New approaches to the preservation of contaminants in water samples /

Jan. 1979.

Radiochemical analysis of Bravo shot soil samples /

"January 15, 1957."

The iodimetric determination of hydrogen sulfide in gas samples /

"Chemistry."

Preparation of water samples for asbestos fiber counting by electron microscopy /

Prepared by Ontario Research Foundation, under contract no. 68-03-2389.

On the inviscid stability of the boundary layer on a flexible wall,

"This report is based on research sponsored by the U.S. Navy through the Office of Naval Research, Contract Nonr-2653(00)"

A sensitive, specific, and cost-effective multiplex reverse transcriptase-PCR assay for the detection of seven common respiratory viruses in respiratory samples

Cell culture and direct fluorescent antibody (DFA) assays have been traditionally used for the laboratory diagnosis of respiratory viral infections. Multiplex reverse transcriptase polymerase chain reaction (m-RT-PCR) is a sensitive, specific, and rapid method for detecting several DNIA and RNA viruses in a single specimen. We developed a m-RT-PCR assay that utilizes multiple virus-specific primer pairs in a single reaction mix combined with an enzyme-linked amplicon hybridization assay (ELAHA) using virus-specific probes targeting unique gene sequences for each virus. Using this m-RT-PCR-ELAHA, we examined the presence of seven respiratory viruses in 598 nasopharyngeal aspirate (NPA) samples from patients with suspected respiratory infection. The specificity of each assay was 100%. The sensitivity of the DFA was 79.7% and the combined DFA/culture amplified-DFA (CA-DFA) was 88.6% when compared to the m-RT-PCR-ELAHA. Of the 598 NPA specimens screened by m-RT-PCR-ELAHA, 3% were positive for adenovirus (ADM), 2% for influenza A (Flu A) virus, 0.3% for influenza B (Flu B) virus, 1% for parainfluenza type I virus (PIV1), 1% for parainfluenza type 2 virus (PIV2), 5.5% for parainfluenza type 3 virus (PIV3), and 21% for respiratory syncytial virus (RSV). The enhanced sensitivity, specificity, rapid result turnaround time and reduced expense of the m-RT-PCR-ELAHA compared to DFA and CA-DFA, suggests that this assay would be a significant improvement over traditional assays for the detection of respiratory viruses in a clinical laboratory.

Detection and differentiation of Plasmodium species by polymerase chain reaction and colorimetric detection in blood samples of patients with suspected malaria

Polymerase chain reaction (PCR) is now recognized as a sensitive and specific method for detecting Plasmodium species in blood. In this Study. we tested 279 blood samples, from patients with Suspected malaria, by a PCR assay utilizing species-specific colorimetric detection. and compared the results to light microscopy. Overall, both assays were in agreement for 270 of the 279 specimens. P. vivax was detected in 131 (47.0%) specimens. P. falciparum in 64 (22.9%) specimens, P. ovale in 6 (2.1%) specimens, and P. malariae in 5 (1.8%) specimens. Both P. falciparum and P. vivax were detected in a further 10 (3.6%) specimens, and 54 (19.3%) specimens were negative by both assays. In the remaining nine specimens, microscopy either failed to detect the parasite or incorrectly identified the species present. In summary, the sensitivity, specificity and simplicity of the PCR assay makes it particularly suitable for use in a diagnostic laboratory. (C) 2004 Elsevier Inc. All rights reserved.

Segregation band formation in Al-Si die castings

Banded defects are often found in high-pressure die castings. These bands can contain segregation, porosity, and/or tears, and changing casting conditions and alloy are known to change the position and make-up of the bands. Due to the complex, dynamic nature of the high-pressure die-casting (HPDC) process, it is very difficult to study the effect of individual parameters on band formation. In the work presented here, bands of segregation similar to those found in cold-chamber HPDC aluminum alloys were found in laboratory gravity die castings. Samples were cast with a range of fraction solids from 0 to 0.3 and the effect of die temperature and external solid fraction on segregation bands was investigated. The results are considered with reference to the theological properties of the filling semisolid metal and a formation mechanism for bands is proposed by considering flow past a solidifying immobile wall layer.

Disaggregation of Microcystis aeruginosa colonies under turbulent mixing: laboratory experiments in a grid-stirred tank

Samples of the cyanobacterium Microcystis aeruginosa from a small pond were used in laboratory experiments with a grid-stirred tank to quantify the effect of turbulent mixing on colony size. Turbulent dissipation in the tank was varied from 10(-9) m(2) s(-3) to 10(-4) m(2) s(-3), covering the range of turbulence intensities experienced by M. aeruginosa colonies in the field and exceeding the maximum dissipation by two orders of magnitude. Large colonies broke up into smaller colonies during the experiments; the mass fraction of colonies with diameter less than 200 mum increased over time. Colony disaggregation was observed to increase with turbulent dissipation. The maximum stable colony diameter across all experiments was in the range 220-420 mum. The overall change in size distribution during the experiments was relatively small, and the colony size distribution remained very broad throughout the experiments. Since colony size affects migration velocity, susceptibility to grazing and surface area to volume ratios, more work is needed to determine how to best represent this broad size distribution when modelling M. aeruginosa populations.

Characterization of activated carbon fibers using argon adsorption

In this paper, we present results of the internal structure (pore size and pore wall thickness distributions) of a series of activated carbon fibers with different degrees of burn-off, determined from interpretation of argon adsorption data at 87 K using infinite and finite wall thickness models. The latter approach has recently been developed in our laboratory. The results show that while the low bun-off samples have nearly uniform pore size (

Dissipation of acetochlor and its distribution in surface and sub-surface soil fractions during laboratory incubations

Pesticides in soil are subject to a number of processes that result in transformation and biodegradation, sorption to and desorption from soil components, and diffusion and leaching. Pesticides leaching through a soil profile will be exposed to changing environmental conditions as different horizons with distinct physical, chemical and biological properties are encountered. The many ways in which soil properties influence pesticide retention and degradation need to be addressed to allow accurate predictions of environmental fate and the potential for groundwater pollution. Degradation and sorption processes were investigated in a long-term (100 days) study of the chloroacetanilide herbicide, acetochlor. Soil cores were collected from a clay soil profile and samples taken from 0-30cm (surface), 1.0-1.3m (mid) and 2.7-3.0m (deep) and treated with acetochlor (2.5, 1.25, 0.67 mu g acetochlor g(-1) dry wt soil, respectively). In sterile and non-sterile conditions, acetochlor concentration in the aqueous phase declined rapidly from the surface and subsoil layers, predominantly through nonextractable residue (NER) formation on soil surfaces, but also through biodegradation and biotic transformation. Abiotic transformation was also evident in the sterile soils. Several metabolites were produced, including acetochlor-ethane sulphonic acid and acetochlor-oxanilic acid. Transformation was principally microbial in origin, as shown by the differences between non-sterile and sterile soils. NER formation increased rapidly over the first 21 days in all soils and was mainly associated with the macroaggregate (> 2000 mu m diameter) size fractions. It is likely that acetochlor is incorporated into the macroaggregates through oxidative coupling, as humification of particulate organic matter progresses. The dissipation (ie total loss of acetochlor) half-life values were 9.3 (surface), 12.3 (mid) and 12.6 days (deep) in the non-sterile soils, compared with 20.9 [surface], 23.5 [mid], and 24 days [deep] in the sterile soils, demonstrating the importance of microbially driven processes in the rapid dissipation of acetochlor in soil.

Laboratory culture studies of Trichodesmium isolated from the great Barrier Reef Lagoon, Australia

Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6 years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR similar to 40-50 mumol quanta m(-2) s(-1)). N-2 fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2-0.3 day(-1) and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR similar to 5-120 mumol quanta m(-2) s(-1)) with the maximum growth occurring at - 40-50 mumol quanta m(-2) s(-1). These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37 psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45 nM. No active growth was observed with the 4.5 nM Fe addition.

Comparison of nitrogen adsorption at 77 K on non-porous silica and pore wall of MCM-41 materials by means of density functional theory

Nitrogen adsorption on a surface of a non-porous reference material is widely used in the characterization. Traditionally, the enhancement of solid-fluid potential in a porous solid is accounted for by incorporating the surface curvature into the solid-fluid Potential of the flat reference surface. However, this calculation procedure has not been justified experimentally. In this paper, we derive the solid-fluid potential of mesoporous MCM-41 solid by using solely the adsorption isotherm of that solid. This solid-fluid potential is then compared with that of the non-porous reference surface. In derivation of the solid-fluid potential for both reference surface and mesoporous MCM-41 silica (diameter ranging front 3 to 6.5 nm) we employ the nonlocal density functional theory developed for amorphous solids. It is found that, to out, surprise, the solid-fluid potential of a porous solid is practically the same as that for the reference surface, indicating that there is no enhancement due to Surface curvature. This requires further investigations to explain this unusual departure from our conventional wisdom of curvature-induced enhancement. Accepting the curvature-independent solid-fluid potential derived from the non-porous reference surface, we analyze the hysteresis features of a series of MCM-41 samples. (c) 2005 Elsevier Inc. All rights reserved.

Raman microscopic investigation of paint samples from the Rosalila building, Copan, Honduras

Micro-Raman spectroscopy was applied to the study of multiple layered wall paints from the Rosalila temple, Copan, Honduras, which dates to the Middle Classic period (A.D. 520 to 655). Samples of red, green and grey paint and a thick white overcoating were analysed. The paint pigments have been identified as hematite, celadonite or green earth and a combined carbon/mica mixture. By combining Raman spectroscopy with micro-ATR infrared spectroscopy and environmental scanning electron microscopy (ESEM), a detailed study has been made of the materials and processes used to make the stucco and paints. The use of green earth as a green pigment on Maya buildings has not been reported before. The combination of carbon and muscovite mica to create a reflective paint is also a novel finding.

Particle tracking in a salinity gradient: A method for measuring sinking rate of individual phytoplankton in the laboratory

This paper presents a new method to measure the sinking rates of individual phytoplankton “particles” (cells, chains, colonies, and aggregates) in the laboratory. Conventional particle tracking and high resolution video imaging were used to measure particle sinking rates and particle size. The stabilizing force of a very mild linear salinity gradient (1 ppt over 15 cm) prevented the formation of convection currents in the laboratory settling chamber. Whereas bulk settling methods such as SETCOL provide a single value of sinking rate for a population, this method allows the measurement of sinking rate and particle size for a large number of individual particles or phytoplankton within a population. The method has applications where sinking rates vary within a population, or where sinking rate-size relationships are important. Preliminary data from experiments with both laboratory and field samples of marine phytoplankton are presented here to illustrate the use of the technique, its applications, and limitations. Whereas this paper deals only with sinking phytoplankton, the method is equally valid for positively buoyant species, as well as nonbiological particles.