Effects of gibberellic acid and kinetin on growth of pea stem sections

The Science of Nature -     

Optimal pollution in the presence of adjustment costs

This paper explores optimal pollution control when pollution is considered a stock and costs of treating pollution are a function both of the level and rate of change of pollution control. It is shown that even if the long run optimum stock of pollution is below the initial level adjustment costs may imply an optimally increasing stock of pollution in the short run. The results obtained are contrasted with those which emerge when adjustment costs are absent and when damages are taken to be a function of the flow of pollution; the appropriate tax rates of polluting discharges are examined.     

Optimal design for water conservation and energy savings using green roofs in a green building under mixed uncertainties

Most water conservation and energy saving strategies for residential homes and commercial buildings have higher initial capital investment than traditional ones. Yet, the added benefits of these “green” building strategies should outweigh the increase of initial capital cost at the end of the house lifetime. Using green roof systems to cool houses gives rise to uncertainties from local precipitation patterns and the unstable market related costs and benefits. The optimal area of green roof to balance cost, benefit, and risk remains unknown. To achieve such a complex systems analysis, a grey stochastic programming model was prepared to address the optimal design strategies under mixed uncertainties. Such a cost-benefit-risk trade-off model was formulated for this study through an optimization framework to retrieve the optimal design strategies with respect to a typical Florida residential home (shingle and metal roofs). It is particularly designed to synergistically integrate a green roof with beneficial reuse of gray water and stormwater while achieving some degree of energy savings. The study identifies the optimal green roof area that keeps within the cost of a conventional home over a specific life time, such as 50 years. Research findings show that as the reliability level associated with the chance constraint was decreased, the upper bound of the green roof area did not vary much for either shingle or metal roofs. The lower bound was found to decrease in the same situation, however, due to the higher minimum cost of the cistern in relation to the greater volume of expected rainfall, forcing the required green roof area to decrease.     

Fish consumption in pregnancy, cord blood mercury level and cognitive and psychomotor development of infants followed over the first three years of life: Krakow epidemiologic study

BACKGROUND: Although the maternal fish consumption is supposed to have beneficial effects on development of infants, it may be harmful for child cognitive development since fish is a common source of methylmercury. PURPOSE OF THE STUDY: Purpose of the study was to describe the usual pattern of fish consumption during pregnancy in Poland and explain the variability of prenatal mercury exposure due to fish intake by mothers. The other endpoint of the study was the assessment of the cognitive and psychomotor development of infants related to prenatal mercury exposure over the 3-year follow-up. MATERIAL AND METHODS: The study sample consisted of 374 infants born at 33-42 weeks of gestation between January 2001 and March 2003 to mothers attending ambulatory prenatal clinics in the first and second trimesters of pregnancy. Total mercury level in whole cord blood was measured and the Bayley Scales of Infant Development (BSID-II) was used to assess the mental (MDI) and psychomotor developmental index (PDI) in children at 12, 24 and 36 months of age. RESULTS: Self-reported weekly amount of fish consumption during the first two trimesters of pregnancy correlated positively with umbilical cord mercury concentrations (r(s)=0.22, p<0.0001). The corresponding correlation coefficient for the fish consumption in the third trimester of pregnancy was 0.21, p<0.0001. There was an inverse association between mercury exposure and both MDI (beta regression coeff.=-2.8, p=0.01) and PDI scores (beta coeff.=-2.3, p=0.04) at 12 months of age. Subsequent BSID-II testing at 24 and 36 months did not confirm significant association between exposure and cognitive or psychomotor function. The estimates of association between mercury prenatal exposure and the development of infants, which were based on the longitudinal analysis of all BSID-II measurements done in the follow-up (generalized estimating equations statistical model) showed that the performance deficit observed at 12 months of age was of border significance.     

Diversity in the later Paleogene proboscidean radiation: a small barytheriid from the Oligocene of Dhofar Governorate,Sultanate of Oman

Despite significant recent improvements to our understanding of the early evolution of the Order Proboscidea (elephants and their extinct relatives), geographic sampling of the group’s Paleogene fossil record remains strongly biased, with the first ~30 million years of proboscidean evolution documented solely in near-coastal deposits of northern Africa. The considerable morphological disparity that is observable among the late Eocene and early Oligocene proboscideans of northern Africa suggests that other, as yet unsampled, parts of Afro-Arabia might have served as important centers for the early diversification of major proboscidean clades. Here we describe the oldest taxonomically diagnostic remains of a fossil proboscidean from the Arabian Peninsula, a partial mandible of Omanitherium dhofarensis (new genus and species), from near the base of the early Oligocene Shizar Member of the Ashawq Formation, in the Dhofar Governorate of the Sultanate of Oman. The molars and premolars of Omanitherium are morphologically intermediate between those of Arcanotherium and Barytherium from northern Africa, but its specialized lower incisors are unlike those of other known Paleogene proboscideans in being greatly enlarged, high-crowned, conical, and tusk-like. Omanitherium is consistently placed close to late Eocene Barytherium in our phylogenetic analyses, and we place the new genus in the Family Barytheriidae. Some features of Omanitherium, such as tusk-like lower second incisors, the possible loss of the lower central incisors, an enlarged anterior mental foramen, and inferred elongate mandibular symphysis and diminutive P₂, suggest a possible phylogenetic link with Deinotheriidae, an extinct family of proboscideans whose origins have long been mysterious.     

Uncertainties related to the identification of the marginal energy technology in consequential life cycle assessments

When performing life cycle assessment (LCA) assumptions regarding the energy use are often decisive for the outcome. In this paper, current approaches of identifying marginal electricity and heat technologies for consequential LCAs are challenged. The identification of marginal energy technologies is examined from three angles: The marginal electricity technology is identified in Danish historical and potential future energy systems. The methods of identifying and using marginal electricity and heat technologies in key LCA studies are analysed. Finally, the differences in applying energy system analysis and assuming one marginal technology are illustrated, using waste incineration with energy substitution as a case. The main problem with the current approach is the use of one single marginal technology. It is recommended to use fundamentally different affected technologies and identify these in several possible and fundamentally different future scenarios. If possible, the affected technologies should also be identified based on energy system analyses considering the technical characteristics of the technologies involved. Some results in this paper may be applicable to other affected technologies than energy.     

Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)

Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time.     

Crab herbivory regulates plant facilitative and competitive processes in Argentinean marshes

Interactions among plants have been hypothesized to be context dependent, shifting between facilitative and competitive in response to variation in physical and biological stresses. This hypothesis has been supported by studies of the importance of positive and negative interactions along abiotic stress gradients (e.g., salinity, desiccation), but few studies have tested how variation in biotic stresses can mediate the nature and strength of plant interactions. We examined the hypothesis that herbivory regulates the strength of competitive and facilitative interactions during succession in Argentinean marshes dominated by Spartina densiflora and Sarcocornia perennis. Spartina densiflora is preferred by the dominant herbivore in the system, the crab Chasmagnathus granulatus. We experimentally manipulated crab herbivory, plant structure, and shade, and we found that, when herbivory was low in the spring and summer, competitive interactions between plants were dominant, but in the fall, when herbivory was highest, facilitative interactions dominated, and Spartina densiflora survival was completely dependent upon association with Sarcocornia perennis. Moreover, experimental removal of Sarcocornia perennis across recently disturbed tidal flats revealed that, while Sarcocornia perennis positively affected small Spartina densiflora patches by decreasing herbivory, as patch size increases and they can withstand the impact of herbivory, competitive interactions predominated and Spartina densiflora ultimately outcompeted Sarcocornia perennis. These results show that herbivory can mediate the balance between facilitative and competitive processes in vascular plant communities and that the strength of consumer regulation of interactions can vary seasonally and with patch size.     

Endemism and dispersal: comparative phylogeography of three surgeonfishes across the Hawaiian Archipelago

To evaluate the hypothesis that a general correlation exists between species range size and dispersal ability, we surveyed mitochondrial cytochrome b sequence variation in three surgeonfish species with vastly different ranges: Ctenochaetus strigosus, Hawaiian endemic, N = 531; Zebrasoma flavescens, North Pacific, N = 560; Acanthurus nigrofuscus, Indo-Pacific, N = 305. Collections were made throughout the 2,500 km expanse of the Hawaiian Archipelago and adjacent Johnston Atoll. Analyses of molecular variance demonstrate that all three species are capable of maintaining population connectivity on a scale of thousands of km (all species global Φ_ST = NS). However, rank order comparison of pairwise Φ_ST results and Exact test P-values revealed modest but significantly different patterns of gene flow among the three species surveyed, with the degree of genetic structure increasing as range size decreases (P = 0.001). These results are consistent with mtDNA surveys of four additional Hawaiian reef fauna in which a wide-spread Indo-Pacific species exhibited genetic homogeneity across the archipelago, while three endemics had significant population subdivision over the same range. Taken together, these seven cases invoke the hypothesis that Hawaii’s endemic reef fishes evolved from species with reduced dispersal ability that, after initial colonization, could not maintain contact with parent populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.