一种新的密码本原:棘轮密钥交换的定义、模型及构造

在传统密码学应用中,人们总假定终端是安全的,并且敌手只存在于通信信道上。然而,主流的恶意软件和系统漏洞给终端安全带来了严重和直接的威胁和挑战,例如容易遭受存储内容被病毒破坏、随机数发生器被腐化等各种攻击。更糟糕的是,协议会话通常有较长的生存期,因此需要在较长的时间内存储与会话相关的秘密信息。在这种情况下,有必要设计高强度的安全协议,以对抗可以暴露存储内容和中间计算结果(包括随机数)的敌手。棘轮密钥交换是解决这一问题的一个基本工具。文中综述了密码本原——棘轮密钥交换,包括单向、半双向和双向等棘轮密钥交换的定义、模型及构造,并展望了棘轮密钥交换的未来发展趋势。     

Flash Lamps as Ignition and Initiation Sources of the VS-2 Pyrotechnic Composition

In the present work it is found that the pyrotechnic composition VS-2 can be initiated with flash lamps IFC-500 and EVIS. VS-2 pyrotechnic composition contains 90% of mercury（Ⅱ） 5-hydrazinotetrazolate perchlorate and 10% of optically transparent copolymer of 2-methyl-5-vinyltetrazole and methacrylic acid （PVMT）. We have found that the flash lamps make it possible to initiate combustion of VS-2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high， and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm^-2 and 90 mg·cm^-2， showing ignition delay times 10 μs and 3 μs， respectively. We also measured detonation velocities for VS-2 composition film charges， which were 4375-4505 m·s^-1 （of the charge being surface mass 60 mg·cm^-2） and 4221-4281 m·s^-1 （of the charge being surface mass 90 mg·cm^-2） and their blasting action on the aluminum plate. The depths of the normal shock wave imprints at the charge-barrier interface were 0.6-0.7 mm （for surface mass of the film charges 60 mg·cm^-2） and 1.2-1.3 mm （for surface mass of the film charges 90 mg·cm^-2）.     

Analysis and proposition of limiting current density measurement protocol

Limiting current density at different temperatures, backpressures, and balance gases can be used to separate molecular diffusion resistance, Knudsen diffusion resistance and local transport resistance of membrane electrode assembly (MEA). However, the measurement of limiting current density has no unified protocol. The diverse choices in the literature, either in the control of current or voltage or in the atmosphere like relative humidity and O₂ concentrations, make it difficult to compare the results and identify the true bottleneck hindering the mass transport. In this work, the current-voltage curves obtained by current scanning/stepping and voltage scanning/stepping methods under dilute O₂ of different concentrations and a wide range of relative humidity were measured and analyzed systematically. It is found that the voltage stepping method is superior to the other three ways of control for the reliable determination of the limiting current density. Aided with simultaneous electrochemical impedance spectroscopy measurement, the limiting current density can be determined with pinpoint accuracy. When the limiting current density is just used to qualitatively evaluate different MEA, the voltage scanning method can be used instead for its high time efficiency. The selection of the atmosphere also plays an important role in suppressing the distortion from excessive water and reducing the spurious contribution from proton conduction resistance. It is found that O₂ concentrations at 0.5 vol% and relative humidity at 90% can give the best estimation of O₂ transport resistance in membrane electrode assembly.     

海蜇Ⅰ型胶原蛋白的提取及结构特性研究

以海蜇为原料，采用盐酸-胃蛋白酶法提取胶原蛋白，并通过聚丙烯酰胺凝胶电泳（SDS-Polyacrylamide gel electrophoresis，SDS-PAGE）、紫外光谱（UV-visible spectroscopy，UV）、氨基酸分析、红外光谱（Fourier-transform infrared spectroscopy，FTIR）、圆二色谱（Circular dichroism，CD）以及扫描电镜（Scanning electron microscope，SEM）对其结构特性进行了系统全面的研究。结果显示，海蜇胶原蛋白在135 kDa左右有一条α-链，在245 kDa以上有一条β-链和γ-链，紫外吸收峰在233 nm处，符合I型胶原蛋白的特征，其亚基组成可能为[α₁(I)]₃。海蜇胶原蛋白中含量最高的氨基酸为甘氨酸，占氨基酸总量的25.99%，且含有15.94%的亚氨基酸。红外光谱和圆二色谱均表明海蜇胶原蛋白分子排布紧凑，具有主要由氢键构成的完整三螺旋结构。扫描电镜结果显示海蜇胶原蛋白具有多层聚集、以纤维为主的无规则网状结构。     

Metaproteomic analysis of enzymatic composition in Baobaoqu fermentation starter for Wuliangye baijiu

Wuliangye is one of the most famous brands of baijiu in China. The typical flavours of Wuliangye baijiu are mainly formed by the multifarious enzymes in fermentation starter (Baobaoqu, BBQ). As the enzymes remained poorly understood, the detailed enzymatic composition of BBQ was analysed by metaproteomics for the first time. It is worth noting that the enzymes from plant, animals and micro-organisms were detected together and oxidoreductases were the dominant enzymes. Next, the analysis of function showed that the enzymes were mainly involved in carbon metabolism and the biosynthesis of amino acids. Additionally, the relationship between differential abundant enzymes and formation of typical flavour substances in premium and normal BBQ was established. Furthermore, the activities of classic enzymes in BBQ were examined to verify the reliability of metaproteomic results. This study will provide clues to further improve the manufacturing technology for Wuliangye baijiu.     

Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.     

Screening of frozen-thawed conditions for keeping nutritive compositions and physicochemical characteristics of goat milk

Frozen milk can help producers overcome the seasonality of goat milk production, low goat production and short lactation periods, and avoid discarding milk during some special periods. We investigated effects of combination between freezing (cryogenic refrigerator of ?16 to ?20°C or ultra-cryogenic refrigerator of ?76 to ?80°C) and thawing (homeothermy of 20 to 25°C or refrigeration of 2 to 4°C) on nutritive compositions and physicochemical characteristics of raw goat milk during storage period (80 d). Compared with fresh goat milk, the frozen-thawed milk decreased contents of fat, protein, and lactose, as well as surface tension and stability coefficient, whereas increased effective diameter and polydispersity index. The average values of color values (L*, a*, and b*) in 4 group samples changed from 83.01 to 82.25, ?1.40 to ?1.54, 3.51 to 3.81, respectively, and the ΔE of most samples did not exceed 2. In contrast to the other 3 frozen-thawed treatments, goat milk treated with ultra-cryogenic freezing-homeothermic thawing (UFHT) possessed higher fat (5.20 g/100 g), smaller effective particle diameter (0.32 µm), and the lowest polydispersity index value (0.26). The color and confocal laser scanning microscopy images of UFHT were similar to those of fresh goat milk, illustrating UFHT was the optimal approach to maintain the natural quality of goat milk. Our finding provides a theoretical basis for producers to freeze surplus milk.     

Interplay of the phase and the chemical composition of the powder feedstock on the properties of porous 8YSZ thermal barrier coatings

Some chemical impurities enhance sintering kinetics of ceramic Thermal Barrier Coatings (TBCs) which can cause their premature failure during operation in gas turbine engine by causing reduction in coating’s strain compliance as well as faster bond-coat oxidation due to increased thermal conductivity. Certain chemical impurities are also believed to suppress resistance to tetragonal to monoclinic phase transformation in 8YSZ, which can also be an important factor regarding TBC’s performance. Most of the impurities and some of the monoclinic phase present in the powder feedstocks can survive into the as-sprayed coating. Therefore, there is a general trend towards OEMs requiring the lowest amounts of chemical impurities and the lowest amounts of monoclinic phase in the powder feedstocks. This paper presents a comprehensive investigation aimed at understanding the role and the relative importance of the chemical and phase purities of the powder feedstock for the properties and performance of thick 8YSZ TBCs.