Creation of hot radiation environments in laser-driven targets

A hot radiation environment, produced by maximizing laser-energy deposition into a small, high- "can," is a platform being developed for investigations of material properties under extreme conditions. In such small targets, almost doubling the laser energy results in only an incremental increase in the x-radiation flux, and almost no increase in the maximum achieved radiation temperature. That most of this additional laser energy is not deposited within the target is a direct consequence of laser-plasma interactions (LPI) outside of the target, which result in high-angle beams never entering the target late in the laser pulse. Accounting for these processes in the modeling results in quantitative agreement for the first time with experiments using very small cans. These findings have provided the scientific foundation for modifying the target geometry to mitigate the LPI and to achieve higher radiation temperatures.     

Experimental demonstration of self-collimation inside a three-dimensional photonic crystal

We present our experimental demonstration of self-collimation inside a three-dimensional (3D) simple cubic photonic crystal at microwave frequencies. The photonic crystal was designed with unique dispersion property and fabricated by a high precision computer-controlled machine. The self-collimation modes were excited by a grounded waveguide feeding and detected by a scanning monopole. Self-collimation of electromagnetic waves in the 3D photonic crystal was demonstrated by measuring the 3D field distribution, which was shown as a narrow collimated beam inside the 3D photonic crystal but a diverged beam in the absence of the photonic crystal.     

ZnO-coated glass fibers for the analysis of trihalomethanes by headspace-solid phase microextraction-gas chromatography

Li₂O-ZrO₂-BaO-SiO₂ glass fibers were produced and their surfaces were coated with zinc oxide. The fibers’ surface morphology was examined by scanning electron microscopy and the zinc oxide layer was characterized by mapping the K_α and L_α lines of zinc by energy dispersive X-ray spectroscopy. The results indicated that a homogeneous and porous layer of ZnO was formed on the fibers’ surface. This layer was subjected to a simultaneous determination of trihalomethanes using headspace-solid phase microextraction-gas chromatography. The study was conducted after evaluating the ideal time of incubation (15 min), extraction (15 min) and desorption (10 min), as well as the effect of the addition of salt (15%, m/v) on the analytical response. A good linear dynamic range was observed individually for trihalomethanes aqueous solutions containing 20 μg L⁻¹ and 500 μg L⁻¹ of trichloromethane, 15 μg L⁻¹ and 250 μg L⁻¹ of dichlorobromomethane and dibromochloromethane and 10 μg L⁻¹ and 100 μg L⁻¹ of tribromomethane, with all the compounds showing correlation coefficients higher than 0.9900.     

Synthesis of musafluorone: a naphthoxanthenone isolated from Musa acuminata

5-Methoxy-3H-naphtho[2,1,8-mna]xanthen-3-one (musafluorone, 1), the only naphthoxanthenone reported so far from Musaceae, was synthesized starting from 2-naphthol in nine steps and resulted in an overall yield of 3%. Grignard addition of phenylmagnesium bromide to 4-methoxyperinaphthenone afforded the corresponding 4-methoxy-9-phenylphenalenone which, after epoxidation and methyl transposition, was subjected to a photochemical cyclization procedure to furnish 1.     

A first structural and theoretical comparison of pyridinylidene-type rNHC (remote N-heterocyclic carbene) and NHC complexes of Ni(II) obtained by oxidative substitution

A series of cationic pyridinylidene and quinolinylidene complexes of chlorobis(triphenylphosphine)-nickel(II) were prepared by oxidative substitution of Ni(PPh3)4 with methylated chloropyridines or chloroquinolines. NMR as well as X-ray crystallographic studies confirmed the trans arrangement of the two phosphines in the products. Calculations, using suitable model compounds at the BP86/TZVP level, clearly differentiate between a standard imidazolylidene complex and new complexes of the NHC-type on the one hand, and new complexes classified as rNHC-types-with the heteroatom distant from the carbene carbon-on the other. The latter form significantly stronger bonds-mainly of an electrostatic nature-with the metal.     

Computational studies on polymer adhesion at the surface of gamma-Al2O3. I. The adsorption of adhesive component molecules from the gas phase

We calculate the minimum energy paths and reaction energies of the adsorption of the epoxide adhesive components diglycidylesterbisphenol A (DGEBA), diethyltriamine (DETA), and the adhesion promoter 3-aminopropylmethoxysilane (AMEO) at two different sites on a model of the native Al2O3 surface, using the nudged elastic band algorithm in conjunction with self-consistent charge-density functional based tight binding. Our results show that the chosen combination of methods is well suited to obtain an overview of the reaction mechanisms and kinetics of the adsorption of organic molecules on inorganic surfaces. The obtained MEP-s show that there is preference for the adsorption of the adhesion promoter, AMEO, over the resin, DGEBA, while the adsorption of the curing agent, DETA, is unfavorable. Our approach also gives an insight into the ranges of the mechanical and electronic influences of the adsorption process on the interface, which neither full ab initio methods nor force field approaches can provide. These results will help to develop a quantum mechanics-molecular mechanics multiscale embedding scheme for more detailed studies of organic/inorganic hybrid interface reactions.     

Products of random variables and the first digit phenomenon

We provide conditions on dependent and on non-stationary random variables $X_n$ ensuring that the mantissa of the sequence of products $\left({\prod }_1^n{X}_k\right)$ is almost surely distributed following Benford’s law or converges in distribution to Benford’s law. This is achieved through proving new generalizations of Lévy’s and Robbins’s results on distribution modulo 1 of sums of independent random variables.     

A hybrid of adaptive large neighborhood search and tabu search for the order-batching problem

Given a set of customer orders and a routing policy, the goal of the order-batching problem?(OBP) is to group customer orders to picking orders (batches) such that the total length of all tours through a rectangular warehouse is minimized. Because order picking is considered the most labor-intensive process in warehousing, effectively batching customer orders can result in considerable savings. The OBP is NP-hard if the number of orders per batch is greater than two, and the exact solution methods proposed in the literature are not able to consistently solve larger instances. To address larger instances, we develop a metaheuristic hybrid based on adaptive large neighborhood search and tabu search, called ALNS/TS. In numerical studies, we conduct an extensive comparison of ALNS/TS to all previously published OBP methods that have used standard benchmark sets to investigate their performance. ALNS/TS outperforms all comparison methods with respect to both average solution quality and run-time. Compared to the state-of-the-art, ALNS/TS shows the clearest advantages on the larger instances of the existing benchmark sets, which assume a higher number of customer orders and higher capacities of the picking device. Finally, ALNS/TS is able to solve newly generated large-scale instances with up to 600 customer orders and six articles per customer order with reasonable run-times and convincing scaling behavior and robustness.