Radical reactions of (2-trimethylsilylallyl)triphenylstannane with alkyl halides: A neutral acetone enolate equivalent

Facile transfer of 2-trimethylsilylallyl group is achieved when (2-trimethylsilylallyl)triphenylstannane is reacted with some halides under radical reaction conditions.     

Cyclopolymerization of dimethyl dipropargylmalonate in supercritical carbon dioxide to give a highly regular polyene containing predominantly five-membered rings

Poly(dimethyl dipropargylmalonate) synthesized in scCO2 contained more than 95% five-membered rings, i.e., highly regular polyene was produced, which shows carbon dioxide as a reaction medium plays a significant role in determining a highly selective polymer structure.     

Mesoscopic resonating valence bond system on a triple dot

We theoretically introduce a mesoscopic pendulum from a triple dot. The pendulum is fastened through a singly occupied dot (spin qubit). Two other strongly capacitively coupled islands form a double-dot charge qubit with one electron in excess oscillating between the two low-energy charge states (1,0) and (0,1). The triple dot is placed between two superconducting leads. Under realistic conditions, the main proximity effect stems from the injection of resonating singlet (valence) bonds on the triple dot. This gives rise to a Josephson current that is charge- and spin-dependent and, as a consequence, exhibits a distinct resonance as a function of the superconducting phase difference.     

Empirical Modeling of a Hydraulic Actuator in a Vehicle Control System

The pressure information of a hydraulic actuator plays a key role in modern vehicle control and fault diagnosis. The difficulty in measuring pressure directly naturally motivates such an indirect approach as an observer whose accuracy depends heavily upon the availability of a high fidelity model of a hydraulic actuator. Notwithstanding its success in understanding the dynamics of the first principle model of a hydraulic actuator, it is not suited to controller/observer design due to its complexity. This paper presents an alternative to the first principle modeling methodology: an empirical approach to hydraulic actuator modeling. Linear and nonlinear system identification techniques are applied to obtain low-order models of a hydraulic actuator. Experimental results show how the empirical models reproduce the key features of a hydraulic actuator with sufficient accuracy.     

Unstable Surface Waves in Running Water

We consider the stability of periodic gravity free-surface water waves traveling downstream at a constant speed over a shear flow of finite depth. In case the free surface is flat, a sharp criterion of linear instability is established for a general class of shear flows with inflection points and the maximal unstable wave number is found. Comparison to the rigid-wall setting testifies that the free surface has a destabilizing effect. For a class of unstable shear flows, the bifurcation of nontrivial periodic traveling waves is demonstrated at all wave numbers. We show the linear instability of small nontrivial waves that appear after bifurcation at an unstable wave number of the background shear flow. The proof uses a new formulation of the linearized water-wave problem and a perturbation argument. An example of the background shear flow of unstable small-amplitude periodic traveling waves is constructed for an arbitrary vorticity strength and for an arbitrary depth, illustrating that vorticity has a subtle influence on the stability of free-surface water waves.     

PubChemSR: A search and retrieval tool for PubChem

Background  

Recent years have seen an explosion in the amount of publicly available chemical and related biological information. A significant step has been the emergence of PubChem, which contains property information for millions of chemical structures, and acts as a repository of compounds and bioassay screening data for the NIH Roadmap. There is a strong need for tools designed for scientists that permit easy download and use of these data. We present one such tool, PubChemSR.     

Two-dimensional colloid crystals templated by polyelectrolyte multilayer patterns

In this paper, we demonstrate that two-dimensional (2D) periodic patterns of polyelectrolyte multilayers (PEMs) can be used as surface templates for assembling highly ordered 2D colloidal microarrays. We report detailed structural features of the 2D colloid crystals produced by depositing silica microspheres onto periodic micrometer-scale PEM patterns arrayed in a square or hexagonal lattice with a pattern pitch (approximately) twice the pattern diameter. Analysis of the images of these 2D colloid monolayers reveals that the distributions of the distances by which the adsorbed particles deviate from the corresponding PEM pattern centers are typically bell-shaped, with the majority of the deposited particles located within a relatively short distance from the respective pattern centers. We show that this behavior reflects the effect of the electrostatic focusing force that (occurs because of the finite size of the PEM pattern and) becomes effective when the depositing particle approaches the pattern site to a small distance. Also, in these 2D colloid crystals, the orientations of the off-center displacements of the deposited particles are strongly correlated spatially over the entire sample size. We present experimental evidence that this unusually long-ranged orientational correlation is due to the close spacing of the patterns, which causes an overlap of the excluded volumes between the neighboring deposited particles.     

Enhanced coercivity in sponge magnets with three dimensionally ordered nanopores

Nanoporous magnets are new promising materials particularly useful in biological assays and ion separations. This letter deals with a simple method for making porous magnets composed of cobalt ferrite, where polymer colloidal spheres were used as sacrificial templates. Compared with the bulk congener the porous cobalt ferrite shows enhancements in coercive field and magnetization, which could be associated with the presence of nanopores ordered three dimensionally. Using the sponge magnet complete removal of magnetic Cu and Fe ions was achieved while partial removal was observed with porous silicate having the same size of nanopores.