Effect of boehmite nanorods on the properties of glycidoxypropyl-trimethoxysilane (GPTS) hybrid coatings

AlOOH boehmite nanorods, synthesized by a solid-based process, were incorporated into a sol–gel coating in which GPTS was used as a precursor. Transparent composite coatings with nanorod content up to 40 wt% were obtained by spin coating the sol–gel mixture on glass substrates. Nanorods in the coating were found be aligned parallel to the substrate surface. Mechanical properties, such as modulus and hardness of the nanorod filled coating, were slightly lower than coatings of the same composition but filled with commercially available nanosized boehmite particles. However, crack toughness was greatly improved, as supported by nanoindentation test results. The improvement in crack toughness was attributed to the high aspect ratio of the rigid nanorods, in addition to the fact that the nanorods were aligned within the composite parallel to the surface.     

The Asymptotic Behavior of the Takhtajan-Zograf Metric

We obtain the asymptotic behavior of the Takhtajan-Zograf metric on the Teichmüller space of punctured Riemann surfaces. The first author is partially supported by JSPS Grant-in-Aid for Exploratory Research 2005-2007. The second author is partially supported by the research grant R-146-000-106-112 from the National University of Singapore and the Ministry of Education.     

Synthesis of large pore-diameter SBA-15 mesostructured spherical silica and its application in ultra-high-performance liquid chromatography

A modified synthesis approach for spherical large pore-diameter SBA-15 mesoporous silica (SLP-SBA-15) with particle size range of 0.5–1 μm was being reported. It was worth mentioning that in this improved methodology, the use of cetyltrimethylammonium bromide (CTAB) as co-template significantly reduced the self-assembly time from 24 h to 45 min. Moreover, under reflux condition, the reaction time could be further shortened by reducing the aging time from 48 h to 6 h. The resultant SLP-SBA-15 was thereafter successfully functionalized and packed into an ultra-high-performance liquid chromatography (UHPLC) column for the separation of aromatic compounds. A variety of characterizations demonstrated that the silica products exhibited a well-ordered 2d hexagonal mesostructure with well-formed spherical morphology. pore-diameter can be enlarged up to 8.2 nm without affecting the structural order. The SLP-SBA-15 samples showed excellent thermal and hydrothermal stabilities. The octadecyltriethoxysilane functionalized SLP-SBA-15 (SLP-C18-SBA-15) was demonstrated to be an effective stationary phase in UHPLC application because the column exhibited significantly reduced column pressure (2800 psi) at a flow rate of 0.4 ml/min. Accordingly, it would afford greater flexibility for tuning of the flow rate to meet the fast separation requirement.     

Asymmetric addition reactions of Grignard reagents to chiral 2-trifluoromethyl tert-butyl (Ellman) sulfinimine-ethanol adducts

The addition of Grignard reagents to chiral trifluoromethyl tert-butyl sulfinimine-ethanol adducts affords protected trifluoromethylamines in high yields with good to excellent diastereoselectivities. The stereochemical outcome of the addition is opposite to that expected via a chelation controlled transition state.     

Fe-Ni-BaTiO3复合材料的介电行为及其机理研究

利用金属铁、镍(Fe与Ni保持mol比为22:78不变)与钛酸钡复合,在保护气氛下成功烧结制备了高介电常数Fe-Ni-BaTiO3复合陶瓷材料,并研究了该复合材料的电导和介电性能及其物理机理.分析结果表明,由于渗流效应,随着陶瓷中金属含量的增加,材料经历了绝缘体-导体突变.同时,在渗流阈值附近,材料的介电常数有了极大的提高.当金属体积含量为0.23时,即在绝缘体向导体转变的渗流阈值附近,复合材料的介电常数达到了22000,为同条件下制备的纯钛酸钡陶瓷体介电常数的12倍,同时材料的介电损耗仍保持为较低值.材料具有明显的Maxwell-Wagner效应特征,这表明传导机理对材料的介电常数的提高起到了很重要的作用.分析了传导机理对介电的影响.     

Electrically induced linear locomotion of polymer gel in air

A electromechanical gel, which could be driven in air by a DC electric field, was developed using poly(vinyl alcohol)/dimethylsulfoxide gel. When the applied electric field exceeds a certain threshold, the gel exhibited a continuous and linear crawling motion. The result indicated that, under the applied electric field of 275 V/mm, the maximum crawling velocity of the gel could reach v = 1.63 mm/s, which is about 80 times larger than that reported in earlier works. At a proper range of the driving time, the average crawling speed and crawling direction could be well controlled by the external electric field. Furthermore, some factors, which have influence on the critical driving electric field of the gel, such as the swelling degree of the gel and the apparent contact area between the gel and substrate, were studied. For the first time, a mechanism based on the strong electrostatic interaction between the external electric field and the charges accumulated in the gel–air and substrate–gel interfacial regions was put forward to explain the novel motion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1187–1197, 2007     

Low-cost Imaging of Fluorescent DNA in Agarose Gel Electrophoresis using Raspberry Pi cameras

Low-cost analytical solutions built around microcomputers like the Raspberry Pi help to facilitate laboratory investigations in resource limited venues. Here, three camera modules (V1.3 with and without filter, as well as NoIR) that work with this microcomputer were assessed for their suitability in imaging fluorescent DNA following agarose gel electrophoresis. Evaluation of their utility was based on signal-to-noise (SNR) and noise variance metrics that were developed. Experiments conducted with samples were subjected to Polymerase Chain Reaction (PCR), and the amplified products were separated using gel electrophoresis and stained with Midori green. Image analysis revealed the NoIR camera performed the best with SNR and noise variance values of 21.7 and 0.222 respectively. In experiments conducted using UV LED lighting to simulate ethidium bromide (EtBr) excitation, the NoIR and V1.3 with filter removed cameras showed comparable SNR values.

     

Synthesis and Herbicidal Activity of 1,2,4‐Triazole Derivatives Containing a Pyrazole Moiety

A series of triazole derivatives containing a pyrazole moiety were synthesized and characterized by ¹H NMR, ¹³C NMR, and HRMS. The herbicidal activities of these compounds were tested against lettuce and bentgrass. Most of the tested compounds were moderately herbicidal activity against lettuce and bentgrass. Among them, compounds 6f and 6g had the highest herbicidal activity (80% inhibitory) against lettuce and bentgrass.     

Eucleanal A and B:Two new napthalene derivatives from Euclea divinorum

Two new naphthalene derivatives named eucleanal A and B（1 and 2） were isolated from Euclea divinorum.The structures of the new compounds were elucidated by detailed spectroscopic analysis such as ¹H,¹³C NMR,COSY,HMQC,HMBC and HREIMS mass spectrometry.