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N-alkyl-substituted polyacrylamides exhibit a thermal coil-to-globule transition in aqueous solution driven by an increase in hydrophobic interactions with rising temperature. With the aim of understanding the role of N-alkyl substituents in the thermal transition, this study focuses on the molecular interactions underlying the phase transition of poly(N,N-diethylacrylamide-co-N-ethylacrylamide) random copolymers. Poly(N,N-diethylacrylamide) (PDEAm), poly(N-ethylacrylamide) (PNEAm), and their random copolymers were synthesized by free radical polymerization and their chemical structure characterized spectroscopically. It was found that the values of the cloud-point temperature increased with PNEAm content, and particle aggregation processes took place, increasing the negative charge density on their surface. The cloud-point temperature of each copolymer decreased with respect to the theoretical values calculated assuming an absence of interactions. It is attributed to the formation of intra- and interchain hydrogen bonding in aqueous solutions. These interactions favor the formation of more hydrophobic macromolecular segments, thereby promoting the cooperative nature of the transition. These results definitively reveal the dominant mechanism occurring during the phase transition in the aqueous solutions of these copolymers. [ABSTRACT FROM AUTHOR]

Data from morphology, linguistics, history, and archaeology have all been used to trace the dispersal of chickens from Asian domestication centers to their current global distribution. Each provides a unique perspective which can aid in the reconstruction of prehistory. This study expands on previous investigations by adding a temporal component from ancient DNA and, in some cases, direct dating of bones of individual chickens from a variety of sites in Europe, the Pacific, and the Americas. The results from the ancient DNA analyses of forty-eight archaeologically derived chicken bones provide support for archaeological hypotheses about the prehistoric human transport of chickens. Haplogroup E mtDNA signatures have been amplified from directly dated samples originating in Europe at 1000 B.P. and in the Pacific at 3000 B.P. indicating multiple prehistoric dispersals from a single Asian centre. These two dispersal pathways converged in the Americas where chickens were introduced both by Polynesians and later by Europeans. The results of this study also highlight the inappropriate application of the small stretch of D-loop, traditionally amplified for use in phylogenetic studies, to understanding discrete episodes of chicken translocation in the past. The results of this study lead to the proposal of four hypotheses which will require further scrutiny and rigorous future testing.

In a recent work (Castanon Quiroz & Di Pietro (2020) A hybrid high-order method for the incompressible Navier–Stokes problem robust for large irrotational body forces. Comput. Math. Appl. , 79 , 2655–2677), we have introduced a pressure-robust hybrid high-order method for the numerical solution of the incompressible Navier–Stokes equations on matching simplicial meshes. Pressure-robust methods are characterized by error estimates for the velocity that are fully independent of the pressure. A crucial question was left open in that work, namely whether the proposed construction could be extended to general polytopal meshes. In this paper, we provide a positive answer to this question. Specifically, we introduce a novel divergence-preserving velocity reconstruction that hinges on the solution inside each element of a mixed problem on a subtriangulation, then use it to design discretizations of the body force and convective terms that lead to pressure robustness. An in-depth theoretical study of the properties of this velocity reconstruction, and their reverberation on the scheme, is carried out for arbitrary polynomial degrees |$k\geq 0$| and meshes composed of general polytopes. The theoretical convergence estimates and the pressure robustness of the method are confirmed by an extensive panel of numerical examples. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chilena de Antropologia is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Given two n-vertex graphs G1 and G2 of bounded treewidth, is there an n-vertex graph G of bounded treewidth having subgraphs isomorphic to G1 and G2? Our main result is a negative answer to this question, in a strong sense: we show that the answer is no even if G1 is a binary tree and G2 is a ternary tree. We also provide an extensive study of cases where such "gluing"" is possible. In particular, we prove that if G1 has treewidth k and G2 has pathwidth \l, then there is an n-vertex graph of treewidth at most k + 3\l + 1 containing both G1 and G2 as subgraphs. [ABSTRACT FROM AUTHOR]

Natural cyclodextrins (CDs) can be formed by 6, 7, or 8 glucose molecules (α-, β-, and γ-, respectively) linked in a ring, creating a cone shape. Its interior has an affinity for hydrophobic molecules, while the exterior is hydrophilic and can interact with water molecules. This feature has been used to develop active packaging applied to food, interacting with the product or its environment to improve one or more aspects of its quality or safety. It also provides monitoring information when food is optimal for consumption, as intelligent packaging is essential for the consumer and the merchant. Therefore, this review will focus on discerning which packaging is most appropriate for each situation, solubility and toxicological considerations, characterization techniques, effect on the guest properties, and other aspects related to forming the inclusion complex with bioactive molecules applied to packaging. [ABSTRACT FROM AUTHOR]

To develop N-(levodopa) chitosan derivatives through click chemistry to study their effect in brain cells. Significance: This study presents a proof-of-concept that macromolecules such as N-(Levodopa) chitosan derivatives traverse brain cell membranes and induce biomedical functionalities. Through click chemistry, we developed N-(levodopa) chitosan derivatives. They were physically and chemically characterized by FT-IR, 1H-NMR, TGA and Dynamic Light Scattering analyses. Solution and nanoparticles of N-(levodopa) chitosan derivatives were tested in primary cell cultures from the postnatal rat olfactory bulb, substantia nigra and corpus callosum. Ca2+ imaging and UPLC experiments were used to investigate if the biomaterial modulated the brain cell physiology. N-(levodopa) chitosan derivatives induced intracellular Ca2+ responses in primary cell cultures of the rat brain. UPLC experiments indicated that levodopa attached to chitosan was converted into dopamine by brain cells. The present study shows that N-(levodopa) chitosan may be useful to develop new treatment strategies, which could serve as molecular reservoirs of biomedical drugs to treat degenerative disorders of the nervous system. Parkinson's disease is a neurodegenerative disorder currently leading to several disabilities worldwide. We addressed this, by developing N-(levodopa) chitosan derivatives through green click chemistry to study their capabilities as dopamine precursors for brain cells. Interestingly, we found that in primary cell cultures and brain tissue of the postnatal rat, these chitosan derivatives (solution & nanoparticles) were homogeneously distributed inside of cells' membranes associated with intracellular Ca2+ responses. Therefore, N-(levodopa) chitosan may be useful as molecular reservoir of drugs to treat degenerative disorders of the nervous system. [ABSTRACT FROM AUTHOR]

In this work, we design and analyse a Hybrid High-Order (HHO) discretization method for incompressible flows of non-Newtonian fluids with power-like convective behaviour. We work under general assumptions on the viscosity and convection laws, which are associated with possibly different Sobolev exponents |$r\in (1,\infty)$| and |$s\in (1,\infty)$|⁠. After providing a novel weak formulation of the continuous problem, we study its well-posedness highlighting how a subtle interplay between the exponents |$r$| and |$s$| determines the existence and uniqueness of a solution. We next design an HHO scheme based on this weak formulation, and perform a comprehensive stability and convergence analysis, including convergence for general data and error estimates for shear-thinning fluids and small data. The HHO scheme is validated on a complete panel of model problems. [ABSTRACT FROM AUTHOR]

This paper focuses on the numerical simulation of geothermal systems in complex geological settings. The physical model is based on two-phase Darcy flows coupling the mass conservation of the water component with the energy conservation and the liquid-vapor thermo dynamical equilibrium. The discretization exploits the flexibility of unstructured meshes to model complex geology including conductive faults as well as complex wells. The polytopal and essentially nodal Vertex Approximate Gradient scheme is used for the approximation of the Darcy and Fourier fluxes combined with a Control Volume approach for the transport of mass and energy. Particular attention is paid to the faults which are modelled as two-dimensional interfaces defined as a collection of faces of the mesh and to the flow inside deviated or multi-branch wells defined as a collection of edges of the mesh with rooted tree data structure. By using an explicit pressure drop calculation, the well model reduces to a single equation based on complementarity constraints and only one well unknown, the bottom hole pressure, implicitly coupled to the reservoir unknowns. The coupled systems are solved at each time step using efficient nonlinear and linear solvers on parallel distributed architectures. The convergence of the discrete model is investigated numerically on a simple test case with a Cartesian geometry and a single vertical producer well. Then, the ability of our approach to deal efficiently with realistic test cases is assessed on a high energy faulted geothermal reservoir operated using a doublet of two deviated wells. [ABSTRACT FROM AUTHOR]

The avocado seeds, considered as waste, were used for the extraction of oil rich in pentosans and starch. The avocado starch (AS) and a commercial starch (CS) are then used for the formation of polymeric films by casting. Avocado oil (AO, as natural crosslinker) and ethylene glycol (EG) are utilized as crosslinkers to modify the properties of the films. All polymeric structures are characterized by physical inspection, FTIR, TGA‐DSC, and water‐insoluble fraction. The results indicate that the incorporation of AO and EG augments the thermal stability by decreasing the degradation rates compared to that of the unmodified AS and CS polymeric films. In addition, the degradation temperature of the polymeric films is modified by the addition of crosslinkers. The degradation temperature of AS, AS‐AO, AS‐EG, were 300, 286, and 306°C, accordingly, whereas those for CS films are 314, 314.5, and 307.7°C for CS, CS‐AO, and CS‐EG, respectively. Our study demonstrates that natural wastes could be useful and increase the profits of the avocado processing industries. [ABSTRACT FROM AUTHOR]

In this paper, we design and analyze a Hybrid High-Order discretization method for the steady motion of non-Newtonian, incompressible fluids in the Stokes approximation of small velocities. The proposed method has several appealing features including the support of general meshes and high-order, unconditional inf-sup stability, and orders of convergence that match those obtained for scalar Leray–Lions problems. A complete well-posedness and convergence analysis of the method is carried out under new, general assumptions on the strain rate-shear stress law, which encompass several common examples such as the power-law and Carreau–Yasuda models. Numerical examples complete the exposition. [ABSTRACT FROM AUTHOR]

We develop a novel Hybrid High-Order method for the incompressible Navier–Stokes problem robust for large irrotational body forces. The key ingredients of the method are discrete versions of the body force and convective contributions in the momentum equation formulated in terms of a globally divergence-free velocity reconstruction. Two key properties are mimicked at the discrete level, namely the invariance of the velocity with respect to irrotational body forces and the non-dissipativity of the convective term. A full convergence analysis is carried out, showing optimal orders of convergence under a smallness condition involving only the solenoidal part of the body force. The performance of the method is illustrated by a complete panel of numerical tests, including comparisons that highlight the benefits with respect to more standard formulations. [ABSTRACT FROM AUTHOR]

Copyright of Bosque (03048799) is the property of Facultad de Ciencias Forestales, Universidad Austral de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chilena de Antropologia is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Conformational changes of the thermal transitions of chitosan- graft-poly( N-vinylcaprolactam) copolymers in aqueous solution were studied by varying of the length of the grafted poly( N-vinylcaprolactam) (PVCL) chains, as well as the ionic strength and the pH of the solution. The conformational properties of the copolymer were monitored by means of dynamic light scattering and ζ-potential measurements. A series of copolymers with defined molecular architecture were synthesized. Obtained results point out that hydrophobic hydration plays a crucial role on the solubility of this copolymer at neutral and slightly alkaline solutions. The evolution of the size of macromolecular aggregates indicates that, in the coil state, there is a monomodal distribution, passing through a bimodal distribution in the pre-transition region, just before the phase separation. The role of the charge of the copolymers on the cooperative transition is also analyzed. The phase transition of these amphiphilic copolymers shows a strong dependence on the ionic strength of the solution. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chilena de Antropologia is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A series of thermoresponsive copolymers based on chitosan- g -poly( N -vinylcaprolactam) were synthesized by amidation reaction using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride as coupling reagent. The effect of molecular architecture on the thermoresponsive properties of the graft copolymers solutions was studied by varying the chain length of the grafted poly( N -vinylcaprolactam), PVCL, (in the range from 4 to 26 kDa) and the spacing between grafted chains onto the chitosan backbone. The most interesting characteristic of these copolymers is their solubility in water at temperatures below their lower critical solution temperature (LCST). These solutions presented a LCST between 36 and 44 °C, which decreases with the spacing and length of grafted PVCL chains onto the chitosan backbone, in contrast with the limited decrease of the LCST of PVCL above a critical M ¯ n value around 18 kDa. This behavior offers tangible possibilities for the preparation and application of sensitive bioactive formulations and “smart” drug delivery systems. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chilena de Antropologia is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)