Matter, spacetime and the vacuum

We distinguish three historical and scientific views of matter, spacetime, and the relationship between them: the absolute approach of Newton, the relational approach most often associated with Mach, and a third, geometrical approach which inspired Einstein and continues to drive efforts toward a unified theory of fundamental interactions today. Which is correct? We suggest that this is, to a large extent, an "ill-posed question," reminiscent of the wave/particle debate in earlier times. The boundary between matter and spacetime is no longer easy to draw, and it is likely that they are complementary aspects of the same reality. There is no clearer illustration of this than the modern view of the vacuum. We review the importance of this concept in cosmology, and explore the extent to which the old idea of an "empty" vacuum might still be maintained. If the real cosmological vacuum is far from empty, as observations now suggest, then it may be possible to achieve an even simpler goal: a Universe with a net energy of zero.     

ON‐FARM WATER CONSERVATION PRACTICES IN SOUTHERN ALBERTA1

ABSTRACT: In southern Alberta, as elsewhere, pressures on limited water supplies are increasing. Not surprisingly, a great deal of attention has been focused on irrigated agriculture, which accounts for the largest share of water consumed in the region. In order to meet broadly accepted water conservation goals, some commentators have suggested that irrigation water use should be metered and that irrigators should be charged based on the amount of water used. An alternative proposal would have water management authorities rely upon the perceived adaptability of irrigators. This paper offers a perspective on the willingness of irrigators to conserve water. Based on a survey of 183 irrigation farmers conducted over the summer and early fall of 1998, we found that irrigators are generally aware of the need to conserve water and soil moisture, and that a variety of water conserving strategies were being employed. Water saving technologies specific to irrigation agriculture were less widely adopted. The findings suggest that there is considerable potential to reduce the amount of water consumed by the irrigation sector through increased efficiency, but that change will be limited if current economic circumstances and institutional arrangements persist.     

UTILIZATION OF LANDSCAPE INDICATORS TO MODEL POTENTIAL PATHOGEN IMPAIRED WATERS1

ABSTRACT: Many water bodies within the United States are contaminated by non‐point source (NPS) pollution, which is defined as those materials posing a threat to water quality arising from a number of individual sources and diffused through hydrologic processes. One such NPS pollutant that is of critical concern are pathogens derived from animal wastes, including humans. The potential presence of pathogens is identified by testing the water for fecal conform, a bacteria also associated with animal wastes. Water contaminated by animal wastes are most often associated with urban and agricultural areas, thus it is postulated that by utilizing land cover indicators, those water bodies that may be at risk of fecal coliform contamination may be identified. This study utilizes land cover information derived from the Multi‐Resolution Land Characterization (MRLC) project to analyze fecal coliform contamination in South Carolina. Also utilized are 14 digit hydro‐logic unit code (HUC) watersheds of the state, a digital elevation model, and test point data stating whether fecal coliform levels exceeded State Water Quality Standards. Proportions of the various land covers are identified within the individual watersheds and then analyzed using a logistic regression. The results reveal that watersheds with large proportions of urban land cover and agriculture on steep slopes had a very high probability of being impaired. (KEY TERMS: Geographic Information Systems; land use planning; nonpoint source pollution; statistical analysis; water quality; watershed management.)     

PM2.5 chemical source profiles for vehicle exhaust, vegetative burning, geological material, and coal burning in Northwestern Colorado during 1995

PM_2.5 (particles with aerodynamic diameters less than 2.5 μm) chemical source profiles applicable to speciated emissions inventories and receptor model source apportionment are reported for geological material, motor vehicle exhaust, residential coal (RCC) and wood combustion (RWC), forest fires, geothermal hot springs; and coal-fired power generation units from northwestern Colorado during 1995. Fuels and combustion conditions are similar to those of other communities of the inland western US. Coal-fired power station profiles differed substantially between different units using similar coals, with the major difference being lack of selenium in emissions from the only unit that was equipped with a dry limestone sulfur dioxide (SO₂) scrubber. SO₂ abundances relative to fine particle mass emissions in power plant emissions were seven to nine times higher than hydrogen sulfide (H₂S) abundances from geothermal springs, and one to two orders of magnitude higher than SO₂ abundances in RCC emissions, implying that the SO₂ abundance is an important marker for primary particle contributions of non-aged coal-fired power station contributions. The sum of organic and elemental carbon ranged from 1% to 10% of fine particle mass in coal-fired power plant emissions, from 5% to 10% in geological material, >50% in forest fire emissions, >60% in RWC emissions, and >95% in RCC and vehicle exhaust emissions. Water-soluble potassium (K⁺) was most abundant in vegetative burning profiles. K⁺/K ratios ranged from 0.1 in geological material profiles to 0.9 in vegetative burning emissions, confirming previous observations that soluble potassium is a good marker for vegetative burning.     

Combined steam distillation and electrochemical peroxidation (ECP) treatment of river sediment contaminated by PCBs

A combined treatment process utilizing steam distillation followed by electrochemical peroxidation (ECP) has been utilized to remove >90% of the polychlorinated biphenyls (PCBs) in St. Lawrence River sediment and destroy 95% of the PCBs recovered in the condensate. 2 l of condensate were collected by boiling 500 grams of sediment containing 4.3 mg PCBs. Most of the PCBs (82.3%) were recovered as a small volume (<1 ml) of yellow oil floating on the condensate and coating glassware surfaces. The aqueous phase PCBs (182 μg/l) were destroyed (95%) by three sequential ECP treatments at 16.8°C and pH 5, utilizing 1 ml of H₂O₂ (3%) and periodically reversed current (0.75–1.0 A @ 10 volts). Oxidation is primarily mediated by hydroxyl radicals produced by the reaction of hydrogen peroxide with electrochemically generated ferrous iron (Fenton's reagent). This work suggests steam extraction, in combination with advanced oxidation technologies, provides an effective treatment strategy for contaminated solids.     

Understanding and predicting ecological dynamics: are major surprises inevitable?

Ecological surprises, substantial and unanticipated changes in the abundance of one or more species that result from previously unsuspected processes, are a common outcome of both experiments and observations in community and population ecology. Here, we give examples of such surprises along with the results of a survey of well-established field ecologists, most of whom have encountered one or more surprises over the course of their careers. Truly surprising results are common enough to require their consideration in any reasonable effort to characterize nature and manage natural resources. We classify surprises as dynamic-, pattern-, or intervention-based, and we speculate on the common processes that cause ecological systems to so often surprise us. A long-standing and still growing concern in the ecological literature is how best to make predictions of future population and community dynamics. Although most work on this subject involves statistical aspects of data analysis and modeling, the frequency and nature of ecological surprises imply that uncertainty cannot be easily tamed through improved analytical procedures, and that prudent management of both exploited and conserved communities will require precautionary and adaptive management approaches.     

Genetic variation in defense chemistry in wild cabbages affects herbivores and their endoparasitoids

Populations of wild Brassica oleracea L. grow naturally along the Atlantic coastlines of the United Kingdom and France. Over a very small spatial scale (i.e., <15 km) these populations differ in the expression of the defensive compounds, glucosinolates (GS). Thus far, very few studies have examined interactions between genetically distinct populations of a wild plant species and associated consumers in a multitrophic framework. Here, we compared the development of a specialist (Pieris rapae) and a generalist (Mamestra brassicae) insect herbivore and their endoparasitoids (Cotesia rubecula and Microplitis mediator, respectively) on three wild populations and one cultivar of B. oleracea under controlled greenhouse conditions. Herbivore performance was differentially affected by the plant population on which they were reared. Plant population influenced only development time and pupal mass in P. rapae, whereas plant population also had a dramatic effect on survival of M. brassicae. Prolonged development time in P. rapae corresponded with high levels of the indole GS, neoglucobrassicin, whereas reduced survival in M. brassicae coincided with high levels of the aliphatic GS, gluconapin and sinigrin. The difference between the two species can be explained by the fact that the specialist P. rapae is adapted to feed on plants containing GS and has evolved an effective detoxification system against aliphatic GS. The different B. oleracea populations also affected development of the endoparasitoids. Differences in food-plant quality for the hosts were reflected in adult size in C. rubecula and survival in M. mediator, and further showed that parasitoid performance is also affected by herbivore diet.     

Movement ecology: size-specific behavioral response of an invasive snail to food availability

Immigration, emigration, migration, and redistribution describe processes that involve movement of individuals. These movements are an essential part of contemporary ecological models, and understanding how movement is affected by biotic and abiotic factors is important for effectively modeling ecological processes that depend on movement. We asked how phenotypic heterogeneity (body size) and environmental heterogeneity (food resource level) affect the movement behavior of an aquatic snail (Tarebia granifera), and whether including these phenotypic and environmental effects improves advection-diffusion models of movement. We postulated various elaborations of the basic advection diffusion model as a priori working hypotheses. To test our hypotheses we measured individual snail movements in experimental streams at high- and low-food resource treatments. Using these experimental movement data, we examined the dependency of model selection on resource level and body size using Akaike's Information Criterion (AIC). At low resources, large individuals moved faster than small individuals, producing a platykurtic movement distribution; including size dependency in the model improved model performance. In stark contrast, at high resources, individuals moved upstream together as a wave, and body size differences largely disappeared. The model selection exercise indicated that population heterogeneity is best described by the advection component of movement for this species, because the top-ranked model included size dependency in advection, but not diffusion. Also, all probable models included resource dependency. Thus population and environmental heterogeneities both influence individual movement behaviors and the population-level distribution kernels, and their interaction may drive variation in movement behaviors in terms of both advection rates and diffusion rates. A behaviorally informed modeling framework will integrate the sentient response of individuals in terms of movement and enhance our ability to accurately model ecological processes that depend on animal movement.     

Phylogenetic analyses of potentially free-living <Emphasis Type="Italic">Symbiodinium</Emphasis> spp. isolated from coral reef sand in Okinawa,Japan

The existence of “free-living” Symbiodinium that can form symbioses with hosts is implied by the presence of hosts that produce Symbiodinium-free gametes and expulsion and/or expelled symbiotic algae from host. However, it is still unclear if potentially symbiotic Symbiodinium are found “free-living” in the coral reef environment. Sixteen Symbiodinium strains were established from samples taken from three sampling locations of coral reef sand in Okinawa, Japan. Phylogenetic analyses of the partial large subunit ribosomal DNA (28S-rDNA) and the internal transcribed spacer of ribosomal DNA (ITS-rDNA) conclusively showed that all 16 isolates belonged to Symbiodinium clade A sensu Rowan and Powers (1991). The lack of other Symbiodinium clades besides clade A in this study may be due to other clades not being readily culturable under culture conditions used here. The new isolates could be phylogenetically divided into four groups, though no sequences were identical to previously reported Symbiodinium. Two of the four groups were closely related to symbiotic Symbiodinium clade A isolated from a variety of host species. One isolate group formed a highly supported monophyly with Symbiodinium types that have previously been characterized as “free-living”. The remaining isolate group, although within clade A, was quite divergent from other clade A Symbiodinium. These results indicate that novel diversity of free-living Symbiodinium exists in coral sand.     

Incorporating anthropogenic variables into a species distribution model to map gypsy moth risk

This paper presents a novel methodology for multi-scale and multi-type spatial data integration in support of insect pest risk/vulnerability assessment in the contiguous United States. Probability of gypsy moth (Lymantria dispar L.) establishment is used as a case study. A neural network facilitates the integration of variables representing dynamic anthropogenic interaction and ecological characteristics. Neural network model (back-propagation network [BPN]) results are compared to logistic regression and multi-criteria evaluation via weighted linear combination, using the receiver operating characteristic area under the curve (AUC) and a simple threshold assessment. The BPN provided the most accurate infestation-forecast predictions producing an AUC of 0.93, followed by multi-criteria evaluation (AUC = 0.92) and logistic regression (AUC = 0.86) when independently validating using post model infestation data. Results suggest that BPN can provide valuable insight into factors contributing to introduction for invasive species whose propagation and establishment requirements are not fully understood. The integration of anthropogenic and ecological variables allowed production of an accurate risk model and provided insight into the impact of human activities.