Sampling pure fetal blood in twin pregnancies by fetoscopy using a single uterine puncture

A technique for sampling pure fetal blood in twin pregnancies using a single uterine entry with a fetoscope is described. The fetoscope was inserted into one sac and after blood had been obtained from that, twin, the fetus in the other sac was sampled by trans-septal passage of the blood-sampling needle. This was done in six out of seven patients, the first in the series having two separate insertions of the fetoscope, one into each sac. Pure fetal blood was taken from all 14 fetuses, either from the placental insertion of the umbilical cord or the umbilicus, and the volume of the samples ranged from 200 μl to 1200 μl. In six patients the fetuses were at risk of β-thalassaemia and in one of haemophilia A. Some observations are made relating zygosity to the ultrasonic and fetoscopic appearance of the septum between the sacs.     

Magnetic and other field effects on prochiral chemical reactions

Experiments are reported in which three prochiral organic reactions were conducted in the presence of a ca. 1T magnetic field which was oriented with reference to the earth's geometric axes. The sign and magnitude of the rotation varied with the macroscopic orientation of the magnetic field and the time that the reaction was performed. Control measurements were in accord with expectations. The fact that the sign of the observed optical rotation of the product was reversed for all three reported reactions when the magnetic field was reversed for reactions conducted on the same day suggests that either the observed asymmetric synthesis was due to the reactions being conducted in a chiral physical field or extremely unusual stochastic processes were involved.     

Protection of the environment from ionising radiation: ethical issues

The paper identifies some of the main ethical issues concerning the protection of the environment from radiation and suggests ways in which ethics can aid in developing a system of protection. After a presentation of background on ethical theory and environmental ethics, three main issues related to environmental protection are discussed: First, the question of valuing the environment and implications for the definition of harm and monetary valuation of environmental goods; second, difficulties with scientific uncertainty and applications of the precautionary principle; and third, issues concerned with the distribution of risk and its relevance for participation in decision-making. In summary, the paper argues that there are strong ethical grounds to provide for the protection of the environment and that, all other things being equal, there is no reason to treat ionising radiation differently to other environmental stressors.     

Inter-Urban Comparison of Ambient Volatile Organic Compound Concentrations in U.S. Cities

Airborne particulate matter from three ferrous foundries was sampled in granulometric fractions and analyzed by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) to determine morphology and qualitative bulk and surface chemical compositions. Cluster and principal components analyses (PCA) were used as an aid for interpretation of results. A clear pattern of composition as a function of size emerges; in particular, trace metals accumulate in fine particles and volatile species on the surface of these. Chemical composition changes are also related to daily schedules where applicable: trace metals appear during pouring operations, silicon is generated during mold making and unmolding. Cluster and PCA greatly ease examination of data and offer pictorial representations of results; in particular, the chemical composition versus particle size relationship is very neatly illustrated by PCA graphs.     

Land change in the southern Yucatán and Calakmul biosphere reserve: effects on habitat and biodiversity.

The southern Yucatán contains the largest expanse of seasonal tropical forests remaining in Mexico, forming an ecocline between the drier north of the peninsula and the humid Petén, Guatemala. The Calakmul Biosphere Reserve resides in the center of this region as part of the Mesoamerican Biological Corridor. The reserve's functions are examined in regard to land changes throughout the region, generated over the last 40 years by increasing settlement and the expansion and intensification of agriculture. These changes are documented from 1987/1988 to 2000, and their implications regarding the capacity of the reserve to protect the ecocline, forest habitats, and butterfly diversity are addressed. The results indicate that the current landscape matrix serves the biotic diversity of the reserve, with several looming caveats involving the loss of humid forests and the interruption of biota flow across the ecocline, and the amount and proximity of older forest patches beyond the reserve. The highly dynamic land cover changes underway in this economic frontier warrant an adaptive management approach that monitors the major changes underway in mature forest types, while the paucity of systematic ecological and environment-development studies is rectified in order to inform policy and practice.     

How resources and encounters affect the distribution of foraging activity in a seed-harvesting ant

We examined how the foraging ecology of the seed-harvesting ant Messor andrei depends upon the distribution of resources and the presence of conspecifics. Bait experiments showed that colonies can recruit to high-density patches of seeds. However, at the seasonal scale, natural resource distribution did not affect the distribution of foraging activity. We conducted the study in years of high rainfall and thus seed availability may not have been a limiting factor. Colonies always preferred to forage in areas closer to their nest, which may reduce travel time between the nest and foraging sites. On a day-to-day scale, encounters between neighboring colonies at a site increased the probability that colonies would return to forage at that site; this was true both for natural and experimental encounters. In the summer, this resulted in colonies foraging at the sites of intraspecific encounters on more days than in areas where no encounter had occurred. Encounters between colonies included fighting, and there was little overlap between the foraging areas of neighboring colonies: both results suggest that one function of encounters is to defend foraging space. The high probability of return to the site of an encounter between colonies suggests that encounters may have a second function: to indicate the presence of resources. Received: 28 June 1999 / Received in revised form: 12 October 1999 / Accepted: 16 October 1999     

Respiratory Responses of Exercising Asthmatic Volunteers Exposed to Sulfuric Acid Aerosol

Young asthmatic adult volunteers (N = 27) were exposed in an environmental chamber to sulfuric acid aerosol at concentrations near 0, 122, 242, and 410 μg/m³, in purified background air at 22° C and 50 percent relative humidity. The polydisperse aerosol had a mass median aerodynamic diameter near 0.6 μm. Exposures occurred in random order at one-week intervals. Each lasted 1 h, during which subjects exercised (mean ventilation 42 L/min) and rested during alternate 10-min periods. Specific airway resistance and forced expiratory function were measured pre-exposure, after the initial exercise, and at end-exposure. Bronchial reactivity was determined by challenge with cold air immediately post-exposure. Symptoms were monitored during exposure for one week afterward. Exercise-induced bronchospasm was observed under all conditions. Physiologic and symptom changes possibly attributable to sulfuric acid exposure were small and not statistically significant. Our largely negative results contrast with positive findings elsewhere at lower acid doses. Possible explanations include different clinical characteristics of subjects and different routes of breathing.     

Increased primary production shifts the structure and composition of a terrestrial arthropod community

Numerous studies have examined relationships between primary production and biodiversity at higher trophic levels. However, altered production in plant communities is often tightly linked with concomitant shifts in diversity and composition, and most studies have not disentangled the direct effects of production on consumers. Furthermore, when studies do examine the effects of plant production on animals in terrestrial systems, they are primarily confined to a subset of taxonomic or functional groups instead of investigating the responses of the entire community. Using natural monocultures of the salt marsh cordgrass Spartina alterniflora, we were able to examine the impacts of increased plant production, independent of changes in plant composition and/or diversity, on the trophic structure, composition, and diversity of the entire arthropod community. If arthropod species richness increased with greater plant production, we predicted that it would be driven by: (1) an increase in the number of rare species, and/or (2) an increase in arthropod abundance. Our results largely supported our predictions: species richness of herbivores, detritivores, predators, and parasitoids increased monotonically with increasing levels of plant production, and the diversity of rare species also increased with plant production. However, rare species that accounted for this difference were predators, parasitoids, and detritivores, not herbivores. Herbivore species richness could be simply explained by the relationship between abundance and diversity. Using nonmetric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM), we also found significant changes in arthropod species composition with increasing levels of production. Our findings have important implications in the intertidal salt marsh, where human activities have increased nitrogen runoff into the marsh, and demonstrate that such nitrogen inputs cascade to affect community structure, diversity, and abundance in higher trophic levels.