- Goal, Scope, Background. The traditional solution for keeping unwanted organisms from attaching to submerged surfaces is to
apply anti-fouling coatings. The most common antifoulant was tributyltin (TBT). TBT systems were highly effective but were
also toxic to non-target organisms. The use of the TBT based coatings will be completely banned by January 1, 2008. Therefore,
there is an urgent need to seek out suitable non-toxic alternatives.
Methods The aim of this work was to evaluate the effectiveness of capsaicin and zosteric acid as natural product antifoulants (NPAs)
in deterring bacterial attachment. Two fresh water bacteria systems Pseudomonas putida (Pp) and bacteria isolated from Lake
Erie (LE) were used to assess the attachment when the NPAs dispersed in the water. Effectiveness was ascertained based on
the decrease in microbial attachment, limited toxicity, and minimum alteration of the coatings properties.
Results and Discussion A significant inhibition of bacteria attachment was achieved when aqueous capsaicin concentration was increased from 0 to
40 mg/L. For instance, after 14 days the LE system depicted 93.5% and 98.5% less biofilm coverage for 20 mg/L and 40 mg/L
capsaicin, respectively when compared to systems without NPA. Biofilm coverage was reduced by 92.5% and 98.2%, respectively
with 50 mg/L and 500 mg/L zosteric acid.
Conclusions Both capsaicin and zosteric acid was effective at preventing bacteria attachment. As the NPA aqueous concentration increased,
biofilm formation decreased. Evaluating changes in aqueous pH, conductivity, dissolved oxygen, aqueous microbial population
and biofilm formation suggested that the primary antifoulant mechanism of these two NPAs was to block the bacteria's active
sites versus posing a lethal level.
Recommendation and Perspective From the attachment study, zosteric acid appeared to be more effective in preventing bacterial attachment when the NPAs were
dispersed in the aqueous environment. For practical applications, the antifoulant needs to be incorporated into a coating
and have a slow release rate. Thus the ability to successfully incorporate zosteric acid into a coating, without deterring
bacterial attachment, needs to be investigated. 相似文献
Variations in the gene encoding the low-density lipoprotein receptor (LDLR) can cause familial hypercholesterolemia (FH), one of the most common inherited metabolic disorders in humans. The functional
effects of the p.Gln92Glu and p.Asn564His alterations are predicted as benign, but the c.313 + 1G>C and p.Lys799_Phe801del
changes are believed to cause disease. Although p.Gln92Glu and c.313 + 1G>C have been observed only in Spain, p.Asn564His
and p.Lys799_Phe801del are widespread in Western Europe. In order to estimate the ages (t generations) of these four variants of the gene, to determine their possible origin and to consider the influence of age
and selective pressure on their spread, we analyzed 86 healthy individuals and 126 FH patients in Spain. Most of the FH patients
investigated carried two of these four LDLR variants simultaneously, while only one patient carried three of them simultaneously. Haplotype analyses were based on five
LDLR SNPs: c.81T>C, c.1413G>A, c.1725C>T, c.1959T>C and c.2232G>A. The results suggest that p.Gln92Glu and c.313 + 1G>C arose
at about the same time (99 and 103 generations ago, respectively) in the CACTG haplotype and that p.Asn564His and p.Lys799_Phe801del
appeared in the CGCCG haplotype and might be slightly more recent variations (92 and 95 generations ago, respectively). Low
selective pressures could explain the maintenance of these variants in spite of their ages. The origin of p.Gln92Glu and c.313 + 1G>C
appears to be in Spain whereas p.Asn564His and p.Lys799_Phe801del could have been introduced in Spain by Celtic migrations
in the seventh to fifth centuries BC. 相似文献
Amphoteric surfactants form part of specialty surfactants available for formulators to improve or design new formulations in response to environmental, toxicity, safety and performance demands. Nevertheless, limited information on the ecological properties of amphoterics is available. In the present work, the aerobic and anaerobic biodegradability and the aquatic toxicity of different types of amphoteric surfactants (three alkyl betaines, one alkylamido betaine and three alkyl imidazoline derivatives) were studied. The amphoteric surfactants tested were readily biodegradable under aerobic conditions (CO(2) headspace test) and alkylamido betaines and alkyl imidazoline derivatives were also easily biodegradable under anaerobic conditions (test based on the ECETOC method). Toxicity to Photobacterium phosphoreum and Daphnia magna increased with the fatty chain length of the surfactant. The EC(50) toxicity values of the amphoterics tested were higher than 5 mg/L, and alkyl imidazoline derivatives, with EC(50) values from 20 to >200 mg/L, showed the lowest aquatic toxicity. 相似文献
Nitrogen (δ15N) and carbon (δ13C) stable isotopes and contaminants, such as mercury, have been widely used to characterise foraging ecology of temperate
and polar seabirds. In this study, for the first time, we used isotopic signatures and mercury levels of feathers and blood
of eight tropical seabird species, that forage in a range-gradient between inshore and offshore areas, to describe the foraging
habits of a large tropical seabird community (from two neighboring islands of the Seychelles archipelago, western Indian Ocean)
during both the breeding and inter-breeding periods. Overall, we found a high overlap in both δ15N and δ13C signatures among species. The high inter-specific overlap in δ15N values was expected, given the similarities in the diet of the species from this community. However, several unexpected
results, such as (1) the consistently higher δ15N signatures of white terns (Gygis alba), (2) the large variation in inter-specific differences in δ15N signatures among the sampling groups (season, age, island and tissue) and (3) the consistent low δ15N values of breeding birds during the northwest monsoon (austral summer), suggest that δ15N signatures cannot be used as indicators of seabird trophic levels in this community. The high inter-specific overlap in
δ13C signatures and the absence, during the breeding season, of a δ13C gradient that follows the inshore-offshore foraging gradient within the community can be explained by the habitat homogeneity
of the Seychelles continental shelf and suggest that birds forage mostly within the limits of this “plateau”. On the other
hand, the similarities in δ13C values between the breeding and inter-breeding periods in species that are known to show post-breeding dispersal, strongly
support the hypothesis of a lack of latitudinal variation in δ13C signatures of POM in the central Indian Ocean, and the consequent inaccuracy of δ13C values to track seabird movements within this geographic area. Inter-specific differences in mercury levels seem to be related
to prey size, while consistent higher mercury concentrations in one of the studied islands suggest different island mercury-backgrounds
and possible segregation in foraging areas between the seabirds of the two islands.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
The removal efficiency of four commonly-used parabens by electrochemical advanced oxidation with boron-doped diamond anodes in two different aqueous matrices, namely ultrapure water and surface water from the Guadiana River, has been analyzed. Response surface methodology and a factorial, composite, central, orthogonal, and rotatable (FCCOR) statistical design of experiments have been used to optimize the process. The experimental results clearly show that the initial concentration of pollutants is the factor that influences the removal efficiency in a more remarkable manner in both aqueous matrices. As a rule, as the initial concentration of parabens increases, the removal efficiency decreases. The current density also affects the removal efficiency in a statistically significant manner in both aqueous matrices. In the water river aqueous matrix, a noticeable synergistic effect on the removal efficiency has been observed, probably due to the presence of chloride ions that increase the conductivity of the solution and contribute to the generation of strong secondary oxidant species such as chlorine or HClO/ClO −. The use of a statistical design of experiments made it possible to determine the optimal conditions necessary to achieve total removal of the four parabens in ultrapure and river water aqueous matrices.
Abstract Pyrolytic product distribution rates and pyrolysis behavior of tire-derived fuels (TDF) were investigated using thermogravimetric analyzer (TGA) techniques. A TGA was designed and built to investigate the behavior and products of pyrolysis of typical TDF specimens. The fundamental knowledge of TGA analysis and principal fuel analysis are applied in this study. Thermogravimetry of the degradation temperature of the TDF confirms the overall decomposition rate of the volatile products during the depolymerization reaction. The principal fuel analysis (proximate and ultimate analysis) of the pyrolytic char products show the correlation of volatilization into the gas and liquid phases and the existence of fixed carbon and other compounds that remain as a solid char. The kinetic parameters were calculated using least square with minimizing sum of error square technique. The results show that the average kinetic parameters of TDF are the activation energy, E = 1322 ± 244 kJ/mol, a pre-exponential constant of A = 2.06 ± 3.47 × 1010 min?1, and a reaction order n = 1.62 ± 0.31. The model-predicted rate equations agree with the experimental data. The overall TDF weight conversion represents the carbon weight conversion in the sample. 相似文献
The performance of two bacteria, Arthrobacter viscosus and Streptococcus equisimilis, and the effect of the interaction of these bacteria with four different clays on the retention of diethylketone were investigated in batch experiments. The uptake, the removal percentages and the kinetics of the processes were determined. S. equisimilis, by itself, had the best performance in terms of removal percentage, for all the initial diethylketone concentrations tested: 200, 350 and 700 mg/L. The uptake values are similar for both bacteria. A possible mechanism to explain the removal of diethylketone includes its degradation by bacteria, followed by the adsorption of the intermediates/sub-products by the functional groups present on the cells' surfaces. The assays performed with bacteria and clays indicated that the uptake values are similar despite of the clay used, for the same microorganism and mass of clay, but in general, higher values are reached when S. equisimilis is used, compared to A. viscosus. Kinetic data were described by pseudo-first- and pseudo-second-order models. 相似文献
Studies from the ecosystem services perspective can provide a useful framework because they allow us to fully examine the
benefits that humans obtain from socio-ecological systems. Mexico City, the second largest city in the world, has faced severe
problems related to water shortages, which have worsened due to increasing population. Demand for space has forced changes
in land cover, including covering areas that are essential for groundwater recharge. The city has 880 km2 of forest areas that are crucial for the water supply. The Magdalena River Watershed was chosen as a model because it is
a well-preserved zone within Mexico City and it provides water for the population. The general aim of this study was to assess
the ecosystem service of the water supply in the Magdalena River Watershed by determining its water balance (SWAT model) and
the number of beneficiaries of the ecosystem services. The results showed that the watershed provides 18.4 hm3 of water per year. Baseflow was dominant, with a contribution of 85%, while surface runoff only accounted for 15%. The zone
provides drinking water to 78,476 inhabitants and could supply 153,203 potential beneficiaries. This work provides an example
for understanding how ecosystem processes determine the provision of ecosystem services and benefits to the population in
a rural–urban watershed in Mexico City. 相似文献