Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

This study reports a facile method for the assembly of large, array style, coupled dye‐doped microsphere resonators by template‐assisted, in which an aqueous suspension of colloidal microspheres assemble on a patterned template. By exploiting the high resolution of 3D (two‐photon) lithography derived templates, closely packed large arrays, hundreds to thousands of dimers with controlled gap spacing, only limited by the size of the substrate can be achieved. Dye‐doped emissive microspheres with Q‐factors >2.5 × 10² can be achieved and trapped into predetermined cavity positions, thereby controlling the distance between adjacent microspheres. This design allows to scale down dimer spacing from usual 400 nm for traditional photolithography to very small spacing of 50 nm. It is found that exciting individual microspheres in the ensemble shows intense optical cavity modes, whereas closely coupled pairs show controlled mode splitting. Coupling between photoluminescent microspheres is strongly influenced by the gap distance, with strong coupling, equating to normal mode splitting, arising as the gap distance is reduced below traditional sub‐micrometer scale. The coupled dimer assemblies are promising candidates for advancing the development of large‐area coupled nanophotonic structures, beyond the spatial resolution‐limited photolithographical derived arrays.     

Magnetoelectrically Driven Catalytic Degradation of Organics

Here, the catalytic degradation of organic compounds is reported by exploiting the magnetoelectric nature of cobalt ferrite–bismuth ferrite (CFO–BFO) core–shell nanoparticles. The combination of magnetostrictive CFO with multiferroic BFO gives rise to a magnetoelectric engine that purifies water under wireless magnetic fields via advanced oxidation processes, without involvement of any sacrificial molecules or cocatalysts. Magnetostrictive CoFe₂O₄ nanoparticles are fabricated using hydrothermal synthesis, followed by sol–gel synthesis to create the multiferroic BiFeO₃ shell. Theoretical modeling is performed to study the magnetic‐field‐induced polarization on the surface of magnetoelectric nanoparticles. The results obtained from these simulations are consistent with experimental findings of the piezoforce microscopy analysis, where changes in piezoresponse of the nanoparticles under magnetic fields are observed. Next, the magnetoelectric‐effect‐induced catalytic degradation of organic pollutants is investigated under AC magnetic fields, and 97% removal efficiency for synthetic dyes and over 85% removal efficiency for routinely used pharmaceuticals are obtained. Additionally, trapping experiments are performed to elucidate the mechanism behind the magnetic‐field‐induced catalytic degradation of organic pollutants by using scavengers for each of the reactive species. The results indicate that hydroxyl and superoxide radicals are the main reactive species in the magnetoelectrically induced catalytic degradation of organic compounds.     

Capillary Assembly of Liquid Particles

Capillary assembly is a versatile method for depositing colloidal particles within templates, resulting in nano/microarrays and colloidal superstructures for optical, plasmonic, and sensory applications. Liquid particles (LPs), comprised of oligomerized 3‐(trimethoxysilyl)propyl methacrylate, are herein shown to deposit into patterned cavities via capillary assembly. In contrast to solid colloids, LPs coalesce upon solvent evaporation and assume the geometry of the template. Incorporating small molecules such as dyes followed by LP solidification generates fluorescent polymer microarrays of any geometry. The LP size is inversely proportional to the quantity of deposited material and the convexity of the final polymer array. Cavity filling can be tuned by increasing the assembly temperature. Extraction of the polymerized regions produces solidified particles with faceted shapes including square prisms, trapezoids, and ellipsoids with sizes up to 14 µm that retain the shape of the cavity in which they are initially held. LP deposition thus presents a highly controllable fabrication scheme for geometrically diverse polymer microarrays and anisotropic colloids of any conceivable polygonal shape due to space filling of the template. The extension of capillary assembly to LPs that can be doped with small molecule dyes and analytes invaluably expands the synthetic toolbox for top‐down, scalable, hierarchically engineered materials.     

Using structural and semantic measures to improve software modularization

Changes during software evolution and poor design decisions often lead to packages that are hard to understand and maintain, because they usually group together classes with unrelated responsibilities. One way to improve such packages is to decompose them into smaller, more cohesive packages. The difficulty lies in the fact that most definitions and interpretations of cohesion are rather vague and the multitude of measures proposed by researchers usually capture only one aspect of cohesion. We propose a new technique for automatic re-modularization of packages, which uses structural and semantic measures to decompose a package into smaller, more cohesive ones. The paper presents the new approach as well as an empirical study, which evaluates the decompositions proposed by the new technique. The results of the evaluation indicate that the decomposed packages have better cohesion without a deterioration of coupling and the re-modularizations proposed by the tool are also meaningful from a functional point of view.     

Weighted minimal hypersurface reconstruction

Many problems in computer vision can be formulated as a minimization problem for an energy functional. If this functional is given as an integral of a scalar-valued weight function over an unknown hypersurface, then the sought-after minimal surface can be determined as a solution of the functional's Euler-Lagrange equation. This paper deals with a general class of weight functions that may depend on surface point coordinates as well as surface orientation. We derive the Euler-Lagrange equation in arbitrary dimensional space without the need for any surface parameterization, generalizing existing proofs. Our work opens up the possibility of solving problems involving minimal hypersurfaces in a dimension higher than three, which were previously impossible to solve in practice. We also introduce two applications of our new framework: We show how to reconstruct temporally coherent geometry from multiple video streams, and we use the same framework for the volumetric reconstruction of refractive and transparent natural phenomena, bodies of flowing water.     

Influence of NO2 on the selective catalytic reduction of NO with ammonia over Fe-ZSM5

The influence of NO₂ on the selective catalytic reduction (SCR) of NO with ammonia was studied over Fe-ZSM5 coated on cordierite monolith. NO₂ in the feed drastically enhanced the NO_x removal efficiency (DeNOx) up to 600 °C, whereas the promoting effect was most pronounced at the low temperature end. The maximum activity was found for NO₂/NO_x = 50%, which is explained by the stoichiometry of the actual SCR reaction over Fe-ZSM5, requiring a NH₃:NO:NO₂ ratio of 2:1:1. In this context, it is a special feature of Fe-ZSM5 to keep this activity level almost up to NO₂/NO_x = 100%. The addition of NO₂ to the feed gas was always accompanied by the production of N₂O at lower and intermediate temperatures. The absence of N₂O at the high temperature end is explained by the N₂O decomposition and N₂O-SCR reaction. Water and oxygen influence the SCR reaction indirectly. Oxygen enhances the oxidation of NO to NO₂ and water suppresses the oxidation of NO to NO₂, which is an essential preceding step of the actual SCR reaction for NO₂/NO_x < 50%. DRIFT spectra of the catalyst under different pre-treatment and operating conditions suggest a common intermediate, from which the main product N₂ is formed with NO and the side-product N₂O by reaction with gas phase NO₂.     

Surface properties of surfactants derived from natural products. Part 2: Structure/property relationships—Foaming,dispersion, and wetting

Several novel and some previously known, mostly sugar-based, surfactants have been synthesized, and their surface properties have been characterized and compared with commercial nonylphenol ethoxylates. The dispersion properties of the surfactants were studied by mixing carbon black into an aqueous surfactant solution. It was found that open sugars, as the headgroup, give rise to higher conformational repulsion and hence more effective dispersion properties than ringclosed sugar headgroups (e.g., furanoside or pyranoside forms). No conclusions could be made about the differences in dispersion properties between surfactants with aliphatic or aromatic tail groups. Increasing the area of the tail group, however, by using twin-chain tail groups increased the dispersion properties of the surfactants further. The surfactants’ ability for wetting a hydrophobic parafilm surface was studied. The sugar-based surfactants were found generally to possess poor wetting properties.     

Nonoxynol‐9‐α‐cyclodextrin inclusion compound and its application for the controlled release of nonoxynol‐9 spermicide

Nonoxynol‐9 (N‐9) is the most active ingredient in commercially available spermicidal products in the United States. There are many applications of cyclodextrin inclusion complexes (CD‐ICs), but there are no reported studies investigating the formation of and controlled release from a N‐9 spermicide‐CD‐IC. We have successfully formed the inclusion compound between N‐9 and α‐CD using a solution‐heating technique. The N‐9‐α‐CD‐IC was characterized by Fourier Transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and wide angle X‐ray diffraction observations. Silicone elastomer (SILASTIC MDX4‐4210) film embedded with crystalline N‐9‐α‐CD‐IC was prepared and evaluated for its efficacy in the controlled release of N‐9 spermicide against bovine sperm. Silicone elastomer with N‐9‐α‐CD‐IC was as successful in reducing the motility and viability of bovine spermtazoa as silicone elastomer swollen with an equivalent amount of neat N‐9. The permeability of the flexible silicone elastomer apparently enables the N‐9 spermicide to diffuse from its embedded inclusion complex crystals to contact, immobilize, and kill bovine sperm cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007