244 research outputs found

    Blind Deblurring Reconstruction Technique with Applications in PET Imaging

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    We developed an empirical PET model taking into account system blurring and a blind iterative reconstruction scheme that estimates both the actual image and the point spread function of the system. Reconstruction images of high quality can be acquired by using the proposed reconstruction technique for both synthetic and experimental data. In the synthetic data study, the algorithm reduces image blurring and preserves the edges without introducing extra artifacts. The localized measurement shows that the performance of the reconstruction image improved by up to 100%. In experimental data studies, the contrast and quality of reconstruction is substantially improved. The proposed method shows promise in tumor localization and quantification

    Hollow Titanium Silicalite Zeolite: From Fundamental Research to Commercial Application in Environmental-Friendly Catalytic Oxidation Processes

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    The systematical investigation on the synthesis, characterization, formation mechanism, and catalytic application of hollow titanium silicalite (HTS) zeolite has been reviewed. HTS is prepared through a “dissolution–recrystallization” post-treatment in the presence of template under hydrothermal conditions. Compared with TS-1, HTS is of unique hollow voids and with high framework Ti content, which significantly increase the mass diffusion and the amount of active sites, respectively. Thus, HTS zeolite displays high catalytic activity and stability in many oxidation processes with H2O2 oxidant, that is, cyclohexanone ammoximation, phenol hydroxylation, propylene epoxidation, Baeyer-Villiger oxidation of cyclohexanone, and selective oxidation of aromatics and cycloalkanes. The former three ones have been commercialized and run smoothly, which have promising economic and environmental significance

    The impact of road environments on rural periodic market travel satisfaction: a heterogeneity analysis of travel modes

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    IntroductionTravel satisfaction as experienced by rural residents is closely related to personal physical and mental health, as well as rural economic conditions. An improved rural road environment can be expected to enhance villagers’ satisfaction with regards to visits to markets, but to date this has not been established empirically.MethodsIn this study, a questionnaire was designed to obtain local residents’ evaluations of road environment characteristics for periodic market travel. And we use an Oprobit regression model and Importance-Performance Map Analysis (IPMA) to explore the heterogeneity of the 14 key elements of the “home-to-market” road environment impact on villagers’ satisfaction under different modes of travel.ResultsThe results of the study reveal that villagers expressed dissatisfaction with the current lack of sidewalks and non-motorized paths, and except for road traffic disturbances and road deterioration, which did not significantly affect mode of travel, other factors proved significant. Significantly, bus services are associated with a significant positive effect on walking, non-motorized and bus travel satisfaction, while distance travel also affects walking, non-motorized and motorized travel satisfaction. It is worth noting that greening and service facilities negatively affect motorized travel satisfaction. In summary, road width, sidewalks, bus service, and road deterioration, are among the elements most in need of urgent improvement for all modes of travel.DiscussionThe characteristics of the road environment that influence satisfaction with travel to the periodic market vary by travel mode, and this study is hoped to provide data support and optimization recommendations for the improvement of the rural road environment in China and other countries

    Environmental-Friendly Catalytic Oxidation Processes Based on Hierarchical Titanium Silicate Zeolites at SINOPEC

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    Since it was claimed by EniChem in 1983 for the first time, titanium silicate‐1 (TS‐1) zeolite presented the most delightful catalytic performance in the area of selective organic oxidation reactions. To enhance the mass diffusion property, hierarchical titanium silicate with hollow cavities within crystal was prepared by using a post‐synthesis treatment in the presence of organic template, and then, it was commercially produced and employed in many industrial catalytic oxidation processes, such as propylene epoxidation, phenol hydroxylation, and cyclohexanone ammoximation. Moreover, we also developed several totally novel oxidation reactions on hollow titanium silicate (HTS) zeolite, i.e., Baeyer‐Villiger oxidation of cyclohexanone and chlorohydrination of allyl chloride with HCl and H2O2. In all cases, HTS shows much better catalytic performance than TS‐1, attributing to the mass diffusion intensification by introducing hollow cavities. On the other hand, enormous works on synthesizing hierarchical TS‐1 zeolites with open intracrystalline mesopores have been done via silanization treatment and recrystallization. Based on them, several bulk molecule oxidation processes with tert‐butyl hydroperoxide, such as epoxidation of fatty acid methyl ester (FAME) and large olefins, have been carried out. As a consequence, hierarchical TS‐1 zeolites supply a platform for developing environmental‐friendly catalytic oxidation processes to remarkably overcome the drawbacks of traditional routes

    Dual RNA-Seq of Trunk Kidneys Extracted From Channel Catfish Infected With Yersinia ruckeri Reveals Novel Insights Into Host-Pathogen Interactions

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    Host-pathogen intectarions are complex, involving large dynamic changes in gene expression through the process of infection. These interactions are essential for understanding anti-infective immunity as well as pathogenesis. In this study, the host-pathogen interaction was analyzed using a model of acute infection where channel catfish were infected with Yersinia ruckeri. The infected fish showed signs of body surface hyperemia as well as hyperemia and swelling in the trunk kidney. Double RNA sequencing was performed on trunk kidneys extracted from infected channel catfish and transcriptome data was compared with data from uninfected trunk kidneys. Results revealed that the host-pathogen interaction was dynamically regulated and that the host-pathogen transcriptome fluctuated during infection. More specifically, these data revealed that the expression levels of immune genes involved in Cytokine-cytokine receptor interactions, the NF-kappa B signaling pathway, the JAK-STAT signaling pathway, Toll-like receptor signaling and other immune-related pathways were significantly upregulated. Y. ruckeri mainly promote pathogenesis through the flagellum gene fliC in channel catfish. The weighted gene co-expression network analysis (WGCNA) R package was used to reveal that the infection of catfish is closely related to metabolic pathways. This study contributes to the understanding of the host-pathogen interaction between channel catfish and Y. ruckeri, more specifically how catfish respond to infection through a transcriptional perspective and how this infection leads to enteric red mouth disease (ERM) in these fish

    Shock control of a low-sweep transonic laminar flow wing

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    This paper presents a combined experimental and computational study of a low-sweep transonic natural laminar flow (NLF) wing with shock-control bumps (SCBs). A transonic NLF wing with a relatively low sweep angle of 20 deg was chosen for this study. To avoid the complexity of the flow introduced by perforated/slotted walls commonly used for transonic wind-tunnel tests for reducing the wall interference, both experimental tests and computational simulations were conducted with solid wind-tunnel wall conditions. This allows for like-to-like validation of the computational simulation. Optimization of the shock-control bumps was first conducted to design the wind-tunnel test model with bumps. Two critical parameters of the three-dimensional SCBs for shock control (i.e., bump crest position and bump height) were optimized in terms of total drag reduction at the given design point in the wind tunnel. We show that the strong shock wave on the low-sweep NLF wing can be effective controlled by well-designed SCBs deployed along the wing span. The optimized SCBs result in 18.5% pressure drag reduction with 5% viscous drag penalty, and the SCBs also bring some benefits at off-design conditions. The wind-tunnel tests include pressure measurement, particle image velocimetry, and temperature-sensitive paint to provide detailed insight into the shock-control flowfield and to validate the computational simulations. Comparisons include surface pressure profile, velocity distribution, and transition location

    Safety and Efficacy of Exclusive Enteral Nutrition for Percutaneously Undrainable Abdominal Abscesses in Crohn’s Disease

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    Background. The percutaneously undrainable abdominal abscesses in Crohn’s disease (CD) are not uncommon. The treatment protocol is still under debate. This study was conducted to assess the safety and efficacy of exclusive enteral nutrition (EEN) for percutaneously undrainable abscesses in CD. Methods. A consecutive cohort of 83 CD patients with percutaneously undrainable abdominal abscesses between January 2011 and June 2015 was retrospectively analyzed. They were divided into the EEN group and the non-EEN group. Results. The cumulative surgical rate was significantly lower in the EEN group than in the non-EEN group (P=0.001). Fifteen percent patients treated with EEN avoided surgery. EEN (P=0.002) was associated with a decreased need for surgery. Previous abdominal surgery (P=0.009) and abscess diameter > 3 cm (P=0.022) were associated with an increased need for operation. EEN increased the albumin level, while decreased ESR and CRP significantly for patients requiring surgery. The risk of postoperative intra-abdominal septic complications (P=0.036) was significantly lower in the EEN group compared with the non-EEN group. Conclusions. EEN is feasible in CD patients presenting with percutaneously undrainable abdominal abscesses. It is associated with a reduction in surgical rate, optimized preoperative condition, and improved postoperative outcomes in these specific groups of patients

    Aerodynamic analysis of a flapping wing aircraft for short landing

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    An investigation into the aerodynamic characteristics has been presented for a bio-inspired flapping wing aircraft. Firstly, a mechanism has been developed to transform the usual rotation powered by a motor to a combined flapping and pitching motion of the flapping wing. Secondly, an experimental model of the flapping wing aircraft has been built and tested to measure the motion and aerodynamic forces produced by the flapping wing. Thirdly, aerodynamic analysis is carried out based on the measured motion of the flapping wing model using an unsteady aerodynamic model (UAM) and validated by a computational fluid dynamics (CFD) method. The difference of the average lift force between the UAM and CFD method is 1.3%, and the difference between the UAM and experimental results is 18%. In addition, a parametric study is carried out by employing the UAM method to analyze the effect of variations of the pitching angle on the aerodynamic lift and drag forces. According to the study, the pitching amplitude for maximum lift is in the range of 60°~70° as the flight velocity decreases from 5 m/s to 1 m/s during landing
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