Multicomponent solute transport with sorption and soluble complexation

A numerical algorithm for predicting the migration of multiple subsurface pollutants has been developed accounting for dispersion, convection, soluble complexation and solid phase accumulations (sorption). The basis of the model is a finite element solution of the mass transport equation. The essence of the algorithm is the treatment of the sorption terms as implicit functions of the total soluble concentrations facilitating a general and modularized treatment of solution phase and solid phase chemistry. Examples are presented illustrating the effects of soluble complexation and competitive sorption on the transport of multicomponent solutions.     

Constructed wetland technology and mosquito populations in Arizona

Constructed wetlands and other aquatic habitat creation or restoration efforts offer both potential benefits and problems for arid areas. An unintentional consequence of these efforts has been the potential for an increase in local adult mosquito populations. Shallow water-emergent plant zones may provide ideal conditions for mosquito larval growth, and areas of high humidity, dense vegetation, and abundant birds and other wildlife may provide ideal conditions for adult mosquitoes. Three constructed wetlands in southern Arizona were studied over a period of years before and after they were constructed and operational. Mosquito populations were sampled using a variety of methods, primarily trapping of adults with CO₂-baited traps. Populations apparently increased, sometimes by several orders of magnitude, after wetlands became operational. Several methods of mosquito abatement were initiated and their results are discussed. However, no definitive conclusions can be drawn because no untreated areas were available for comparison and many factors that may have affected mosquito populations also changed. Based on the experience gained at these three sites, mosquito control is an especially important design and management component for constructed wetlands in arid environments with low background populations of mosquitoes.     

Inhibitory activities of microalgal fucoxanthin againstα-amylase,α-glucosidase,and glucose oxidase in 3T3-L1cells linked to type 2 diabetes

Postprandial hyperglycemia is an early indication of type 2 diabetes and the target of many anti-diabetic and anti-obesity studies. a-Glucosidase and a-amylase are the crucial factors in regulating starch digestion and glucose absorption, making them key targets for many studies to treat postprandial hyperglycemia. We studied the inhibitory activities of microalgal fucoxanthin against rat-intestinal a-glucosidase and pancreatic a-amylase along with the antidiabetic effect to induce differentiation in 3T3-L1 pre-adipocytes using Oil Red-O staining. Fucoxanthin displayed strong hindrance activities toward a-amylase in a concentration-dependent manner, with an IC_(50) value of 0.68 mmol/L, whereas weak inhibitory activity against a-glucosidase, with an IC_(50) value of 4.75 mmol/L. Fucoxanthin also considerably elevated glucose oxidase activity in 3T3-LI cells by 31.3% at 5 μmol/L. During adipocyte differentiation, fucoxanthin showed lipid accumulation in 3T3-L1 cells with no cytotoxicity up to 20 μmol/L. However, fucoxanthin had no inhibitory activity on glucose-6-phosphate dehydrogenase. These results suggest that fucoxanthin might be useful for the prevention of obesity or diabetes by inhibiting carbohydrate-hydrolyzing enzymes and lipid accumulation and be utilized as an ingredient for a functional food or dietary supplement.     

The epoch of helium reionization

We study the reionization of He  ii by quasars using a numerical approach that combines 3D radiative transfer calculations with cosmological hydrodynamical simulations. Sources producing the ionizing radiation are selected according to an empirical quasar luminosity function, and are assigned luminosities according to their intrinsic masses. The free parameters associated with this procedure are (1) a universal source lifetime, (2) a minimum mass cut-off, (3) a minimum luminosity cut-off, (4) a solid angle specifying the extent to which radiation is beamed, and (5) a tail-end spectral index for the radiative energy distribution of the sources. We present models in which these parameters are varied, and examine characteristics of the resultant reionization process that distinguish the various cases. In addition, we extract artificial spectra from the simulations and quantify statistical properties of the spectral features in each model.
We find that the most important factor affecting the evolution of He  ii reionization is the cumulative number of ionizing photons that are produced by the sources. Comparisons between He  ii opacities measured observationally and those obtained by our analysis reveal that the available ranges in plausible values for the parameters provide enough leeway to provide a satisfactory match. However, one property common to all our calculations is that the epoch of He  ii reionization must have occurred at a redshift in the range  3≲ z ≲4  . If so, future observational programmes will be able to directly trace the details of the ionization history of helium and to probe the low-density phase of the intergalactic medium during this phase of the evolution of the Universe.     

Sensitivity of Mesoscale Surface Dynamics to Surface Soil and Vegetation Contrasts over the Carolina Sandhills

A region of contrasting soils exists over the Carolinas region of the southeastern United States. Previous research has shown an increase in mesoscale summertime precipitation over this region. Numerical simulations are analyzed to investigate the relationships between mesoscale surface dynamics and the transition from clay to sandy soils over this region. Numerical modeling experiments using four different soil and vegetation patterns suggest that the presence of the clay-to-sand transition zone produces a surface heat flux gradient and enhanced convergence. The soil contrasts appear to dominate over vegetation contrasts in affecting local surface heating and convergence in the model atmosphere.     

Petrology of lavas from the Puu Oo eruption of Kilauea Volcano: III. The Kupaianaha episode (1986–1992)

 The Puu Oo eruption has been remarkable in the historical record of Kilauea Volcano for its duration (over 13 years), volume (>1 km³) and compositional variation (5.7–10 wt.% MgO). During the summer of 1986, the main vent for lava production moved 3 km down the east rift zone and the eruption style changed from episodic geyser-like fountaining at Puu Oo to virtually continuous, relatively quiescent effusion at the Kupaianaha vent. This paper examines this next chapter in the Puu Oo eruption, episodes 48 and 49, and presents new ICP-MS trace element and Pb-, Sr-, and Nd-isotope data for the entire eruption (1983–1994). Nearly aphyric to weakly olivine-phyric lavas were erupted during episodes 48 and 49. The variation in MgO content of Kupaianaha lavas erupted before 1990 correlates with changes in tilt at the summit of Kilauea, both of which probably were controlled by variations in Kilauea's magma supply rate. These lavas contain euhedral olivines which generally are in equilibrium with whole-rock compositions, although some of the more mafic lavas which erupted during 1990, a period of frequent pauses in the eruption, accumulated 2–4 vol.% olivine. The highest forsterite content of olivines (∼85%) in Kupaianaha lavas indicates that the parental magmas for these lavas had MgO contents of ∼10 wt.%, which equals the highest observed value for lavas during this eruption. The composition of the Puu Oo lavas has progressively changed during the eruption. Since early 1985 (episode 30), when mixing between an evolved rift zone magma and a more mafic summit reservoir-derived magma ended, the normalized (to 10 wt.% MgO) abundances of highly incompatible elements and CaO have systematically decreased with time, whereas ratios of these trace elements and Pb, Sr, and Nd isotopes, and the abundances of Y and Yb, have remained relatively unchanged. These results indicate that the Hawaiian plume source for Puu Oo magmas must be relatively homogeneous on a scale of 10–20 km³ (assuming 5–10% partial melting), and that localized melting within the plume has apparently progressively depleted its incompatible elements and clinopyroxene component as the eruption continued. The rate of variation of highly incompatible elements in Puu Oo lavas is much greater than that observed for Kilauea historical summit lavas (e.g., Ba/Y 0.09 a^–1 vs ∼0.03 a^–1). This rapid change indicates that Puu Oo magmas did not mix thoroughly with magma in the summit reservoir. Thus, except for variable amounts of olivine fractionation, the geochemical variation in these lavas is predominantly controlled by mantle processes. Received: 8 March 1996 / Accepted: 30 April 1996     

Factors influencing the calculation of periodic secondary circulation in a tidal river: numerical modelling of the lower Sacramento River,USA

Secondary circulation is the component of three‐dimensional (3D) flow in river channels perpendicular to the primary flow direction. Secondary circulation calculated from acoustic Doppler current profiler (ADCP) transects is sensitive to the calculation method and is affected by the transect angle relative to the mean flow direction and variations in the flow direction along a transect. To quantify bounds on transect alignment relative to river flow for field data collection and examine tidal time‐scale variability in secondary circulation, the 3D hydrodynamic model UnTRIM was applied to simulate the hydrodynamics in the lower reach of the Sacramento River (CA, USA). Secondary circulation was calculated using the Rozovskii and the zero net discharge methods on repeated transects extracted from the model results in regions of both relatively uniform and complex flows. When the depth‐averaged flow direction along a transect varied by more than about 5 °, occurring when the transect was as little as 10 to 20 ° out of normal to the mean flow direction, the Rozovskii method produced more realistic secondary circulation than the zero net discharge method. Analysis indicated that ADCP transects should be within 20 ° of perpendicular to the mean flow direction when calculating secondary circulation. Secondary circulation strength around two tidally influenced bends generally increased with increasing flow and broke down near slack water. However, the strength of the secondary circulation was not only a function of the flow magnitude, but also depended on the direction of the water flow and the transect location relative to the river curvature, which varied with the tidal flow direction. Copyright © 2015 John Wiley & Sons, Ltd.     

Perceived scientific agreement and support for government action on climate change in the USA

Given the well-documented campaign in the USA to deny the reality and seriousness of anthropogenic climate change (a major goal of which is to “manufacture uncertainty” in the minds of policy-makers and the general public), we examine the influence that perception of the scientific agreement on global warming has on the public’s beliefs about global warming and support for government action to reduce emissions. A recent study by Ding et al. (Nat Clim Chang 1:462–466, 2011) using nationally representative survey data from 2010 finds that misperception of scientific agreement among climate scientists is associated with lower levels of support for climate policy and beliefs that action should be taken to deal with global warming. Our study replicates and extends Ding et al. (Nat Clim Chang 1:462–466, 2011) using nationally representative survey data from March 2012. We generally confirm their findings, suggesting that the crucial role of perceived scientific agreement on views of global warming and support for climate policy is robust. Further, we show that political orientation has a significant influence on perceived scientific agreement, global warming beliefs, and support for government action to reduce emissions. Our results suggest the importance of improving public perception of the scientific agreement on global warming, but in ways that do not trigger or aggravate ideological or partisan divisions.