646 research outputs found
Amphiphilic block copolymers : synthesis, self-assembly and applications
No full textSelf-assembly of amphiphilic block copolymers in aqueous solution is one of the most important nanotechnological methods to prepare nanocarriers for
different applications, such as drug delivery, biosensor, nanoreactor and so on. Synthesis of new types of amphiphilic block copolymers with novel
functionality and detailed characterization of self-assembly, influenced by self-assembly methods and different other parameters (molecular weight,
hydrophilic to hydrophobic ratio), are important. Especially, building up the relationship between the self-assembled nanomorphologies and molecule
constitution are helpful to understand amphiphilic block copolymer self-assemble theroy.
In this thesis, I present to you the influence of different parameters on the self-assembly nanostructures for the poly(dimethylsiloxane)-
block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) amphiphilic block copolymers.3D phase diagram clearly shows in which domain the PDMS-b-PMOXA
self-assemble into polymersome. The polymersome are possible for us to constribute the nano-sized based nanoreactor.
In addition, in order to develop more functional amphiphilic block copolymers and enlarge the potential application areas, another two types of
copolymers, grafted poly(2-methyl-2-oxazoline)-graft(ss)-poly(e-caprolactone) (PMOXA-graft(ss)-PCL) and linear poly(2-ethyl-2-oxazoline)-block-
poly(e-caprolactone)-ss-poly(L-lysine) (PEtOXA-b-PCL-ss-PLL), were designed and synthesized with reduction responsiveness, utilizing different
polymerization techniques, including ring openning polymerization and "graft-to" technology. Due to the amphiphilicity of these two types of
copolymers, nanoparticles are formed by them in aqueous solution. The primary evaluation of these two new type amphiphilic block copolymers
demonstrated that they can be promising candidates as smart nanocarries for the application of drug delivery.
In this dissertation, the result of our research have been comprehensivly compared with other publications and results from different groups.
We have new findingS. We find one new nano-object with 80-100 nm diameter, but without hollow aqueous cavity.
We also realize that basing on poly(2-ethyl-2-oxazoline)-block-poly(e-caprolactone)-ss-poly(L-lysine) (PEtOXA-b-PCL-ss-PLL) copolymer, it is possible
to synthesize more functional copolymer, for example introducing the pH-cleavable linker between PEtOXA and PCL, to mimic more closely the virus delivery
gene into cells
Water Debt Indicator Reveals Where Agricultural Water Use Exceeds Sustainable Levels
No full textAgriculture overexploits water resources in many regions, as water stress metrics highlight. Tracing back the causes of water overuses and separately accounting for soil water, surface water and groundwater resources is an open challenge to monitor the sustainability of agricultural water use. We introduce the “water debt repayment time” indicator, measuring the time required to replenish water resources used for annual crop production. This indicator disentangles source‐ and crop‐specific water overuses at a high spatial resolution. Globally, we find that wheat and rice production critically overuses groundwater resources and cotton production overuses both surface water and groundwater. Locally, unsustainable production is found over the Sabarmati Basin and in the Chao Phraya Basin, where the repayment time exceeds 5 years in many cultivated areas. Critical overuses are also found over the High Plain and Indo‐Gangetic Plains, where the repayment times reach 50 years. Unsustainable irrigation is often a consequence of growing crops during local dry seasons
Talesätt och talemaader: om ordförbindelser hos Dalin och Molbech
No full textIn this paper I present a study which contributes to the description of lexicographic traditions in Sweden and Denmark. More exactly, the study concerns the treatment of word combinations, which are followed by some kind of explanation, in two 19th century monolingual dictionaries. The works are the Swedish dictionary Ordbok öfver svenska språket (1850–55) by A. F. Dalin and the Danish dictionary Dansk Ordbog (…) (1833) by C. Molbech. The focus is, among other things, on the frequencies and types of word combinations that are represented in the data. Furthermore, I consider in which entries the word combinations are found, and the position of the expressions in the microstrucure of the articles. Moreover, I discuss the form and meaning of the word combinations and, finally, the authors’ use of (signed) examples
Evolution of the global virtual water trade network
No full textGlobal freshwater resources are under increasing pressure from economic development, population growth, and climate change. The international trade of water-intensive products (e.g., agricultural commodities) or virtual water trade has been suggested as a way to save water globally. We focus on the virtual water trade network associated with international food trade built with annual trade data and annual modeled virtual water content. The evolution of this network from 1986 to 2007 is analyzed and linked to trade policies, socioeconomic circumstances, and agricultural efficiency. We find that the number of trade connections and the volume of water associated with global food trade more than doubled in 22 years. Despite this growth, constant organizational features were observed in the network. However, both regional and national virtual water trade patterns significantly changed. Indeed, Asia increased its virtual water imports by more than 170%, switching from North America to South America as its main partner, whereas North America oriented to a growing intraregional trade. A dramatic rise in China's virtual water imports is associated with its increased soy imports after a domestic policy shift in 2000. Significantly, this shift has led the global soy market to save water on a global scale, but it also relies on expanding soy production in Brazil, which contributes to deforestation in the Amazon. We find that the international food trade has led to enhanced savings in global water resources over time, indicating its growing efficiency in terms of global water use.ECH
Talesätt och talemaader: om ordförbindelser hos Dalin och Molbech
No full textIn this paper I present a study which contributes to the description of lexicographic
traditions in Sweden and Denmark. More exactly, the study concerns the treatment
of word combinations, which are followed by some kind of explanation, in two 19th
century monolingual dictionaries. The works are the Swedish dictionary Ordbok
öfver svenska språket (1850–55) by A. F. Dalin and the Danish dictionary Dansk
Ordbog (…) (1833) by C. Molbech. The focus is, among other things, on the frequencies
and types of word combinations that are represented in the data. Furthermore,
I consider in which entries the word combinations are found, and the position
of the expressions in the microstrucure of the articles. Moreover, I discuss the form
and meaning of the word combinations and, finally, the authors’ use of (signed)
examples
Modeling past and future structure of the global virtual water trade network
No full textClimate change and socio-economic development place an increasing pressure on essential natural resources, such as arable land and freshwater. The international food trade can save water globally by redistributing commodities produced relatively more water-efficiently. We focus on the global virtual water trade network associated with international staple food trade from 1986–2008. This study aims to determine which variables control the network's structure and temporal evolution, and to estimate changes in the network under future scenarios. Our fitness model reproduces both the topological and weighted characteristics of the network for the whole period. Undirected and directed network properties are well reproduced in each year, assuming as sole controls each nation's GDP, mean annual rainfall, agricultural area and population. The future structure of the network is estimated using climate and socio-economic projections, showing that volumes of virtual water traded will become increasingly heterogeneous and the importance of dominant importing nations will further strengthen
Water for food: The global virtual water trade network
No full textWe present a novel conceptual framework and methodology for studying virtual water trade. We utilize complex network theory to analyze the structure of the global virtual water trade associated with the international food trade. In the global virtual water trade network, the nations that participate in the international food trade correspond to the nodes, and the links represent the flows of virtual water associated with the trade of food from the country of export to the country of import. We find that the number of trade connections follows an exponential distribution, except for the case of import trade relationships, while the volume of water that each nation trades compares well with a stretched exponential distribution, indicating high heterogeneity of flows between nations. There is a power law relationship between the volume of virtual water traded and the number of trade connections of each nation. Highly connected nations are preferentially linked to poorly connected nations and exhibit low levels of clustering. However, when the volume of virtual water traded is taken into account, this structure breaks down. This indicates a global hierarchy, in which nations that trade large volumes of water are more likely to link to and cluster with other nations that trade large volumes of water, particularly when the direction of trade is considered. Nations that play a critical role in maintaining the global network architecture are highlighted. Our analysis provides the necessary framework for the development of a model of global virtual water trade aimed at applications ranging from network optimization to climate change impact evaluations.ECH
Structure and controls of the global virtual water trade network
No full textRecurrent or ephemeral water shortages are a crucial global challenge, in particular because of their impacts on food production. The global character of this challenge is reflected in the trade among nations of virtual water, i.e., the amount of water used to produce a given commodity. We build, analyze and model the network describing the transfer of virtual water between world nations for staple food products. We find that all the key features of the network are well described by a model that reproduces both the topological and weighted properties of the global virtual water trade network, by assuming as sole controls each country's gross domestic product and yearly rainfall on agricultural areas. We capture and quantitatively describe the high degree of globalization of water trade and show that a small group of nations play a key role in the connectivity of the network and in the global redistribution of virtual water. Finally, we illustrate examples of prediction of the structure of the network under future political, economic and climatic scenarios, suggesting that the crucial importance of the countries that trade large volumes of water will be strengthened
Plant diversity in grasslands and feed quality
No full textPlant diversity in complex grassland swards is structured in three levels of organization, i.e. plant functional groups, species within functional group and genotypes within each species. This structure of diversity has to be considered when analysing feed quality for the ruminants and trying to improve it. The paper will first review the relationship between species diversity, forage composition and feed value for the ruminant, both in permanent and temporary grasslands. Special attention will be drawn on the effect of specific composition, plant functional groups and agronomic practices. Nutrient use and interactions of major nutrients with secondary plant metabolites such as condensed tannins or phenol oxidase will be considered. In the second part, perspectives of forage composition improvement in a context of multi-species temporary grasslands will be analysed with a special focus on water soluble carbohydrate fraction and polyphenol oxidase which may reduce proteolysis and lipolysis and thus improve feed value. The possible interactions between macro and micro nutrients are discussed as they are relevant in grasslands with complex species composition. As a conclusion, main objectives for future research and breeding are identified and prospects offered by crop modelling are discussed
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