Preferential Adsorption of Prominent Amino Acids in the Urease Enzyme of Sporosarcina pasteurii on Arid Soil Components: A Periodic DFT Study

The urease enzyme is commonly used in microbially induced carbonate precipitation (MICP) and enzyme-induced carbonate precipitation (EICP) to heal and strengthen soil. Improving our understanding of the adsorption of the urease enzyme with various soil surfaces can lead to advancements in the MICP and EICP engineering methods as well as other areas of soil science. In this work, we use density functional theory (DFT) to investigate the urease enzyme's binding ability with four common arid soil components: quartz, corundum, albite, and hematite. As the urease enzyme cannot directly be simulated with DFT due to its size, the amino acids comprising at least 5% of the urease enzyme were simulated instead. An adsorption model incorporating the Gibbs free energy was used to determine the existence of amino acid-mineral binding modes. It was found that the nine simulated amino acids bind preferentially to the different soil components. Alanine favors corundum, glycine and threonine favor hematite, and aspartic acid favors albite. It was found that, under the standard environmental conditions considered here, amino acid binding to quartz is unfavorable. In the polymeric form where the side chains would dominate the binding interactions, hematite favors aspartic acid through its R-OH group and corundum favors glutamic acid through its R-Ket group. Overall, our model predicts that the urease enzyme produced by Sporosarcina pasteurii can bind to various oxides found in arid soil through its alanine, glycine, aspartic/glutamic acid, or threonine residues.

A laboratory preparation procedure for studying bioaccumulation of U and its subcellular form in earthworms (Diplocardia spp.)

Uranium (U) is a ubiquitous trace element in soils. With increasing in application of U in nuclear energy and nuclear weapon, a large amount of U was dissipated into the environment including soil and water. Earthworm may be an eco-indicator for U bioaccumulation, transformation and transport across the ecosystem. There have been a variety of methods preformed to assess the bioaccumulation of uranium in small organisms such as earthworms, including uranium speciation, subcellular separation, and total U accumulation. All methods require an initial grinding preparation process that allows for the further fractionation of metals and metalloids in earthworms. The slime like mucus that coats the body of a worm presents a challenge in the disintegration and dissolution of the worm body. In order to analyze U subcellular forms, we developed a reliable and effective procedure to grind the worm body into a uniform fine suspension. We conducted a comparative study of disintegration of worms with 3 grinding techniques (agate mortar, liquid nitrogen freezing then agate mortar, and direct sonication) that would assist U subcellular analyses and bioaccumulation. The essences of this new development was as follows:•A scheme for preparation of earthworm samples for investigation of subcellular U forms in earthworms from U.S. army weapon test range soil with various U forms.•The direct sonication of earthworms was found to be the most proficient process in achieving the best preparation for U subcellular analyses with the high precision.

A laboratory simulation to investigate effects of moistures on U distribution among solid phase components in army range soils

Uranium is a naturally occurring radioactive trace element found in rocks, soils, and coals. U may contaminate groundwater and soil from nuclear power plant operations, spent fuel reprocessing, high-level waste disposal, ore mining and processing, or manufacturing processes. Yuma Proving Ground in Arizona, USA has been used depleted uranium ballistics for 36 years where U has accumulated in this army testing site. The objective of this study is to develop a laboratory scheme on the effects of soil moisture regiments on the distribution and partitioning of U in army range soil among solid phase components to mimic U biogeochemical processes in the field. Three moisture regiments were saturated paste, field capacity, and wetting-drying cycle which covered major scenarios in fields from the wet summer season to the dry winter season. Uranium in soils with different forms of U (UO₂, UO₃, uranyl, and schoepite) was fractionated into 8 operationally defined solid components with sequential selective dissolution procedure. The essences of this new development were as following:•

A scheme was developed for investigation of U distribution, partitioning and transformation among solid phase components in army weapon test range soils with various U forms under 3 soil moisture regimes.

•

Soil moisture was one of major environmental factors in controlling biogeochemical processes and fates of U in army weapon test site.

The Adsorption Characteristics of Uranium(VI) from Aqueous Solution on Leonardite and Leonardite-Derived Humic Acid: A Comparative Study

The humic substance is a low-cost and effective adsorbent with abundant functional groups in remediating uranium (U) (VI)-contaminated water. In this research study, leonardite together with leonardite-derived humic acid (L-HA) was used to eliminate U(VI) from water under diverse temperatures (298, 308, and 318 K). L-HA showed a higher adsorption volume for U(VI) than leonardite. U adsorption was varied with pH and increased with temperature. The adsorption kinetics of L-HA had a higher determination coefficient (R²) for pseudo-second-order (R² > 0.993) and Elovich (R² > 0.987) models, indicating possible chemisorption-assisted adsorption. This was further supported with the activation energies (15.9 and 13.2 kJ/mol for leonardite and L-HA, respectively). Moreover, U(VI) equilibrium adsorption on leonardite was better depicted with the Freundlich model (R² > 0.970), suggesting heterogeneous U(VI) adsorption onto the leonardite surface. However, U(VI) adsorption onto L-HA followed the Langmuir equation (R² > 0.971), which implied the dominant role of monolayer adsorption in controlling the adsorption process. Thermodynamic parameters, including standard entropy change (ΔS⁰ > 0), Gibbs free energy (ΔG⁰ < 0), and standard enthalpy change (ΔH⁰ > 0), suggested a spontaneous and endothermal adsorption process. In addition, ionic species negatively affected U(VI) adsorption by leonardite and L-HA.

Functionalization of clay surface for the removal of uranium from water

A modification method of clay mineral surface was developed to improve its adsorption capacity of uranium. Uranium is a radionuclide with high toxicity and extremely long half-life, which can pollute the environment and endanger human health. This study proposes a new method of activation of clay mineral surface with phosphoric acid for rapid adsorption of uranium from aqueous solution. Compared with other modification methods, this method has the advantages of availability of raw materials, simple operation and good adsorption effects. It provides a cost-effective material to capture uranium ions from water. The essences of this new development are as following: • Activation and changes of clay minerals' surface functionalities with the treatment of phosphoric acid • Controlled modifications of the surface properties of the clay towards the enhancement of U adsorption capacity • Rapid removal of uranium from water.

Amendment for increased methane production rate in municipal solid waste landfill gas collection systems

Optimization of methane production rate can potentially decrease the operational lifetime of the landfill site and assist with better management of methane harvesting from the landfill cells. Increased moisture content in landfill cells is known to increase the rate of methane production. Several natural biopolymers can sustain moisture content in a solid matrix while providing a scaffolding for microbial communities to grow. This research examined the effect of the biopolymer, produced by Rhizobium tropici, on bench-scale methane generation from municipal solid waste. The addition of the R. tropici biopolymer increased the rate of methane production from 27% to 78% when compared to the control study for low and high concentrations of biopolymer amendment, respectively. R. tropici biopolymer shortened the lag phase by up to six days over the control, depending on the level of biopolymer amendment added to the solid waste. The mechanism appears to be facilitating biofilm formation through the combination of increased moisture retention and surface modification of the solid waste. Incorporation of biopolymer amendment in the alternative daily cover activities at commercial landfills could provide a viable approach for full scale application.

A simple method for the synthesis of biochar nanodots using hydrothermal reactor

Biochar is a stable carbon rich by-product synthesized through pyrolysis of plant and animal based biomass, and nano-biochar material has gained increasing attention due to its unique properties for environmental applications. In the present study, a simple cost-effective method for the synthesis of biochar nanoparticles through hydrothermally using agricultural residuals and by-products was developed. Both soybean straw and cattle manure were selected as the feedstock to produce the bulk-biochar. The synthesis procedure involved the digestion of the bulk-biochar with concentrated nitric acid and sulfuric acid in a high pressure condition using a hydrothermal reactor. The suspension was isolated using vacuum filtration with 0.22-μm membrane followed by drying at 65 °C in an oven. Scanning electron microscopy results revealed that both of the biochars had a well-developed porous structure following pyrolysis. Both transmission electron microscopy and the dynamic light scattering results of the hydrothermally treated biochar indicated that the soybean straw and cattle manure biochar nanodots had an average of 5-nm and 4-nm in size, respectively. Overall two raw materials produced 8.5–10% biochar nanodots. The present method presents a simple, quick and cost-effective method for synthesis of biochar nanodots. The method provided a useful tool discovering the applicability biochar nanodots for environmental applications.

• Nano-biochar formation from bulk-biochar using hydrothermal reactor

• Evaluate nano-biochar's environmental fate and behavior in soil and water

• Synthesize multifunctional adsorbent using nano-biochar as primary material

A novel laboratory simulation system to uncover the mechanisms of uranium upward transport in a desert landscape

After depleted uranium (DU) is deposited in the environment, it corrodes producing mobile uranium species. The upward transport mechanism in a desert landscape is associated with the dissolution/precipitation of uranium minerals that vary in composition and solubility in soil pore water. The objective of this study is to develop the laboratory column simulation to investigate the upward transport mechanism with cyclic capillary wetting and drying moisture regimes. Results showed that evaporation driven upward transport occurred even during the first 2 months of wetting-drying regimes. Evaporation driven upward transport may control the U movement in the soil profile in an arid climate. The new system did not generate any uranium-containing wastewater. •Simulates the upward transport process of pollutants with different pollution levels and species.•Simultaneously simulate the transport process of multiple pollutants simultaneously.•Evaluate the influence of biogeochemical factors on pollutant transport such as various cations and anions (Ca, Mg and carbonates) in water.

Electrokinetic-enhanced phytoremediation of uranium-contaminated soil using sunflower and Indian mustard

Electrokinetic-enhanced phytoremediation is an effective technology to decontaminate heavy metal contaminated soil. In this study, we examined the effects of electrokinetic treatments on plant uptake and bioaccumulation of U from soils with various U sources. Redistribution of uranium in soils as affected by planting and electrokinetic treatments was investigated. The soil was spiked with 100 mg kg^-1 UO₂, UO₃, and UO₂(NO₃)₂. After sunflower and Indian mustard grew for 60 days, 1 voltage of direct-current was applied across the soils for 9 days. The results indicated that U uptake in both plants were significantly enhanced by electrokinetic treatments from soil with UO₃ and UO₂(NO₃)₂. U was more accumulated in roots than in shoots. Electrokinetic treatments were effective on lowering soil pH near the anode region. Overall, uranium (U) removal efficiency reached 3.4-4.3% from soils with UO₃ and uranyl with both plants while that from soil with UO₂ was 0.7-0.8%. Electrokinetic remediation treatment significantly enhanced the U removal efficiency (5-6%) from soils with UO₃ and uranyl but it was 0.8-1.3% from soil with UO₂, indicating significant effects of U species and electrokinetic enhancement on U bioaccumulation. This study implies the potential feasibility of electrokinetic-enhanced phytoremediation of U soils with sunflower and Indian mustard.

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g^-1 at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO₃ and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO₃and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils.

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4}  years. We infer the component masses of the binary to be between 0.86 and 2.26  M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60  M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28  deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8}  Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

Gravity Spy: integrating advanced LIGO detector characterization, machine learning, and citizen science

With the first direct detection of gravitational waves, the advanced laser interferometer gravitational-wave observatory (LIGO) has initiated a new field of astronomy by providing an alternative means of sensing the universe. The extreme sensitivity required to make such detections is achieved through exquisite isolation of all sensitive components of LIGO from non-gravitational-wave disturbances. Nonetheless, LIGO is still susceptible to a variety of instrumental and environmental sources of noise that contaminate the data. Of particular concern are noise features known as glitches, which are transient and non-Gaussian in their nature, and occur at a high enough rate so that accidental coincidence between the two LIGO detectors is non-negligible. Glitches come in a wide range of time-frequency-amplitude morphologies, with new morphologies appearing as the detector evolves. Since they can obscure or mimic true gravitational-wave signals, a robust characterization of glitches is paramount in the effort to achieve the gravitational-wave detection rates that are predicted by the design sensitivity of LIGO. This proves a daunting task for members of the LIGO Scientific Collaboration alone due to the sheer amount of data. In this paper we describe an innovative project that combines crowdsourcing with machine learning to aid in the challenging task of categorizing all of the glitches recorded by the LIGO detectors. Through the Zooniverse platform, we engage and recruit volunteers from the public to categorize images of time-frequency representations of glitches into pre-identified morphological classes and to discover new classes that appear as the detectors evolve. In addition, machine learning algorithms are used to categorize images after being trained on human-classified examples of the morphological classes. Leveraging the strengths of both classification methods, we create a combined method with the aim of improving the efficiency and accuracy of each individual classifier. The resulting classification and characterization should help LIGO scientists to identify causes of glitches and subsequently eliminate them from the data or the detector entirely, thereby improving the rate and accuracy of gravitational-wave observations. We demonstrate these methods using a small subset of data from LIGO's first observing run.

Bullet on bullet fragmentation profile in soils

Lead-antimony alloy slugs encased in a brass jackets are common small arms caliber ammunition used for training and target practice. When small caliber ammunition is fired at testing and training ranges, these metals--some of which are toxic--are introduced into the environment. Research was conducted on the effects of bullet on bullet impacts and the resulting bullet fragmentation. The extent of bullet fragmentation, among other factors, affects the formation of mobile metal species from small arms firing ranges. Bullet on bullet impact can increase the surface area to mass ratio of the bullet metal alloys in the soil. The solubility of a metal is typically associated with the specific corrosion rate in the berm environment which is dependent on the surface area of the fragments. The purpose of the study was to analyze the bullet on bullet impact effects in six soil types. Changes in the metal distribution as a result of bullet impact was evaluated through sieve analysis and changes in the particle size distribution. The bullet on bullet impact observed in this study demonstrated a significant and observable shift in the fragmentation profiles for the lead, antimony, and copper in soils after shooting an average of 1050 tungsten-nylon bullets into the legacy lead soils. This study provides new information to assist with determining the potential environmental fate, transport, and environmental availability associated with constant bullet on bullet impact at testing and training ranges.

Impact of molecular adsorbent recirculating system therapy on tacrolimus elimination: a case report

BACKGROUND

We report a unique case which quantifies the effect of molecular adsorbent recirculating system (MARS [Gambro, Sweden]) therapy on blood concentrations of tacrolimus in a patient treated for refractory pruritus associated with recurrent hepatitis C of the liver allograft. Tacrolimus is a low-molecular-weight, highly protein-bound drug with the potential to be removed during MARS therapy.

CASE REPORT

Results of therapeutic drug monitoring revealed extracorporeal tacrolimus elimination accounted for only 0.3% of total drug removal during the session.

CONCLUSIONS

Although no explanation can be offered as to why MARS contributed so little to overall tacrolimus elimination, the data clearly show minimal impact of MARS on tacrolimus blood level.

Formation of Manganese Oxide Coatings onto Sand for Adsorption of Trace Metals from Groundwater

Manganese oxide (MnO) occurs naturally in soil and has a high affinity for trace metals adsorption. In this work, we quantified the factors (pH; flow rate; use of oxidants such as bleach, HO, and O; initial Mn(II) concentrations; and two types of geologic media) affecting MnO coatings onto Ottawa and aquifer sand using batch and column experiments. The batch experiments consisted of manual and automated titration, and the column experiments mimicked natural MnO adsorption and oxidation cycles as a strategy for in situ adsorption. A Pb solution of 50 mg L was passed through MnO-coated sand at a flow rate of 4 mL min to determine its adsorption capacity. Batch experimental results showed that MnO coatings increased from pH 6 to 8, with maximum MnO coating occurring at pH 8. Regarding MnO coatings, bleach and O were highly effective compared with HO. The Ottawa sand had approximately twice the MnO coating of aquifer sand. The sequential increase in initial Mn(II) concentrations on both sands resulted in incremental buildup of MnO. The automated procedure enhanced MnO coatings by 3.5 times compared with manual batch experiments. Column results showed that MnO coatings were highly dependent on initial Mn(II) and oxidant concentrations, pH, flow rate, number of cycles (h), and the type of geologic media used. Manganese oxide coating exceeded 1700 mg kg for Ottawa sand and 130 mg kg for aquifer sand. The Pb adsorption exceeded 2200 mg kg for the Ottawa sand and 300 mg kg for the aquifer sand.

Hydrated lime for metals immobilization and explosives transformation: Treatability study

Fragmentation grenades contain Composition B (RDX and TNT) within a steel shell casing. There is the potential for off-site migration of high explosives and metals from hand grenade training ranges by transport in surface water and subsurface transport in leachate. This treatability study used bench-scale columns and mesocosm-scale laboratory lysimeters to investigate the potential of hydrated lime as a soil amendment for in situ remediation of explosives and metals stabilization in hand grenade range soils. Compared to the unamended soil there was a 26-92% reduction of RDX in the leachate and runoff water from the lime treated soils and a 66-83% reduction of zinc in the leachate and runoff water samples; where the hand grenade range metals of concern were zinc, iron, and manganese. The amended soil was maintained at the target pH of greater than 10.5 for optimum explosives decomposition. The treatability study indicated a high potential of success for scale-up to an in situ field study.

The effect of phosphate application on the mobility of antimony in firing range soils

Chemical and biogenic sources of phosphate are commonly accepted in situ treatment methods for immobilization of lead (Pb) in soil. The metalloid antimony (Sb), commonly associated with Pb in the environment, exists as either a neutral species or a negatively charged oxyanion. Antimony is used in the manufacture of bullets as a hardening agent, constituting approximately 3% of the bullet mass. Technological solutions to reduce the migration of metals from small arms firing range (SAFR) soils for environmental compliance purposes must be robust with respect to multi-component systems containing both cationic and anionic contaminants. The effect of varying physico-chemical soil properties on Sb mobility post-firing was assessed in this study for six soil types using common analytical protocols and methods related to regulatory criteria. The sands (SM and SP) demonstrated the greatest Sb solubility in post-firing leachate samples and therefore were selected to evaluate the effects of five commercially available stabilization amendments on Sb mobility. Enhanced Sb leaching was experimentally confirmed in the phosphate-treated soils compared to both the untreated control soil and the sulfur-based amendment, and thus suggests competition for negative sorption sites between Sb and phosphate. However, the 5% Buffer Block® calcium phosphate amendment did not exhibit the same enhanced Sb release. This can be attributed to the inclusion of aluminum hydroxide in the amendment composition. Technologies are needed that will adequately immobilize Pb without mobilizing oxyanions such as Sb. Further research will be required to elucidate binding mechanisms and redox conditions that govern the mobility of Sb on SAFRs.

Dissolution, sorption, and kinetics involved in systems containing explosives, water, and soil

Knowledge of explosives sorption and transformation processes is required to ensure that the proper fate and transport of such contaminants is understood at military ranges and ammunition production sites. Bioremediation of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and related nitroaromatic compounds has met with mixed success, which is potentially due to the uncertainty of how energetic compounds are bound to different soil types. This study investigated the dissolution and sorption properties of TNT and RDX explosives associated with six different soil types. Understanding the associations that explosives have with a different soil type assists with the development of conceptual models used for the sequestration process, risk analysis guidelines, and site assessment tools. In three-way systems of crystalline explosives, soil, and water, the maximum explosive solubility was not achieved due to the sorption of the explosive onto the soil particles and observed production of transformation byproducts. Significantly different sorption effects were also observed between sterile (gamma-irradiated) and nonsterile (nonirradiated) soils with the introduction of crystalline TNT and RDX into soil-water systems.

Geochemical parameters influencing tungsten mobility in soils

The biogeochemistry of tungsten and its effects on mobility have recently gained attention due to the existence of human cancer clusters, such as in Fallon, NV. Tungsten exists in many environmental matrices as the soluble and mobile tungstate anion. However, tungsten can polymerize with itself and other anions, creating poly- and heteropoly-tungstates with variable geochemical and toxicological properties. In the present work, geochemical parameters are determined for tungstate species in a model soil that describe the potential for tungsten mobility. Soluble tungsten leached from a metallic tungsten-spiked soil after six to twelve months aging reached an equilibrium concentration >150 mg/L within 4 h of extraction with deionized water. Partition coefficients determined for various tungstate and polytungstate compounds in the model soil suggest a dynamic system in which speciation changes over time affect tungsten geochemical behavior. Partition coefficients for tungstate and some poly-species have been observed to increase by a factor of 3 to 6 over a four month period, indicating decreased mobility with soil aging.

Effects of organic matter on the distribution of uranium in soil and plant matrices

This work studied interactions of uranium with pure organic compounds, such as glutathione, and more complex mixtures, such as humic acid and aqueous plant extracts. High performance liquid chromatography with UV absorption interfaced to inductively coupled plasma mass spectrometry sequential detection was used to detect organouranium complexes in a variety of soils and plant materials, indicating that nearly 100% of the uranium extracted from certain plant tissues was bound to organic ligands. In addition, soil sorption experiments indicated that humic acid generally decreased uranium sorption to soils and promoted subsequent desorption of uranium because of uranium partitioning to the organic phase. These experiments demonstrate that organic compounds influence the mobility and chemistry of uranium in the environment.

Applicability of alkaline hydrolysis for remediation of TNT-contaminated water

This study was conducted to assess the applicability of alkaline hydrolysis as an alternative ex situ technology for remediating 2,4,6-trinitrotoluene (TNT)-contaminated water. TNT reactivity had a strong dependence on the reaction pH (11-12) and initial TNT (5-25 mg L(-1)) in batch systems, resulting in pseudo first-order transformation rate, k ranging between 1.9 x 10(-3) and 9.3 x 10(-5) min(-1). In continuous flow stirred-tank reactor (CFSTR) systems with initial TNT of 1 mg L(-1), the highest 74% of TNT reduction was achieved at the reaction pH of 11.9 and 2-day hydraulic retention time under steady-state condition. Oxalate was produced as the major hydrolysate in the CFSTRs, indicating a ring cleavage during alkaline hydrolysis. It was also believed that TNT alkaline hydrolysis occurred through the production of color-forming intermediates via dimerization. It is concluded that alkaline hydrolysis can be an alternative treatment technology for remediation of TNT-contaminated water.

Characterization of a military training site containing 232Thorium

Understanding contaminant distribution is critical to selection and implementation of effective and affordable containment and remediation efforts. This article describes the characterization of soil containing thorium at a training site on Kirtland Air Force Base, Albuquerque, NM. The site has been used by the Defense Nuclear Weapons School since the early 1960's to train personnel in emergency response to nuclear weapons accidents and for characterization and containment of radioactive contamination. The purpose of work reported herein is to describe the primary location and migration pattern of 232Thorium (232Th) and 232Th progeny (decay products) at the site. Soil containing thorium oxide (ThO2) was applied to the site for approximately 30 years (early 1960-1990) and was used to simulate a plutonium release from a nuclear weapons accident. Data presented indicate that surface 232Th and 232Th progeny at approximately 5 times background levels are approaching test site boundaries. However, the data also indicate that vertical migration has not exceeded 0.9 m because of the insoluble nature of ThO2. The major mechanisms of 232Th mobility appear to be surface migration mediated by precipitation runoff and wind-blown soil.

Perchlorate Analysis Using Solid-Phase Extraction Cartridges

Perchlorate is a compound of increasing concern as an environmental contaminant and is being regulated at increasingly stringent levels. Reliable methods are needed to consistently analyze perchlorate at low concentration levels. This research investigates the use of solid-phase extraction cartridges as an alternative to large-volume injection loops to achieve low-level (microg/L level) perchlorate quantitation. The method involves commercially available strong anion exchange (SAX) cartridges. Water samples are filtered (100 to 1000 mL) using the cartridge, which removes the perchlorate from the solution by anion exchange. Then, after the desired volume is filtered, the perchlorate is extracted using 4 mL of 1% NaOH. In addition, a cleanup method is developed to remove competing anions (chloride, sulfate, and carbonate) that are often found in environmental samples. Analyses are performed with an ion chromatograph using a 10-microL injection loop, yielding a perchlorate method detection limit (MDL) of 210 microg/L. One-liter volumes of a 2-microg/L perchlorate spiked deionized water solution are filtered with SAX SPE. Following extraction and analysis, an MDL of 0.82 microg/L is obtained, comparable to that found for 1-mL injection loop systems (reported as low as 0.53 microg/L). MDL studies are then conducted on perchlorate-amended groundwater (solution concentration of 70 microg/L) and surface water (solution concentration of 10 microg/L) using a filtration volume of 200 mL. The MDLs are 6.7 microg/L for the groundwater and 2.4 microg/L for the surface water.

Mechanisms of thorium migration in a semiarid soil

Thorium concentrations at Kirtland Air Force Base training sites in Albuquerque, NM, have been previously described; however, the mechanisms of thorium migration were not fully understood. This work describes the processes affecting thorium mobility in this semiarid soil, which has implications for future remedial action. Aqueous extraction and filtration experiments have demonstrated the colloidal nature of thorium in the soil, due in part to the low solubility of thorium oxide. Colloidal material was defined as that removed by a 0.22-microm or smaller filter after being filtered to nominally dissolved size (0.45 microm). Additionally, association of thorium with natural organic matter is suggested by micro- and ultrafiltration methods, and electrokinetic data, which indicate thorium migration as a negatively charged particle or anionic complex with organic matter. Soil fractionation and digestion experiments show a bimodal distribution of thorium in the largest and smallest size fractions, most likely associated with detrital plant material and inorganic oxide particles, respectively. Plant uptake studies suggest this could also be a mode of thorium migration as plants grown in thorium-containing soil had a higher thorium concentration than those in control soils. Soil erosion laboratory experiments with wind and surface water overflow were performed to determine bulk soil material movement as a possible mechanism of mobility. Information from these experiments is being used to determine viable soil stabilization techniques at the site to maintain a usable training facility with minimal environmental impact.

Bench- and field-scale evaluation of chromium and cadmium extraction by electrokinetics

The results of bench-scale laboratory tests and in situ, pilot-scale demonstration of electrokinetic extraction of chromium and cadmium from contaminated soil are presented. The laboratory tests were conducted using 10 cm long samples under current density of 5A/m(2) for 1200 h. Tests were conducted with and without citric acid amendment at the cathode. The results showed that citric acid improved extraction, especially in the sections near the cathode. However, processing was not enough to result in complete cleanup. The field demo was conducted at the Naval Air Weapon Station (NAWS), Point Mugu, California. Three cathodes were centered between six anodes. The anode-cathode spacing was 4.45 m (15 ft). Constant voltage of 60 V ( approximately 13 V/m) was applied for 20 days and then was reduced to 45 V (10 V/m) for 6 months. Citric acid was used to maintain the cathode pH at 4. After 6 months of treatment, 78% of the soil volume has been cleared of chromium or treated to below natural background levels. The results also indicated that 70% of the soil between the electrodes had been cleared of cadmium contamination. A comparison between the bench-scale and field demo showed that the field process was more effective than the lab tests. This indicated that small sample size will induce a negative effect on the efficiency of the process due to an increased impact of the boundaries on the overall process.

Treatment of trinitrotoluene by crude plant extracts

Crude plant extract solutions (spinach and parrotfeather) were prepared and spiked with 2,4,6-trinitrotoluene (TNT) (20 mgl(-1)). 90-h TNT removal by these solutions was compared to controls. Spinach and parrotfeather extract solutions removed 99% and 50% of the initial TNT, respectively; TNT was not eliminated in the controls or in extract solutions where removal activity was deactivated by boiling. A first-order removal constant of 0.052 h(-1) was estimated for spinach extract solutions treating 20 mgl(-1) TNT concentrations, which compared favorably to intact plant removal. Concentration variation was described by Michaelis-Menton kinetics. Detectable TNT degradation products represented only a fraction of the total TNT transformed, and the transformation favored the formation of 4-aminodinitrotoluene. The results indicated that crude plant extracts transform TNT, without the presence of the live plant.

Decolorization of alkaline TNT hydrolysis effluents using UV/H(2)O(2)

Effects of H(2)O(2) dosage (0, 10, 50, 100 and 300 mg/l), reaction pH (11.9, 6.5 and 2.5) and initial color intensity (85, 80 and 60 color unit) on decolorization of alkaline 2,4,6-trinitrotoluene (TNT) hydrolysis effluents were investigated at a fixed UV strength (40 W/m(2)). Results indicated that UV/H(2)O(2) oxidation could efficiently achieve decolorization and further mineralization. Pseudo first-order decolorization rate constants, k, ranged between 2.9 and 5.4 h(-1) with higher values for lower H(2)O(2) dosage (i.e., 10 mg/l H(2)O(2)) when the decolorization occurred at the reaction pH of 11.9, whereas a faster decolorization was achieved with increase in H(2)O(2) dosage at both pH 6.5 and 2.5, resulting in the values of k as fast as 15.4 and 26.6 h(-1) with 300 mg/l H(2)O(2) at pH 6.5 and 2.5, respectively. Difference in decolorization rates was attributed to the reaction pH rather than to the initial color intensity, resulting from the scavenging of hydroxyl radical by carbonate ion. About 40% of spontaneous mineralization was achieved with addition of 10 mg/l H(2)O(2) at pH 6.5. Efficient decolorization and extension of H(2)O(2) longevity were observed at pH 6.5 conditions. It is recommended that the colored effluents from alkaline TNT hydrolysis be neutralized prior to a decolorization step.

Depressive disorder as a long-term antecedent risk factor for incident back pain: a 13-year follow-up study from the Baltimore Epidemiological Catchment Area sample

BACKGROUND

The co-occurrence of affective distress and back pain is well documented but the relationship between them is less certain. This study examines the relationship between lifetime occurrence of depressive disorder and incident back pain reported over a 13-year period.

METHOD

The Baltimore Epidemiologic Catchment Area Study is a prospective study of a household-residing cohort, selected probabilistically from East Baltimore in 1981. Between 1982-3 (wave 2) and again between 1993-6 (wave 3), a follow-up study of the original cohort was conducted. Questions on depressive disorder and back pain were drawn from the Diagnostic Interview Schedule. Logistic regression analyses were used to evaluate whether depressive disorder acts as a risk factor for incident back pain.

RESULTS

In cross-sectional analyses, lifetime occurrence of depressive disorder was a significant correlate of lifetime prevalence of back pain at wave 1 (OR = 1.6, P = 0.01). During the 13-year follow-up, across three data collection points, there was an increase in the risk for incident back pain when depressive disorder was present at baseline (OR = 1.9, 95% CI 1.03, 3.4). However, during the short-term follow-up period of 1 year, between baseline and wave 2, depressive disorder at baseline was unrelated to first-ever reports of back pain. Lifetime depressive disorder in both waves 1 (baseline) and 2 (1 year later) was associated with a more than three times greater risk for a first-ever report of back pain during the 12 to 13 year follow-up period, in comparison to those who did not have depressive disorder at waves 1 or 2 (OR = 3.4, 95% CI 1.4, 7.8). Back pain at wave 1 was not significantly associated with an increased risk for depression in the longitudinal analysis (OR = 0.8, 95% CI 0.5, 1.4).

CONCLUSIONS

Depressive disorder appears to be a risk factor for incident back pain independent of other characteristics often associated with back pain. Back pain is not a short-term consequence of depressive disorder but emerges over periods longer than 1 year. Moreover, in this study the alternative pathway of back pain as a risk factor for depressive disorder could not be supported.

UV-VIS spectroscopy of 2,4,6-trinitrotoluene-hydroxide reaction

Contamination of groundwater, surface water and soil by explosives has occurred at military sites throughout the world as a result of manufacture of explosive compounds, assembly of munitions, and deployment of explosives containing devices. Due to the adverse effects of explosives on humans and other natural receptors, a low cost means of decontaminating these areas of contamination is needed. Base-induced transformation of explosives has shown promise as a rapid, low cost, and minimally resource-intensive technology for detoxifying explosives in soil and water. In order to understand the reaction mechanism, a reaction mixture of 2:1:1 (water:2,4,6-trinitrotoluene (TNT):1 N KOH) was analyzed by UV/VIS spectrometry from 190 to 1,100 nm. Time course measurements were conducted at 25, 20, 15, and 12 degrees C. A factor analysis program was used to analyze the spectral data. Principal component analysis indicated that six principal components explained the spectra to within experimental error, with four factors explaining the majority of the variance. Test spectral vectors for four components were developed, including TNT, two intermediates, and the final product, and were tested against the abstract vectors. Two possible reaction mechanisms were suggested and tested to explain the spectral data.

Analysis of CL-20 in environmental matrices: water and soil

Analytical techniques for the detection of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo(5.5.0.05,9.03,11)dodecane (CL-20) in water and soil are developed by adapting methods traditionally used for the analysis of nitroaromatics. CL-20 (a new explosives compound) is thermally labile, exhibits high polarity, and has low solubility in water. These constraints make the use of specialized sample handling, preparation, extraction, and analysis necessary. The ability to determine the concentrations of this new explosive compound in environmental matrices is helpful in understanding the environmental fate and effects of CL-20; understanding the physical, chemical, and biological fate of CL-20; and can be used in developing remediation technologies and determining their efficiency. The toxicity and mobility of new explosives in soil and groundwater are also of interest, and analytical techniques for quantitating CL-20 and its degradation products in soil and natural waters make these investigations possible.

Treatment of munitions in soils using phytoslurries

Phytoremediation is an established technology for the treatment of explosives in water and soil. This study investigated the possibility of using slurried plants (or phytoslurries) to treat explosives (TNT and RDX). The degradation of TNT in solution using intact and slurried parrotfeather (Myriophyllum aquaticum), spinach (Spinicia oleracea), and mustard greens (Brassica juncea) was evaluated. Phytoslurries of parrotfeather and spinach removed the TNT faster than the intact plant. Conversely, the removal rate constants for slurried and intact mustard greens were about the same. A study using pressurized heating to destroy enzymatic activity in the phytoslurries was also conducted to compare removal from released plant chemicals to adsorptive removal. Aqueous phase removal of TNT by autoclaved spinach phytoslurry was compared with nonautoclaved spinach phytoslurry. The autoclaved phytoslurry did remove TNT, but not as completely as nonautoclaved slurry. This suggests that some removal is due to adsorption, but not all. Phytoslurries of mustard greens and parrotfeather had higher RDX removal rates compared with intact plant removal, but the rates for parrotfeather in either case were relatively low. Phytoslurries of spinach had relatively modest increases in RDX removal rates compared with intact plant. Studies were then conducted with phytoslurry/soil mixtures at two scales: 60 ml and 1.5 l. In both cases, phytoslurries of mustard greens and spinach removed TNT and RDX at higher levels than control slurries.

A critical assessment of proximal macrotexturing on cemented femoral components

We analyzed the cement-metal interface of 3 different types of femoral components that had proximal macrotexturing after in vitro insertion and after fatigue testing designed to produce debonding and micromotion. These components were compared with clinical retrieval specimens. The cement did not flow into the macrotexturing; rather, hollow, brittle volcanoes or calderas were formed. These fragile protrusions of cement become worn down or abraded by debonded components. This abrasion of cement may contribute to the early and aggressive osteolysis seen in some of these early failures with proximal macrotextured components. The formation of these volcanos and calderas can be aborted by placing bone-cement onto the macrotexturing before stem insertion. This simple technique allows the macrotexturing to be filled with cement.

Preventable adverse patient outcomes: a closed claims analysis of respiratory incidents

Closed claims analysis of adverse anesthesia outcomes was initiated through the AANA Foundation in 1995 to examine adverse outcomes of anesthesia care provided by Certified Registered Nurse Anesthetists (CRNAs). A research team of 8 CRNAs using an instrument incorporating more than 150 variables undertook document analyses of closed claim files. All files reviewed involved incidents in which the CRNA named in the policy was potentially involved in the adverse patient outcome. Thirty-eight percent (58/151) of CRNA-related claims involved a respiratory incident as the primary cause of the negative patient outcome. Patient outcomes involving respiratory incidents were more likely to result in death or permanent injury compared with nonrespiratory incidents (P < .01). Reviewers found that respiratory claims were more likely to have involved inappropriate anesthesia management (P < .01), more likely to have involved a lack of vigilance (P < .01), and more likely to have been judged by the reviewer as preventable (P < .01). A higher percentage of respiratory incidents occurred in emergency cases (75% vs 34%, P < .01) and in cases involving general anesthesia (44% vs 17%, P < .01). Adverse respiratory incidents are largely preventable and frequently result in serious patient morbidity and mortality.

Depressive disorder, dysthymia, and risk of stroke: thirteen-year follow-up from the Baltimore epidemiologic catchment area study

BACKGROUND AND PURPOSE

This study examined depressive disorder as a risk factor for incident stroke in a prospective, population-based design.

METHODS

The Baltimore Epidemiologic Catchment Area Study is a prospective 13-year follow-up of a probability sample of household residents from Baltimore, Md. Depressive disorder was measured with the diagnostic interview schedule, and stroke was assessed by questions from the health interview survey or by documentation on a death certificate.

RESULTS

During the 13-year follow-up of 1703 individuals, 66 strokes were reported and 29 strokes were identified by death certificate search. Individuals with a history of depressive disorder were 2.6 times more likely to report stroke than those without this disorder after controlling for heart disease, hypertension, diabetes, and current and previous use of tobacco. Medications used in the treatment of depressive disorder at baseline did not alter this finding. A history of dysthymia demonstrated a similar relationship to stroke, although the estimate was not statistically significant.

CONCLUSIONS

Depressive disorder is a risk factor for stroke that appears to be independent of traditional cardiovascular risk factors. Further research on mechanisms for the association and the impact of treatment for depressive disorder on subsequent stroke is needed.

Tolerance towards explosives, and explosives removal from groundwater in treatment wetland mesocosms

A short-term study was performed to determine the feasibility of using constructed wetlands to remove explosives from groundwater, and to assess accumulation of parent explosives compounds and their known degradation compounds in wetland plants. Tolerance towards explosives in submersed and emergent plants was screened over a range of 0 to 40 mg L(-1). Tolerance varied per compound, with TNT evoking the highest, 2NT the lowest, and 24DNT, 26DNT, and RDX an intermediate growth reducing effect. Submersed plants were more sensitive to TNT than emergent ones. A small-scale 4-month field study was carried out at the Volunteer Army Ammunition Plant, Chattanooga, TN. In this surface-flow, modular system, the influent contained high levels (>2.1 mg L(-1)) of TNT, 2,4DNT, 2,6DNT, 2NT, 3NT, and 4NT, and the HRT was 7 days. The performance criteria of US EPA treatment goals for local discharge of 2,4DNT concentration <0.32 mg L(-1), and 26DNT concentration <0.55 mg L(-1) were not met at the end of the experiment, although explosives levels were greatly reduced. Low levels of 2ADNT and 4ADNT were transiently observed in the plant biomass. Results of two other, older, constructed wetlands, however, indicated that in these systems treatment goals were met most of the time, residues of explosives parent compounds and known degradation compounds in plant tissues were low and/or transient, and in substrates were low.

Interruption and bizarreness effects in the recall of script-based text

Recall of script, script-irrelevant, and script-interruptive actions in script-based stories was examined in four experiments. By varying the plausibility of the script-irrelevant and the script-interruptive actions, the bizarreness effect (i.e., enhanced recall for bizarre, implausible actions) was assessed within the context of script-based text. In addition, presentation of script-interruptive actions actions allowed for an assessment of the interruption effect (i.e., enhanced recall for interruptive actions). A bizarreness effect was found, to the extent that implausible script-irrelevant actions were better recalled than their more plausible counterparts and script actions. However, implausible actions were not better recalled than script-interruptive actions, nor did bizarreness significantly enhance recall of script-interruptive actions. These results are discussed in terms of recent assumptions underlying interruptions underlying interruption and bizarreness effects, and in terms of recent assumptions about how scripted and nonscripted actions are retained in memory.

Environmental behavior of explosives in groundwater from the Milan Army Ammunition Plant in aquatic and wetland plant treatments. Uptake and fate of TNT and RDX in plants

Uptake and fate of TNT and RDX by three aquatic and four wetland plants were studied using hydroponic, batch, incubations in explosives-contaminated groundwater amended with [U-14C]-TNT or [U-14C]-RDX in the laboratory. Substrates in which the plants were rooted were also tested. Plants and substrates were collected from a small-scale wetland constructed for explosives removal, and groundwater originated from a local aquifer at the Milan Army Ammunition Plant. This study demonstrated rapid uptake of [U-14C]-TNT derived 14C, concentration at the uptake sites and limited transport in all plants. Per unit of mass, uptake was higher in submersed than in emergent species. Biotransformation of TNT had occurred in all plant treatments after 7-day incubation in 1.6 to 3.4 mg TNT L-i, with labeled amino-dinitrotoluenes (ADNTs), three unidentified compounds unique for plants, and mostly polar products as results. Biotransformation occurred also in the substrates, yielding labeled ADNT, one unidentified compound unique for substrates, and polar products. TNT was not recovered by HPLC in plants and substrates after incubation. Uptake of [U-14C]-RDX derived 14C in plants was slower than that of TNT, transport was substantial, and concentration occurred at sites where new plant material was synthesized. As for TNT, uptake per unit of mass was higher in submersed than in emergent species. Biotransformation of RDX had occurred in all plant treatments after 13-day incubation in 1.5 mg RDX L-1, with one unidentified compound unique for plants, and mostly polar products as results. Biotransformation had occurred also in the substrates, but to a far lower extent than in plants. Substrates and plants had one unidentified 14C-RDX metabolite in common. HPLC analysis confirmed the presence of RDX in most plants and in three out of four substrates at the end of the incubation period.

Influence of fast-track anesthetic technique on cardiovascular infusions and weight gain

OBJECTIVE

To evaluate whether cardiac surgical patients receiving conventional versus fast-track anesthetic management are statistically significantly different with regard to cardiovascular drug infusions, weight gain, cardiac and pulmonary morbidity, length of intubation, and length of stay.

DESIGN

Retrospective, (partially) sequential, cohort design.

SETTING

Surgical suite and intensive care unit (ICU) at a community hospital.

PARTICIPANTS

Two hundred seven patients who presented for coronary artery bypass graft and/or cardiac valve replacement.

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

Group comparisons of the seven individual cardiovascular drug infusions showed less frequent use in the fast-track patients for lidocaine (9% v 28%; p = 0.00046) only. However, the fast-track group received fewer combinations of cardiovascular drug infusions overall for the first 24-hour postoperative period (p < 0.0005). Hourly comparisons of inotropes showed significantly fewer combinations of dobutamine, norepinephrine, and epinephrine for the first postoperative hour and for postoperative hours 7 through 12 (p < 0.01 for each hour). Fast-track patients had less postoperative weight gain for days 1 through 4 (p < 0.01 for each day), shorter length of ICU stay (p < 0.00005), and shorter total length of postoperative hospital stay (p = 0.0004). No differences were found with respect to myocardial infarction, death, pulmonary complications, rate of reintubation, or length of hospital stay once discharged from the ICU.

CONCLUSIONS

Fast-track anesthetic management may be associated with decreased need for inotropic and antiarrhythmic drug infusions and decreased weight gain.

Environmental behavior of explosives in groundwater from the Milan Army Ammunition Plant in aquatic and wetland plant treatments. Removal, mass balances and fate in groundwater of TNT and RDX

Phytoremediation of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater using constructed wetlands is a potentially economical remediation alternative. To evaluate Explosives removal and fate was evaluated using hydroponic batch incubations of plant and substrate treatments with explosives-contaminated groundwater amended with [U-14C]-TNT or [U-14C]-RDX. Plants and substrates were collected from a small-scale wetland constructed for explosives removal, and groundwater originated from a local aquifer at the Milan Army Ammunition Plant. The study surveyed three aquatic, four wetland plant species and two substrates in independent incubations of 7 days with TNT and 13 days with RDX. Parent compounds and transformation products were followed using 14C and chemical (HPLC) analyses. Mass balance of water, plants, substrates and air was determined. It was demonstrated that TNT disappeared completely from groundwater incubated with plants, although growth of most plants except parrot-feather was low in groundwater amended to contain 1.6 to 3.4 mg TNT L-1. Highest specific removal rates were found in submersed plants in water star-grass and in all emergent plants except wool-grass. TNT declined less with substrates, and least in controls without plants. Radiolabel was present in all plants after incubation. Mineralization to 14CO2 was very low, and evolution into 14C-volatile organics negligible. RDX disappeared less rapidly than TNT from groundwater. Growth of submersed plants was normal, but that of emergent plants reduced in groundwater amended to contain 1.5 mg RDX L-1. Highest specific RDX removal rates were found in submersed plants in elodea, and in emergent plants in reed canary grass. RDX failed to disappear with substrates. Mineralization to 14CO2 was low, but relatively higher than in the TNT experiment. Evolution into 14C-volatile organics was negligible. Important considerations for using certain aquatic and wetland plants in constructed wetlands aimed at removing explosives from water are: (1) plant persistence at the explosives level to which it is exposed, (2) specific plant-mass based explosives removal rates, (3) plant productivity, and (4) fate of parent compounds and transformation products in water, plants, and sediments.

Do parent practices to encourage academic competence influence the social adjustment of young European American and Chinese American children?

The predominant early childhood education philosophy in the United States views formal academic instruction as inappropriate and harmful to the social development of young children. Chinese American immigrants to the United States, however, have been found to teach their young children in more formal ways, to be more directive, and to structure their children's use of time to a greater degree (C. S. Huntsinger, P. E. Jose, F.-R. Liaw, & W.-D. Ching, 1997). Forty European American (20 boys, 20 girls) and 36 2nd-generation Chinese American (18 boys, 18 girls) 1st- and 2nd-grade children and their mothers, fathers, and teachers participated in the Time 2 data collection of this longitudinal study to assess whether the formal academic environment provided by Chinese American parents is linked to poorer social adjustment in their children. Regressions showed that parents' work-oriented methods influenced academic performance but not social adjustment of their children.

Screening of aquatic and wetland plant species for phytoremediation of explosives-contaminated groundwater from the Iowa Army Ammunition Plant

The results of this study indicate that the presence of plants did enhance TNT and TNB removal from IAAP groundwater. Most effective at 25 degrees C were reed canary grass, coontail and pondweed. Groundwater and plant tissue analyses indicate that in presence of the plants tested TNT is degraded to reduced by-products and to other metabolites that were not analyzed. TNT removal was best modeled using first order kinetics, with rate constants at 25 degrees C incubations ranging from 0.038 microgram L-1 h-1 for reed canary grass to 0.012 microgram L-1 h-1 for parrot-feather. These kinetics predict hydraulic retention times (HRTs) ranging from 4.9 days to 19.8 days to reach a TNT concentration of 2 micrograms L-1. Decreasing incubation temperature to 10 degrees C affected reed canary grass more than parrot-feather, increasing estimated HRTs by factors of four and two, respectively. The plant species tested showed a far lower potential for RDX removal from the IAAP groundwater. Most effective at 25 degrees C were reed canary grass and fox sedge. Analyses of plant material indicated the presence of RDX in under-water plant portions and in aerial plant portions, and RDX accumulation in the latter. RDX removal was best modeled using zero order kinetics, with rate constants for the 25 degrees C incubation ranging from 13.45 micrograms L-1 h-1 for reed canary grass to no removal in four species. Based on these kinetics, estimated HRTs to reach 2 micrograms L-1 RDX increased from 39 days. Decreasing the temperature to 10 degrees C increased HRT 24-fold for reed canary grass. By using the biomass-normalized K value, submersed plants are identified as having the highest explosives-removing activity (microgram explosive L-1 h-1 g DW-1). However, biomass production of submersed plants is normally five to ten times less than that of emergent plants per unit area, and, thus, in plant selection for wetland construction, both, explosives removal potential and biomass production are important determinants.

Fate of explosive contaminants in plants

A great deal of interest has been generated recently in the determination of explosives and explosives by-products in exotic matrices including composts, bioslurries, and plants. The methods traditionally utilized for the analysis of organic and inorganic contaminants in these types of environmental samples are not adequate owing to the unique properties of the material being studied. The methods used to detect the nitramines and their degradation products in a variety of environmental samples requires matrix-specific sample preparation, separation by reversed phase high performance liquid chromatography, and ultra-violet detection. Knowledge of the concentration of the contaminants and the molecular state of their degradation products is helpful in assessing the environmental risks associated with the contaminants as well as the design of remediation technologies. Data that are obtained using analytical methods not designed for the specific matrix encountered may lead to incorrect quantitation. Examples of remediation technologies that necessitate the analysis of other than standard matrices for explosives include composting, aerobic and anaerobic microbial degradation, and plant-assisted degradation. The toxicity and mobility of explosives in the food chain are also of interest, and analytical techniques for studying explosives in plant and animal tissues that provide valid information regarding trace levels in these matrices are also required. The report will address three important points in connection with the problem. The extraction of the contaminants from the matrix requires a different set of extraction techniques than those utilized for standard water and soil extractions. These exotic matrices contain much higher organic content than soil or water and, as a result, are prone to interference from biological molecules.

Alerting effects on choice reaction time and the photic eyeblink reflex

To test the possibility that a common mechanism might be responsible for alerting effects on voluntary and reflexive reactions, choice reaction times (RT) to intense flashes of light were compared with eyeblink reflexes simultaneously evoked by those stimuli. An acoustic accessory stimulus, irrelevant to the RT task, facilitated both voluntary and reflexive reactions. A time uncertainty manipulation also generated facilitation of both responses under conditions in which phasic arousal was presumably greatest. However, there were several dissociations between alerting effects on voluntary and reflexive reactions and between effects on the early and late subcomponents of the photic orbicularis oculi reflex. In conjunction with other research in humans and animals, these data support the assumption that alerting involves the activation of multiple neuromodulatory (e.g. monoamine) systems, each of which is characterized by a distinct behavioral, neuropharmacological, and electrophysiological profile.

Computer-assisted scheduling of radiology resident call

The difficulties inherent in assigning an entire residency group fair and equivalent daily call prompted the development of a computerized scheduling program at The University of Texas at Houston. Written in COBOL, the program is run on a CDC mainframe computer. Logic parameters restrict the number and frequency of calls per month, and each resident is coded for five available call types at two university hospitals. The foundation of the program's operation is an arbitrary point scale applied to each call type determined by its difficulty and time commitment. Residents' point totals each month are roughly balanced within a prescribed range, with call exchanges made by the computer if necessary. The computer-generated schedules are flexible and equitable, require little manual correction, and save time for the chief resident and the residency secretary.