ALBERT

Description: Methane hydrate, a potential future energy resource, is known to occur naturally in vast quantities beneath the ocean floor and in permafrost regions. It is important to evaluate how much methane is recoverable from these hydrate reserves. This article introduces the theoretical background of HydrateResSim, the National Energy Technology Laboratory (NETL) methane production simulator for hydrate-containing reservoirs, originally developed for NETL by Lawrence Berkeley National Laboratory (LBNL). It describes the mathematical model that governs the dissociation of methane hydrate by depressurization or thermal stimulation of the system, including the transport of multiple temperature-dependent components in multiple phases through a porous medium. The model equations are obtained by incorporating the multiphase Darcy’s law for gas and liquid into both the mass component balances and the energy conservation equations. Two submodels in HydrateResSim for hydrate dissociation are also considered: a kinetic model and a pure thermodynamic model. Contrary to more traditional reservoir simulations, the set of model unknowns or primary variables in HydrateResSim changes throughout the simulation as a result of the formation or dissociation of ice and hydrate phases during the simulation. The primary variable switch method (PVSM) is used to effectively track these phase changes. The equations are solved by utilizing the implicit time finite-difference method on the grid system, which can properly describe phase appearance or disappearance as well as the boundary conditions. The Newton-Raphson method is used to solve the linear equations after discretization and setup of the Jacobian matrix. We report here the application of HydrateResSim to a three-component, four-phase flow system in order to predict the methane produced from a laboratory-scale reservoir. The first results of HydrateResSim code in a peer-reviewed publication are presented in this article. The numerical solution was verified against the state-of-the art simulator TOUGH+Hydrate. The model was then used to compare twodissociation theories: kinetic and pure equilibrium. Generally, the kinetic model revealed a lower dissociation rate than the equilibrium model. The hydrate dissociation patterns differed significantly when the thermal boundary condition was shifted from adiabatic to constant-temperature. The surface area factor was found to have an important effect on the rate of hydrate dissociation for the kinetic model. The deviation between the kinetic and equilibrium models was found to increase with decreasing surface area factor.

Description: Two new cyclic peroxides, 2 and 3, were isolated from a sample of the Norwegian sponge Plakortis simplex. Their structures including relative stereochemistry were elucidated by interpretation of MS and NMR data. Compound 3 exhibited moderate in vitro activity against six solid human tumor cell lines with IC50 values in the range 7−15 μg/mL.

Description: We determined the coordination environment of Zn2+ in aqueous Cl- brines at 25 °C and 300 °C using ab initio molecular dynamics simulations. The ZnCl+ and ZnCl2 complexes exist as pseudo-octahedral ZnClm(H2O)6-m clusters at 25 °C but occur as pseudo-tetrahedral ZnClm(H2O)4-m clusters at 300 °C. The ZnCl3- complex occurs as the pseudo-tetrahedral ZnCl3(H2O)- cluster at 25 and 300 °C. The tetrahedral ZnCl42- complex, however, is the dominant Zn−Cl complex at 25 °C, at least in highly concentrated (7.4 m) Cl- brines. The change in hydration number with temperature for the ZnCl+ and ZnCl2 complexes will complicate extrapolations of solvation energies to hydrothermal conditions using a Born-model-based equation of state.

Description: The valuable nutraceutical γ-linolenic acid (GLA, (6Z,9Z,12Z)-octadecatrienoic acid) is biosynthesized by a series of regio- and stereoselective dehydrogenation reactions that are catalyzed by a set of enzymes known as fatty acid desaturases. As part of ongoing research into the mechanism of these remarkable catalysts, we have examined the cryptoregiochemistry (site of initial oxidation) of Δ6 desaturation as it occurs in the protozoan Tetrahymena thermophila. Two complementary approaches that address this issue are described. In the first set of experiments, we measured the individual primary deuterium kinetic isotope effects associated with the C−H bond cleavages at C-6 and C-7. Competition experiments using appropriately deuterium-labeled 4-thiasubstrates revealed that a large KIE (kH/kD = 7.1 ± 0.5) was observed for the C−H bond-breaking step at C-6, whereas the C−H bond cleavage at C-7 was insensitive to deuterium substitution (kH/kD = 1.04 ± 0.05). These results point to C-6 as the site of initial oxidation in Δ6 desaturation since the first chemical step in this type of reaction is rupture of a strong, unactivated C−H bond, an energetically difficult process that typically exhibits a large KIE. This conclusion was supported by the results of our second approach, which involved locating the position of the putative diiron oxo oxidant with respect to substrate by monitoring the efficiency of oxo transfer to a series of thia fatty acid probes. Thus only a 6-thia-analogue is converted to significant amounts of the corresponding sulfoxide (9% yield). The absolute configuration of this product was determined to be S using (S)-MPAA as a chiral shift reagent. Taken together, these results point to the abstraction of the C-6 pro S hydrogen as the initial event in Δ6 desaturation as it occurs in T. thermophila.

Description: Calculations of the size and density of atmospheric aerosols are complicated by the fact that they can exist at concentrations highly supersaturated with respect to dissolved salts and supercooled with respect to ice. Densities and apparent molar volumes of solutes in aqueous solutions containing the solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl have been critically evaluated and represented using fitted equations from 0 to 50 °C or greater and from infinite dilution to concentrations saturated or supersaturated with respect to the dissolved salts. Using extrapolated densities of high-temperature solutions and melts, the relationship between density and concentration is extended to the hypothetical pure liquid solutes. Above a given reference concentration of a few mol kg−1, it is observed that density increases almost linearly with decreasing temperature, and comparisons with available data below 0 °C suggest that the fitted equations for density can be extrapolated to very low temperatures. As concentration is decreased below the reference concentration, the variation of density with temperature tends to that of water (which decreases as temperature is reduced below 3.98 °C). In this region below the reference concentration, and below 0 °C, densities are calculated using extrapolated apparent molar volumes which are constrained to agree at the reference concentrations with an equation for the directly fitted density. Calculated volume properties agree well with available data at low temperatures, for both concentrated and dilute solutions. Comparisons are made with literature data for temperatures of maximum density. Apparent molar volumes at infinite dilution are consistent, on a single ion basis, to better than ±0.1 cm3 mol−1 from 0 to 50 °C. Volume properties of aqueous NaHSO4, NaOH, and NH3 have also been evaluated, at 25 °C only. In part 2 of this work (ref 1) an ion interaction (Pitzer) model has been used to calculate apparent molar volumes of H2SO4 in 0−3 mol kg−1 aqueous solutions of the pure acid and to represent directly the effect of the HSO4− ↔ H+ + SO42− reaction. The results are incorporated into the treatment of aqueous H2SO4 density described here. Densities and apparent molar volumes from −20 to 50 °C, and from 0 to 100 wt % of solute, are tabulated for the electrolytes listed in the title and have also been incorporated into the extended aerosol inorganics model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) together with densities of the solid salts and hydrates.

Description: High-performance liquid chromatography-electrospray ionization mass spectrometry was applied to the detection of the iron(III) complexes of the hydroxamate siderophores rhodotoluric acid, deferrioxamine B, and deferrichrome. Separation of the iron(III) complexes was obtained using a polystyrene-divinylbenzene stationary phase. The retention and responses of ferrioxamine and ferrichrome were optimal when a gradient elution program with methanol and 0.1% (v/v) formic acid as the mobile phases was used. These conditions were also suitable for the retention and separation of the uncomplexed ligands. Retention of iron(III) rhodotoluate was improved when formic acid was replaced by the ion-pairing reagent heptafluorobutyric acid (0.1%). Detection limits for the ferric complexes, defined as 3 SD of the lowest determined standard, were 26 nM for iron(III) rhodotoluate, 0.23 nM for ferrioxamine, and 0.40 nM for ferrichrome. A protocol for the solid-phase extraction of these hydroxamate siderophores from seawater was developed and applied to the extraction of siderophores from enriched incubated seawater samples.

Description: High-performance liquid chromatography-electrospray ionization mass spectrometry was applied to the detection of the iron(III) complexes of the hydroxamate siderophores rhodotoluric acid, deferrioxamine B, and deferrichrome. Separation of the iron(III) complexes was obtained using a polystyrene-divinylbenzene stationary phase. The retention and responses of ferrioxamine and ferrichrome were optimal when a gradient elution program with methanol and 0.1% (v/v) formic acid as the mobile phases was used. These conditions were also suitable for the retention and separation of the uncomplexed ligands. Retention of iron(III) rhodotoluate was improved when formic acid was replaced by the ion-pairing reagent heptafluorobutyric acid (0.1%). Detection limits for the ferric complexes, defined as 3 SD of the lowest determined standard, were 26 nM for iron(III) rhodotoluate, 0.23 nM for ferrioxamine, and 0.40 nM for ferrichrome. A protocol for the solid-phase extraction of these hydroxamate siderophores from seawater was developed and applied to the extraction of siderophores from enriched incubated seawater samples.

Description: A total of 19 naturally occurring bromophenols, with six new and 13 known structures, were isolated and identified from the methanolic extract of the marine red alga Rhodomela confervoides. The new compounds were identified by spectroscopic methods as 3,4-dibromo-5-((methylsulfonyl)methyl)benzene-1,2-diol (1), 3,4-dibromo-5-((2,3-dihydroxypropoxy)methyl)benzene-1,2-diol (2), 5-(aminomethyl)-3,4-dibromobenzene-1,2-diol (3), 2-(2,3-dibromo-4,5-dihydroxyphenyl)acetic acid (4), 2-methoxy-3-bromo-5-hydroxymethylphenol (5), and (E)-4-(2-bromo-4,5-dihydroxyphenyl)but-3-en-2-one (6). Each compound was evaluated for free radical scavenging activity against DPPH (α,α-diphenyl-β-dipicrylhydrazyl) and ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt] radicals. Most of them exhibited potent activities stronger than or comparable to the positive controls butylated hydroxytoluene (BHT) and ascorbic acid. The results from this study suggest that R. confervoides is an excellent source of natural antioxidants, and inclusion of these antioxidant-rich algal components would likely help prevent the oxidative deterioration of food.

Description: Implantable endovascular devices such as bare metal, drug eluting, and bioresorbable stents have transformed interventional care by providing continuous structural and mechanical support to many peripheral, neural, and coronary arteries affected by blockage. Although effective in achieving immediate restoration of blood flow, the long-term re-endothelialization and inflammation induced by mechanical stents are difficult to diagnose or treat. Here we present nanomaterial designs and integration strategies for the bioresorbable electronic stent with drug-infused functionalized nanoparticles to enable flow sensing, temperature monitoring, data storage, wireless power/data transmission, inflammation suppression, localized drug delivery, and hyperthermia therapy. In vivo and ex vivo animal experiments as well as in vitro cell studies demonstrate the previously unrecognized potential for bioresorbable electronic implants coupled with bioinert therapeutic nanoparticles in the endovascular system.