The heterogeneous decarboxylative cyclization reaction between 2-benzoylpyridines and α-amino acids was achieved in toluene at 120 °C in the presence of 15 mol% of l-proline-functionalized ...MCM-41-supported copper(II) complex l-Proline-MCM-41-Cu(OTf)2 and iodine with di-tert-butyl peroxide (DTBP) as oxidant, yielding a variety of 1,3-disubstituted imidazo1,5-apyridines in good to excellent yields. The new supported copper catalyst can be prepared from commercially available and inexpensive reagents, and recovered from the reaction mixture by a simple filtration and recycled up to eight times with almost consistent activity.
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•The heterogeneous l-Proline-MCM-41-Cu(OTf)2 complex was first prepared.•This copper catalyst exhibited the same catalytic activity as Cu(OTf)2.•The reaction generated a variety of imidazo1,5-apyridines in good to high yields.•The catalyst can be recycled up to eight times with almost consistent activity.•Our catalytic system provides a practical route to imidazo1,5-apyridines.
A highly efficient heterogeneous gold(I)-catalyzed hydration of haloalkynes has been developed that proceeds smoothly under mild and neutral conditions and provides a general and practical route for ...the synthesis of a variety of α-halomethyl ketones with high atom-economy, excellent yield, and recyclability of the gold(I) catalyst. The presented method delivers an attractive alternative to classical α-halogenation of ketones.
In this study, a new type of deck arch bridge was proposed based on the triangle stability principle, and its mechanical properties were tested. The new deck arch bridge—named the superposed truss ...arch bridge—consists of main arches, auxiliary arches, a girder, and web members. These components adopt steel structures and are connected into a series of triangles to form a superposed truss structure. The new structural system design retains the advantages of the truss and arch structure. Additionally, the rise-span ratio of the main arch can be smaller in the new system design, so the rise height is smaller, which can decrease construction difficulty. The underlying mechanical principles of the new bridge were explained. A new type of railway deck arch bridge with a 650 m span was designed, and the finite element method was used to analyze its stiffness, strength, stability, and dynamic properties and the corresponding effects of the arch-axis coefficient, rise-span ratio, and span length on the mechanical properties. An experiment was carried out on a new deck arch bridge and a conventional deck arch bridge with the same span (10 m) to compare their performance. The results showed that the new deck arch bridge exhibited good mechanical properties while being inexpensive and easy to construct, which makes it suitable for high-speed railway bridges.
Network Flow Spanners Dragan, Feodor F.; Yan, Chenyu
LATIN 2006: Theoretical Informatics,
2006
Book Chapter, Conference Proceeding
Recenzirano
In this paper, motivated by applications of ordinary (distance) spanners in communication networks and to address such issues as bandwidth constraints on network links, link failures, network ...survivability, etc., we introduce a new notion of flow spanner, where one seeks a spanning subgraph H = (V,E′) of a graph G = (V,E) which provides a “good” approximation of the source-sink flows in G. We formulate few variants of this problem and investigate their complexities. A special attention is given to the version where H is required to be a tree.
Software-defined network (SDN) controllers, the core of SDN network architecture, need to deal with network events of the whole network, which has huge program state space and complex logic ...dependency, with security issues related. Vulnerabilities in the SDN controller can paralyze the whole network. Existing controller testing methods are difficult to dig into the hidden logic vulnerability for their ignorance of the complex events interactions among controllers, apps, and data plane inputs. Different from file processing software, network software is driven by events, and the event flow can more accurately and comprehensively reflect the execution process. In this work, we propose an SDN controller vulnerability digging method based on event flow graph analysis. The proposed method consists of three main steps: first, we execute the instrumented controller in a normal environment and generate event flow graphs and then extract their features as reference. Second, we generate and execute test cases using the fuzzing method and dig the newly built event flow graphs with potential vulnerabilities. Finally, we manually examine and validate the potential vulnerabilities. To accurately discover abnormal subgraphs, we utilize graph feature extraction and analysis technologies, such as graph mining and clustering, to distinguish the normal graph and abnormal graph. We implement our method on the Ryu controller and compare it with other SDN testing methods, such as BEADS and Delta. The evaluation indicates that our method uncovered three new vulnerabilities that other methods failed to find.
Multiprocessor computer systems are currently widely used in commercial settings to run critical applications. These applications often operate on sensitive data such as customer records, credit card ...numbers, and financial data. As a result, these systems are the frequent targets of attacks because of the potentially significant gain an attacker could obtain from stealing or tampering with such data. This provides strong motivation to protect the confidentiality and integrity of data in commercial multiprocessor systems through architectural support. Architectural support is able to protect against software-based attacks, and is necessary to protect against hardware-based attacks. In this work, we propose architectural mechanisms to ensure data confidentiality and integrity in Distributed Shared Memory multiprocessors which utilize a point-to-point based interconnection network. Our approach improves upon previous work in this area, mainly in the fact that our approach reduces performance overheads by significantly reducing the amount of cryptographic operations required. Evaluation results show that our approach can protect data confidentiality and integrity in a 16-processor DSM system with an average overhead of 1.6% and a maximum of only 7% across all SPLASH-2 applications.
This review provides an overview of recent advances in hydrothermal liquefaction (HTL) biocrude production processes using plastics as feedstock, seawater as the processing medium, and microwave ...irradiation as a process intensification method. Additionally, the review examines the application of aid-in investigation tools such as kinetics, machine learning, and feasibility analysis to HTL research. All these aspects have been underexplored in review literature compared to process optimization, biocrude upgrading, continuous HTL, and aqueous phase reutilization. The potential of HTL as an effective method for the depolymerization of plastics is initially evaluated. The ease of plastic depolymerization follows the order of polycarbonate (300 °C) > polystyrene (350 °C) > polyethylene = polypropylene (420 °C) > polyethylene terephthalate (>450 °C). Both synergism and antagonism are observed for co-HTL of plastics with biomass, ranging from −48.3% to 79.2%. Using seawater as an alternative HTL processing medium shows promising potential, while the effect of sea salts on biocrude yield/quality is still controversial especially when carbohydrate-rich feedstocks are utilized, necessitating more comprehensive examination. Microwave irradiation has been shown to increase biocrude yield from lipid, produce comparable yields from protein and lignin, and decrease yield from carbohydrate compared to conventional heating. As for the aid-in investigation tools, limited efforts have been made to apply kinetic modeling to the HTL of plastics, which could be particularly useful when synergism or antagonism is observed during co-HTL of plastics and biomass. Machine learning-enabled predictions of product yield and quality have been found to be more accurate than traditional mathematical models. Future research could focus on using machine learning algorithms to elucidate product formation mechanisms. The techno-economic and life cycle assessment reveal that the commercialization of HTL technology remains a distant prospect, further improvements in product yield, quality, and process energy efficiency are essential. Overall, this review offers augmented insights into HTL technology and facilitates the identification of novel opportunities, which is of value to promote the biocrude production.
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•Plastics as feedstock, seawater as the processing medium, and microwave irradiation as a heating method.•Aid-in investigation tools such as kinetics, machine learning, and feasibility analysis to HTL research.•Augmented insights into HTL technology and the identification of novel opportunities.
A highly efficient heterogeneous gold(I)-catalyzed hydration of haloalkynes has been developed that proceeds smoothly under mild and neutral conditions and provides a general and practical route for ...the synthesis of a variety of α-halomethyl ketones with high atom-economy, excellent yield, and recyclability of the gold(I) catalyst. The presented method delivers an attractive alternative to classical α-halogenation of ketones.
Craving is a significant predicator of smoking relapse. Thus, revealing the neural correlates of craving to smoke in young smokers is important to improve the success of quit attempts. The ...abstinence-induced craving to smoke has not been explored extensively, although previous studies had investigated the neural substrates of cue-induced craving. Especially, the critical roles of thalamus had been revealed in cigarettes smoking. However, the implication of thalamus resting state functional connectivity (RSFC) in abstinence-induced craving remains unclear. In the current study, by employing a within-subject design in 25 young smokers, both the left and right thalamus RSFC patterns differences were investigated between smoking abstinence condition and smoking satiety condition in young smokers. Moreover, a correlation analysis was employed to assess the relationship between these RSFC changes and abstinence-induced changes in subjective craving. We found young smokers in abstinence state showed reduced RSFC between the left thalamus and right dorsal lateral prefrontal cortex (dlPFC) as well as the right anterior cingulate cortex (ACC) compared with smoking satiety state. There were no significant different RSFC of right thalamus detected across the two sessions. Additionally, the left thalamus-right dlPFC RSFC changes were correlated with the changes in craving induced by 12-h abstinence (i.e., abstinence minus satiety). The present findings provides new evidence that abstinence-induced cravings to smoke are associated with abnormal thalamus RSFC and may shed new insights into the neural mechanism of abstinence-induced craving in young smokers.
An aspargine-glycine-arginine (NGR) peptide modified single-walled carbon nanotubes (SWCNTs) system, developed by a simple non-covalent approach, could be loaded with the anticancer drug doxorubicin ...(DOX) and magnetic resonance imaging (MRI) contrast agent gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). This DOX- and Gd-DTPA-loaded NGR functionalized SWCNTs (DOX/NGR-SWCNTs/Gd-DPTA) retained both cytotoxicity of DOX and MRI contrast effect of Gd-DPTA. This drug delivery system showed excellent stability in physiological solutions. This DOX/NGR-SWCNTs/Gd-DPTA system could accumulate in tumors and enter into tumor cells, which facilitated combination chemotherapy with diagnosis of tumor in one system. An excellent in vitro anti-tumor effect was shown in MCF-7 cells treated by DOX/NGR-SWCNTs/Gd-DPTA, compared with DOX solution, DOX/SWCNTs and DOX/SWCNTs/Gd-DPTA. In vivo data of DOX/NGR-SWCNTs/Gd-DPTA group in tumor-bearing mice further confirmed that this system performed much higher tumor targeting capacity and anti-tumor efficacy than other control groups.
