碱性体系下修饰纤维素酶米氏常数的测定

用四种修饰纤维素酶Cell-MAL(5,10,20 K)和Cell-SPA 5 K和天然纤维素酶在p H=13.63,T=45℃反应时间为1 h的7%(wt)Na OH/12%(wt)尿素溶液中降解羧甲基纤维素。得到四种修饰纤维素酶的活性均比天然纤维素酶的活性高。其中Cell-MAL 5 K的活性最高。然后浓度分别为1/100、1/300、1/500和1/700的7%(wt)Na OH/12%(wt)尿素水溶液中分别测定了天然纤维素酶和四种修饰纤维素酶的米氏常数分别为2.853、1.735、1.777、4.622和10.01 mg/L。     

大豆脂肪氧合酶的分离纯化及其性质研究

研究了从大豆种子中分离、纯化大豆脂肪氧合酶的方法,研究表明经过缓冲液提取、差速离心、盐析沉淀和离子交换层析可以得到电泳纯级的大豆脂肪氧合酶。特性研究表明大豆脂肪氧合酶的最适pH为9,在较低温度下酶活能保持较高水平,用双倒数法求得大豆中脂肪氧合酶Km=80.6μmol/L,Vmax=54.2μmol/(L·min)。     

Growth and optical properties of ZnO nanorod arrays on Al-doped ZnO transparent conductive film

ZnO nanorod arrays (NRAs) on transparent conductive oxide (TCO) films have been grown by a solution-free, catalyst-free, vapor-phase synthesis method at 600°C. TCO films, Al-doped ZnO films, were deposited on quartz substrates by magnetron sputtering. In order to study the effect of the growth duration on the morphological and optical properties of NRAs, the growth duration was changed from 3 to 12 min. The results show that the electrical performance of the TCO films does not degrade after the growth of NRAs and the nanorods are highly crystalline. As the growth duration increases from 3 to 8 min, the diffuse transmittance of the samples decreases, while the total transmittance and UV emission enhance. Two possible nanorod self-attraction models were proposed to interpret the phenomena in the sample with 9-min growth duration. The sample with 8-min growth duration has the highest total transmittance of 87.0%, proper density about 75 μm⁻², diameter about 26 nm, and length about 500 nm, indicating that it can be used in hybrid solar cells.     

Dielectric mismatch effect on coupled impurity states in a freestanding nanowire

We studied the coupled impurity states in a freestanding semiconductor nanowire (NW), within the effective mass approximation and including the effect of the dielectric mismatch, by using finite element method. Bonding and anti-bonding states are found and their energies converge with increasing distance d_i between the two impurities. The dependence of the binding energy on the wire radius R and the distance d_i between the two impurities is investigated, and we compare it with the result of a freestanding NW that contains a single impurity.     

Synthesis,structural, thermal and optical studies of rare earth coordinated complex: Tb(Sal)3Phen

Complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized coordinated with terbium ion (Tb³⁺) in crystalline phases. The structural characterizations of the lanthanide complex were made using FT-IR, NMR (¹H and ¹³C) and XRD techniques. These measurements confirm the formation of Tb(Sal)₃Phen complex structure. The thermal aspects of the complex were examined using DTA and TGA techniques. An enhancement in luminescence intensity of Tb³⁺ ion bands were observed in Tb(Sal)₃Phen complex as compared to TbCl₃ crystals on 355 nm laser excitation. Enhancement is reported due to the efficient energy transfer process from Sal to Tb³⁺ ions. This is also confirmed by the time resolved photoluminescence spectroscopy with increase in lifetime of Tb³⁺ ions due to encapsulation in Sal/Phen network. Our system in itself can be a deserving candidate for luminescent solar collector material when coupled with solar cells.     

喷气燃料润滑性的评定

采用ASTM D5001-90a和SH／T 0073两种方法对我国3号喷气燃料的润滑性进行评定，同时评定了进口JetA-1喷气燃料的磨痕宽度(WSD值)。结果表明，我国成品3号喷气燃料的润滑性优于进口JetA-1喷气燃料。进一步分析了WSD值与Km值两者存在线性关系，当WSD为0．65mm和0．79mm时，Km值分别为126和90。     

Large-scale and uniform preparation of pure-phase wurtzite GaAs NWs on non-crystalline substrates

One of the challenges to prepare high-performance and uniform III-V semiconductor nanowires (NWs) is to control the crystal structure in large-scale. A mixed crystal phase is usually observed due to the small surface energy difference between the cubic zincblende (ZB) and hexagonal wurtzite (WZ) structures, especially on non-crystalline substrates. Here, utilizing Au film as thin as 0.1 nm as the catalyst, we successfully demonstrate the large-scale synthesis of pure-phase WZ GaAs NWs on amorphous SiO₂/Si substrates. The obtained NWs are smooth, uniform with a high aspect ratio, and have a narrow diameter distribution of 9.5 ± 1.4 nm. The WZ structure is verified by crystallographic investigations, and the corresponding electronic bandgap is also determined to be approximately 1.62 eV by the reflectance measurement. The formation mechanism of WZ NWs is mainly attributed to the ultra-small NW diameter and the very narrow diameter distribution associated, where the WZ phase is more thermodynamically stable compared to the ZB structure. After configured as NW field-effect-transistors, a high I_ON/I_OFF ratio of 10⁴ − 10⁵ is obtained, operating in the enhancement device mode. The preparation technology and good uniform performance here have illustrated a great promise for the large-scale synthesis of pure phase NWs for electronic and optical applications.     

DC-field-induced synthesis of ZnO nanowhiskers in water-in-oil microemulsions

ZnO nanowhiskers were successfully fabricated using DC-field induced water-in-oil microemulsions method. Phase structure, morphology and microstructure of the product were investigated by X-ray diffraction and transmission electron microscopy. Parameters in preparation process such as electric field intensity and surfactant were discussed and the product formation mechanism was studied. XRD and TEM results showed that the obtained ZnO particle was hexagonal wurtzite-type with 1-3 nm in diameter and 20-70 nm in length, and morphology of the particles was shown to be correlated not only with the electric field intensity but also with the surfactant. There was a threshold when the electric field intensity was 80 V/mm. The morphology of the particles was basically spherical before the threshold, while L/D increased with the raise of electric field intensity. ZnO nanowhiskers were obtained under mixed surfactants but spherical particles were got with a single surfactant.     

Km4City ontology building vs data harvesting and cleaning for smart-city services

Presently, a very large number of public and private data sets are available from local governments. In most cases, they are not semantically interoperable and a huge human effort would be needed to create integrated ontologies and knowledge base for smart city. Smart City ontology is not yet standardized, and a lot of research work is needed to identify models that can easily support the data reconciliation, the management of the complexity, to allow the data reasoning. In this paper, a system for data ingestion and reconciliation of smart cities related aspects as road graph, services available on the roads, traffic sensors etc., is proposed. The system allows managing a big data volume of data coming from a variety of sources considering both static and dynamic data. These data are mapped to a smart-city ontology, called KM4City (Knowledge Model for City), and stored into an RDF-Store where they are available for applications via SPARQL queries to provide new services to the users via specific applications of public administration and enterprises. The paper presents the process adopted to produce the ontology and the big data architecture for the knowledge base feeding on the basis of open and private data, and the mechanisms adopted for the data verification, reconciliation and validation. Some examples about the possible usage of the coherent big data knowledge base produced are also offered and are accessible from the RDF-store and related services. The article also presented the work performed about reconciliation algorithms and their comparative assessment and selection.     

Growth of III-V semiconductor nanowires by molecular beam epitaxy

We present here the growth of GaAs, InAs and InGaAs nanowires by molecular beam epitaxy. The nanowires have been grown on different substrates [GaAs(0 0 1), GaAs(1 1 1), SiO₂ and Si(1 1 1)] using gold as the growth catalyst. We show how the different substrates affect the results in terms of nanowire density and morphology. We also show that the growth temperature for the InGaAs nanowires has to be carefully chosen to obtain homogeneous alloys.