A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization of Amine–Boranes to Cyclic Boranes under Mild Conditions

We recently disclosed a new ruthenium‐catalyzed dehydrogenative cyclization process (CDC) of diamine–monoboranes leading to cyclic diaminoboranes. In the present study, the CDC reaction has been successfully extended to a larger number of diamine–monoboranes ( 4 – 7 ) and to one amine–borane alcohol precursor ( 8 ). The corresponding NB(H)N‐ and NB(H)O‐containing cyclic diaminoboranes ( 12 – 15 ) and oxazaborolidine ( 16 ) were obtained in good to high yields. Multiple substitution patterns on the starting amine–borane substrates were evaluated and the reaction was also performed with chiral substrates. Efforts have been spent to understand the mechanism of the ruthenium CDC process. In addition to a computational approach, a strategy enabling the kinetic discrimination on successive events of the catalytic process leading to the formation of the NB(H)N linkage was performed on the six‐carbon chain diamine–monoborane 21 and completed with a ¹⁵N NMR study. The long‐life bis‐σ‐borane ruthenium intermediate 23 possessing a reactive NHMe ending was characterized in situ and proved to catalyze the dehydrogenative cyclization of 1 , ascertaining that bis σ‐borane ruthenium complexes are key intermediates in the CDC process.     

Buzzwords on their way to a tipping‐point: A view from the blogosphere

“Buzzwords” are new words (i.e., neologisms) that enter the language and acquire great popularity as “fashion words.” To date, the dynamic aspect of buzzwords has not been the subject of a rigorous scientific analysis. In this study, we analyzed the appearance of buzzwords in the blogosphere and compared their dynamics to the one of nonpopular neologisms and well‐established words. It was found that the growth rate of buzzwords is exponential and higher than that of the blogosphere. Moreover, we have identified general early warning signals for an approaching tipping point in the dynamics of buzzwords indicating that as fashion words they are on their way to a tipping‐point of decline. The article presents these findings and others and concludes by presenting a model for studying the dynamics of new words entering the language. © 2010 Wiley Periodicals, Inc. Complexity 16: 58‐68, 2011     

A novel homogeneous immunoassay for anthrax detection based on the AlphaLISA method: detection of B. anthracis spores and protective antigen (PA) in complex samples

Amplified Luminescent Proximity Homogeneous Assay (AlphaLISA) technology is an energy-transfer-based assay, utilizing singlet oxygen as an energy donor to a fluorescent acceptor. The long singlet oxygen migration distance allows the energy transfer mechanism to go up to ～200 nm, facilitating flexible and sensitive homogeneous immunoassays. While soluble protein detection using AlphaLISA was previously described, the detection of particles such as bacteria and viruses was not reported. In this work, we show for the first time the implementation of the AlphaLISA technology for the detection of a particulate antigen, i.e., Bacillus anthracis spores. Here, we show that an efficient particle immunoassay requires a high acceptor-to-donor ratio (>4:1). The results suggested that the high acceptor/donor ratio is required to avoid donor aggregation (“islands”) on the spore surface, hence facilitating donor/acceptor interaction. The developed assay enabled the detection of 10⁶ spores/mL spiked in PBS. We also demonstrate the development of a highly sensitive AlphaLISA assay for the detection of the main toxin component of anthrax, protective antigen (PA). The assay enabled the detection of 10 and 100 pg/mL PA in buffer and spiked naïve rabbit sera, respectively, and was successfully implemented in sera of anthrax-infected rabbits. To summarize, this study demonstrates that AlphaLISA enables detection of anthrax spores and toxin, utilizing short homogeneous assays. Moreover, it is shown for the first time that this technology facilitates the detection of particulate entities and might be suitable for the detection of other bacteria or viruses.     

Lefschetz properties and basic constructions on simplicial spheres

The well known g-conjecture for homology spheres follows from the stronger conjecture that the face ring over the reals of a homology sphere, modulo a linear system of parameters, admits the strong-Lefschetz property. We prove that the strong-Lefschetz property is preserved under the following constructions on homology spheres: join, connected sum, and stellar subdivisions. The last construction is a step towards proving the g-conjecture for piecewise-linear spheres.     

A nonlinear symmetry breaking effect in shear cracks

Shear cracks propagation is a basic dynamical process that mediates interfacial failure. We develop a general weakly nonlinear elastic theory of shear cracks and show that these experience tensile-mode crack tip deformation, including possibly opening displacements, in agreement with Stephenson's prediction. We quantify this nonlinear symmetry breaking effect, under two-dimensional deformation conditions, by an explicit inequality in terms of the first and second order elastic constants in the quasi-static regime and by semi-analytic calculations in the fully dynamic regime. Our general results are applied to various materials. Finally, we discuss related works in the literature and note the potential relevance of elastic nonlinearities for various problem, including frictional sliding.     

Separation/preconcentration of trace amounts of Cr, Cu and Pb in environmental samples by magnetic solid-phase extraction with Bismuthiol-II-immobilized magnetic nanoparticles and their determination by ICP-OES

A new method for separation/preconcentration of trace amounts of Cr, Cu and Pb in environmental samples by magnetic solid-phase extraction (SPE) with Bismuthiol-II-immobilized magnetic nanoparticles and their determination by ICP-OES has been developed. The separation of the target analytes from the aqueous solution containing the target analytes and Bismuthiol-II-immobilized magnetic nanoparticles was simply achieved by applying external magnetic field. Optimal experimental conditions including pH, sample volume, eluent concentration and volume and co-existing ions have been studied and established. Under the optimal experimental conditions, the detection limits for Cr, Cu and Pb with enrichment factors of 96, 95 and 87 were found to be 0.043, 0.058 and 0.085 ng mL⁻¹ and their relative standard deviations (R.S.D.s) were 3.5%, 4.6% and 3.7% (n = 5, C = 2 ng mL⁻¹), respectively. The method was validated with certified reference material (GBW50009-88) of environmental water sample and the analytical results coincided well with the certified values. Furthermore, the method was successfully applied to the determination of target analytes in river and lake water samples. Compared with established methods, the proposed method is characterized with high enrichment factor, fast separation and low detection limits.