Blockchain-based Internet of Things (BC-IoT) brings the advantages of blockchain into traditional IoT systems. In BC-IoT, the smart contract has been widely used for automatic, trusted, and decentralized applications. Smart contracts require frequent adjust and fast update due to various reasons, such as inevitable code bugs, changes of applications, or security requirements. However, previous smart contract architecture and updating mechanism are low speed and cause high overhead, because they are based on recompilation and redeployment in BC-IoT. Meanwhile, smart contract execution is so time consuming due to contract instruction dispatching and operand loading in the stack-based Ethereum virtual machine (EVM). To address these issues, we propose a new smart contract architecture and optimization mechanism for BC-IoTs, ATOM, which provides architectural supports to update contract economically and fast executing in instructionwise for the first time, to the best of our knowledge. We design a compact Application-oriented Instruction (AoI) set to describe application operations. We can construct the bytecode of smart contract from application by directly assembling templates prebuilt upon the AoIs rather than by compilation. We also present an optimized mechanism for AoI execution to enable access addressable storage place rather than the indirect access through stack. We perform ATOM on a BC-IoT testbed based on private Ethereum and Hyperledger Burrow. The experimental results highlight that ATOM is more efficient than state-of-the-art approaches. ATOM can reduce update latency by 62.7%, ledger size by 70%, and gas usage by 90% on average, respectively. Compared with the traditional smart contract architecture, ATOM can improve EVM Memory access efficiency significantly by up to $10\times $ and achieve improvement of execution efficiency with up to $1.6\times $ .
Objective:To evaluate diagnositic value of prostate specific antigen (PSA),free/total PSA (F/T PSA),and PSA density (PSAD) in prostate biopsy. Methods:Total serum PSA and free PSA were detected while F/T PSA value and PSAD were calculated in 285 patients who underwent transrectal ultrasonography-guided prosate biopsy. Optimum PSA,F/T PSA value and PSAD for detecting Pca were discussed. Results:When the cut off value of PSA was set as15 ng/ml,the diagnostic sensitivity,specificity and the positive predictive value were 70.0%,68.5% and 58.6% respectively. When PSA 15 ng/ml,the difference of PSA between BPA and Pca groups was not significant(t=0.018,P 0.05),while F/T value and PSAD showed significant differences(t=4.137,3.158,P0.01). When the cue off value of F/T was set as 0.16 and the cue off value of PSAD as 0.35 ng/(ml·cm3),the sensitivity,specificity and the positive predictive values were higher. Conclusion:PCa should be highly suspected when PSA is more than 15 ng/ml. The detection rate of prostate cancer could be significantly improved in combination of F/T and/or PSAD.
Abstract A major hurdle for single particle cryo-EM in structural determination lies in the specimen preparation impaired by the air-water interface (AWI) and preferential particle-orientation problems. In this work, we develop functionalized graphene grids with various charges via a dediazoniation reaction for cryo-EM specimen preparation. The graphene grids are paraffin-assistant fabricated, which appear with less contaminations compared with those produced by polymer transfer method. By applying onto three different types of macromolecules, we demonstrate that the high-yield charged graphene grids bring macromolecules away from the AWI and enable adjustable particle-orientation distribution for more robust single particle cryo-EM structural determination.
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