Structure and Dielectric Properties of the Ba(Mg1/3Nb2/3)O3-La(Mg2/3Nb1/3)O3 System

A complete range of perovskite solid solutions can be formed in the (1 − x )Ba(Mg_1/3Nb_2/3)O₃- x La(Mg_2/3Nb_1/3)O₃ (BMN-LMN) pseudobinary system. While pure BMN adopts a 1:2 cation ordered structure, 1:1 ordered phases are stabilized for 0.05 ≤ x ≤ 1.0. Dark-field TEM images indicate that the La-doped solid solutions are comprised of large 1:1 ordered domains and no evidence was found for a phase-separated structure. This observation coupled with the systematic variations in the intensities of the supercell reflections supports a charge-balanced "random-site" model for the 1:1 ordering. The substitution of La also induces a transformation from a negative to positive temperature coefficient of capacitance in the region 0.25 ≤ x ≤ 0.5.     

Low Loss,High NA Chalcogenide Glass Fibers for Broadband Mid‐Infrared Supercontinuum Generation

High‐purity Ge–As–Se and Ge–As–S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step‐index fibers with a small core (~5.5 μm) and large numerical aperture (~1.3) were fabricated. When a 13.5‐cm‐long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 μm, supercontinuum spanning from ~1.8 to ~9.8 μm with a dynamic range of ±10 dB and an average power of ~3 mW was generated.     

Predicting Blast Waves from the Axial Direction of a Cylindrical Charge

Bare, cylindrical, explosive charges produce secondary shock waves in the direction of least presented area. Whilst the source of these shock waves was explored in the 1940’s, no attempt was made to predict them. This paper describes the detonation of bare, cylindrical charges of PE4 (RDX binder 88/12 %), mass 0.2 to 0.46 kg and with a length to diameter ratio of 4 to 1. High speed camera footage showed (i) the formation of the separate, primary, shock waves from the sides and ends of the charge, (ii) Mach reflection of these separate shock waves, giving rise to reflected, secondary shock waves, and (iii) the secondary shock waves catching and merging with the primary shock wave. In the axial direction, the secondary shock wave’s peak overpressure and impulse exceeded that of the primary shock wave for scaled distances, Z=R/M^1/3 ≥3.9 m kg^−1/3, where M is the mass in kg and R the distance from the charge in m. It was found possible to predict the primary peak overpressure, P, at all distances in the axial direction, for a constant length to diameter ratio, using P=3075 Z⁻³−1732 Z⁻²+305 Z⁻¹. Close in the primary peak overpressure is proportional to M/R³ in the axial direction. It was not possible to predict the secondary peak overpressure with the data obtained. The total impulse from both shock waves, I, in the axial direction can be predicted using I=746(M^2/3/R)³−708(M^2/3/R)²+306(M^2/3/R).     

Comment on ``Comments on controlling reaction selectivity in the oxidation of methanol at Cu(110) surfaces'

No abstract available. This revised version was published online in July 2006 with corrections to the Cover Date.     

Controlling reaction selectivity in the oxidation of methanol at Cu(110) surfaces

When deuterated methanol (CD₃OH) and dioxygen mixtures are coadsorbed at Cu(110) surfaces at room temperature and above, the main reaction product can be switched between formaldehyde and formate by changing the mixture composition. For oxygen-rich mixtures formaldehyde is the major product but when methanol is in 5 : 1 excess only formate is produced. It is proposed that the reaction mechanism is controlled by the microscopic structure of the surface: when the reactants are adsorbed sequentially, separate islands of oxygen and methoxy develop which inhibit further oxidation but when reactants are coadsorbed a homogeneous mixture of adsorbates is produced creating a facile pathway to formate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mirror Constant for Tyranno® Silicon-Titanium-Carbon-Oxygen Fibers Measured in Situ in a Three-Dimensional Woven Silicon Carbide/Silicon Carbide Composite

The strength, S , of ceramic and glass fibers often can be estimated from fractographic investigation using the fracture mirror radius, r _m, and the relationship S = A _m/( r _m)^1/2, where A _mis the "mirror constant." The present work estimates the value of A _mfor Tyranno^® Si-Ti-C-O fibers in situ in a three-dimensional woven SiC/SiC-based composite to be 2.50 ± 0.09 MPa·m^1/2. This value is within the range of 2–2.51 MPa·m^1/2 previously obtained for nominally similar Nicalon^® Si-C-O fibers.     

The effect of protein binding on ibuprofen adsorption to activated carbons

The potential of a range of polymer-based activated carbons to remove a non-steroidal anti-inflammatory drug ibuprofen from protein containing and protein-free solutions was studied. The adsorption capacity of five activated carbons produced from phenol-formaldehyde resin precursors (MAST Carbon Ltd) was compared to a cellulose coated activated carbon Norit RBX used in a commercial Adsorba^®300C haemoperfusion column (Gambro).Ibuprofen adsorption was studied in batch experiments over 24 h at pH=7.6 and 25 °C and adsorption equilibrium data were correlated with the Langmuir and Freundlich equations.Results showed that uncoated mesoporous MAST carbons can remove ibuprofen from model solutions both in the presence and absence of serum albumin. Ibuprofen is a highly protein-bound drug and the presence of serum albumin significantly affects the adsorption of ibuprofen by cellulose-coated microporous carbon used in Adsorba^®300C column.     

High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber

An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy.     

A-Site and B-Site Order in (Na1/2La1/2)(Mg1/3Nb2/3)O3 Perovskite

(Na_1/2La_1/2)(Mg_1/3Nb_2/3)O₃ undergoes a series of phase transitions that involve cation order on the A- and B-sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a 〈111〉 layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A-site positions along the 〈001〉 direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B-site, a fourth variant of this compound was obtained by inducing A-site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (ɛ_r∼ 35), they do have a significant effect on the value of the temperature coefficient of the capacitance.     

The Phosphoinositide 3‐Kinase Signaling Pathway is Involved in the Control of Modified Low‐Density Lipoprotein Uptake by Human Macrophages

The transformation of macrophages into lipid‐loaded foam cells is a critical early event in the pathogenesis of atherosclerosis. Both receptor‐mediated uptake of modified LDL, mediated primarily by scavenger receptors‐A (SR‐A) and CD36 along with other proteins such as lipoprotein lipase (LPL), and macropinocytosis contribute to macrophage foam cell formation. The signaling pathways that are involved in the control of foam cell formation are not fully understood. In this study, we have investigated the role of phosphoinositide 3‐kinase (PI3K) in relation to foam cell formation in human macrophages. The pan PI3K inhibitor LY294002 attenuated the uptake of modified LDL and macropinocytosis, as measured by Lucifer Yellow uptake, by human macrophages. In addition, the expression of SR‐A, CD36 and LPL was attenuated by LY294002. The use of isoform‐selective PI3K inhibitors showed that PI3K‐β, ‐γ and ‐δ were all required for the expression of SR‐A and CD36 whereas only PI3K‐γ was necessary in the case of LPL. These studies reveal a pivotal role of PI3K in the control of macrophage foam cell formation and provide further evidence for their potential as therapeutic target against atherosclerosis.