Sorption of mercuric ion by synthetic nanocrystalline mackinawite (FeS)

Iron sulfides are known to be efficient scavengers of heavy metals. In this study, Hg(II) sorption was investigated using synthetic nanocrystalline mackinawite (a disordered phase) as a function of initial Hg(II) concentration [Hg(II)]0, initial FeS concentration [FeS]0, total chloride concentration CIT, and pH. Hg(II) sorption mechanisms are dependent on relative concentrations of [Hg(II)]0 and [FeS]0 (the molar ratio of [Hg(II)0/[FeS]0). When the molar ratio of [Hg(II)]0/[FeS]o is as low as 0.05, adsorption is mainly responsible for Hg(II) removal, with its contribution to the overall sorption increasing at lower Cl(T). As the molar ratio increases, the adsorption capacity becomes saturated, resulting in precipitation of a sparingly soluble HgS(s). XRD analysis indicates formation of metacinnabar (beta-HgS). Concurrently with HgS(s) precipitation, the released Fe(II) from FeS(s) is resorbed by adsorption at acidic pH and either adsorption or precipitation as Fe (hydr)-oxides at neutral to basic pH. Subsequently, the Fe precipitate formed at neutral to basic pH serves as an adsorbent for Hg(II). Under the conditions where either adsorption or HgS(s) precipitation is dominant, more than 99% of [Hg(II)]0 is immobilized. When the molar ratio of [Hg(II)]0/[FeS]0 exceeds 1, the sulfide concentration is no longer sufficient for HgS(s) precipitation, and formation of chloride salts (Hg2Cl2 at acidic pH and HgCl2 x 3HgO at basic pH) occurs.     

Changes in major proteins in the embryonic capsule during immobilization (fixation) of the conceptus in the third week of pregnancy in the mare

During the third week of pregnancy, the equine conceptus is enclosed within a capsule, the glycan composition of which changes at around day 16 (ovulation = day 0) when the conceptus becomes immobilized (fixed) in the uterine lumen. Our objective was to characterize the process of fixation by identifying changes in major capsule-associated proteins. Individual equine conceptuses (n = 55) were collected transcervically by uterine lavage between days 13.5 and 26.5. Major proteins extracted from capsules were compared with those in fluids from the uterus and yolk sac by SDS-PAGE. Until day 14, a major capsule-associated protein that migrated at approximately 10 kDa was identified by N-terminal sequencing as equine beta2 microglobulin (beta2M). During fixation, beta2M in the capsule underwent limited proteolysis to an approximately 8 kDa form lacking nine amino acids from the N terminus, and was subsequently degraded. Expression of beta2M mRNA was detected in the yolk-sac wall tissues and endometrium between days 13.5 and 17.5. During this period, beta2M in the capsule was evidently not part of a complex with major histocompatibility complex class 1 heavy alpha chain bands because these were undetectable in the capsule and uterine lavage. Uterocalin (p19) was detected in uterine lavage and capsule throughout fixation, but in yolk-sac fluid only before fixation. These studies indicate that intact beta2M is a major protein associated with the embryonic capsule before fixation, after which it undergoes limited proteolysis to a truncated approximately 8 kDa form that remains in the capsule after the conceptus is immobilized.     

Low temperature preparation of bismuth-related ferroelectrics powder and thin films by hydrothermal synthesis

Bi(4)Ti(3)O(12) (BIT) thin films were prepared by low temperature hydrothermal synthesis on Pt/TiO(x)/SiO(2)/Si. Bi(4)Ti(3)O(12) or TiO(2) gel solution was formed and annealed at 350 degrees C. The BIT thin films were crystallized as a Bi-layer structural ferroelectric. During the hydrothermal treatment, the TiO(2) anatase (101) peak appears and seems to play the role as an intermediate layer. Randomly oriented BIT thin films were obtained. As a result, the BIT thin films have ferroelectric property. The as-deposited BIT thin films include spherical grains with the grain size of 120 nm.     

Experimental Investigation of Gas/Matte/Spinel Equilibria in the Cu-Fe-O-S System at 1473 K (1200 °C) and <Emphasis Type="Italic">P</Emphasis>(SO<Subscript>2</Subscript>) = 0.25 atm

The Cu-Fe-O-S system is the key system for the characterisation of the phase chemistry in high-temperature copper making processes. An experimental study was undertaken to investigate the gas/matte/spinel equilibria in the Cu-Fe-O-S system at 1473 K (1200 °C), P(SO₂) = 0.25 atm, and a range of oxygen partial pressures. The experimental methodology involved high temperature equilibration using a primary phase substrate technique in controlled gas atmospheres (CO/CO₂/SO₂/Ar), rapid quenching of the equilibrated phases, followed by direct measurement of phase compositions using electron probe x-ray microanalysis. Particular attention was given to the analysis of reactions during equilibration and confirmation of the achievement of equilibrium in the present study. The new data provide important information for understanding of the gas/matte/spinel interactions at high temperature and provide an essential foundation for the development of the multicomponent thermodynamic database for copper-containing systems.     

Experimental study of phase equilibria in the system PbO-ZnO-SiO2

An experimental study on the ternary system PbO-ZnO-SiO₂ in air by high-temperature equilibration and quenching techniques followed by electron probe X-ray microanalysis was carried out as part of the wider research program on the six-component system PbO-ZnO-SiO₂-CaO-FeO-Fe₂O₃, which combines experimental and thermodynamic computer modeling techniques to characterize zinc and lead industrial slags. Liquidus and solidus data were reported for all primary phase fields in the system PbO-ZnO-SiO₂ in the temperature range 640 °C to 1400 °C (913 to 1673 K).     

Self-adhesive honeycomb prepreg systems for secondary structural applications

Porosity in cured honeycomb parts was investigated using model prepreg systems and compared with a commercial solvent produced prepreg. Woven glass fabric was used as the reinforcement in both of the systems. Three main solvents were identified in the commercial prepreg. These solvents were found to cause porosity or reduce thermal properties in model solvent prepreg based laminates when used either separately or in combination. Lowering the solvent content reduced the porosity in the prepreg but was limited by resin staging. The high level of porosity, resulting from solvents, found in these commercial prepreg systems motivated the investigation of the feasibility of changing the method of impregnation from solvent to hot-melt. Hot-melt model prepreg produced essentially void-free laminates as well as honeycomb parts. Model prepreg produced by hot-melt impregnation was found to be more robust, providing the capability of changing the degree of resin impregnation in the fiber bed. A low level of impregnation resulted in the best fillets to the honeycomb core, while still producing essentially void free parts. The use of both solid and liquid carboxyl-functional elastomers was incorporated in the epoxy based resin to provide flow control and self-adhesive characteristics. Mechanical properties of both the model hot-melt and commercial prepreg based honeycomb structures and laminates were compared. The model hot-melt prepreg was found to have better cured properties along with the necessary prepreg characteristics providing an optimized self-adhesive controlled flow prepreg system.     

Metal particle modification of composite matrices for customized density applications

A key aspect of composite technology lies in the ability to design a part to a specific strength and thickness. Recently, new applications were identified where it was desirable to vary the density in specific areas of a part. In this work, a model prepreg system was modified with fine metal and thermoplastic particles for specific weight tailoring. These particles were placed on the prepreg surface, forming a partially interlayer modified composite when laid up and cured. Experiments were performed on the specific gravity and fracture toughness of laminates made from the prepregs. The results showed that it is possible to tailor the density of a composite system without changing the manufacturing process or fracture toughness requirements.     

Effects of in situ esterification on the performance of carboxyl functionalized rubber‐modified epoxy film adhesives

Epoxy‐based film adhesive formulations were developed with 10 wt % solid carboxyl functional rubber. Due to the high rubber content and resulting viscosity restrictions, the rubber could not be prereacted with the epoxy before hot‐melt filming. Therefore, an esterification catalyst was used to perform this reaction in situ before the epoxy curing reactions. The performance of this adhesive system is compared to that of one without the esterification catalyst. A significant difference in the flow characteristics was observed with incorporation of the esterification catalyst, but only small variations in mechanical performance were found. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 728–734, 2000     

Sequential flow membraneless microfluidic fuel cell with porous electrodes

A novel convective flow membraneless microfluidic fuel cell with porous disk electrodes is described. In this fuel cell design, the fuel flows radially outward through a thin disk shaped anode and across a gap to a ring shaped cathode. An oxidant is introduced into the gap between anode and cathode and advects radially outward to the cathode. This fuel cell differs from previous membraneless designs in that the fuel and the oxidant flow in series, rather than in parallel, enabling independent control over the fuel and oxidant flow rate and the electrode areas. The cell uses formic acid as a fuel and potassium permanganate as the oxidant, both contained in a sulfuric acid electrolyte. The flow velocity field is examined using microscale particle image velocimetry and shown to be nearly axisymmetric and steady. The results show that increasing the electrolyte concentration reduces the cell Ohmic resistance, resulting in larger maximum currents and peak power densities. Increasing the flow rate delays the onset of mass transport and reduces Ohmic losses resulting in larger maximum currents and peak power densities. An average open circuit potential of 1.2 V is obtained with maximum current and power densities of 5.35 mA cm⁻² and 2.8 mW cm⁻², respectively (cell electrode area of 4.3 cm²). At a flow rate of 100 μL min⁻¹ a fuel utilization of 58% is obtained.     

Tone diversity for OFDMA in broadband wireless communications

This paper presents two group‐based tone diversity schemes, namely, group‐orthogonal tone‐combining‐diversity (GO‐TCD) and group‐optimal tone‐selection‐diversity (GO‐TSD), for orthogonal frequency division multiple access (OFDMA) system in broadband wireless communications. In both schemes, the entire frequency band of N sub‐carriers is divided into N_G = N/L_f sub‐carrier groups with each having L_f sub‐carriers. When the channel knowledge is not available at the transmitter, GO‐TCD, which has a split‐and‐group structure to reduce the peak‐to‐average ratio (PAR) and employs the multi‐user detection for maximum‐likelihood (ML) estimation to increase the number of active users, is proposed and shown to provide a lower PAR and similar performance as compared with the group‐orthogonal multi‐carrier CDMA, and outperforms the random‐hopping (RH)‐OFDMA and matched‐filter based MC‐CDMA. When the channel knowledge is available at the transmitter, GO‐TSD can be used to select the best sub‐carrier in a given sub‐carrier group for any active user and shown to offer a throughput comparable to the optimal tone selection but with much less complexity. Copyright © 2006 John Wiley & Sons, Ltd.