Copper(II) triflate catalyzed amination and aziridination of 2-alkyl substituted 1,3-dicarbonyl compounds

A method to prepare α-acyl-β-amino acid and 2,2-diacyl aziridine derivatives efficiently from Cu(OTf)(2) + 1,10-phenanthroline (1,10-phen)-catalyzed amination and aziridination of 2-alkyl substituted 1,3-dicarbonyl compounds with PhI═NTs is described. By taking advantage of the orthogonal modes of reactivity of the substrate through slight modification of the reaction conditions, a divergence in product selectivity was observed. In the presence of 1.2 equiv of the iminoiodane, amination of the allylic C-H bond of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, was found to selectively occur and give the β-aminated adduct. On the other hand, increasing the amount of the nitrogen source from 1.2 to 2-3 equiv was discovered to result in preferential formal aziridination of the C-C bond of the 2-alkyl substituent of the starting material and formation of the aziridine product.     

All-cellulose nanocomposites by surface selective dissolution of bacterial cellulose

All-cellulose nanocomposites using bacterial cellulose (BC) as a single raw material were prepared by a surface selective dissolution method. The effect of the immersion time of BC in the solvent (lithium chloride/N,N-dimethylacetamide) during preparation on the nanocomposite properties was investigated. The structure, morphology and mechanical properties of the nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and tensile testing. The optimum immersion time of 10 min allowed the preparation of nanocomposites with an average tensile strength of 411 MPa and Young’s modulus of 18 GPa. With the longest immersion time of 60 min, the prepared composite sheet turns to express a very high toughness characteristic possessing a work-to-fracture as high as 16 MJ/m³. These biobased nanocomposites show high performances thanks to their unique structure and properties.     

Combined Raman spectroscopy and optical coherence tomography device for tissue characterization

We report a dual-modal device capable of sequential acquisition of Raman spectroscopy (RS) and optical coherence tomography (OCT) along a common optical axis. The device enhances application of both RS and OCT by precisely guiding RS acquisition with OCT images while also compensating for the lack of molecular specificity in OCT with the biochemical specificity of RS. We characterize the system performance and demonstrate the capability to identify structurally ambiguous features within an OCT image with RS in a scattering phantom, guide acquisition of RS from a localized malignancy in ex vivo breast tissue, and perform in vivo tissue analysis of a scab.     

嗜碱芽孢杆菌NTT89启动子的克隆及其表达

报导了以启动子探测质粒pKK232-8为载体克隆嗜碱芽孢杆菌NTT89启动子的研究.用限制性内切酶Hindl分别消化嗜碱芽孢杆菌NTT89染色体DNA和质粒pKK232-8,在体外重组,转化大肠杆菌DH5a感受态细胞,在含氨苄青霉素和氯霉素的选择性平板上筛选转化子,结果从NTT89染色体DNA中克隆到一系列带有启动子活性的DNA片段,并在大肠杆菌中得到表达,这些转化子抗氯霉素水平在34～500mg/L不等,随机挑选10个转化子,提取其重组质粒进行限制性酶切,表明转化子中的重组质粒外源片段插入的效率很高,插入片段大小在500～5500bp之间,通过地高辛标记的点杂交和Southern杂交均证明重组质粒上插入的具启动子功能的DNA片段来自于嗜碱芽孢杆菌的染色体DNA.     

On a free-boundary problem arising in the study of flame propagation

The existence of a weak solution of a two-dimensional non-stationary free-boundary problem related to flame propagation is established. The main feature of the problem is that the nonlinear coupling of the two parabolic equations occur on the free boundary and has exponential growth.     

Optimal Shape Control Problem for the Navier–Stokes Equations, Part 2

Feedback laws for a closed-loop multicontrol inverse problem for a plane viscous nonstationary incompressible flow are established. The shape and the inflow are to be determined from partial measurements of the flow in a fixed subregion.     

Generalized median solutions,strategy-proofness and strictly convex norms

Generalized location problems withn agents are considered, who each report a point inm-dimensional Euclidean space. A solution assigns a compromise point to thesen points, and the individual utilities for this compromise point are equal to the negatives of the distances to the individual positions. These distances are measured by a given strictly convex norm, common to all agents. Form=2, it is shown that if a Pareto optimal, strategy-proof and anonymous solution exists, thenn must be odd, and the solution is obtained by taking the median coordinatewise, where the coordinates refer to a basis that is orthogonal with respect to the given norm. Furthermore, in that case (m=2) such a solution always exists. Form > 2, existence of a solution depends on the norm.Supported by a grant from the Cooperation Centre Tilburg and Eindhoven University.     

Effect of Bulk and Interfacial Rheological Properties on Bubble Dissolution

This paper describes theoretical calculations of the combined effect of bulk and interfacial rheological properties on dissolution behavior of a bubble in an infinite medium at saturated conditions. Either bulk or interfacial elasticity can stop the bubble dissolution process, and stability criteria are defined for the elastic cases. In the case of an elastic interface with dilation modulus E(d) and a bubble with an initial radius R(0) and initial interfacial tension sigma(0), the bubble is stabilized as it has shrunk to a relative radius of varepsilon=R/R(0)=exp(-sigma(0)/2E(d))). In case of an elastic bulk with modulus G a bubble will shrink until GR(0)=4sigma(0)varepsilon(3)/(1-5varepsilon(4)+4varepsilon(3)) is fulfilled. Bulk and interfacial viscosity can retard the dissolution process if their magnitude exceeds a certain critical value but will never completely stop bubble dissolution. Copyright 2001 Academic Press.     

Determination of tritium in natural waters

A study of the tritium content of precipitation and of river water samples, collected during a seasonal maximum of tritium concentration in 1976 is given. The measurements were made for precipitation in Belgrade from April to December 1976, and for river water from the Sava (in Belgrade), the Tisa at 137 km, and the Danube at 1425 km, 1174 km, 861 km from the confluence. The maximum monthly value of the tritium content of precipitation is 135 TU, and the Danube at 1425 km has a maximum of 196 TU (627 pCi/l). In general, there is no correlation between the amount of precipitation and river water with tritium content.     

Modular approach for novel nanostructered polycondensates enabled by the unique selectivity of carbonyl biscaprolactam

New enabling chemistries have been developed to produce novel well‐defined polymeric materials through the additions of small amounts of reactive functional compounds to standard polymers during regular processing steps. We found that carbonyl biscaprolactam and its derivatives couple polymer chains in a strictly linear fashion. The requirements for fast and well‐controlled coupling reactions, a prerequisite to apply this modular concept, were met. The breakthrough to produce a wide variety of novel polymers came when we found that many building blocks, provided with functional groups and blocked isocyanate groups, could be made on the basis of this chemistry. Blocked isocyanate groups are very suitable coupling units to fix desired functions onto polymer backbones. In one example, antifouling coatings were prepared by introducing fluorine groups. In another case, blocked isocyanate functional acrylates were built into a polyacrylate to make self‐crosslinkable coatings. In another illustration, the concept was demonstrated by a novel route to prepare polyrotaxanes from rotaxane monomers provided with blocked isocyanates as polymerizable stopper groups. These reactive functional compounds gave, in a controlled manner, polymeric materials with substantially improved properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3198–3205, 2003