Microbial and Geochemical Dynamics of an Aquifer Stimulated for Microbial Induced Calcite Precipitation (MICP).

Microbially induced calcite precipitation (MICP) is an alternative to existing soil stabilization techniques for construction and erosion. As with any biologically induced process in soils or aquifers, it is important to track changes in the microbial communities that occur as a result of the treatment. Our research assessed how native microbial communities developed in response to injections of reactants (dilute molasses as a carbon source; urea as a source of nitrogen and alkalinity) that promoted MICP in a shallow aquifer. Microbial community composition (16S rRNA gene) and ureolytic potential (ureC gene copy numbers) were also measured in groundwater and artificial sediment. Aquifer geochemistry showed evidence of sulfate reduction, nitrification, denitrification, ureolysis, and iron reduction during the treatment. The observed changes in geochemistry corresponded to microbial community succession in the groundwater and this matched parallel geophysical and mineralogical evidence of calcite precipitation in the aquifer. We detected an increase in the number of ureC genes in the microbial communities at the end of the injection period, suggesting an increase in the abundance of microbes possessing this gene as needed to hydrolyze urea and stimulate MICP. We identify geochemical and biological markers that highlight the microbial community response that can be used along with geophysical and geotechnical evidence to assess progress of MICP.

Chronic combined hyperandrogenemia and western-style diet in young female rhesus macaques causes greater metabolic impairments compared to either treatment alone.

STUDY QUESTION: Does developmental exposure to the combination of hyperandrogenemia and western-style diet (WSD) worsen adult metabolic function compared to either treatment alone? SUMMARY ANSWER: Young female rhesus macaques treated for 3 years, beginning at menarche, with combined testosterone (T) and WSD have increased weight gain and insulin resistance compared to controls and animals treated with either T or WSD alone. WHAT IS KNOWN ALREADY: Hyperandrogenemia is a well-established component of polycystic ovary syndrome (PCOS) and can be observed in peripubertal girls, indicating a potential pubertal onset of the disease. Obesity is often associated with hyperandrogenemia in peripubertal girls, and overweight girls appear to be at higher risk for the development of PCOS later in life. STUDY DESIGN, SIZE, DURATION: Juvenile (2.5- year old) female rhesus macaques were divided into four groups (n = 10/group): control animals receiving cholesterol implants and a control diet with 15% of calories derived from fat (C), animals receiving T implants (mean serum levels: 1.35 ± 0.01 ng/ml) and a control diet (T), animals receiving a cholesterol implant and a WSD with 36% of calories derived from fat (WSD) and animals receiving a T implant and a WSD (T + WSD). Animals were maintained on the treatments for 36 months and were 5.5 years old at study completion. PARTICIPANTS/MATERIALS, SETTING, METHODS: Metabolic testing consisted of body measurements including weight, dual-energy X-ray absorptiometry scans, activity monitoring, and glucose tolerance testing at zero months and at least once every 12 months for the remainder of the study. Indirect calorimetry and serum hormone assays were performed following 36 months of treatment. MAIN RESULTS AND THE ROLE OF CHANCE: Body weight and fat mass gain were significantly increased in T + WSD at 24 and 36 months of treatment compared to the other three groups. Log transformed fasting insulin and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) were significantly increased in T + WSD animals at 3 years of treatment compared to all other groups. T-treatment caused a greater rate of decline in activity after 18 months, while food intake and metabolic rate were largely unaffected by treatments. LIMITATIONS REASONS FOR CAUTION: Variability was present in the metabolic parameters measured; however, this is similar to the heterogeneity observed in human populations. WIDER IMPLICATIONS OF THE FINDINGS: Chronic hyperandrogenemia beginning at puberty may exacerbate metabolic dysfunction in women consuming a WSD and account for the increased rates of obesity and insulin resistance observed in PCOS patients. Counseling of female patient populations with elevated androgens about the potential benefit of consuming a lower fat diet could improve long-term metabolic health outcomes. STUDY FUNDING/COMPETING INTEREST(S): Eunice Kennedy Shriver National Institute of Child Health & Human Development P50HD071836 and Oregon National Primate Center Grant P51 OD011092. The authors have no competing conflict of interests to disclose.

Evolution of surface area-to-volume ratio for a water meniscus evaporating between contacting silica spheres.

An experimental investigation was performed under isothermal conditions to quantify the rate of evaporation of water from a receding pendular meniscus connecting two silica spheres. Optically based measurements were used to determine the relevant meniscus dimensions, and the meniscus was modeled using a toroidal approximation. The rate of change of meniscus surface area and volume was then predicted using mathematical modeling software. The results demonstrated that once the meniscus transitioned from a relatively flat surface to one with an increasing radius of curvature, the rate of change of the ratio of surface area-to-volume was relatively constant over the range of water contents that were observable using the optical investigation techniques implemented in this study. Comparison of the flux of water from the meniscus surface demonstrated that the evaporation of bound water was four orders of magnitude slower than evaporation from a free water surface.

Effect of total organic carbon content and structure on the electrokinetic behavior of organoclay suspensions.

This experimental investigation measured the zeta potential of the clay mineral, montmorillonite, which was modified with six different quaternary ammonium cations. The organic cations were chosen to quantify the effect of cation functional groups, including chain length and cation size, on the resulting zeta potential; each of the six cations were exchanged onto the clay surface at three levels of total organic carbon. The zeta potential of the unmodified and the organically modified clays was measured as a function of pH, and in all cases, became less negative as the total organic carbon was increased and as the length of the attached carbon chain was increased, indicating that the organic cations were more strongly bound within the particle's shear plane as total organic carbon content was increased. Measured zeta potential was also less negative for all clays tested (including unmodified montmorillonite) as pH was decreased. When compared on the basis of total organic carbon content, increasing the length of one carbon chain in the quaternary positions was a more effective method of neutralizing surface charge than was increasing the overall size of the cation (i.e., increasing the chain length in all quaternary positions).

Sorption of nitroaromatic compounds to synthesized organoclays.

This project quantifies the ability of seven engineered organoclays to sorb TNT and two of its reduction products: 2-amino-4,6-dinitrotoluene (2-A-4,6-DNT) and 4-amino-2,6-dinitrotoluene (4-A-2,6-DNT). The organoclays used in the TNT sorption studies were synthesized in the laboratory by combining bentonite with benzyltriethylammonium chloride (BTEA) at 50, 75, and 100% of the bentonite's cation exchange capacity and with hexadecyltrimethylammonium bromide (HDTMA) at 25, 50, 75, and 100% of the bentonite's cation exchange capacity. For sorption of 2-A-4,6-DNT and 4-A-2,6-DNT, two organoclays were tested: BTEA at 50% CEC and HDTMA at 75% CEC. Sorption data with HDTMA organoclay and TNT were fit to linear isotherms and demonstrated that the clay's sorptive capacity increased as the amount of total organic carbon exchanged onto the clay increased. Sorption data with BTEA organoclay and TNT were fit to Langmuir isotherms; however, the clay's sorptive capacity increased as the amount of total organic carbon sorbed to the clay's surface was decreased. Sorption behavior for TNT reduction products 2-A-4,6-DNT and 4-A-2,6-DNT to one HDTMA organoclay and one BTEA organoclay demonstrated that HDTMA organoclay at 10.3% total organic carbon was a more effective sorbent than BTEA organoclay at 5.2% total organic carbon.

Degradation kinetics of TNT in the presence of six mineral surfaces and ferrous iron.

Trinitrotoluene (TNT), a nitroaromatic explosive, is a commonly encountered groundwater contaminant in the United States that can pose a human health risk, even at very low aqueous concentrations. This study describes the process characteristics of abiotic degradation of dissolved TNT in the presence of ferrous iron (Fe2+) and six different minerals-processes relevant to a more complete understanding of reduced iron technologies in TNT cleanup. Kinetic degradation batch reactions involving combinations of TNT, ferrous iron, six minerals with varying cation exchange capacity, and two pH buffers were performed. The rate of TNT degradation was quantified using high performance liquid chromatography (HPLC). Unbuffered reactions between TNT, Fe2+, and magnetite, pyrite, quartz, and goethite/quartz were insignificant. However, unbuffered reactions between TNT, Fe2+, and calcite and siderite proceeded rapidly to completion. The difference in reaction rates was attributable to the elevated pH in the presence of the latter minerals. For reactions performed in buffered systems with pH 7.4, degradation followed a second-order kinetics rate law. For reactions in buffered systems with pH 9.0, the reactions proceeded to completion almost instantaneously. The presence of the mineral solid surface was necessary for TNT reduction to proceed, with the most rapid reaction rates occurring in the presence of a suspected hydroxy solid phase that formed at high pH.

Organoclay sorption of benzene as a function of total organic carbon content.

The sorption of benzene to bentonite, activated carbon, and two organo-clays synthesized with the quaternary ammonium organic cations hexadecyltrimethylammonium (HDTMA) and benzyltriethylammonium (BTEA) was quantified as a function of total organic carbon content. The unmodified bentonite sorbed no benzene, while the activated carbon exhibited the strongest benzene uptake. For the organoclays, organic cations were exchanged onto Wyoming bentonite at four different percentages of the clay's cation exchange capacity. For HDTMA clay, in which partitioning is the dominant sorptive medium, it was determined that benzene sorption increased as the total organic carbon content increased (as the clay became more hydrophobic). In contrast, the sorption of benzene to BTEA clay, an adsorptive clay, decreased as the total organic carbon content of the clay was increased. It is believed that the sorptive capacity of BTEA clay decreases due to the formation of positively charged dimers on the clay's surface that block access to the sorptive sites. The organoclays sorbed more benzene than the unmodified bentonite, but less than the activated carbon.

Effects of system parameters on the physical characteristics of bubbles produced through air sparging.

Air sparging is a relatively new, cost-effective technology for the remediation of soil and groundwater contaminated with volatile organic compounds (VOCs). While the method has met with reasonable success at a large number of field sites, implementation of the technique is restricted to relatively coarse-grained soils with large values of air permeability, which significantly limits its applicability. An understanding of the fundamental parameters that control the formation and distribution of air in the sparging process is useful for optimizing the system implementation and extending its range of applicability. This work presents the results of an experimental investigation into the effect of process control parameters on the size and size distribution of air bubbles produced in aqueous and idealized saturated porous media systems. The experiments used digital image analysis to image and quantify the physical characteristics of the bubbles generated in a bench scale test cell. Results demonstrated that the average bubble size and range of size distribution increased as the injection pressure and size of the injection orifice were increased. Larger diameter bubbles with wider size distributions were produced in the presence of particles when compared to aqueous systems. As the particle size was decreased, the size of bubbles produced increased. Finally, the presence of trace quantities of the surfactant Triton X100 led to uniformly small diameter bubbles under all experimental conditions. The presence of the surfactant coating produced bubbles with physical characteristics that are more suited to in situ stripping of VOCs than the bubbles produced in the absence of a surfactant.

Improvement of EPA method 8330: complete separation using a two-phase approach.

Complete separation of the 14 nitroaromatic and nitramine analytes targeted in EPA Method 8330 was achieved using a 30 x 4.6 mm Bondesil CN guard column in series with a 250 x 4.6 mm Bondesil C18 column (5 microns particles). Consistent with Method 8330 specifications, the mobile phase in the separation was 1:1 methanol:water and the flow-rate was 1.5 ml min-1. The success of this two-phase system proved to be largely a consequence of the unique resolution afforded by the Bondesil C18 column: complete separation of the 14 explosives could not be achieved using other CN/C18 column combinations. Additionally, while Method 8330 calls for a 100-microliter injection loop, separation on the Bondesil CN/C18 system was possible only using a 20-microliter injection loop. The loss of resolution with larger injection volume appears to be a result of the injection solvent, methanol, modifying the composition of the mobile phase both in the CN guard column and in the initial portion of the C18 column. The current method nevertheless represents an improvement over Method 8330, which calls for both a screening and confirming analysis. By separating the 14 Method 8330 analytes in a single run, the two-phase approach can increase sample throughput by decreasing analysis times.

Virus infections of the respiratory tract in HIV-infected children.

In order to determine whether the rates of respiratory viral infection and the severity of respiratory symptoms in HIV-infected children were higher than those in noninfected children, nose and throat swabs for viral isolation were taken at 3-month intervals during the first 2 years of life from 50 children born to HIV-infected women. Similar samples were obtained during the first year of life from 19 control children born to HIV seronegative mothers. Of the 50 children, five proved to be HIV-infected while 45 were presumed to be uninfected. HIV-infected children had significantly more respiratory symptoms and a higher proportion of samples from which viruses were isolated than the non-HIV-infected children. Also, more infected episodes required admission to hospital in the HIV-infected group. There was no such difference between the non-HIV-infected and the control children. Three HIV-infected children received intravenous immunoglobulin therapy. Among these the proportion of positive samples for viral isolation was greater before than after treatment began. These results suggest that HIV-infected children are more susceptible to recurrent viral infection and that passive immunotherapy may be of benefit to such children.

Diagnosis of Pneumocystis carinii pneumonia from non-invasive sampling of respiratory secretions.

An infant infected with HIV presented with fever, tachypnoea, hypoxia, and radiological evidence of bilateral pneumonitis. Fluorescent antibody technique identified Pneumocystis carinii within 24 hours from secretions obtained by nasopharyngeal aspiration. This rapid, non-invasive method should be the first line investigation of suspected P carinii pneumonia in immunocompromised patients.

Effect of vibratory acoustic stimulation on the duration of fetal heart rate monitoring tests.

The ability of vibratory acoustic stimulation to shorten the duration of antepartum fetal heart rate monitoring was investigated by a randomized controlled trial. Vibratory acoustic stimulation did not shorten the overall duration of testing. This failure to improve the performance of antepartum monitoring appeared to result from prolonged accelerations, which complicated one third of the tests in which vibratory acoustic stimulation was employed. Further investigation is warranted using less profound methods of fetal stimulation.

Contraction stress fetal heart rate monitoring at preterm gestational ages.

The evaluation of fetal well-being by fetal heart rate monitoring at preterm gestational ages remains a difficult and important area for investigation. While the nonstress test has achieved widespread usage, a role for the contraction stress test remains uncertain. This study describes the outcome of 113 contraction stress tests which were performed for persistent fetal heart rate nonreactivity in 78 pregnancies of less than 37 completed weeks' gestation. There were no fetal deaths and no obstetric complications which could be attributed to these tests. The finding of a negative contraction stress test provided reassurance which facilitated significant prolongation of pregnancy. Contraction stress test appear to be a safe and effective method of investigating further the clinical dilemma of persistent fetal heart rate nonreactivity in high risk pregnancies at preterm gestational ages.

Nonstress and contraction stress fetal heart rate monitoring. A randomized trial to determine which is the faster primary test.

Antepartum fetal heart rate monitoring can be performed with either the nonstress or contraction stress method. The recent introduction of nipple stimulation as a means of achieving uterine contraction has simplified performance of contraction stress tests and raises the possibility that that test may be a more rapid approach to antepartum fetal heart rate testing than the nonstress test. In order to investigate the time taken to achieve a satisfactory end point of fetal heart rate monitoring, 186 women were randomized to either "intention to perform nonstress test" or "intention to perform nipple stimulation contraction stress test." Neither approach was found to be significantly faster than the other. One-third of all completed contraction stress tests were classified as equivocal and required further investigation or management. The nipple stimulation contraction stress test was not found to be a more rapid approach to antepartum fetal heart rate monitoring than the nonstress test.