Estimation of the weight of chorionic villus samples obtained from first trimester pregnancies by transcervical aspiration

Eight obstetricians experienced in chorionic villus sampling were asked to estimate the weight of samples of villi with and without a reference photograph. Referral to the photograph significantly improved the accuracy of their estimations.     

世界可持续发展峰会(WSSD):约翰内斯堡2002

本文对即将召开的世界可持续发展峰会（WSSD）作了简单介绍，并简要回顾了里约会议以来取得的进展。强调了可持续发展需要全球合作的重要性，并给出了英国政府可持续发展指标体系。     

Genetic Analysis of the Endangered Island Endemic Malacothamnus fasciculatus (Nutt.) Greene var. nesioticus (Rob.) Kearn. (Malvaceae)

Isozyme, randomly amplified polymorphic DNA, and ribosomal DNA analyses were used to evaluate the genetic distinctness and diversity of the endangered island endemic Malacothamnus fasciculatus var. nesioticus (Santa Cruz Island bush mallow). Analysis of amplified DNA profiles and electrophoretic data indicates that var. nesioticus is genetically distinct from other varieties within the species. No isozyme or amplified DNA variation was detected among individuals of nesioticus populations, but restriction site analysis of ribosomal DNA revealed the presence of three closely related genotypes within one of the nesioticus populations. Apparent clonal structuring was found in both nesioticus populations and in one mainland population, var. nuttallli . Results from these analyses provide the background necessary for the design of conservation efforts with recovery goals that insure the long-term survival of Malacothamnus fasciculatus var. nesioticus .     

Predictive Model of the Effects on Lake Metabolism of Decreased Airborne Litterfall through Riparian Deforestation

The importance of airborne allochthonous litter to the carbon and nutrient budgets of lakes has been seldom studied. We complied data on the input of terrestrial litter to develop a simple and speculative model to predict the potential consequences of riparian deforestation on one aspect of lake metabolism, specifically the balance between phytoplankton production and plankton respiration. During the autumn of 1992, 56 litter traps were deployed around the littoral zones of four oligotrophic lakes in a densely forested region of northwestern Ontario, Canada. The airborne litter input was estimated to be 32 g dry weight per meter of forested shoreline per year. Allochthonous litter input per unit offshore distance was related to the size of riparian trees, their proximity to the shoreline, and the elevation of their canopy. Combining our data with those from other studies suggests that terrestrial litter can contribute up to 15% of the total carbon supply to oligotrophic lakes and up to 10% of the total phosphorus supply to lakes with a large surface area relative to that of their drainage basin. These results were incorporated into a simple model that predicts that removal of shoreline trees could increase the ratio of plankton production to respiration in oligotrophic lakes situated within small drainage basins. Such lakes may therefore shift from allotrophy to increasing autotropy (energy self-sustenance) following riparian deforestation.     

Analysis by slow-motion picture photography and scanning electron microscopy of radular function in Urosalpinx cinerea follyensis (Muricidae,Gastropoda) during shell penetration

Radular function in the muricid gastropod Urosalpinx cinerea follyensis Baker during shell penetration was examined with slow-motion picture photography and scanning electron microscopy. Particular attention was paid to possible injury of buccal structures by radular cusps. The presence of a flexible cuticulated buccal armature, and delicate synchronization of movements of odontophoral cartilages, subradular membrane, teeth, and buccal mass, explain the absence of shredding of live buccal tissues. Some light abrasion was evident, but generally only in the cuticulated gully of the subodontophoral shield, on the rim of the jaw, and on the anterior edge of the esophageal valve. Rasping at the surface of incomplete bore-holes is done by major cusps of rachidian teeth over the bending plane. Marginal teeth lie on the slopes of the odontophore, generally remain depressed below the level of rachidian teeth, and thus scrape the shell only lightly, if at all. The sharp posteriorly recurved shape of central and lateral rachidian cusps enhances their scooping effectiveness. These teeth produce smooth, conspicuous traces in the soft shell of Mya arenaria and shallow traces in the harder shell of Mytilus edulis Linné. The impact of individual cusp strikes was not evident in traces. With wear, rachidian cusps become increasingly blunted, a reflection of their ploughing action over chemically weakened shell, and are eventually sanded flat. Marginal teeth wear primarily at their ends, the tips becoming truncated as they pass lightly over the shell surface. The advancing edge of the odontophore during rasping strokes, plotted on the image from motion pictures moves slowly at first, then more rapidly in the middle of the stroke, and slows again at the end. Duration of strokes ranged from 0.45 to 0.75 sec. Duration of rasping cycles varied from 1.3 to 2.0 sec. The number of transverse rows of teeth passing over the bending plane during the rasping stroke varied from 14 to 32, and the average time for the passage of one transverse row over the bending plane ranged from 20 to 48 msec. The number of transverse rows of teeth remaining exposed beneath the odontophore below the bending plane at the end of the rasping stroke, and between the bending plane and the anterior end of the sulcus in the radular diverticulum, was approximately 10.     

Temperature tolerance and latitudinal range of brown algae from temperate Pacific South America

Lower and upper survival temperatures of microthalli of 25 species of South American Phaeophyceae isolated from central Peru (14°S) to the Canal Beagle (55°S) were determined using 2-wk exposure for the upper and 4-wk exposure for the lower limit. All species survive 4 wks at -2°C. With respect to the upper limit, species reported only from southernmost South America tolerate 19.9 to 24.5°C (n=8), and species occurring from Cape Horn to central Chile 24.6 to 27.4°C (n=7). Three species that occurred as far north as northern Chile and Peru before the 1982–1983 El Niño event, and whose northern limit was dramatically shifted southwards in 1983, tolerate 20.8 to 25.3°C, whereas five species that have survived in Peru tolerate 25.6 to 28.5°C. Tinocladia falklandica which tolerates 27.8 to 28.1°C but lives only in southernmost South America and Striaria attenuata, which tolerates 31.6 to 31.9°C but occurs at ca. 42°S, are exceptional. Their high temperature tolerance may have no adaptive value in South America. They are restricted to the cold-temperate region due to low temperature requirements for reproduction or for reasons yet unknown. In general, the northern distributional limits of the Phaeophyceae studied along the temperate Pacific coast of South America are reproduction boundaries, except in El Niño years when they are redefined according to the species' upper suvival limits. Temperature tolerance of isolates from northern Chile and Peru agrees well with maximum temperatures reached during the 1983 El Niño.     

Employed mothers: Interrole conflict,spouse support and marital functioning

Increased participation by mothers in the labour force may exert a negative effect on working mothers themselves (e.g. interrole conflict) and influence the marital relationship negatively. Recent research suggests that not all individuals experiencing psychological distress suffer psychological strain (e.g. marital discord). Rather, variables such as social support moderate negative effects of psychological stressors. To test this, sixty-four employed mothers (M age = 36 years) completed interrole conflict and spouse support scales. Marital satisfaction, verbal and nonverbal communication were the criteria operationalized to assess marital functioning. Using moderated multiple regression analyses, interrole conflict and spouse support predicted marital satisfaction and verbal communication significantly. In addition, spouse support may moderate negative effects of interrole conflict on marital satisfaction and verbal communication. With regard to nonverbal communication, spouse support was both a significant main effect and possibly a moderator of interrole conflict. The role of spouse support, conceptual and treatment implications, and future research priorities are identified.     

Predicting turnover: A comparison of part-time and full-time employees

The predictability of turnover was compared for part-time versus full-time workers. This was accomplished using variables (1) that were hypothesized by Mobley (1977) to precede the turnover decision and (2) that have been shown in previous research to be significantly related to turnover. Measures of these variables were assessed via questionnaires following the second month of employment. Turnover was assessed directly from company records for a period of up to twelve months following employment. None of the hypothesized antecedent variables were significantly related to turnover within the part-time group. However, within the full-time group, all of the hypothesized precursors to turnover were found to be at least marginally related to actual turnover. Further, there was evidence to suggest differential predictability of turnover across full-time and part-time employment status groups, suggesting that the two groups may have a different ‘psychology of work’. These results are discussed in terms of the supportive evidence provided.     

Pathway of CH4 formation in anoxic rice field soil and rice roots determined by 13C-stable isotope fractionation

In anoxic rice fields methane is produced by either reduction of CO2 or cleavage of acetate. We measured the delta 13C-values of CH4 and CO2, acetate and organic carbon during time course experiments with anoxic methanogenic soil and root samples and used these values to calculate the fractions of CH4 (and acetate) produced from CO2 reduction. Comparison with radiotracer and/or inhibitor studies constrained the kinetic fractionation factors used for calculation. The fractionation factors for the conversion of CO2 to CH4 and of acetate to CH4 were on the order of alpha = 1.07 (epsilon = -70%) and epsilon > or = - 20%, respectively. The pathway of CH4 production changed with time of anoxic incubation. Anoxic slurries of rice field soil first produced CH4 predominantly (>50%) from CO2, then predominantly (>80%) from acetate and finally (after about one month) according to the theoretically expected ratio (33% CO2 and 67% acetate). Anoxic rice roots, on the other hand, initially produced CH4 exclusively from CO2, followed by contribution of acetate of about 40-60%. Rice roots also produced acetate that partially originated (< or = 1 30%) from reduction of CO2 as determined by calculation of isotopic fractionation using fractionation factors from the literature. The results demonstrate that there is quite some variability in pathways of CH4 production, and also indicate that isotopic fractionation factors may be different in different habitats and change with time.     

Perspectives of a large scale environmental survey for chlorinated dioxins: overview and soil data

On November 5, 1984, The Dow Chemical Company issued a report entitled: “Point Sources and Environmental Levels of 2378-TCDD on the Midland Plant Site of The Dow Chemical Company and in the City of Midland, Michigan.” This report is based upon the efforts of a 22-person task force who dedicated approx. 21 months of effort to the generation and analysis of over 6000 analytical data points regarding specific CDD/CDF concentrations in the four basic environmental elements of air, earth, fire (incineration), and water. A summarization of this study will be presented which includes methodology, analytical QA-QC criteria, and representative soil analyses, as they pertain to the survey conclusions.