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111.
Statistical copolymers of 2-hydroxy-3-benzophenoxy propyl methacrylate (HBPPMA) and benzyl methacrylate (BzMA) in different feed ratios were synthesized by free radical copolymerization method at 60 °C in presence of AIBN initiator. The compositions of copolymer were estimated from 1H-NMR technique. The monomer reactivity ratios of HBPPMA and BzMA were calculated as r1 (rHBPPMA)=0.51±0.076 and r2 (rBzMA)=1.07±0.140 for Kelen-Tüdos method, and was estimated as r1=0.37±0.0006 and r2=0.64±0.0485 according to Fineman Ross equation. The average values estimated from the two methods showed that monomer reactivity ratio of benzyl methacrylate was a slightly high in comparison to HBPPMA. The copolymer system showed an azeotropic point, which is equal to M BzMA =m BzMA =0.43. DSC measurements showed that the Tg’s of poly(HBPPMA) and poly(BzMA) were 84 °C and 73 °C, respectively. The Tg in the copolymer system decreased with increase in benzyl methacrylate content. The decomposition temperature of poly(BzMA) and poly(HBPPMA) occurs in a single stage at about 207 °C and 260 °C, respectively. Those of HBPPMA-BzMA copolymer systems are between decomposition temperatures of two homopolymers. The dielectric constant, dielectric loss factor and electrical conductivity were investigated depend on the frequency of the copolymers. The highest dielectric constants depending on all the studied frequencies were recorded for the poly(HBPPMA) and the copolymer containing the highest HBPPMA unit. The dielectric constant for P(HBPPMA) and P(BzMA) at 1 kHz are 6.56 and 3.22, respectively. Also, those of copolymer systems were estimated between these two values. Similarly, poly(HBPPMA) and copolymers, which are prepared under the same conditions show the dissipation factor and conductivity as well. 相似文献
112.
Du Hwan Chun 《Fibers and Polymers》2017,18(9):1790-1795
The numerical analysis was performed to predict the potential problem, often occurring during the manufacturing process of the disposable medical device of a great volume. The cavity filling analyses were performed for the new design of the 3cc Syringe Barrel using polypropylene(PP1), and a new nucleated polypropylene(PP2) material for better clarity. These analyses have been performed for different processing conditions as well as various wall thickness designs for both materials. With the nucleated material, only the original wall thickness design has been studied at two different processing conditions for comparison purpose. This study was conducted to investigate the optimum part design and processing condition for two different materials. The most desirable design was selected with Design 3 for material utilization and reduced flow stresses by comparing the field results. The new nucleated polypropylene provided slightly better product quality and processing. 相似文献
113.
Smaro Lykidou Evangelos Karanikas Ioannis Tsagalias Nikolaos Nikolaidis Eforia Tsatsaroni 《Fibers and Polymers》2017,18(9):1697-1707
Three new bis azo reactive dyes of different metallic salts (Na, K, Li) were synthesized. The synthesis was obtained by diazotization of 4-amino-2:5 di methoxy phenylene-beta hydroxyl ethyl sulphone sulphate ester and coupling with 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid (H-acid) (moles ratio 2:1). The dyes were purified-concentrated by ultrafiltration technology, characterized and applied on cotton, wool and nylon 6,6 fabric by exhaustion (dyeing) and by ink-jet printing. Fastness properties of the dyeings were measured. Wash fastness was investigated according to international standard methods and was found to be very good to excellent in all cases, while light fastness values were medium to low. Ink-jet ink formulations were prepared using the ultra filtrated reactive blue dyes UF RB(a-c) and their properties pH, conductivity, surface tension and viscosity were monitored over a period of 90 days. The inks were used to print digitally cotton and nylon 6,6 samples and wash- and light fastness properties of the prints were measured. Wash fastness properties were excellent while light fastness values are low Colour measurements of the dyeings and prints were conducted. 相似文献
114.
Dorothee Ehrich Maite Cerezo Anna Y. Rodnikova Natalya A. Sokolova Eva Fuglei Victor G. Shtro Aleksandr A. Sokolov 《BMC ecology》2017,17(1):32
Background
High latitude ecosystems are at present changing rapidly under the influence of climate warming, and specialized Arctic species at the southern margin of the Arctic may be particularly affected. The Arctic fox (Vulpes lagopus), a small mammalian predator endemic to northern tundra areas, is able to exploit different resources in the context of varying tundra ecosystems. Although generally widespread, it is critically endangered in subarctic Fennoscandia, where a fading out of the characteristic lemming cycles and competition with abundant red foxes have been identified as main threats. We studied an Arctic fox population at the Erkuta Tundra Monitoring site in low Arctic Yamal (Russia) during 10 years in order to determine which resources support the breeding activity in this population. In the study area, lemmings have been rare during the last 15 years and red foxes are nearly absent, creating an interesting contrast to the situation in Fennoscandia.Results
Arctic fox was breeding in nine of the 10 years of the study. The number of active dens was on average 2.6 (range 0–6) per 100 km2 and increased with small rodent abundance. It was also higher after winters with many reindeer carcasses, which occurred when mortality was unusually high due to icy pastures following rain-on-snow events. Average litter size was 5.2 (SD = 2.1). Scat dissection suggested that small rodents (mostly Microtus spp.) were the most important prey category. Prey remains observed at dens show that birds, notably waterfowl, were also an important resource in summer.Conclusions
The Arctic fox in southern Yamal, which is part of a species-rich low Arctic food web, seems at present able to cope with a state shift of the small rodent community from high amplitude cyclicity with lemming dominated peaks, to a vole community with low amplitude fluctuations. The estimated breeding parameters characterized the population as intermediate between the lemming fox and the coastal fox ecotype. Only continued ecosystem-based monitoring will reveal their fate in a changing tundra ecosystem.115.
Background
One of the core issues of forest community ecology is the exploration of how ecological processes affect community structure. The relative importance of different processes is still under debate. This study addresses four questions: (1) how is the taxonomic structure of a forest community affected by spatial scale? (2) does the taxonomic structure reveal effects of local processes such as environmental filtering, dispersal limitation or interspecific competition at a local scale? (3) does the effect of local processes on the taxonomic structure vary with the spatial scale? (4) does the analysis based on taxonomic structures provide similar insights when compared with the use of phylogenetic information? Based on the data collected in two large forest observational field studies, the taxonomic structures of the plant communities were analyzed at different sampling scales using taxonomic ratios (number of genera/number of species, number of families/number of species), and the relationship between the number of higher taxa and the number of species. Two random null models were used and the “standardized effect size” (SES) of taxonomic ratios was calculated, to assess possible differences between the observed and simulated taxonomic structures, which may be caused by specific ecological processes. We further applied a phylogeny-based method to compare results with those of the taxonomic approach.Results
As expected, the taxonomic ratios decline with increasing grain size. The quantitative relationship between genera/families and species, described by a linearized power function, showed a good fit. With the exception of the family-species relationship in the Jiaohe study area, the exponents of the genus/family-species relationships did not show any scale dependent effects. The taxonomic ratios of the observed communities had significantly lower values than those of the simulated random community under the test of two null models at almost all scales. Null Model 2 which considered the spatial dispersion of species generated a taxonomic structure which proved to be more consistent with that in the observed community. As sampling sizes increased from 20 m × 20 m to 50 m × 50 m, the magnitudes of SESs of taxonomic ratios increased. Based on the phylogenetic analysis, we found that the Jiaohe plot was phylogenetically clustered at almost all scales. We detected significant phylogenetically overdispersion at the 20 m × 20 m and 30 m × 30 m scales in the Liangshui plot.Conclusions
The results suggest that the effect of abiotic filtering is greater than the effects of interspecific competition in shaping the local community at almost all scales. Local processes influence the taxonomic structures, but their combined effects vary with the spatial scale. The taxonomic approach provides similar insights as the phylogenetic approach, especially when we applied a more conservative null model. Analysing taxonomic structure may be a useful tool for communities where well-resolved phylogenetic data are not available.116.
Christopher Foote Chris T. Darimont Michel Baguette Simon Blanchet Luke M. Jacobus Dominique Mazzi Josef Settele 《BMC ecology》2017,17(1):28
For the fifth year, BMC Ecology is proud to present the winning images from our annual image competition. The 2017 edition received entries by talented shutterbug-ecologists from across the world, showcasing research that is increasing our understanding of ecosystems worldwide and the beauty and diversity of life on our planet. In this editorial we showcase the winning images, as chosen by our Editorial Board and guest judge Chris Darimont, as well as our selection of highly commended images. Enjoy! 相似文献
117.
Background
Invasive ecosystem engineers can facilitate their invasions by modifying the physical environment to improve their own performance, but this positive feedback process has rarely been tested empirically except in sessile organisms. The invasive crayfish Procambarus clarkii is an ecosystem engineer that destroys aquatic macrophytes, which provide a physical refuge for animal prey, and this destruction is likely to enhance vulnerability to predators. Using two series of mesocosm experiments, we tested the hypothesis that the invasive crayfish increases its feeding efficiency on animal prey by reducing submerged macrophytes, thus increasing its individual growth rate in a positive density-dependent manner.Results
In the first experiment, increasing crayfish density reduced both macrophytes and animal prey (dragonfly and chironomid larvae) and, importantly, increased the growth rate of individual crayfish, in accordance with our expectation. In the second experiment, we used artificial macrophytes to clarify whether the physical architecture of macrophytes itself protects animal prey and limits crayfish growth rate. Increasing the artificial macrophyte quantity not only increased the survival of animal prey, but also retarded the crayfish growth rate.Conclusions
We conclude that macrophytes strengthen bottom-up control of crayfish, but this effect can be relaxed by increasing the density of crayfish via reduction in macrophytes. This positive feedback process may explain the crayfish outbreaks and regime shifts occasionally observed in invaded freshwater ecosystems.118.
The main objective of this study was to find the best practice of inducing the sprouting of dormant potato tubers. We compared two protocols of breakage of dormancy, which are based on dipping excised potato eyes in an aqueous solution of gibberellic acid (GA3) and kinetin (standard 1) or in the aqueous solution of GA3, thiourea, and daminozide (standard 2), with a newly reported approach based on ethanol. We tested the effect of ethanol alone or in combination with GA3 and/or kinetin on dormancy release and sprouting of the potato tubers. As a model, we used two potato genotypes (cultivars Pasat and Dorota), with long dormancy of 5 and 10 weeks respectively. We showed that the standard 2 was the most effective treatment both for dormancy breaking and in promoting sprout growth, especially for cv. Dorota, for which the treatment induced 82.3% of tuber eye-plugs to sprout 28 days after treatment and to produce 93.2% of emerged plants after subsequent 28 days of cultivation in the greenhouse. For this cultivar, similar efficacy was observed for the combination of 4% ethanol with GA3 and kinetin. The same concentration of ethanol combined with GA3 but without kinetin was the most efficient treatment for breaking dormancy of cultivar Pasat. However, the difference between the various treatment combinations was statistically insignificant. Ethanol alone or in combination with kinetin poorly induced breakage of dormancy, confirming the main role of GA3 in artificial dormancy breaking. Thus our study showed that the standard 2 is the most effective approach for breakage of dormancy at least with long term-dormancy cultivars. 相似文献
119.
Gebru Hailu Dechassa Nigussie Mohammed Ali Belew Derbew 《American Journal of Potato Research》2017,94(6):617-631
Use of nutrient efficient crop species or cultivars within species in combination with improved crop production practices offer the best option for meeting the future food requirements of growing world populations. Efficiency improvement has a key role for nutrient use and it improves both productivity of yield and minimizes risks of losses that potentially harm the environment. To improve nutrient use efficiency (NUE), one strategy is to select cultivars of crops with high NUE. Both nitrogen (N) and phosphorus (P) are among essential macronutrients commonly applied to agricultural crops to optimize yields. Evaluation of potato cultivars with high N and P efficiency is essential for sustainable production of the crop. In Ethiopia, however, little research has been done to elucidate better NUE of potato crop until recently. This study was, thus, designed to evaluate selected potato cultivars (Belete, Gudene, Jalene, Marachere and one local check) for NP use efficiency under low levels of the nutrients in Wolaita Sodo University, Ethiopia during 2014 and 2015. Factorial combination of 3 levels of each N (0, 55.5 and 111 kg N ha?1 ) and P (0, 19.5 and 39 kg P ha?1 ) were assigned to the main plots and the 5 cultivars to subplots of split-plot design in three replications. Efficiency indices such as agronomic efficiency, physiological efficiency and recovery efficiency were computed for combined NP nutrients. Results showed that agronomic nitrogen use efficiency, apparent phosphorus use efficiency and phosphorus use efficiencies were significantly influenced by the interaction effect of rates of NP nutrition and variety. Application of NP more than 55.5:19.5 kg ha?1 will not beneficial due to their less or equal use and recovery efficiencies to 55.5:19.5 kg NP ha?1. Belete was the most NP efficient variety followed by Jalene and Gudene in all efficiency indices. Therefore, Belete, Jalene and Gudene return better for NP at 55.5:19.5 kg ha?1 for economical use of fertilizes while obtaining satisfactory yield. It can be concluded that yield response variation of the varieties was related to their differences in NP uptake and use efficiencies; and the improved potato varieties were superior to local check in using NP nutrients efficiently. 相似文献
120.
Abdur Razzaque Pavla Tesinova Lubos Hes Jana Salacova Hafiz Affan Abid 《Fibers and Polymers》2017,18(10):1924-1930
Waterproof breathable layered fabrics allow water vapor passing through, but resist liquid water to pass. This ability of the fabrics to protect rain and snow water while allowing sweat vapor to evaporate from inside to outside atmosphere, leads them to be used as outdoor sportswear or protective clothing. The big challenge of enhanced hydrostatic resistance of these fabrics with proper breathability and thermal comfort has widened the research scope. This study presents an experimental investigation on hydrostatic resistance and thermal behavior of layered waterproof breathable fabrics. Six different types of hydrophobic and hydrophilic membrane laminated layered fabrics were evaluated by varying different fabric parameters in the experiment. Hydrostatic resistance and water vapor permeability of the laminated fabrics were measured by SDL ATLAS Hydrostatic Head Tester and PERMETEST respectively. Thermal properties were evaluated by ALAMBETA instrument. Moreover, FX-3300 air permeability tester was used to measure air permeability which represents the porosity of the fabrics and computer based See System software was used for water contact angle measurement on the outer fabric surface in order to determine the hydrophobic and hydrophilic properties. This experiment clearly discusses the influence of different fabric characteristics and parameters on hydrostatic resistance and thermal properties of the breathable laminated fabrics. The results show that fabric material composition, density, thickness, and hydrophobic and hydrophilic membranes have significant effects on hydrostatic resistance, breathability and thermal properties of different laminated fabrics. 相似文献