Scattering of singular beams by subwavelength objects

In recent years, there has been a mounting interest in better methods of measuring nanoscale objects, especially in fields such as nanotechnology, biomedicine, cleantech, and microelectronics. Conventional methods have proved insufficient, due to the classical diffraction limit or slow and complicated measuring procedures. The purpose of this paper is to explore the special characteristics of singular beams with respect to the investigation of subwavelength objects. Singular beams are light beams that contain one or more singularities in their physical parameters, such as phase or polarization. We focus on the three-dimensional interaction between electromagnetic waves and subwavelength objects to extract information about the object from the scattered light patterns.     

Near-infrared hollow waveguide gas sensors

The development of a hollow core waveguide (HWG) gas sensor in combination with a fast and compact near-infrared (NIR) spectrometer is presented. The spectrometer operates in the spectral range of 1200-1400 nm and may thus be applied for the detection of gas-phase analytes providing NIR absorptions in that spectral window such as, e.g., methane. Since mid-infrared spectroscopy in combination with HWGs has already been successfully demonstrated for probing hydrocarbons in the gas phase, the present study investigates the achievable sensitivity in the NIR spectral regime. Methane has been selected as an exemplary analyte due to the fact that it shows strong absorption features in the mid-infrared (mid-IR) fingerprint area, but also overtone bands in the NIR. Since the HWG simultaneously serves as a miniaturized absorption gas cell and as an optical waveguide for NIR radiation, a compact yet optical and cost-efficient sensor device was established providing an interesting alternative in target sensing for mid-IR devices. The achieved limit of detection (LOD) was 5.7% (vol./vol.) methane for a 9.5 cm long HWG, 1.6% (vol./vol.) methane for a 39.1 cm long HWG, and 1.3% (vol./vol.) methane for a setup using a 77.4 cm long HWG, which provides the most practical HWG dimensions among the three investigated setups. Limit of quantitation (LOQ) values were calculated at 20.1% (vol./vol.) methane, 8.7% (vol./vol.) methane, and 5.6% (vol./vol.) methane, respectively.     

Synthesis, X-ray structure and luminescent properties of Sm~(3+) ternary complex with novel heterocyclic β-diketone and 1,10-phenanthroline (Phen)

A new neutral ternary samarium complex Sm(Phen)HL3 in which Phen is 1,10-phenanthroline and HL is (1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)-1,3-propanedione) was synthesized. Molecular structure of this complex was determined by X-ray diffraction. Under UV-light this complex is demonstrated bright red luminescence (λmax=647 nm), which was corresponding to the electric dipole 4G5/2→6H9/2 transition in Sm3+ ion. UV-absorption, excitation and emission spectra of the title compound were investigated.     

Soil Uncertainty and Its Influence on Simulated G/Gmax and Damping Behavior

In this paper, recently developed probabilistic elastoplasticity was applied in simulating cyclic behavior of clay. A simple von Mises elastic–perfectly plastic material model was used for simulation. Probabilistic soil parameters, elastic shear modulus (Gmax) and undrained shear strength (su), needed for the simulation were obtained from correlations with the standard penetration test (SPT) N-value. It has been shown that the probabilistic approach to geo-material modeling captures some of the important aspects—the modulus reduction, material damping ratio, and modulus degradation—of cyclic behavior of clay reasonably well, even with the simple elastic–perfectly plastic material model.     

Influence of the external electric field on propagation of Lamb waves in piezoelectric plates

The influence of the electric field on the properties of the Lamb and SH-waves in piezoelectric Bi(12)GeO(20) and La(3)Ga(5)SiO1(4) crystal plates has been investigated. Using basic equations and boundary conditions, the formulas for computer simulation have been obtained. The effect of acoustic modes hybridization has been considered.     

A recyclable supramolecular membrane for size-selective separation of nanoparticles

Most practical materials are held together by covalent bonds, which are irreversible. Materials based on noncovalent interactions can undergo reversible self-assembly, which offers advantages in terms of fabrication, processing and recyclability, but the majority of noncovalent systems are too fragile to be competitive with covalent materials for practical applications, despite significant attempts to develop robust noncovalent arrays. Here, we report nanostructured supramolecular membranes prepared from fibrous assemblies in water. The membranes are robust due to strong hydrophobic interactions, allowing their application in the size-selective separation of both metal and semiconductor nanoparticles. A thin (12 μm) membrane is used for filtration (～5 nm cutoff), and a thicker (45 μm) membrane allows for size-selective chromatography in the sub-5 nm domain. Unlike conventional membranes, our supramolecular membranes can be disassembled using organic solvent, cleaned, reassembled and reused multiple times.     

Interface toughness of carbon nanotube reinforced epoxy composites

Traditional single-fiber pull-out type experiments were conducted on individual multiwalled carbon nanotubes (MWNT) embedded in an epoxy matrix using a novel technique. Remarkably, the results are qualitatively consistent with the predictions of continuum fracture mechanics models. Unstable interface crack propagation occurred at short MWNT embedments, which essentially exhibited a linear load-displacement response prior to peak load. Deep embedments, however, enabled stable crack extension and produced a nonlinear load-displacement response prior to peak load. The maximum pull-out forces corresponding to a wide range of embedments were used to compute the nominal interfacial shear strength and the interfacial fracture energy of the pristine MWNT-epoxy interface.     

Nanotextured metal copper substrates as powerful and long-lasting fuel cell anodes

Fuel cells (FCs) are promising electrochemical devices that convert chemical energy of fuels directly into electrical energy. We present a new anode material based on nanotextured metal copper for fuel cell applications. We have demonstrated that low-cost copper catalyst anodes act as highly efficient and ultra-long-lasting materials for the direct electro-oxidation of ammonia-borane and additional amine derivatives. High power densities of ca. 1W·cm(-2) (ca. -1 V vs Ag/AgCl at 1 A) are readily achieved at room temperature. We fabricate fuel cell devices based on our nanotextured Cu anodes in combination with commercial air cathodes.     

Quantification of sequential chlorinated ethene degradation by use of a reactive transport model incorporating isotope fractionation

Compound-specific isotope analysis (CSIA) enables quantification of biodegradation by use of the Rayleigh equation. The Rayleigh equation fails, however, to describe the sequential degradation of chlorinated aliphatic hydrocarbons (CAHs) involving various intermediates that are controlled by simultaneous degradation and production. This paper shows how isotope fractionation during sequential degradation can be simulated in a 1D reactive transport code (PHREEQC-2). 12C and 13C isotopes of each CAH were simulated as separate species, and the ratio of the rate constants of the heavy to light isotope equaled the kinetic isotope fractionation factor for each degradation step. The developed multistep isotope fractionation reactive transport model (IF-RTM) adequately simulated reductive dechlorination of tetrachloroethene (PCE) to ethene in a microcosm experiment. Transport scenarios were performed to evaluate the effect of sorption and of different degradation rate constant ratios among CAH species on the downgradient isotope evolution. The power of the model to quantify degradation is illustrated for situations where mixed sources degrade and for situations where daughter products are removed by oxidative processes. Finally, the model was used to interpret the occurrence of reductive dechlorination at a field site. The developed methodology can easily be incorporated in 3D solute transport models to enable quantification of sequential CAH degradation in the field by CSIA.