Maternal serum levels of total activin-A in first-trimester trisomy 21 pregnancies

Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10–14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log₁₀ SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free β-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free β-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21. Copyright © 2001 John Wiley & Sons, Ltd.     

Boater preferences for beach characteristics downstream from Glen Canyon Dam, Arizona

Release flow decisions are increasingly being influenced by an array of social values, including those related to river-based recreation. A substantial portion of past recreation research on downstream impacts of dams has focused on variability of instream flows. This study complements past research by assessing user preferences for beach characteristics affected by long-term impacts of flow regimes. Based upon a study of three recreational user groups (private trip leaders, commercial passengers, and river guides) of the Colorado River in Grand Canyon, preferences for beach size, presence of shade on beach, and presence of vegetation on beach are examined. Results indicate that large size beaches with shade from trees are setting characteristics with highly reliable and strong user preferences. The multinomial regression models developed for each user group indicate that 80% of all respondents would choose beach campsites 800 m(2); results were the same regardless of respondents' past boating experience, boat type (i.e. oar or motorized), or group size. In addition, size of beach was consistently reported to be a trip feature of moderate importance to respondents' river trip. Implications of this research are related to future prospects for controlled floods (i.e. spike flows) released from Glen Canyon Dam.     

Validation of procedures to quantify nonextractable polycyclic aromatic hydrocarbon residues in soil

This study was conducted to optimize butanol solvent shake extraction, dichloromethane soxtec extraction, and methanolic saponification extraction for the selective extraction of aged polycyclic aromatic hydrocarbons from soil. Extraction kinetics for these methods was established to determine the optimal time necessary to achieve exhaustive compound extraction. This resulted in times of 12, 6, and 5 h, respectively, for butanol, dichloromethane, and saponification, to extract polycyclic aromatic hydrocarbons from previously spiked, then aged soil. Increasing the soil mass to butanol volume ratio reduced the proportion of polycyclic aromatic hydrocarbon extracted by butanol, highlighting the importance of determining and maintaining a constant soil to solvent ratio for comparative purposes. Drying soil samples before dichloromethane soxtec extraction reduced by 30 to 76% the amount of polycyclic aromatic hydrocarbons extracted. The effect of sample drying is discussed with relevance to enhancing the formation of nonextractable compounds in soil and compound losses previously assumed by volatilization. The optimized extraction procedures provided low variability with relative standard deviations < or = 5.2% for analysis of multiple replicates. The results obtained by the optimized procedures provided equivalent or improved reproducibility to those obtained by other methods reported in the literature.     

The provisional license: nighttime and passenger restrictions--a literature review

PROBLEM: Due to inexperience and inadequate driving skills, the road is a very risky place for young and beginning drivers, yet such experience and skills can only be built by increased driving and exposure to risks on the road. Graduated driver licensing (GDL) allows beginning drivers to get their initial driving experience under less risky conditions and gradually eases them into more complex driving situations. This paper reviews the literature exploring two key features of the intermediate licensing phase of GDL, nighttime driving restrictions and passenger restrictions. METHOD: Literature review. RESULTS: Nighttime driving restrictions have been shown to effectively reduce the number and rate of crash involvements on the part of teenage drivers. Data suggest that having passengers in the car increases the likelihood of a fatal injury in young drivers and that this risk increases with the number of passengers. Young drivers were more likely to cause a crash when accompanied by their peers. DISCUSSION: Nighttime driving and passenger restrictions are effective in decreasing injuries among teenage drivers and their passengers, especially in the context of a full GDL system. Several research questions remain to be answered in order to fully refine and optimize the impact of these provisional measures.     

Modeling postfire conifer mortality for long-range planning

A model is presented for predicting mortality of conifers after wildfire. The model requires stand data inputs and is linked with a mathematical fire behavior model that calculates fireline intensity. Fraction of crown volume killed is calculated for each species in a stand based on mensurational data. Duration of lethal heat at the base of trees is calculated from fuel consumption and burning time values. Fraction of crown volume killed and the ratio of critical time for cambial kill to duration of lethal heat are independent variables in a function that calculates probability of mortality. The model produces reasonable estimates of stand mortality for fire and site characteristics found in the northern Rocky Mountains, USA. It has a broad resolution appropriate for use in fire management planning and has potential applications for coniferous forests throughout the United States.     

Quantitative determination of arsenobetaine,the major water-soluble arsenical in three species of crab,using high pressure liquid chromatography and an inductively coupled argon plasma emission spectrometer as the arsenic-specific detector

The major water-soluble arsenic compound in the Alaskan king crab, the Alaskan snow crab, and the Dungeness crab was identified as arsenobetaine by HPLC/ICP analysis. This technique is suitable for the identification and quantitative determination of naturally occurring organic arsenic compounds in purified and partially purified extracts from biota.     

A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry

The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.     

High Pressure Inactivation of HAV Within Oysters: Comparison of Shucked Oysters with Whole-In-Shell Meats

High pressure inactivation of hepatitis A virus (HAV) within oysters bioaccumulated under simulated natural conditions to levels >10⁵ PFU/oyster has been evaluated. Five minute treatments at 20°C were administered at 350, 375, and 400 MegaPascals (MPa). Shucked and whole-in-shell oysters were directly compared to determine if there were any differences in inactivation levels. For whole-in-shell oysters and shucked oysters, average values obtained were 2.56 and 2.96 log₁₀ inactivation of HAV, respectively, after a 400-MPa treatment. Results indicate that there is no significant inactivation difference (P = 0.05) between inactivation for whole-in-shell oysters as compared to shucked oysters observed for all pressure treatments. This study indicates that commercial high pressure processing applied to whole-in-shell oysters will be capable of inactivating HAV pathogens.     

Food webs and fishing affect parasitism of the sea urchin Eucidaris galapagensis in the Galápagos

In the Galápagos Islands, two eulimid snails parasitize the common pencil sea urchin, Eucidaris galapagensis. Past work in the Galápagos suggests that fishing reduces lobster and fish densities and, due to this relaxation of predation pressure, indirectly increases urchin densities, creating the potential for complex indirect interactions between fishing and parasitic snails. To measure indirect effects of fishing on these parasitic snails, we investigated the spatial relationships among urchins, parasitic snails, commensal crabs, and large urchin predators (hogfish and lobsters). Parasitic snails had higher densities at sites where urchins were abundant, probably due to increased resource availability. Commensal crabs that shelter under urchin spines, particularly the endemic Mithrax nodosus, preyed on the parasitic snails in aquaria, and snails were less abundant at field sites where these crabs were common. In aquaria, hogfish and lobsters readily ate crabs, but crabs were protected from predation under urchin spines, leading to a facultative mutualism between commensal crabs and urchins. In the field, fishing appeared to indirectly increase the abundance of urchins and their commensal crabs by reducing predation pressure from fish and lobsters. Fished sites had fewer snails per urchin, probably due to increased predation from commensal crabs. However, because fished sites also tended to have more urchins, there was no significant net effect of fishing on the number of snails per square meter. These results suggest that fishing can have complex indirect effects on parasites by altering food webs.     

Escherichia coli load reduction from runoff by vegetative filter strips: a laboratory-scale study

Vegetative filter strips (VFS) are commonly used best management practices for removing contaminants from runoff. Additional research is warranted to determine their efficiency and the most appropriate metrics for predicting fecal bacteria reductions. The objective of this research was to determine VFS effectiveness in removing from runoff relative to inflow rate, infiltration capacity, and flow concentration. This research also investigated the presence of in runoff from clean water runon after diluted manure runon events. A laboratory-scale VFS soil box (200 cm long, 100 cm wide, 7.5% slope) was packed with a sandy loam soil. Ten constant-flow VFS experiments were conducted with and without vegetation (8-10 cm ryegrass [ L.]) at low (20-40 cm s), medium (40-60 cm s), and high (85-120 cm s) flow rates and for a full (100 cm) or concentrated (40 cm) VFS flow width to simulate a channelizing flow condition. Two runon events were investigated for each experimental condition: (i) diluted liquid swine manure runon and (ii) clean water runon 48 h afterward. was used as an indicator of fecal contamination and was quantified by the most probable number (MPN) technique. No concentration reductions were observed based on peak outflow concentrations, and only small concentration reductions were observed based on outflow event mean concentrations. The mass reductions ranged from 22 to 71% and were strongly correlated to infiltration or runoff reduction ( = 0.88), which was dependent on the degree of flow concentration. Little to no effect of sedimentation on transport was observed, hypothesized to be due to minimum attachment to sediment particles because the bacteria originated from manure sources. Therefore, the design of VFS for bacteria removal should be based on the infiltration capacity in the VFS and should prevent concentrated flow, which limits total infiltration. The event mean concentrations in clean water runon experiments were between 10 and 100 MPN per 100 mL; therefore, under these conditions, VFS served as a source of residual from previous runon events.