Mesozoic continental margins in Arabia and southern Asia, (4) the age and geochemistry of Jurassic igneous rocks in southernmost Eurasia; and (5) the preservation of Early to Middle Jurassic eclogite metamorphism and exhumation on the northern side of the Arabia-Eurasia suture. Reconciliation of each of these omissions and contradictions of their model would be welcome, and perhaps an advisory that readers may wish to evaluate their concept of Cretaceous subduction initiation with due circumspection

    Comment on "Neotethyan subduction ignited the Iran arc and back-arc differently" by Shafaii Moghadam et al. (2020)

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    Shafaii Moghadam et al. (2020) contribute important new data on Late Cretaceous-Tertiary subduction- related magmatism in Iran, but their plate convergence model, wherein Neotethyan subduction begins in mid-Cretaceous time (c. 100 Ma), overlooks well established facts relating to the tectonic history of Neotethys, in regard to global plate reconstructions, paleolatitude data, the regional stratigraphy, geochronology and geochemistry, and metamorphic history. Based on their model, Neotethys subduction beneath Eurasia began at ~100 Ma, meaning that the Neotethys was spreading and bounded by opposing passive margins during Jurassic and Early Cretaceous time, for ~100 Ma prior to their proposed onset of Neotethyan convergence. Consequently, their subduction model contradicts (1) the Indian Ocean spreading history derived from magnetic anomalies; (2) continental paleolatitude data from paleomagnetism; (3) sedimentary and igneous evolution of the Mesozoic continental margins in Arabia and southern Asia, (4) the age and geochemistry of Jurassic igneous rocks in southernmost Eurasia; and (5) the preservation of Early to Middle Jurassic eclogite metamorphism and exhumation on the northern side of the Arabia-Eurasia suture. Reconciliation of each of these omissions and contradictions of their model would be welcome, and perhaps an advisory that readers may wish to evaluate their concept of Cretaceous subduction initiation with due circumspection

    Silver Coated Bioactive Glass Particles for Wound Healing Applications

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    Hench and colleagues discovered that bone could bond chemically to certain glass compositions in 1969 [1]. This group of glasses is known as bioactive glasses [1]. Some special compositions of bioactive glasses will bond to soft tissues as well as bone [1]. One of the important characteristics of bioactive glasses is their ability to release beneficial ions such as Ca2+, Na+, Zn2+, Sr2+, and PO 43- in the body, which promote self-healing [2]. Bioactive glasses generally contain much less glass former (e.g., SiO2, B2O3 etc.) than conventional glasses [3]. Network modifiers encourage the formation of Non-Bridging Oxygens (NBO) groups. These NBO groups decrease aqueous durability and increase bioactivity [4]. © 2012 IEEE

    Assessment of physical risk factors among artisans using occupational repetitive actions and Nordic questionnaire

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    Aims: The aims of present study is to determine the level of exposure to physical risk factors of work related repetitive movements in the upper limbs among the artisans in Isfahan, using occupational repetitive actions index and the Nordic Questionnaire. Material and Methods: In this cross-sectional study, the study population consisted of 94 males employed in Artisan production. The tools that be used for assessing physical ergonomic risk factors among artisans was Nordic Questionnaire and OCRA index. The different handicraft tasks and work activities included: Simple etching, embossing, reticular embossing, enameling, tiling, illumination, inlay, copper smithing and, miniature painting have been chosen for the study. The Study was carried out on the both left and right hands. The results were analyzed by statistical tests included Chi square, Kruskal Wallis and one-way variance analysis. Results: The highest OCRA index score was related to simple etching job, and the other tasks such as embossing, copper smithing, reticular embossing, tiling, miniature painting, and illumination were in lower risk category. Our finding showed that there are a significant difference between OCRA scores of the various jobs (P value < 0.001), and also the relationship between OCRA index and the type of jobs was statistically significant (P value < 0.001). Risk level in the right hand was significantly higher than the left hand (P value < 0.001). Moreover, in both right and left hands, OCRA index was different among several types of jobs (P value < 0.001). Conclusion: Our assessment showed that in overall there are different physical risk factors among artisans which make them susceptible to musculoskeletal disorders

    Silver Coated Bioactive Glass Particles for Wound Healing Applications

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    Bioactive glass particles (0.42SiO2-0.15CaO-0.23Na 2O-0.20ZnO) of varying size (\u3c90 \u3eμm and 425-850 μm) were synthesized and coated with silver (Ag) to produce Ag coated particles (PAg). These were compared against the uncoated analogous particles (Pcon.). Surface area analysis determined that Ag coating of the glass particles resulted in increased the surface area from 2.90 to 9.12 m2/g (90 μm) and 1.09-7.71 m2/g (425-850 μm). Scanning electron microscopy determined that the Ag coating remained at the surface and there was little diffusion through the bulk. Antibacterial (Escherichia coli - 13 mm and Staphylococcus epidermidis - 12 mm) and antifungal testing (Candida albicans - 7.7 mm) determined that small Ag-coated glass particles exhibited the largest inhibition zones compared to uncoated particles. pH analysis determined an overall higher pH consider in the smaller particles, where after 24 h the large uncoated and Ag coated particles were 8.27 and 8.74 respectively, while the smaller uncoated and Ag coated particles attained pH values of 9.63 and 9.35 respectively. © Springer Science+Business Media, LLC 2012

    The Neotethyan Sanandaj-Sirjan zone of Iran as an archetype for passive margin-arc transitions

    Get PDF
    The Sanandaj-Sirjan zone of Iran is a northwest trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. The zone contains the most extensive, best preserved record of key events in the formation and evolution of the Neotethys, from its birth in Late Paleozoic time through its demise during the mid-Tertiary collision of Arabia with Eurasia. The record includes rifting of continental fragments off of the northern margin of Gondwanaland, formation of facing passive continental margins, initiation of subduction along the northern margin, and progressive development of a continental magmatic arc. The latter two of these events are critical phases of the Wilson Cycle that, elsewhere in the world, are poorly preserved in the geologic record because of superimposed events. Our new synthesis reaffirms the similarity between this zone and various terranes to the north in Central Iran. Late Paleozoic rifting, preserved as A-type granites and accelerated subsidence, was followed by a phase of pronounced subsidence and shallow marine sedimentation in Permian through Triassic time, marking the formation and evolution of passive margins on both sides of the suture. Subduction and arc magmatism began in latest Triassic/Early Jurassic time, culminating at ~170 Ma. The extinction of arc magmatism in this zone, and its shift northeastward to form the subparallel Urumieh-Dokhtar arc, occurred diachronously along strike, in Late Cretaceous or Paleogene time. Post-Cretaceous uplift transformed the zone from a primarily marine borderland into a marine archipelago that persisted until mid-Tertiary time
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