Landau’s description of the excitations in a macroscopic system in terms of quasiparticles stands out as one of the highlights in quantum physics. It provides an accurate description of otherwise ...prohibitively complex many-body systems and has led to the development of several key technologies. In this paper, we investigate theoretically the Landau effective interaction between quasiparticles, so-called Bose polarons, formed by impurity particles immersed in a Bose-Einstein condensate (BEC). In the limit of weak interactions between the impurities and the BEC, we derive rigorous results for the effective interaction. They show that it can be strong even for a weak impurity-boson interaction, if the transferred momentum-energy between the quasiparticles is resonant with a sound mode in the BEC. We then develop a diagrammatic scheme to calculate the effective interaction for arbitrary coupling strengths, which recovers the correct weak-coupling results. Using this scheme, we show that the Landau effective interaction, in general, is significantly stronger than that between quasiparticles in a Fermi gas, mainly because a BEC is more compressible than a Fermi gas. The interaction is particularly large near the unitarity limit of the impurity-boson scattering or when the quasiparticle momentum is close to the threshold for momentum relaxation in the BEC. Finally, we show how the Landau effective interaction leads to a sizable shift of the quasiparticle energy with an increasing impurity concentration, which should be detectable with present-day experimental techniques.
A facile bottom–up “green” synthetic route using green tea (
Camellia sinensis) extract as reducing and stabilizing agent produced gold nanoparticles and silver nanostructures in aqueous solution at ...ambient conditions. Colloidal systems of silver and gold nanoparticles exhibit highly efficient single photon-induced luminescence. This optical response can be manipulated by changing concentrations of metal ions and the quantity of reducing agent, which plays a crucial role in formation, growth and luminescence response of these noble-metal nanostructures.
Based on colony spreading, chitosan from shrimp waste in agar media inhibited the growth of
Aspergillus niger by 47.26%; there were not differences (
P
>
0.05) with respect to commercial chitosan ...(Fluka, BioChemika) (56.16%). All chitosan films showed similar glass transition temperatures (
P
>
0.05) with respect to cellophane control; however, chemically, all chitosan films showed an increase in the
T
g values that could be related with the decrease (
P
≤
0.05) in elongation percentage with respect to the control film. According to FT-IR spectroscopic analysis of chitosan films, the fungistatic activity can be related to the hydrogen bonds’ formation between the amino groups of chitosan with the hydroxyl groups from polymer or sorbitol. The plasticizer addition increased (
P
≤
0.05) the elongation of chitosan films. The Young's module,
E, was lower (
P
≤
0.05) for all chitosan films comparing with cellophane. When incorporated into the composite films elaborated by casting, chitosan retained its fungistatic activity. Even though the activity against fungi growth was lower (15.66% for non-plasticized silage chitosan films, pC
S), a reduction (
P
≤
0.05) in the hyphae diameter of
A. niger was observed. Results suggest that it is feasible to elaborate antifungal chitosan films, with good thermal stability and acceptable mechanical properties for food packaging.
Thioamides are useful biophysical probes for the study of peptide structure and folding. The α-C stereochemistry of thioamide amino acids, however, is easily epimerized during solid-phase peptide ...synthesis (SPPS), which limits the sequence space that is available to thioamide incorporation. This work demonstrates that the α-C stereochemistry of thioamides can be reversibly protected in a manner that is compatible with the standard methodology of SPPS to enable the facile implementation of thioamide probes.
The relationship between culture, creativity and sustainable development has been placed on the agenda of institutions that promote human development and sustainability at an international level, ...such as The United Nations Program for the Environment, Sustainable Development Goals of the UN, UNESCO's Creative Cities Network. Therefore, it is worth investigating how this approach is being implemented in the development strategies of cities in Chile. First, this article presents the result of the review of national development policies in the field of culture, the environment and urban development, to identify how it is approached the relationship between culture and sustainable urban development. In the second place, it presents case studies of cities that have implemented culture and creativity in their local development strategies, with positive results in some of the four variables of sustainable development: culture, social development, environment and economic development. In conclusion, it can be identified that although the link between culture and sustainability is beginning to be present in the guiding instruments of public policies for the development of cities, this is not an approach incorporated in most of them, contrasting with the importance of the link between culture and sustainable development in the practice of civil society organizations and municipalities.
Despite possessing a high theoretical capacity, MnS has a rather complex lithium kinetic diffusion and poor mechanical stability that hinders its application in energy storage devices like ...lithium-ion batteries. This study is focused on overcoming the drawbacks of MnS anode material by assembling a carbon-constraint MnS nanocomposite in a core-shell configuration. This structure is obtained by a simple route involving DC plasma evaporation of Mn@C nanoparticles and posterior thermal sulfurization process. As anode material in a Li-ion battery, MnS@C-300 attains high specific capacity of 890 mAh g−1 after 500 cycles at 500 mA g−1. It also shows remarkable high rate capability with capacity values of 705, 684, 643, 578, and 495 mAh g−1 at current densities of 100, 200, 500, 1000, and 2000 mA g−1, respectively. This exceptional electrochemical response is endorsed to the synergetic effect of the smart design of a core-shell architecture. The carbonaceous shell enhances the lithium-ion diffusion towards the active MnS core and preserves structural stability during the long cycling process.
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•Simple plasma evaporation and sulfuration are used to produce MnS@C nanocomposites.•Carbon constraint avoids the sintering of MnS nanoparticles during synthesis.•Core-shell structure provides outstanding stability and lithium storage properties.•High capacitive contribution generates excellent high-rate capability results.
Amidines are a structural surrogate for peptide bonds, yet have received considerably little attention in peptides due to limitations in existing methods to access them. The synthetic strategy ...developed in this study represents the first robust and general procedure for the introduction of amidines into the peptide backbone. We exploit and further develop the utility and efficiency of thioimidate protecting groups as a means to side-step reactivity that ultimately renders existing methods unsuitable for the installation of amidines along the main-chain of peptides. This work is significant because it describes a generally applicable path to access unexplored peptide designs and architectures for new therapeutics made possible by the unique properties of amidines.
Cytosolic mRNA translation is subject to global and mRNA-specific controls. Phosphorylation of the translation initiation factor eIF2α anchors a reversible regulatory switch that represses cytosolic ...translation globally. The stress-responsive GCN2 kinase is the only known kinase for eIF2α serine 56 in Arabidopsis (
). Here, we show that conditions that generate reactive oxygen species (ROS) in the chloroplast, including dark-light transitions, high light, and the herbicide methyl viologen, rapidly activated GCN2 kinase, whereas mitochondrial and endoplasmic reticulum stress did not. GCN2 activation was light dependent and mitigated by photosynthesis inhibitors and ROS quenchers. Accordingly, the seedling growth of multiple Arabidopsis
mutants was retarded under excess light conditions, implicating the GCN2-eIF2α pathway in responses to light and associated ROS. Once activated, GCN2 kinase preferentially suppressed the ribosome loading of mRNAs for functions such as mitochondrial ATP synthesis, the chloroplast thylakoids, vesicle trafficking, and translation. The
mutant overaccumulated transcripts functionally related to abiotic stress, including oxidative stress, as well as innate immune responses. Accordingly,
displayed defects in immune priming by the fungal elicitor, chitin. Therefore, we provide evidence that reactive oxygen species produced by the photosynthetic apparatus help activate the highly conserved GCN2 kinase, leading to eIF2α phosphorylation and thus affecting the status of the cytosolic protein synthesis apparatus.
Biogas production from animal manure produced in farms in the Canary Islands may represent an additional energy source for producing heat and/or electricity. Data of different animal farms ...distributed all around the islands were used for evaluating the potential biogas generation and contribution to the production of renewable energy in the Canary Islands. Total manure production is 495,622 tons per year. Results show that animal manure as a source of biogas may be associated with an overall biogas potential of 27.1 Mm3 year−1 with an equivalent installed power capacity of 6.8 MWe. Considering 0.5 t day−1 manure as the lowest limit for implementing biogas projects, 546 farms raising different animal types (poultry, sheep, swine, cows or goats) have potential for producing and using their own biogas for generating heat and/or electricity with electrical powers ranging from 3 to 185 kWe. Potential GHG emissions savings due to the production of biogas from animal manure could reach yearly 55,745.1 tons of carbon dioxide equivalents, including both substitution of fossil fuels and appropriate management of animal manure.
The application of appropriate policies described in this study should contribute to overcome main challenges identified for the development of the biogas industry in the Canary Islands, which are related to the small size of the livestock holdings, the lack of a culture of association in the livestock sector and the lack of specific subsidies for biogas production. This study could be used as a basis for further studies in other European outermost regions with similar characteristics to the Canary Islands, such as Madeira and Azores.
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•Manure production on the Canary Islands amounts to 495,622 t year−1.•Potential biogas production is 27.1 millions of m3 year−1.•Biogas potential can contribute up to 14.6 toe year−1 and 6.8 MWe.•Potential electricity is 0.68% and 8.56% of total and renewable electricity of 2016.•Potential GHG emissions savings could reach 55,745.1 tCO2e year−1.
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