Experimental Study of Strongly Nonlinear Resonances and Anti-Resonances in Granular Dimer Chains

Previous theoretical works considered the intrinsic dynamics of one-dimensional uncompressed granular dimer (diatomic) chains composed of pairs of dissimilar spherical elastic beads in Hertzian interaction. Such ordered granular media exhibit essentially nonlinear acoustics and have been characterized as ‘sonic vacua’ due to the fact that the speed of sound in these media (as defined in classical acoustics) is zero. Yet, depending on the mass ratios of the pairs of dissimilar beads of these dimers, it was proven that they may possess countable infinities of anti-resonances leading to solitary waves (this in spite of their high inhomogeneity), or countable infinities of strongly nonlinear resonances leading to passive strong attenuation of propagating pulses through energy radiation by means of excitation of traveling waves. The aim of this work is to experimentally verify the existence of these strongly nonlinear dynamics through a series of experiments involving granular dimer chains supported by flexures. By carefully designing the supporting flexures so that their dynamics is sufficiently ‘soft’ and thus separate from the ‘stiff’ dynamics governing the bead to bead interactions, we overcome a basic limitation for the experimental realization of such dimer systems, namely the construction of one-dimensional dimer chains with beads of different radii. Our results confirm experimentally the occurrence of nonlinear resonances and anti-resonances in dimer chains, and conclusively prove the capacity of appropriately designed granular dimers for passive strong attenuation of propagating pulses due to nonlinear resonance. Moreover, we validate the theoretical prediction that within the elastic range of bead to bead dynamical interactions the results are fully re-scalable with respect to energy. This work provides the first experimental evidence of strongly nonlinear resonances and anti-resonances in essentially nonlinear ordered granular media.     

Thiol‐Directed Synthesis of Highly Fluorescent Gold Clusters and Their Conversion into Stable Imaging Nanoprobes

Fluorescent gold clusters (FGCs) with tunable emission from blue to red and quantum yields in the range of 6–17 % have been synthesized by simple modification of the conditions used for the synthesis of gold nanoparticles, namely by replacing the stronger reducing agent with a controlled amount of thiol. Various functional FGCs with hydrodynamic diameters of 5–12 nm have been successfully synthesized and used as cell labels. The results of our investigations strongly indicate that FGCs composed of Au⁰ are more stable imaging probes than commonly reported red/NIR‐emitting FGCs with a composition of Au⁰/Au^I, as this combination rapidly transforms into nonfluorescent large clusters on exposure to light. The FGC‐based nanoprobes reported herein exhibit stable fluorescence upon continuous light exposure and can be used as imaging probes with low cytotoxicity.     

Intracellular Photophysics of an Osmium Complex bearing an Oligothiophene Extended Ligand

This contribution describes the excited-state properties of an Osmium-complex when taken up into human cells. The complex 1 [Os(bpy)₂(IP-4T)](PF₆)₂ with bpy=2,2′-bipyridine and IP-4T=2-{5′-[3′,4′-diethyl-(2,2′-bithien-5-yl)]-3,4-diethyl-2,2′-bithiophene}imidazo[4,5-f][1,10]phenanthroline) can be discussed as a candidate for photodynamic therapy in the biological red/NIR window. The complex is taken up by MCF7 cells and localizes rather homogeneously within in the cytoplasm. To detail the sub-ns photophysics of 1 , comparative transient absorption measurements were carried out in different solvents to derive a model of the photoinduced processes. Key to rationalize the excited-state relaxation is a long-lived ³ILCT state associated with the oligothiophene chain. This model was then tested with the complex internalized into MCF7 cells, since the intracellular environment has long been suspected to take big influence on the excited state properties. In our study of 1 in cells, we were able to show that, though the overall model remained the same, the excited-state dynamics are affected strongly by the intracellular environment. Our study represents the first in depth correlation towards ex-vivo and in vivo ultrafast spectroscopy for a possible photodrug.     

Strong field ionization to multiple electronic states in water

High harmonic spectra show that laser-induced strong field ionization of water has a significant contribution from an inner-valence orbital. Our experiment uses the ratio of H(2)O and D(2)O high harmonic yields to isolate the characteristic nuclear motion of the molecular ionic states. The nuclear motion initiated via ionization of the highest occupied molecular orbital (HOMO) is small and is expected to lead to similar harmonic yields for the two isotopes. In contrast, ionization of the second least bound orbital (HOMO-1) exhibits itself via a strong bending motion which creates a significant isotope effect. We elaborate on this interpretation by solving the time-dependent Schr?dinger equation to simulate strong field ionization and high harmonic generation from the water isotopes. We expect that this isotope marking scheme for probing excited ionic states in strong field processes can be generalized to other molecules.     

Aspherical‐Atom Modeling of Coordination Compounds by Single‐Crystal X‐ray Diffraction Allows the Correct Metal Atom To Be Identified

Single‐crystal X‐ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid‐state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical‐atom least‐squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld‐atom refinement (Acta Crystallogr. Sect. A­ 2008 , 64, 383–393; IUCrJ. 2014 , 1,61–79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B­ 2013 , 69, 91–104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear‐coordinate 3d metal complexes, for which the wrong element is found if standard independent‐atom model scattering factors are relied upon, are studied, and it is shown that only aspherical‐atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed.     

A market-based martingale valuation approach to optimum inventory control in a doubly stochastic jump-diffusion economy

We propose a novel market-based approach to optimum inventory control in a doubly stochastic jump-diffusion economy by modelling a commodity distributor’s inventory investment as a portfolio of forward commitments with explicit accounting of the jump-diffusion dynamics of demands, costs, and prices in open markets. We apply the robust real-asset martingale valuation methodology to derive a closed-form solution for the inventory value and a simple and intuitive optimality condition. Numerical analysis verifies this condition and demonstrates that the resulting optimum policy has robust properties in relation to the stylized effects.     

The analysis of alkyl-capped alcohol ethoxylates and alcohol ethoxycarboxylates from alcohol ethoxylates by atmospheric pressure chemical ionization mass spectrometry

Alcohol ethoxylates (AEs) are nonionic surfactants. They are industrially important compounds that have historically been difficult to analyze, with the best results to date achieved through derivatization (e.g., silylation) followed by analysis by gas chromatography/mass spectrometry (GC/MS). Recently, mass spectrometric techniques such as field desorption (FD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) have been employed to analyze surfynol(R) 4xx. In an effort to produce low-cost alkyl-capped AEs and anionic detergents from AEs, a fast and reliable measure of the product yields and conversions from AEs is required in research. We found that the product yields and conversions from reactions of AEs, obtained by the employment of atmospheric pressure chemical ionization (APCI), were in good agreement with those obtained from proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Therefore, APCI can be used as a validated tool for studying AE reactions. Mixtures that contain either silylated or unsilylated ethoxylates and/or carboxylates yield the same APCI mass spectra. Copyright -Copyright 1999 John Wiley & Sons, Ltd.     

Aerodynamic Focusing Effect in a Rectangular Slit Real Impactor at Different Reynolds Numbers

Numerical investigations were performed to assess the effect of “aerodynamic focusing” achievable by varying the angle of approach in the convergence section of a rectangular slit real impactor, at different Reynolds numbers. Computational Fluid Dynamics (CFD) approach was used as a tool in the study. Simulations were performed on a slit impactor in which the angle of approach in the inlet section was varied from 15° to 75°, at three different Reynolds number values namely 200, 1000, and 2000, to characterize the effect of “aerodynamic focusing”. It is found from the results of the study that the impactor efficiency curve and cut‐point SQRT (Stk)₅₀ value are strong functions of the above parameters. Aerodynamic focusing effect achievable by varying the angle of inlet convergence section is delineated with appropriate particle tracks. Results of the study are expressed as a surface plot of the cut‐point SQRT (Stk)₅₀ value as a function of the Reynolds number and the angle of approach and a correlation relating the parameters is presented.