Chiral imidazo[1,5-a]tetrahydroquinoline N-heterocyclic carbenes and their copper complexes for asymmetric catalysis

Novel chiral imidazo[1,5-a]tetrahydroquinoline N-heterocyclic carbenes derived from β-pinene have been developed. The preliminary studies with both the in situ generated and preformed copper–carbene complexes have shown these chiral NHCs are efficient and selective ligands in the Cu-catalyzed asymmetric conjugate borylation of α,β-unsaturated esters.     

Surface properties of titanium nitride: A first-principles study

The low-index surfaces of TiN are calculated using the first-principles method based on density functional theory. It is found that the relaxation effect is mainly localized in the outmost three layers for all surfaces, and the distance reduction of the outmost interlayer for the N-terminated (111) surface is much larger than other surfaces. The N-terminated (111) surface is thermodynamically favorable at high nitrogen chemical potential, which is consistent with the experimental results.     

An efficient one-step synthesis of fulleroisoxazolines and fulleropyrazolines mediated by (diacetoxyiodo)benzene

An efficient one-step strategy for the synthesis of fulleroisoxazolines/fulleropyrazolines from fullerene and aldoximes/hydrazones mediated by PhI(OAc)₂ has been described.     

Synthesis and photoluminescence properties of ZnO nanowire arrays

In this paper we report a chemical method named coordination reaction method to synthesize ZnO nanowire arreys. ZnO nanowires with the diameter about 80nm were successfully fabricated in the channels of the porous anodic alumina (PAA) template by the above coordination reaction method. The microstructures of ZnO/PAA assembly were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The results showed that the ZnO nanowires can be uniformly assembled into the nanochannels of PAA template. The growth mechanism of ZnO nanowires and the conditions of the coordination reaction are discussed. Photoluminescence (PL) measurement shows that the ZnO/PAA assembly system has a blue emission band caused by the various defects of ZnO. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spatial concentration, congener profiles and inhalation risk assessment of PCDD/Fs and PCBs in the atmosphere of Tianjin, China

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were monitored in a seasonal passive sampling scheme during June 2008 and January 2009 to investigate the spatial concentration, congener profiles and evaluate the potential inhalation risk in different functional areas in Tianjin, China. The spatial air concentrations and I-TEQs ranged 1.08×10²–8.19×10³ fg m^?3 (average 2.63×10³ fg m^?3) and 4.08–325 fg I-TEQ m^?3 (average 91.4 fg I-TEQ m^?3) respectively for PCDD/Fs. The concentration and I-TEQs of PCBs were 3.08×10⁴–3.01×10⁵ fg m^?3 (average 1.39×10⁵ fg m^?3) and 1.72–49.6 fg I-TEQ m^?3 (average 18.5 fg I-TEQ m^?3). It is obvious that PCB concentrations were several hundred times higher than the PCDD/Fs. However, the ambient air PCDD/Fs contributed a major part to the total toxicity equivalents, varying from 72.7% to 89.0% (average 81.8%). The atmospheric PCDD/F levels were observed to be higher in winter for most of sampling sites in the downtown. Besides, inhalation risk assessment showed that local residents might suffer more risk near the point sources than those in living area, industrial zones and background area in Tianjin City. However, the total daily dioxin intake was approximately several to hundreds of times lower than the WHO criteria, showing relatively low exposure risks from the impact of industry point sources in Tianjin City.     

TIFAflow: Enhancing Traffic Archiving System with Flow Granularity for Forensic Analysis in Network Security

The archiving of Internet traffic is an essential function for retrospective network event analysis and forensic computer communication. The state-of-the-art approach for network monitoring and analysis involves storage and analysis of network flow statistic. However, this approach loses much valuable information within the Internet traffic. With the advancement of commodity hardware, in particular the volume of storage devices and the speed of interconnect technologies used in network adapter cards and multi-core processors, it is now possible to capture 10 Gbps and beyond real-time network traffic using a commodity computer, such as n2disk. Also with the advancement of distributed file system (such as Hadoop, ZFS, etc.) and open cloud computing platform (such as OpenStack, CloudStack, and Eucalyptus, etc.), it is practical to store such large volume of traffic data and fully in-depth analyse the inside communication within an acceptable latency. In this paper, based on well- known TimeMachine, we present TIFAflow, the design and implementation of a novel system for archiving and querying network flows. Firstly, we enhance the traffic archiving system named TImemachine+FAstbit (TIFA) with flow granularity, i.e., supply the system with flow table and flow module. Secondly, based on real network traces, we conduct performance comparison experiments of TIFAflow with other implementations such as common database solution, TimeMachine and TIFA system. Finally, based on comparison results, we demonstrate that TIFAflow has a higher performance improvement in storing and querying performance than TimeMachine and TIFA, both in time and space metrics.     

Sensitive Electrochemical Determination of Catechol with a Graphene Modified Carbon Ionic Liquid Electrode

In this paper a graphene (GR) modified carbon ionic liquid electrode (CILE) was fabricated and used as the voltammetric sensor for the sensitive detection of catechol. Due to the specific physicochemical characteristics of GR such as high surface area, excellent conductivity and good electrochemical properties, the modified electrode exhibits rapid response and strong catalytic activity with high stability toward the electrochemical oxidation of catechol. A pair of well‐defined redox peaks appeared with the anodic and the cathodic peak potential located at 225 mV and 133 mV (vs.SCE) in pH 6.5 phosphate buffer solution, respectively. Electrochemical behaviors of catechol on the GR modified CILE were carefully investigated and the electrochemical parameters were calculated with the results of the electrode reaction standard rate constant (k_s) as 1.24 s^?1, the charge transfer coefficient (α) as 0.4 and the electron transfer number (n) as 2. Under the selected conditions the differential pulse voltammetric peak current increased linearly with the catechol concentrations in the range from 1.0 × 10^‐7 to 7.0 × 10^?4mol L‐1 with the detection limit as 3.0 × 10^?8mol L‐1 (3σ). The proposed method was further applied to the synthetic waste water samples determination with satisfactory results     

Influence of Exogenous CO2 on Biomass and Lipid Accumulation of Microalgae Auxenochlorella protothecoides Cultivated in Concentrated Municipal Wastewater

The effects of exogenous CO₂ on the growth and lipid accumulation of a local screened facultative heterotrophic microalgae strain Auxenochlorella protothecoides (UMN280) as well as nutrient removal from concentrated municipal wastewater stream (centrate) were examined in this study. A 12-day batch experiment was conducted with CO₂ aeration at three levels, namely, 0%, 1%, and 5% (v/v) CO₂ mixed with air, under light intensity of 60???mol/(m² @@s). A two-stage growth pattern was observed. The first stage (first?Cfifth day) was dominated by heterotrophic growth in which organic carbon was the main carbon source. The second stage (6th?C12th day) was dominated by autotrophic growth in which exogenous CO₂ had a positive effect on algal biomass accumulation. The addition of 5% CO₂ was better than that of 1% CO₂ on the biomass and lipid production. The uptakes of nutrients were similar between injection and no injection of CO₂, except on phosphorus removal which was affected by the acidification of CO₂.     

镨物种的掺杂量对Co0.1Ce0.9-yPryOx水蒸气重整乙醇反应催化性能的影响

采用XRD,TPR,DSC和TG等方法对共沉淀法制备的Pr物种掺杂Co0.1Ce0.9-yPryOx催化剂的晶相结构、还原性能及反应后催化剂的热性能等进行了表征,并以水蒸气重整乙醇为探针反应考察了催化剂的活性、选择性和稳定性。结果表明:随着镨物种含量的增加,镨离子取代铈离子数量增多,引起晶格畸变,氧空位增多,并有利于钴物种的分散和还原,引导体相氧的溢出和传递。在水蒸气重整乙醇反应中,催化活性、H2的选择性随镨物种含量的增加而提高,而CO和CH4的选择性降低,Co0.1Ce0.70Pr0.2Ox样品在反应50 h后活性和H2的选择性仅下降4.6%和7.9%。     

Particle removal by a single cavitation bubble

In the paper,the behavior of the particle acted by the oscillating bubble is studied using a high-speed video camera.The bubble is generated using a very low voltage of 55 V.Images are captured at a speed of 15000 fps(frames per second).It is found that the velocity of the particle is dependent on the liquid viscosity,particle size,and tube diameter.Particle velocity decreases with the increase of the glycron-water mixture viscosity.A model is presented to predict the velocity and verified by experimental results.These observations may be beneficial for the application in medical treatment.