Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

Particulate PAH emissions from residential biomass combustion: time-resolved analysis with aerosol mass spectrometry.

Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (AMS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. AMS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (Dva ∼ 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (Dva ∼ 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions.

Adolescents report their need for and use of health care services.

PURPOSE: The goals of this study were to describe student access to health care services, identify populations of students who remained in need of health care services, and highlight particular unmet needs for health care identified by these adolescents. METHODS: Students in Grades 9-12 attending 50 schools in Oregon completed the Youth Risk Behavior Surveillance Survey (YRBS). Questions requesting adolescents to report their need for specific types of health care, and access to general and specific types of care were added to the core YRBS. Multivariate logistic regression analysis was used to determine independent relationships between student or community characteristics and health care access or unmet needs for care. RESULTS: Almost 14,000 adolescents completed surveys, of whom 75% reported visiting one or more health care provider within the last 12 months. Nineteen percent of adolescents reported that they had not received 1 or more of 10 specific types of care when needed in the last year. Females, some racial/ethnic minorities, rural, and sexually active adolescents were more likely to report unmet needs for health care. Most frequently, adolescents reported they needed but did not receive care for an illness (7%) or for personal or emotional problems (6%). In addition, about 400 (3%) students reported they needed birth control that they did not receive. CONCLUSIONS: A majority of high school-age adolescents had visited health care providers within the year prior to study. However, the number of adolescents who reported unmet specific health care needs within the same time period remained substantial.

PIP: This study was conducted to describe students access to health care services, to identify populations of students who remained in need of health care services, and to highlight particular unmet needs for health care identified by these adolescents. A total of 14,891 students in grades 9-12 attending in 50 schools in Oregon completed the 1995 Youth Risk Behavior Surveillance Survey (YRBS). 899 (6%) of the 14,891 were excluded because of inaccurate survey responses, leaving 13,992 surveys for the final data set. The results revealed that more than three-quarters of adolescents had visited a health care provider in the past year. A higher proportion of females had consulted health care providers than males, and females were more likely to receive care for illnesses, birth control, STDs, and personal or emotional problems. Males were most likely to receive care for injuries, accidents, and drug or alcohol problems. Sexually active students were more likely to receive all types of care except care for check-ups and sports physicals. There were still many students who had not visited a health care provider in the past 2 years and reported health care needs that were not met. Slightly more than 19% of students reported that they needed at least one type of health care but did not receive that care. This study indicates that a majority of high school-age adolescents had visited health care providers within the year prior to study. However, the number of adolescents who reported unmet specific health care needs within the same time period remained substantial.

Disruption of active zones in frog neuromuscular junctions following treatment with proteolytic enzymes.

Frog neuromuscular junction treated with proteolytic enzymes to remove the basal lamina were studied with freeze-fracture techniques in order to examine the influence of the basal lamina in the maintenance of active zone ultrastructure. The active zone is believed to be the site of transmitter release and has a unique membrane organization and location in the neuromuscular junction. After removal of the basal lamina by successive treatment of 0.01% collagenase and 0.1% protease for 1 h each, active zone disruption was observed. Some active zones became segmented, and some were also randomly located and oriented, but they still had normal double-row particle organization. Others contained only clusters of large intramembrane particles. These disorganized active zones were still functional as indicated by the presence of vesicle openings. Some enzyme-treated junctions were also exposed to the membrane cholesterol probe, filipin, to examine the expression of membrane lipid heterogeneity in disrupted active zones. As in normal active zones, filipin-sterol complexes were absent. The densities of background particles in the presynaptic membranes and of large particles thought to be acetylcholine receptors were not significantly altered by the enzyme treatment. Although a direct effect of the enzymes on active zone ultrastructure can not be totally excluded, the present work is consistent with a maintenance role of the basal lamina in active zone organization and location.

Immunoglobulin M antibody capture enzyme-linked immunosorbent assay for diagnosis of St. Louis encephalitis.

Sera from patients with St. Louis encephalitis were tested with an immunoglobulin M (IgM) antibody capture enzyme immunoassay (MAC ELISA). The assay used five reagents: antihuman IgM, test serum, sucrose-acetone-extracted mouse brain antigen, broadly cross-reactive flavivirus monoclonal antibody conjugated to alkaline phosphatase, and substrate (p-nitrophenyl phosphate). MAC ELISA endpoint titers correlated (r = 0.893) with the absorbance value of a 1:100 dilution of patient serum. Significant (fourfold or greater) changes in the endpoint titers between paired sera corresponded to a critical ratio (ratio of absorbance values at the 1:100 dilution) of greater than or equal to 1.3. IgM antibodies were detected in 71% of patients bled at 0 to 3 days after the onset of illness, in 99% bled at 4 to 21 days, and in 91% bled at 22 to 67 days. Thereafter, the IgM seropositivity rate declined; however, 29% of sera were still positive at 115 to 251 days after the onset of illness. MAC ELISA titers were significantly correlated with hemagglutination inhibition (r = 0.258) and neutralization (r = 0.711) titers. Because IgM antibodies appeared early and waned rapidly, a diagnosis was made on the basis of a decrease in titer more often by MAC ELISA than by hemagglutination inhibition, complement fixation, or neutralization tests. IgM antibodies generally showed a high degree of specificity; heterologous cross-reactions were, however, present in 4 of 14 sera examined. The MAC ELISA is useful for the rapid, early diagnosis of St. Louis encephalitis.

Cytological changes occurring in the liver of coturnix quail with an acute arsenic exposure.

Coturnix quail (Coturnix coturnix) were given acute oral doses of sodium arsenite (NaAsO2). On each of two successive days they received 1 mg sodium arsenite, followed by 3 mg on the third day. There was no observable difference between the arsenic-exposed quail liver and the controls at the light microscope level; however, swelling of granular endoplasmic reticulum (GER) in the hepatocytes of the arsenic-exposed quail was detected with electron microscopy. The swollen organelles were determined to be GER by their peripheral orientation around the mitochondria and the ribosomes attached to their cytoplasm-exposed membrane surfaces. The degree of swelling ranged from slight to severe, and was due to an osmotic imbalance possibly brought about by the indirect inhibition of the sodium pump by arsenic.

Detection of yellow fever virus in serum by enzyme immunoassay.

Yellow fever (YF) virus is present in patient's blood during the acute phase of illness. Virus isolation and identification provide a potential method of early diagnosis, but available techniques are slow and require specialized materials and equipment. An alternative approach is direct detection of YF antigen in serum by means of an enzyme-linked immunosorbent assay (ELISA). An antigen-capture ELISA was developed, which used anti-YF antibodies, immobilized on a solid phase (polystyrene plates), to capture YF virus from serum samples. After addition of the virus-containing sample, anti-YF detecting antibody conjugated to alkaline phosphatase was added to detect viral antigen. Trials with various capture and detecting antibodies in systems employing purified YF 17D virus, led to the selection of: 1) two capture antibodies (pooled human serum containing high titer YF IgM antibodies and a type-specific YF monoclonal antibody), and 2) a detecting antibody conjugate consisting of monoclonal antibody broadly cross-reactive with all flaviviruses, purified by affinity chromatography, and conjugated to alkaline phosphatase. The limit of sensitivity in tests against purified YF 17D virus diluted in buffer or normal human serum was 10(3.0) - 10(3.6) PFU/0.05 ml or 0.007-0.029 microgram viral protein/0.05 ml. Sera obtained at intervals from rhesus and cynomolgus monkeys after infection with a wild YF virus strain were tested. The limit of sensitivity of the assay applied to viremic monkey serum was similar (approximately 3.5 log10PFU/0.05 ml).(ABSTRACT TRUNCATED AT 250 WORDS)