8,231 research outputs found

    On the inverse Compton scattering model of radio pulsars

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    Some characteristics of the inverse Compton scattering (ICS) model are reviewed. At least the following properties of radio pulsars can be reproduced in the model: core or central emission beam, one or two hollow emission cones, different emission heights of these components, diverse pulse profiles at various frequencies, linear and circular polarization features of core and cones.Comment: 5 pages, no figures, LaTeX, a proceeding paper for Pacific Rim Conference on Stellar Astrophysics, Aug. 1999, HongKong, Chin

    Capture zone simulation for boreholes located in fractured dykes using the linesink concept

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    Delineation of capture zones for groundwater source protection is normally performed by using numerical codes which are based on the porous medium flow equation. However, boreholes are often sited in or along permeable dykes or single fracture zones through which aquifers are drained. It is very important to take into account dyke-influenced aquifers. This paper makes use of Linesink to simulate permeable dyke or fractured zones and utilises the pathline distribution to delineate the capture zones. Conditions when the influence of a fractured dyke can be considered negligible are also discussed through comparison with stagnation point in a uniform flow field. The approach may be sufficient to illustrate protection zoning requirements when dyke aquifers are considered. WaterSA Vol.28(2) 2002: 165-17

    Static and Dynamic Properties of Semi-Crystalline Polyethylene.

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    Properties of extruded polymers are strongly affected by molecular structure. For two different semi-crystalline polymers, low-density polyethylene (LDPE) and ultra-high molecular weight polyethylene (UHMWPE), this investigation measures the elastic modulus, plastic flow stress and strain-rate dependence of yield stress. Also, it examines the effect of molecular structure on post-necking tensile fracture. The static and dynamic material tests reveal that extruded UHMWPE has a somewhat larger yield stress and much larger strain to failure than LDPE. For both types of polyethylene, the strain at tensile failure decreases with increasing strain-rate. For strain-rates 0.001⁻3400 s-1, the yield stress variation is accurately represented by the Cowper⁻Symonds equation. These results indicate that, at high strain rates, UHMWPE is more energy absorbent than LDPE as a result of its long chain molecular structure with few branches.This work was partially sponsored by Foundation of State Key Laboratory of Explosion Science and Technology of China under Grant No.KFJJ13-1Z, No. YBKT15-02 and Natural Science Foundation of China under Grant No.11102023. The authors would like to thank Chunmei Liu of the First Research Institute of the China Ministry of Public Security for assistance with the static tensile tests.This is the final version of the article. It first appeared from the Multidisciplinary Digital Publishing Institute via http://dx.doi.org/10.3390/polym804007

    Perforation resistance of aluminum/polyethylene sandwich structure

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    © 2016 Elsevier Ltd. Ballistic tests were performed on two types of polyethylene core sandwich structures (AA6082/LDPE/AA6082 and AA6082/UHMWPE/AA6082) to investigate their perforation resistance. Bulging and dishing deformation of layered plates were compared under low-velocity impact by hemispherical-nosed projectiles. Different impact failure mechanisms leading to perforation were revealed for laminates composed of a pair of aluminum alloy face sheets separated by a polyethylene interlayer. Using the finite element code Abaqus/Explicit, the perforation behavior and distribution of energy dissipation of each layer during penetration were simulated and analysed. The deformation resistance and anti-penetration properties of polyethylene core sandwich structures were compared with those of monolithic AA6082-T6 plates that had the same areal density. Although the polyethylene interlayer enlarged the plastic deformation zone of the back face, the polyethylene core sandwich structure was a little less effective than the monolithic Al alloy target at resisting hemispherical-nosed projectile impact.The authors gratefully acknowledge the Foundation of State Key Laboratory of Explosion Science and Technology of China under Grant No. KFJJ13-1Z, and Natural Science Foundation of China under Grant No. 11102023, 11172071

    Penetration Enhancement Effect of Turpentine Oil on Transdermal Film of Ketorolac

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    Purpose: To prepare transdermal films of ketorolac tromethamine (KT) and study the effect of turpentine oil as a penetration enhancer for the drug.Methods: Transdermal films of KT were prepared with Carbopol-934 and ethyl cellulose, with turpentine oil as the penetration enhancer, using solvent evaporation method. The films were characterized for physicochemical properties, ex vivo permeation, as well as in vivo anti-inflammatory and analgesic activities in Wistar rats. Results: The transdermal films were uniform in weight and thickness, flat, with high drug content (93.9 to 98.5 %) and of high folding endurance (134.0 to 180.0). Drug permeation through excised rat abdominal skin was prolonged, with the total drug release ranging from 58.88 to 88.98 % in 24 h. The films containing penetration enhancer showed higher drug permeation than the one without the enhancer; furthermore, drug permeation increased with increase in the concentration of the enhancer. The films were non-irritant to the skin. The transdermal films prepared with permeation enhancers showed greater anti-inflammatory activity (87.55 ± 2.50 and 83.24 ± 2.29 % inhibition of rat paw edema at the end of 12 h for formulations F2 and F3, respectively, compared to that of the formulation without enhancer with 69.99 %) as well as greater analgesic activity (quicker onset of analgesia in 1.5 h with longer duration of 10 to 12 h).Conclusion: Transdermal films of ketorolac have a potential for use in the treatment of pain andinflammation. Incorporation of turpentine oil in the films enhances not only drug flux but also analgesic and anti-inflammatory activities in rats

    Sibling Differences in Internalizing and Externalizing Behavior Problems: A Meta-Analysis

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    Parental differential treatment of siblings is associated with differences in children’s behavioral adjustment. The current meta-analysis examined the extent to which associations between relative parental differential treatment and differences in siblings’ behavior problems differ by type of parenting behavior (i.e., differential hostility versus differential warmth) and type of behavior problems (i.e., differential externalizing versus internalizing behavior problems). In September 2021, we systematically searched PsycINFO and Web of Science, yielding 2,259 unique hits with 19 eligible papers reporting on 215 effect sizes from 13 unique samples. The overall association between relative parental differential treatment (i.e., receiving less warmth and more hostility than one’s sibling) and behavior problems was small but significant. Associations were stronger for differential hostility compared to differential warmth and for differential externalizing compared to differential internalizing behavior problems. Particularly marked was the finding that siblings who received more hostility from their parents showed higher levels of externalizing problems. Future research investing in further dismantling the association between within-family parental differential treatment and sibling differences in adjustment is warranted to better understand why parents treat siblings differentially and to guide family support initiatives

    Evolution of H9N2 influenza A viruses in quail from southern China

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    Oral Presentations: Genetic and Antigenic EvolutionH9N2 influenza A viruses have become established and maintain long-term endemicity in terrestrial poultry in Asian countries. Occasionally these viruses transmit to other mammals including humans. Increasing epidemiological and laboratory findings suggest that quail may be an important host as they are susceptible to different subtypes of influenza viruses. To better understand the role of quail in influenza ecology and evolution, H9N2 viruses isolated from quail during 2000 to 2005 were antigenically and genetically characterized. Our results showed that only three subtypes of influenza viruses (H5, H6, H9) could be detected in quail in southern China. Furthermore, H9N2 viruses are prevalent year-round in southern China with higher isolation rates observed in the winter, and that those viruses mainly replicate asymptomatically in the respiratory tract of quail. Antigenic and genetic analysis revealed that both the G1-like (genotype A series) and Ck/Bei-like H9N2 lineages (genotype B series) were co-circulating in quail since 2000. Phylogenetic analyses demonstrated that most of the isolates tested were double or multiple reassortant variants, with four G1-like (A0-A3) and 16 Ck/Bei-like genotypes (B1-16) recognized. Non-reassortants of Ck/Bei-like viruses were not detected in quail. A novel genotype of G1-like virus, designated as genotype A3, had become predominant in quail since 2003, while multiple Ck/Bei-like genotypes were introduced to quail wherein they incorporated G1-like gene segments, but none of them became established in this host. Those Ck/Bei-like reassortants generated in quail have then been introduced to other poultry. These complex interactions form a two-way transmission system between quail and other types of poultry. The identification of HA and NP genes with high homology to Ty/WI/1/66 in some H9N2 viruses isolated from quail in 2001 suggested that those viruses had not evolved naturally. The present study provides evidence that H9N2 and H5N1 subtype viruses have also exchanged gene segments to generate currently circulating reassortants of both subtypes that have pandemic potential. Continuing influenza surveillance in poultry is critical to understanding the genesis and emergence of potentially pandemic strains in this region.postprin

    Playing for Data: Ground Truth from Computer Games

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    Recent progress in computer vision has been driven by high-capacity models trained on large datasets. Unfortunately, creating large datasets with pixel-level labels has been extremely costly due to the amount of human effort required. In this paper, we present an approach to rapidly creating pixel-accurate semantic label maps for images extracted from modern computer games. Although the source code and the internal operation of commercial games are inaccessible, we show that associations between image patches can be reconstructed from the communication between the game and the graphics hardware. This enables rapid propagation of semantic labels within and across images synthesized by the game, with no access to the source code or the content. We validate the presented approach by producing dense pixel-level semantic annotations for 25 thousand images synthesized by a photorealistic open-world computer game. Experiments on semantic segmentation datasets show that using the acquired data to supplement real-world images significantly increases accuracy and that the acquired data enables reducing the amount of hand-labeled real-world data: models trained with game data and just 1/3 of the CamVid training set outperform models trained on the complete CamVid training set.Comment: Accepted to the 14th European Conference on Computer Vision (ECCV 2016

    Model Adaptation with Synthetic and Real Data for Semantic Dense Foggy Scene Understanding

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    This work addresses the problem of semantic scene understanding under dense fog. Although considerable progress has been made in semantic scene understanding, it is mainly related to clear-weather scenes. Extending recognition methods to adverse weather conditions such as fog is crucial for outdoor applications. In this paper, we propose a novel method, named Curriculum Model Adaptation (CMAda), which gradually adapts a semantic segmentation model from light synthetic fog to dense real fog in multiple steps, using both synthetic and real foggy data. In addition, we present three other main stand-alone contributions: 1) a novel method to add synthetic fog to real, clear-weather scenes using semantic input; 2) a new fog density estimator; 3) the Foggy Zurich dataset comprising 38083808 real foggy images, with pixel-level semantic annotations for 1616 images with dense fog. Our experiments show that 1) our fog simulation slightly outperforms a state-of-the-art competing simulation with respect to the task of semantic foggy scene understanding (SFSU); 2) CMAda improves the performance of state-of-the-art models for SFSU significantly by leveraging unlabeled real foggy data. The datasets and code are publicly available.Comment: final version, ECCV 201
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