Yang-mills magnetofluid unification

We generalize the hybrid magnetofluid model of a charged fluid interacting with an electromagnetic field to the dynamics of a relativistic hot fluid interacting with a non-Abelian field. The fluid itself is endowed with a non-Abelian charge and the consequences of this generalization are worked out. Applications of this formalism to the quark gluon plasma are suggested.     

An influence of deposition temperature on structural,optical and electrical properties of sprayed ZnO thin films of identical thickness

Nanocrystalline ZnO thin films were deposited at different temperatures (T_s = 325 °C–500 °C) by intermittent spray pyrolysis technique. The thickness (300 ± 10 nm) independent effect of T_s on physical properties was explored. X-Ray diffraction analysis revealed the growth of wurtzite type polycrystalline ZnO films with dominant c-axis orientation along [002] direction. The crystallite size increased (31 nm–60 nm) and optical band-gap energy decreased (3.272 eV–3.242 eV) due to rise in T_s. Scanning electron microscopic analysis of films deposited at 450 °C confirmed uniform growth of vertically aligned ZnO nanorods. The films deposited at higher T_s demonstrated increased hydrophobic behavior. These films exhibited high transmittance (>91%), low dark resistivity (～10^?2 Ω-cm), superior figure of merit (～10^?3 Ω^?1) and low sheet resistance (～10² Ω/□). The charge carrier concentration (η -/cm³) and mobility (μ – cm²V^?1s^?1) are primarily governed by crystallinity, grain boundary passivation and oxygen desorption effects.     

Martini coarse-grained model for polyethylenimine

As a polycation with diverse applications in biomedical and environmental engineering, polyethylenimine (PEI) can be synthesized with varying degrees of branching, polymerization, and can exist in different protonation states. There have been some interests in molecular modeling of PEI at all-atom or coarse-grained (CG) levels, but present CG models are limited to linear PEIs. Here we present the methodology to systematically categorize bond lengths, bond angles and dihedral angles, which allows us to model branched PEIs. The CG model was developed under the Martini scheme based on eight ~600 Da PEIs, with four different degree of branching at two different protonation states. Comparison of the CG model with all-atom simulations shows good agreement for both local (distributions for bonded interactions) and global (end-to-end distance, radius of gyration) properties, with and without salt. Compatibility of the PEI model with other CG bio-molecules developed under the Martini scheme will allow for large-scale simulations of many PEI-enabled processes. © 2018 Wiley Periodicals, Inc.     

Mechanism for CuPt-type ordering in mixed III–V epitaxial layers

A model is proposed to rationalize the occurence of CuPt-type ordering in mixed III–V epitaxial layers grown on (001) substrates. It is invoked that 2× surface reconstruction occuring on group V terminated (001) surfaces produces dilated and compressed regions in sub-surface layers. The presence of these regions biases the occupation of certain sites during the growth of a layer consisting of atoms differing in their tetrahedral radii. By assuming that the reconstruction always occurs at the growing surface, it is possible to explain the evolution of CuPt-type ordering in epitaxial layers. Also, based on the model, experimental observations pertaining to the influence of growth conditions, surface misorientation and steps on ordering can be rationalized.     

Maximizing the descent statistic

For a subsetS, let the descent statistic (S) be the number of permutations that have descent setS. We study inequalities between the descent statistics of subsets. Each subset (and its complement) is encoded by a list containing the lengths of the runs. We define two preorders that compare different lists based on the descent statistic. Using these preorders, we obtain a complete order on lists of the form (k ⁱ ,P,k ^n–i , whereP is a palindrome, whose first entry is larger thank. We prove a conjecture due to Gessel, which determines the list that maximizes the descent statistic, among lists of a given size and given length. We also have a generalization of the boustrophedon transform of Millar, Sloane and Young.     

Poisson's effects in electrical field flow fractionation

Recent and earlier models of electrical field flow fractionation (ELFFF) have assumed that the electric field within the fluid domain is governed by Laplace's equation. This assumption results in a linear potential and a spatially constant field across the channel and is generally true for very dilute systems and relatively high effective potentials. Experimental studies show, however, that the effective potential within the channel may be less than 1% of the applied potential; this is apparently due to double layer formation and charge buildup at the poles. In such cases, local analyte concentrations can, nonetheless, be orders of magnitude higher than the bulk mean and the local potential small, both of which can lead to a nonlinear spatial distribution of the field strength. In such cases Poisson's equation must be used rather than Laplace's equation. Steady-state ELFFF simulations were performed using a Poisson's equation-based model. The domain in which Laplace's equation is valid was identified and the effects of concentration and effective field strength on device performance were explored.     

Reproducible SERRS from structured gold surfaces

Metallic substrates with ordered spherical cavities have been shown to be very effective for surface-enhanced Raman scattering (SERS) and can be fabricated reproducibly using electrodeposition. The sensitivity of detection is increased by several orders of magnitude by using surface-enhanced resonance Raman scattering (SERRS). In this report we demonstrate SERRS for the first time on electrodeposited gold films templated with colloidal spheres and demonstrate the reproducibility of the response. We also obtain a direct comparison between SERRS and SERS by choosing two dyes, Cy5 and Cy3, which are similar in structure but differ in their excitation maxima, such that one is resonant and the other non-resonant with our laser excitation. As expected, the resonant enhancement is found to be of the order of 10(3) over and above that for SERS. The net SERRS enhancements are shown to be of the order of 10(9). We also find that the resonant enhancement profile of the different peaks for the chromophore follows the plasmonic resonance absorption spectrum obtained for the structured surface.     

Synthesis of lariat organochalcogenoethers based on azacalix[3]arenes for the potentiometric detection of [UO2] ions

The syntheses of organochalcogen-supported azacalix[3]arenes are described in a one-pot manner in satisfactory yields. A remarkably selective potentiometric response was accomplished for uranyl ions over a variety of other metal ions, including alkali (Na⁺, K⁺), alkaline-earth (Mg²⁺, Ca²⁺, Ba²⁺), transition and heavy metal ions (Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Fe³⁺, Zn²⁺, Cd²⁺ and Pb²⁺) using an ion-selective electrode based on compound 3 incorporated into a polymeric (PVC) membrane.     

SERS at structured palladium and platinum surfaces

Palladium and platinum are important catalytic metals, and it would be highly advantageous to be able to use surface enhanced Raman spectroscopy (SERS) to study reactive species and intermediates on their surfaces. In this paper we describe the use of templated electrodeposition through colloidal templates to produce thin (<1 microm) films of palladium and platinum containing close packed hexagonal arrays of uniform sphere segment voids. We show that, even though these films are not rough, when the appropriate film thickness and sphere diameter are employed these surfaces give stable, reproducible surface enhancements for Raman scattering from molecules adsorbed at the metal surface. We report SERS spectra for benzenethiol adsorbed on the structured palladium and platinum surfaces of different thicknesses and void diameters and show that, for 633 nm radiation, enhancements of 1800 and 550 can be obtained for palladium and platinum, respectively.