Strong Light‐Molecule Coupling on Plasmonic Arrays of Different Symmetry

The strong coupling of porphyrin J‐aggregates to plasmonic nanostructures of different symmetry is investigated. The nanostructures of higher symmetry show the strongest interaction with the molecular layer, suggesting that surface plasmon mode degeneracy plays an important role in the coupling efficiency. At high coupling strengths a new, weakly dispersive mode appears which has recently been predicted theoretically to be due to long‐range energy transfer between molecules mediated by surface plasmons. These findings point to new ways for optimizing strong coupling and thereby realize its full potential for molecular and material science.     

Online time-constrained scheduling in linear and ring networks

We consider the problem of scheduling a sequence of packets over a linear network, where every packet has a source and a target, as well as a release time and a deadline by which it must arrive at its target. The model we consider is bufferless, where packets are not allowed to be buffered in nodes along their paths other than at their source. This model applies to optical networks where opto-electronic conversion is costly, and packets mostly travel through bufferless hops. The offline version of this problem was previously studied in M. Adler et al. (2002) [3]. In this paper we study the online version of the problem, where we are required to schedule the packets without knowledge of future packet arrivals. We use competitive analysis to evaluate the performance of our algorithms. We present the first online algorithms for several versions of the problem. For the problem of throughput maximization, where all packets have uniform weights, we give an algorithm with a logarithmic competitive ratio, and present some lower bounds. For other weight functions, we show algorithms that achieve optimal competitive ratios.     

Submerged Arc Breakdown of Methylene Blue in Aqueous Solutions

Low voltage, low energy submerged pulsed arcs between a pair of carbon or iron electrodes with a pulse repetition rate of 100?Hz, energies of 2.6?C192?mJ and durations of 20, 50 and 100???s were used to remove methylene blue (MB) contamination from 30?ml aqueous solutions. The MB concentration decreased exponentially with rates of 0.0006?C0.0143?s^?1 during processing with the carbon electrode pair. With the iron electrodes, the MB concentration initially decreased faster (0.030?s^?1) than with the carbon electrodes, but later saturated. However when microparticles produced with the iron electrodes were periodically filtered, the high removal rate was maintained. Under these conditions, the volume of water which can be treated per unit energy expenditure was much higher with the submerged arc than with other plasma processes. A kinetic model based on MB degradation by OH· radicals formed by the discharge was formulated. The higher initial MB removal rate with iron electrodes is explained by additional OH· production from Fenton??s reaction between Fe⁺⁺ and H₂O₂ produced by the discharge. This rate is maintained if the eroded iron particles are filtered, but if eroded iron particles accumulate, degradation slows down and stops, possibly because the iron particles catalytically decompose H₂O₂ and hence stops Fenton??s reaction, and either directly or via increased Fe⁺⁺ dissolved from the particles, scavenge the OH· radicals.     

Microstructure-controlled aerosol-gel synthesis of ZnO quantum dots dispersed in SiO2 nanospheres

ZnO quantum dots dispersed in a silica matrix were synthesized from a TEOS:Zn(NO(3))(2) solution by a one-step aerosol-gel method. It was demonstrated that the molar concentration ratio of Zn to Si (Zn/Si) in the aqueous solution was an efficient parameter with which to control the size, the degree of agglomeration, and the microstructure of ZnO quantum dots (QDs) in the SiO(2) matrix. When Zn/Si ≤ 0.5, unaggregated quantum dots as small as 2 nm were distributed preferentially inside SiO(2) spheres. When Zn/Si ≥ 1.0, however, ZnO QDs of ～7 nm were agglomerated and reached the SiO(2) surface. When decreasing the ratio of the Zn/Si, a blue shift in the band gap of ZnO was observed from the UV/Visible absorption spectra, representing the quantum size effect. The photoluminescence emission spectra at room temperature denoted two wide peaks of deep-level defect-related emissions at 2.2-2.8 eV. When decreasing Zn/Si, the first peak at ～2.3 eV was blue-shifted in keeping with the decrease in the size of the QDs. Interestingly, the second visible peak at 2.8 eV disappeared in the surface-exposed ZnO QDs when Zn/Si ≥ 1.0.     

Aerobic oxidation of benzylic alcohols with solid alkaline metal hydroxides

Solid alkaline metal hydroxides displayed high catalytic activity and full selectivity in the aerobic oxidation of benzylic alcohols in a non-polar medium. The activity of the solid bases, in decreasing order of reactivity, was KOH > NaOH ≫ LiOH. Water, which is the only by-product of the reaction, plays a crucial role in KOH deactivation by converting the crystal phase of KOH to KOH · H₂O, as confirmed by XRD measurements.     

Quality assurance systems in research and routine analytical laboratories

 In our article we explain the connections between the implementation of quality assurance (QA) in research and routine analytical laboratories. J. K. Taylor claims that QA in an analytical laboratory consists of two independent but closely related terms, quality control and quality assessment. If we construct the QA system according to his ideas, problems concerning quality can be solved with only one concept regardless of the type of analytical laboratory. Therefore there is no need to introduce new QA standards for research laboratories as suggested in some papers. In the routine laboratory quality control is more important, while in the research laboratory quality assessment is dominant.

     

Analytical Methods for Determination of Non-Nutritive Sweeteners in Foodstuffs

Sweeteners have been used in food for centuries to increase both taste and appearance. However, the consumption of sweeteners, mainly sugars, has an adverse effect on human health when consumed in excessive doses for a certain period, including alteration in gut microbiota, obesity, and diabetes. Therefore, the application of non-nutritive sweeteners in foodstuffs has risen dramatically in the last decade to substitute sugars. These sweeteners are commonly recognized as high-intensity sweeteners because, in a lower amount, they could achieve the same sweetness of sugar. Regulatory authorities and supervisory agencies around the globe have established the maximum amount of these high-intensity sweeteners used in food products. While the regulation is getting tighter on the market to ensure food safety, reliable analytical methods are required to assist the surveillance in monitoring the use of high-intensity sweeteners. Hence, it is also necessary to comprehend the most appropriate method for rapid and effective analyses applied for quality control in food industries, surveillance and monitoring on the market, etc. Apart from various analytical methods discussed here, extraction techniques, as an essential step of sample preparation, are also highlighted. The proper procedure, efficiency, and the use of solvents are discussed in this review to assist in selecting a suitable extraction method for a food matrix. Single- and multianalyte analyses of sweeteners are also described, employing various regular techniques, such as HPLC, and advanced techniques. Furthermore, to support on-site surveillance of sweeteners’ usage in food products on the market, non-destructive analytical methods that provide practical, fast, and relatively low-cost analysis are widely implemented.     

“Raft” Formation by Two‐Dimensional Self‐Assembly of Block Copolymer Rod Micelles in Aqueous Solution

Block copolymers can form a broad range of self‐assembled aggregates. In solution, planar assemblies usually form closed structures such as vesicles; thus, free‐standing sheet formation can be challenging. While most polymer single crystals are planar, their growth usually occurs by uptake of individual chains. Here we report a novel lamella formation mechanism: core‐crystalline spherical micelles link up to form rods in solution, which then associate to yield planar arrays. For the system of poly(ethylene oxide)‐block‐polycaprolactone in water, co‐assembly with homopolycaprolactone can induce a series of morphological changes that yield either rods or lamellae. The underlying lamella formation mechanism was elucidated by electron microscopy, while light scattering was used to probe the kinetics. The hierarchical growth of lamellae from one‐dimensional rod subunits, which had been formed from spherical assemblies, is novel and controllable in terms of product size and aspect ratio.     

I/f noise in systems showing stochastic resonance

Stochastic resonator systems with input and/or output 1/f noise have been studied. Disordered magnets/dielectrics serve as examples for the case of output 1/f noise with white noise (thermal excitation) at the input of the resonators. Due to the fluctuation-dissipation theorem, the output noise is related to the out-of-phase component of the periodic peak of the output spectrum. Spin glasses and ferromagnets serve as interesting examples of coupled stochastic resonators. A proper coupling can lead to an extremely large signal-to-noise ratio. As a model system, a l/f-noise-driven Schmitt trigger has been investigated experimentally to study stochastic resonance with input 1/f noise. Under proper conditions, we have found several new nonlinearity effects, such as peaks at even harmonics, holes at even harmonics, and 1/f noise also in the output spectrum.