Comparison of nonequilibrium molecular dynamics with experimental measurements in the nonlinear shear-thinning regime

Nonequilibrium molecular dynamics of a low-molecular-weight fluid (squalane) are compared with experimental measurements in both the linear (Newtonian) and nonlinear (non-Newtonian) regimes. The experimental and simulation data are shown to follow the same time-temperature superposition master curve. This represents the first comparison of the nonlinear rheology predicted by nonequilibrium molecular dynamics with experiment, and is thus the first experimental test of nonequilibrium molecular dynamics simulations in the nonlinear regime.     

The spin-strain coupling tensor in ruby: Measurement of the line-splitting elements

Two combinations of the four line-splitting elements of the spin-strain coupling tensor $\text{G}\text{?}$ for ruby have been measured using second-harmonic detection of ultrasonically-modulated EPR. With the assumption G₁₆ = G₄₅ = 0 these yield G₂₅ = ±1.45 ±0.08 and G₅₂ = ±1.47 ±0.06 cm^-1/unit strain with G₂₅/G₅₂ positive.     

Ground-state entanglement of the BCS model

The concept of local concurrence is used to quantify the entanglement between a single qubit and the remainder of a multiqubit system. For the ground state of the BCS model in the thermodynamic limit the set of local concurrences completely describes the entanglement. As a measure for the entanglement of the full system we investigate the average local concurrence (ALC). We find that the ALC satisfies a simple relation with the order parameter. We then show that for finite systems with a fixed particle number, a relation between the ALC and the condensation energy exposes a threshold coupling. Below the threshold, entanglement measures besides the ALC are significant.     

Comparison of the (17)O NMR spectra of zeolites LTA and LSX

¹⁷O NMR studies of various cation-exchanged LTA and LSX zeolites have shown similarities between the two systems. LSX samples containing divalent cations contain resonances with similar chemical shifts to those previously assigned to ‘bare’ framework oxygen atoms in Ca-LTA and Sr-LTA. The assignments are consistent with the trends seen in the spectra of monovalent cation-containing LSX and LTA zeolites, which show an increase in the average chemical shift with increasing cationic radius. The spectrum of Li-LSX, like Na-LSX, can be assigned based on the T–O–T bond angles. Gas sorption studies on Li-LSX are used to help identify the framework oxygen atoms that form the β-cages and demonstrate the sensitivity of the ¹⁷O shifts to gas loading.     

Hypochlorite-mediated fragmentation of hyaluronan, chondroitin sulfates, and related N-acetyl glycosamines: evidence for chloramide intermediates, free radical transfer reactions, and site-specific fragmentation

Myeloperoxidase released from activated phagocytes reacts with H(2)O(2) in the presence of chloride ions to give hypochlorous acid. This oxidant has been implicated in the fragmentation of glycosaminoglycans, such as hyaluronan and chondroitin sulfates. In this study it is shown that reaction of HOCl with glycosaminoglycans and model compounds yields chloramides derived from the N-acetyl function of the glycosamine rings. The results of EPR spin trapping and product studies are consistent with the formation of amidyl radicals from these chloramides via both metal ion-dependent and -independent processes. In the case of glycosaminoglycan-derived amidyl radicals, evidence has been obtained in studies with model glycosides that these radicals undergo rapid intramolecular abstraction reactions to give carbon-centered radicals at C-2 on the N-acetyl glycosamine rings (via a 1,2-hydrogen atom shift) and at C-4 on the neighboring uronic acid residues (via 1,5-hydrogen atom shifts). The C-4 carbon-centered radicals, and analogous species derived from model glycosides, undergo pH-independent beta-scission reactions that result in glycosidic bond cleavage. With N-acetyl glucosamine C-1 alkyl glycosides, product formation via this mechanism is near quantitative with respect to chloramide loss. Analogous reactions with the glycosaminoglycans result in selective fragmentation at disaccharide intervals, as evidenced by the formation of "ladders" on gels; this selectivity is less marked under atmospheric oxygen concentrations than under anoxic conditions, due to competing peroxyl radical reactions. As the extracellular matrix plays a key role in mediating cell adhesion, growth, activation, and signaling, such HOCl-mediated glycosaminoglycan fragmentation may play a key role in disease progression and resolution, with the resulting fragments modulating the magnitude and quality of the immune response in inflammatory conditions.     

Cytotoxicity and inflammation in human alveolar epithelial cells following exposure to occupational levels of gold and silver nanoparticles

This study explores the viability of rare earth-doped zirconia nanophosphors as probable candidates for white light emission. Undoped ZrO₂ and single- and double-doped ZrO₂:M (where M?=?Tb³⁺ and Eu³⁺) nanophosphors have been synthesized using a simple sonochemical process. The products were characterized using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), and photoluminescence spectrophotometry. The SEM micrographs show that resultant nanoparticles have dendritic shape. TEM and HRTEM studies showed that the size of the majority of the nanoparticles were around 28?±?5?nm. Characteristic blue and green emission from Tb³⁺ ions and red from Eu³⁺ dopant ions were observed. The CIE coordinates of the double-doped ZrO₂:Tb³⁺ (1.2?%):Eu³⁺ (0.8?%) nanophosphor lie in the white light region of the chromaticity diagram and show promise as good phosphor materials for new lighting devices.     

Linking local environments and hyperfine shifts: a combined experimental and theoretical (31)P and (7)Li solid-state NMR study of paramagnetic Fe(III) phosphates

Iron phosphates (FePO(4)) are among the most promising candidate materials for advanced Li-ion battery cathodes. This work reports upon a combined nuclear magnetic resonance (NMR) experimental and periodic density functional theory (DFT) computational study of the environments and electronic structures occurring in a range of paramagnetic Fe(III) phosphates comprising FePO(4) (heterosite), monoclinic Li(3)Fe(2)(PO(4))(3) (anti-NASICON A type), rhombohedral Li(3)Fe(2)(PO(4))(3) (NASICON B type), LiFeP(2)O(7), orthorhombic FePO(4)·2H(2)O (strengite), monoclinic FePO(4)·2H(2)O (phosphosiderite), and the dehydrated forms of the latter two phases. Many of these materials serve as model compounds relevant to battery chemistry. The (31)P spin-echo mapping and (7)Li magic angle spinning NMR techniques yield the hyperfine shifts of the species of interest, complemented by periodic hybrid functional DFT calculations of the respective hyperfine and quadrupolar tensors. A Curie-Weiss-based magnetic model scaling the DFT-calculated hyperfine parameters from the ferromagnetic into the experimentally relevant paramagnetic state is derived and applied, providing quantitative finite temperature values for each phase. The sensitivity of the hyperfine parameters to the composition of the DFT exchange functional is characterized by the application of hybrid Hamiltonians containing admixtures 0%, 20%, and 35% of Fock exchange. Good agreement between experimental and calculated values is obtained, provided that the residual magnetic couplings persisting in the paramagnetic state are included. The potential applications of a similar combined experimental and theoretical NMR approach to a wider range of cathode materials are discussed.     

Human neuronal stargazin-like proteins, γ2, γ3 and γ4; an investigation of their specific localization in human brain and their influence on CaV2.1 voltage-dependent calcium channels expressed in Xenopus oocytes.

Background  

Stargazin (γ₂) and the closely related γ₃, and γ₄ transmembrane proteins are part of a family of proteins that may act as both neuronal voltage-dependent calcium channel (VDCC) γ subunits and transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazoleproponinc (AMPA) receptor regulatory proteins (TARPs). In this investigation, we examined the distribution patterns of the stargazin-like proteins γ₂, γ₃, and γ₄ in the human central nervous system (CNS). In addition, we investigated whether human γ₂ or γ₄ could modulate the electrophysiological properties of a neuronal VDCC complex transiently expressed in Xenopus oocytes.