3,186 research outputs found
Chemical nature, molecular structure, and formation mechanism of biochar: Molecular dynamics studies and experimental approach
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Past, present and future global influence and technological applications of iron-bearing metastable nanominerals
Iron-bearing nanominerals such as ferrihydrite, schwertmannite, and green rust behave as metastable precursors leading to the formation of more thermodynamically stable iron mineral phases (e.g., jarosite, goethite, hematite, and magnetite). However, this transformation may last from days to tens or even hundreds of years, making them the most predominant iron-bearing minerals at environmental conditions and at the human time scale. The present review characterizes ferrihydrite, schwertmannite, and green rust nanominerals according to their main physical and chemical properties, and at both nano- and meso-scales. It also presents a comprehensive review of the multiple past and present Earth environments where these nanominerals have played, and still play, a pivotal role in the geochemistry, mineralogy and environmental nanogeosciences of these environments. Finally, the present and future technological applications of these nanominerals as well as their role in the generation of a more sustainable human-Earth relationship is discussed, with a special emphasis on their use in new circular economies and green based technologies
The Hilbert space of Chern-Simons theory on the cylinder. A Loop Quantum Gravity approach
As a laboratory for loop quantum gravity, we consider the canonical
quantization of the three-dimensional Chern-Simons theory on a noncompact space
with the topology of a cylinder. Working within the loop quantization
formalism, we define at the quantum level the constraints appearing in the
canonical approach and completely solve them, thus constructing a gauge and
diffeomorphism invariant physical Hilbert space for the theory. This space
turns out to be infinite dimensional, but separable.Comment: Minor changes and some references added. Latex, 16 pages, 1 figur
Temperature Bias and the Primordial Helium Abundance Determination
We study the effect that the temperature structure has on the determination
of the primordial helium abundance, Yp. We provide an equation linking T(OIII),
the temperature derived from the [OIII] lines, and T(HeII), the temperature of
the He I lines, both for HII regions with O++ only and for HII regions where a
fraction of O+ is present. By means of T(HeII), which is always smaller than
T(OIII), we derive the helium abundances of 5 objects with low and very low
metallicity (NGC 346, NGC 2363, Haro29, SBS 0335-052, and I Zw 18); these
objects were selected from the literature because they include the 3 low
metallicity objects with the best line determinations and the 2 objects with
the lowest metallicity. From these abundances we obtain that
Yp(nHc)=0.2356+-0.0020, a value 0.0088 lower than that derived by using
T(OIII). We call this determination Yp(nHc) because the collisional
contribution to the Balmer line intensities has not been taken into account.
All the recent Yp determinations in the literature have not taken into account
the collisional contribution to the Balmer line intensities. By considering the
collisional contribution to the Balmer line intensities of these five objects
we derive that Yp(+Hc)=0.2384+-0.0025.Comment: 28 pages + 4 figures. Revised version, accepted for publication in
The Astrophysical Journa
Experimental study and calculation of the electron transfer coefficients on the dissolution behavior of chitosan in organic acids
Chitosan (CH) consists of water-insoluble N-acetylglucosamine and D-glucosamine molecules and has a higher solubility at a pH below six. This studyevaluated the solubility of chitosan in solutions of organic acids for the formation of films. HyperChemTMsoftware was used to perform the quantum analysis. In the experimental trials, the total soluble mass (TSM) and the viscosity of the solutions were measured by capillary viscometer. The chitosan filmswere made by the plate melting method, and the filmcharacteristics were evaluated. A quantum simulation suggested that lactic acid (LA) has a greater stability to react with chitosan. It was then verified experimentally that LA is a better solvent for chitosan due to the increase in its viscosity. The chemical interaction between CH and LA in solution favors the polymerization of films with better physical properties. We thereforeconclude that the uniformity in the formation of films of this polymer depends on the chemical interaction between the CH and the acid and not on the degree of solubility of the polymer
Challenges of poor surface water drainage and wastewater management in refugee camps
Since refugee camps are meant to be temporary and setting them up usually require urgency, little attention has been given to provision of surface water drainage and to a lesser extent wastewater management. As the population of refugees in these camps continues to grow, the effectiveness of drainage infrastructure continues to diminish. In addition, availability of sufficient safe drinking water and wastewater management have become difficult in the refugee camps across the world. The present situation in refugee camps across the world, such as flooding and outbreak of water-related diseases in South Sudan refugee camps, has made the need for sustainable approach to solving the problems to be very urgent. One sustainable way of solving the problems of flooding and outbreak of diseases in refugee camps is to provide effective drainage and wastewater infrastructure that ensures all the wastewater are properly collected, treated and reused for various purposes such as agriculture, drinking, laundry and other relevant uses. This paper therefore presents the current state of drainage and wastewater management in two refugee camps and propose low-cost technologies for stormwater management, wastewater collection, treatment and potential reuse, suitable for these refugee camps
High conductance values in p -folded molecular junctions
Folding processes play a crucial role in the development of function in biomacromolecules. Recreating this feature on synthetic systems would not only allow understanding and reproducing biological functions but also developing new functions. This has inspired the development of conformationally ordered synthetic oligomers known as foldamers. Herein, a new family of foldamers, consisting of an increasing number of anthracene units that adopt a folded sigmoidal conformation by a combination of intramolecular hydrogen bonds and aromatic interactions, is reported. Such folding process opens up an efficient through-space charge transport channel across the interacting anthracene moieties. In fact, single-molecule conductance measurements carried out on this series of foldamers, using the scanning tunnelling microscopy-based break-junction technique, reveal exceptionally high conductance values in the order of 10(-1) G(0) and a low length decay constant of 0.02 angstrom(-1) that exceed the values observed in molecular junctions that make use of through-space charge transport pathways.We thank Dr J.I. Miranda (University of the Basque Country) for assistance on NMR characterization. We are grateful to the Basque Science Foundation for Science (Ikerbasque), POLYMAT, the University of the Basque Country (SGIker and UFI11/23), the Deutsche Forschungsgemeinschaft (AU 373/3-1 and MA 5215/4-1), Gobierno de Espana (Ministerio de Economia y Competitividad CTQ2016-77970-R, CTQ2015-71936-REDT, CTQ2015-71406-ERC, CTQ2015-64579-C3-3P, CTQ-2014-54464-R and CTQ-2015-68148), Gobierno Vasco (BERC programme, Consolidated Groups IT520-10 and PC2015-1-01(06-37)), Diputacion Foral de Guipuzcoa (OF215/2016(ES)), CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/2013), ON2 (NORTE-07-0162-FEDER-000086) and the European Union (ERA Chemistry, Marie Curie Career Integration Grant No. 618247, and FET-Open (2D-INK) Grant No. 664878)
Bone morphogenetic protein 2 induces pulmonary angiogenesis via Wnt–β-catenin and Wnt–RhoA–Rac1 pathways
Mutations in bone morphogenetic protein (BMP) receptor II (BMPRII) are associated with pulmonary artery endothelial cell (PAEC) apoptosis and the loss of small vessels seen in idiopathic pulmonary arterial hypertension. Given the low penetrance of BMPRII mutations, abnormalities in other converging signaling pathways may be necessary for disease development. We hypothesized that BMPRII supports normal PAEC function by recruiting Wingless (Wnt) signaling pathways to promote proliferation, survival, and motility. In this study, we report that BMP-2, via BMPRII-mediated inhibition of GSK3-β, induces β-catenin (β-C) accumulation and transcriptional activity necessary for PAEC survival and proliferation. At the same time, BMP-2 mediates phosphorylated Smad1 (pSmad1) or, with loss of BMPRII, pSmad3-dependent recruitment of Disheveled (Dvl) to promote RhoA–Rac1 signaling necessary for motility. Finally, using an angiogenesis assay in severe combined immunodeficient mice, we demonstrate that both β-C– and Dvl-mediated RhoA–Rac1 activation are necessary for vascular growth in vivo. These findings suggest that the recruitment of both canonical and noncanonical Wnt pathways is required in BMP-2–mediated angiogenesis
Holography, Pade Approximants and Deconstruction
We investigate the relation between holographic calculations in 5D and the
Migdal approach to correlation functions in large N theories. The latter
employs Pade approximation to extrapolate short distance correlation functions
to large distances. We make the Migdal/5D relation more precise by quantifying
the correspondence between Pade approximation and the background and boundary
conditions in 5D. We also establish a connection between the Migdal approach
and the models of deconstructed dimensions.Comment: 28 page
Robotic manipulation for the shoe-packaging process
[EN] This paper presents the integration of a robotic system in a human-centered environment, as it can be found in the shoe manufacturing industry. Fashion footwear is nowadays mainly handcrafted due to the big amount of small production tasks. Therefore, the introduction of intelligent robotic systems in this industry may contribute to automate and improve the manual production steps, such us polishing, cleaning, packaging, and visual inspection. Due to the high complexity of the manual tasks in shoe production, cooperative robotic systems (which can work in collaboration with humans) are required. Thus, the focus of the robot lays on grasping, collision detection, and avoidance, as well as on considering the human intervention to supervise the work being performed. For this research, the robot has been equipped with a Kinect camera and a wrist force/ torque sensor so that it is able to detect human interaction and the dynamic environment in order to modify the robot¿s behavior. To illustrate the applicability of the proposed approach, this work presents the experimental results obtained for two actual platforms, which are located at different research laboratories, that share similarities in their morphology, sensor equipment and actuation system.This work has been partly supported by the Ministerio de Economia y Competitividad of the Spanish Government (Key No.: 0201603139 of Invest in Spain program and Grant No. RTC-2016-5408-6) and by the Deutscher Akademischer Austauschdienst (DAAD) of the German Government (Projekt-ID 54368155).Gracia Calandin, LI.; Perez-Vidal, C.; Mronga, D.; Paco, JD.; Azorin, J.; Gea, JD. (2017). Robotic manipulation for the shoe-packaging process. The International Journal of Advanced Manufacturing Technology. 92(1-4):1053-1067. https://doi.org/10.1007/s00170-017-0212-6S10531067921-4Pedrocchi N, Villagrossi E, Cenati C, Tosatti LM (2017) Design of fuzzy logic controller of industrial robot for roughing the uppers of fashion shoes. 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