天然产物Penicilliazine类似物的合成

以7-甲氧基-4,4a,5,6,8a-五氢-1,2-苯并口恶嗪-3-羧酸乙酯(1a)为起始原料,经NaOH醇溶液和酸化处理,再通过二甲基氨基吡啶(DMAP)催化、1,3-双环己基碳二亚胺(DCC)脱水与7,8-二甲氧基-3-羟基-2(1氢)-喹诺酮(2)的酯化反应,成功合成了天然产物Penicilliazine的类似物P-1,总收率为54.4%,用1HNMR、13CNMR、MS和元素分析等对P-1进行了结构表征;对DCC投料量等反应条件进行了初步优化;对水解反应过程的研究发现,烯醇醚结构的化合物1a可水解失去甲基得到酮式结构的化合物7-羰基-4,4a,5,6,8,8a-六氢-1,2-苯并口恶嗪-3-羧酸(1c),而使用酮式结构1c的乙酯,未发现相应酮式结构羧酸1c的生成。     

The adaptive chirplet transform and visual evoked potentials

We propose a new approach based upon the adaptive chirplet transform (ACT) to characterize the time-dependent behavior of the visual evoked potential (VEP) from its initial transient portion (tVEP) to the steady-state portion (ssVEP). This approach employs a matching pursuit (MP) algorithm to estimate the chirplets and then a maximum-likelihood estimation (MLE) algorithm to refine the results. The ACT decomposes signals into Gaussian chirplet basis functions with four adjustable parameters, i.e., time-spread, chirp rate, time-center and frequency-center. In this paper, we show how these four parameters can be used to distinguish between the transient and the steady-state phase of the response. We also show that as few as three chirplets are required to represent a VEP response. Compared to decomposition with Gabor logons, a more compact representation can be achieved by using Gaussian chirplets. Finally, we argue that the adaptive chirplet spectrogram gives a superior visualization of VEP signals' time-frequency structures when compared to the conventional spectrogram.     

Secure access privilege delegation using attribute-based encryption

International Journal of Information Security - Attribute-based encryption (ABE) is widely used for a secure and efficient data sharing. The predetermined access policy of ABE shares the data with...     

Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes

The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the association of silver nanoparticles with the bacterial cell surface of Lactobacillus fermentum (referred to as biogenic silver or bio-Ag⁰) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag⁰ particles, preventing aggregation during encapsulation. In this study, bio-Ag⁰ was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag⁰ and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag⁺ from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag⁰_powder m⁻² in a submerged plate membrane reactor operated at a flux of 3.1 L m⁻² h⁻¹. Upon startup, the silver concentration in the effluent initially increased to 271 μg L⁻¹ but after filtration of 31 L m⁻², the concentration approached the drinking water limit ( = 100 μg L⁻¹). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m⁻² h⁻¹, showing the potential of this membrane technology for water disinfection on small scale.     

A short ID‐based proxy signature scheme

The notion of identity‐based proxy signature with message recovery feature has been proposed to shorten identity‐based proxy signatures and improve their communication overhead because signed messages are not transmitted with these kinds of signatures. There are a few schemes for this notion: the schemes of Singh and Verma and Yoon et al. Unfortunately, Tian et al., by presenting two forgery attacks, show that Singh and Verma scheme is not secure, and also, the scheme of Yoon et al. does not support provable security. The contributions of this paper are twofold. First, we review the scheme by Yoon et al. and discuss why it does not have message recovery property, and consequently, it is not short. Second, we propose a short identity‐based proxy signature scheme with the help of message recovery property and show that it is secure under computational Diffie–Hellman assumption in the random oracle model. Furthermore, our scheme is more efficient than (as efficient as) previous identity‐based proxy signatures. Copyright © 2014 John Wiley & Sons, Ltd.     

Derivation of the Landau quantum hydrodynamics for interacting bose systems

In this work we demonstrate that the basic equations of the Landau hydrodynamics may be derived directly from the quantum-mechanical microscopic N-body Hamiltonian, which is expressed as a functional of the local observables, namely, particle and current densities. The Landau quantum hydrodynamic equations are then the Heisenberg equations of motion of these quantities.     

LC-atmospheric pressure chemical ionization-MS/ MS analysis of multiple illicit drugs,methadone, and their metabolites in oral fluid following protein precipitation

A quantitative LC-APCI-MS/MS method for simultaneous determination of multiple illicit drugs, methadone, and their metabolites in oral fluid was developed and validated. Sample pretreatment was limited to acetonitrile protein precipitation. LC separation was performed in 25.5 min, with a total analysis time of 35 min. Identification and quantitation were based on selected reaction monitoring. Calibration by linear regression analysis utilized deuterated internal standards and a weighing factor 1/x. Limits of detection and lower limits of quantitation (LOQ) were established between 0.25 and 5 ng/ mL and 0.5-10 ng/mL, respectively. linearity was obtained with an average correlation coefficient (R2) of >0.99, over a dynamic range from the LOQ up to maximum 500 ng/mL The method demonstrated good accuracy, intra- and interbatch precision, recovery, and stability for all compounds. No oral fluid matrix effect was observed throughout the chromatographic run. Protein precipitation provided a fast and simple sample pretreatment, while LC-APCI-MS/MS proved to be a sensitive and rugged quantitative method for multiple illicit and legal drugs in oral fluid. The method proved to be suitable for the evaluation of oral fluid as an alternative matrix to urine for monitoring illicit drug use and for determining oral fluid methadone concentrations in pregnant opiate and/or cocaine addicts.     

Real time modelling of the dynamic mechanical behaviour of PEMFC thanks to neural networks

Modelling complex dynamic mechanical systems, such as PEMFC, without any physical models is a difficult challenge but it could allow the monitoring of endurance tests of fuel cell systems. Neural networks are recognised as powerful numerical tools for predicting complex and nonlinear dynamic behaviours. They require only data limited to experimental inputs and outputs but the choice of an adapted architecture is critical. This paper presents a method for defining a neural network architecture optimised for the fuel cell systems. The associated experimental conditions specifying the vibration tests to train and validate were defined. They consist of swept sinus as well as random excitation forces. The resulting simulations are presented and analysed.