Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser

Single mode laser action in a diode-pumped gain-guided, index- antiguided Nd³⁺-doped phosphate glass fiber having a 200-μm-diameter core is demonstrated. Near-Gaussian beam quality was maintained, even when pumped up to four times the threshold pump power, indicating robust lowest order mode oscillation. Subtle differences associated with the effectiveness of diode pumping gain-guided, index-antiguided fibers are discussed. PACS 42.55.Wd; 42.55.Xi     

The active and passive sampling of benzene, toluene, ethyl benzene and xylenes compounds using the inside needle capillary adsorption trap device

A new and simple method of solventless extraction of volatile organic compounds (VOCs) from air is presented. The sampling device has an adsorbing carbon coating on the interior surface of a hollow needle, and is called the inside needle capillary adsorption trap (INCAT). This paper describes a study of the reproducibility in the preparation and sampling of the INCAT device. In addition, this paper examines the effects of sample volume in active sampling and exposure time in passive sampling on the analyte adsorption. Analysis was achieved by sampling the air from an environmental chamber doped with benzene, toluene, ethyl benzene and xylenes (BTEX) compounds. Initial rates of adsorption were found to vary among the different compounds, but ranged from 0.0099 to 0.016 nmol h(-1) for passive sampling and from 2.2 to 10 nmol h(-1) for active sampling. Analysis was done by thermal desorption of the adsorbed compounds directly into a gas chromatograph injection port. Quantification of the analysis was done by comparison to actively sampled activated carbon solid phase extraction (SPE) measurements.     

Two Typical Steady-State Bifurcations for Time-Reversible Vector Field Families

Two typical steady-state bifurcations for time-reversible vector field families are studied, including allowance for a nontrivial nullspace forced by time-reversal symmetry. Under certain nondegeneracy conditions, it is shown that either a non- time-symmetric pitchfork or a time-symmetric transcritical bifurcation occurs. The method is extended to the equivariant case and applied by way of example to a class of time-reversible problems with D_n×O(2) symmetries which includes the particle sedimentation model known as the Stokeslet model.     

ATR-IR spectroscopic study of antimonate adsorption to iron oxide

Antimonate ions adsorb to iron oxides in mining contexts, but the nature of the adsorbed antimonate species has not frequently been investigated. In this study, ATR-IR spectroscopy was used to reveal that the adsorption of Sb(OH)6- ion from aqueous solutions onto an amorphous iron oxide particle film is accompanied by changes in the Sb(OH)6- spectrum and the loss of OH stretching absorptions from iron oxide surface hydroxyl groups. These spectral changes upon adsorption imply an inner-sphere surface interaction with the formation of Sb-O-Fe bonds as well as some outer-sphere adsorption. The corresponding results from solutions of antimonate in D2O confirm that chemisorption occurs. The dependence of antimonate adsorption on pH in the range from 8 to 3 follows that expected for anions on iron oxide considering its pH-dependent surface charge, with the greatest amount of adsorbed antimonate at pH 3. The study of adsorption/desorption kinetics showed a more rapid desorption of adsorbed antimonate under alkaline conditions. This trend is expected from the pH dependence of the antimonate charge and iron oxide surface charge, but it might be partly due to the fact that high pH favors hydrolysis of antimonate oligomers formed on the iron oxide surface from adsorption under acidic conditions.     

Chemical speciation of nanoparticles surrounding metal-on-metal hips

Spectromicroscopy of tissue surrounding failed CoCr metal-on-metal hip replacements detected corroded nanoscale debris in periprosthetic tissue in two chemical states, with concomitant mitochondrial damage. The majority of debris contained Cr(3+), with trace amounts of oxidised cobalt. A minority phase containing a core of metallic chromium and cobalt was also observed.     

Contamination of holey/lacey carbon films in STEM

In many cases, the key to obtaining good TEM results is in the sample preparation itself. Even once a thin specimen is achieved, other factors determine how well the sample will behave in the microscope. One of the main hindrances to TEM and STEM-EELS analysis is the build up of carbon contamination on the sample under the electron beam. This process may occur due to the nature of the sample itself or the support grids or films on which the sample sits. Here, we investigate contamination on holey and lacey carbon films from three different suppliers. We find that all grids have a large amount of mobile hydrocarbon contamination on them, as well as other larger contaminant species on the surface. Even after a variety of cleaning routines, none of the films are clean enough for STEM-EELS experiments requiring long acquisition times.