Shell-crosslinked nanoparticles through self-assembly of thermoresponsive block copolymers by RAFT polymerization

A reversible addition-fragmentation chain transfer (RAFT) agent, the methyl-2-(n-butyltrithiocarbonyl)propanoate (MBTTCP) has shown to be efficient in controlling the polymerization of N,N-dimethylacrylamide (DMA), N-isopropylacrylamide (NIPAM) and N-acryloyloxysuccinimide (NAS). Two different strategies have been studied to synthesize block copolymers based on one PNIPAN block and the other a random copolymer of DMA and NAS. When a PNIPAM trithiocarbonate-terminated is used as macromolecular chain transfer agent for the polymerization of a mixture of NAS and DMA, well-defined P(NIPAM-b-(NAS-co-DMA)) block copolymers were obtained with a low polydispersity index. These thermoresponsive block copolymers dissolved in aqueous solution at 25 °C and self-assembled into micelles when the temperature was raised above the LCST of the PNIPAM block. The micelle shell containing NAS units was further crosslinked using a primary diamine in order to get shell-crosslinked nanoparticles. Upon cooling below the LCST of PNIPAM this structure may easily reorganize to form nanoparticles with a water filled hydrophilic core.     

A receding horizon control approach for integrated vector management of Aedes aegypti using chemical and biological control: A mono and a multiobjective approach

This paper addresses an integrated vector management (IVM) approach for combating Aedes aegypti, the transmission vector of dengue, zika, and chikungunya diseases, some of the most important viral epidemics worldwide. In order to tackle this problem, a receding horizon control (RHC) strategy is adopted, considering a mono-objective and a multiobjective version of the optimal control model of combating the mosquito using chemical and biological control. RHC is essentially a suboptimal scheme of classical optimal control strategies considering discrete-time approximations. The integrated vector control actions used in this work consist in applying insecticides and inserting sterile males produced by irradiation in the population of mosquitoes. The cost function is defined in terms of social and economic costs, in order to quantify the effectiveness of the proposed epidemiological control throughout a time window of 4 months. Numerical simulations show that the obtained results are better than those from the optimal control strategies found in literature. Furthermore, through the application of the multiobjetive approach, varying the scenarios in the mono-objective formulation is no longer necessary and a set of optimal strategies can be obtained at once. Finally, in order to help health authorities in the choice of the best solution of the Pareto-optimal set to be implemented in practice, a cost-effectiveness analysis is performed and a strategy representing the most cost-effective control policy is obtained.     

Optimization of the Acid Cleavage of Proanthocyanidins and Other Polyphenols Extracted from Plant Matrices

The chemical mechanism of the acid cleavage of proanthocyanidins (PAs) has been known for decades but has yet to be optimized. Therefore, we optimized this process in Byrsonima crassifolia, Euterpe oleracea and Inga edulis extracts using the response surface methodology and assessed the effect of hydrochloric acid concentration (0.3–3.7 N), time (39–291 min), and temperature (56–98 °C) on the following response variables: PAs reduction, astringency reduction, antioxidant capacity/total polyphenols (TEAC/TP) ratio, and cyanidin content. The response variables were maximized when cleavage was performed with 3 N HCl at 88 °C for 165 min. Under these conditions, the mean PAs value and astringency in the three extracts decreased by 91% and 75%, respectively, the TEAC/TP ratio remained unchanged after treatment (p > 0.05), and the increase in cyanidin confirmed the occurrence of cleavage. Thus, the results suggest that acid cleavage efficiently minimizes undesirable technological PAs characteristics, expanding the industrial applications.     

Reply to the J. Provis and S.A. Bernal comment about the article “Structural characterization of geomaterial foams. Thermal behavior” published in J. Non-Cryst. Solids, 2011

In this paper, we discuss the alternative interpretation of NMR spectra from (i) “Structural characterization of geomaterial foams—Thermal behavior” by Prud'homme et al. published in Journal of Non-Crystalline Solid, 2011, and from (ii) the reply proposed by J. Provis and S.A. Bernal in this journal. In this contribution, other alternatives for the NMR bands assignment are discussed and compared with infrared spectroscopy and thermo-gravimetric results since closed relationship between NMR-IR-TG is effective. In agreement with these authors, the analysis of prepared foams requires additional work addressed to detect the presence of two phases with different tetrahedral condensation. Relative arrangement of these two phases could affect in a significant way the physical chemical properties of prepared foams.     

Phytochemical Profile and Herbicidal (Phytotoxic), Antioxidants Potential of Essential Oils from Calycolpus goetheanus (Myrtaceae) Specimens,and in Silico Study

The essential oil (EO) of Calycolpus goetheanus (Myrtaceae) specimens (A, B, and C) were obtained through hydrodistillation. The analysis of the chemical composition of the EOs was by gas chromatography coupled with mass spectrometry CG-MS, and gas chromatography coupled with a flame ionization detector CG-FID. The phytotoxic activity of those EOs was evaluated against two weed species from common pasture areas in the Amazon region: Mimosa pudica L. and Senna obtusifolia (L.) The antioxidant capacity of the EOs was determined by (DPPH^•) and (ABTS^•+). Using molecular docking, we evaluated the interaction mode of the major EO compounds with the molecular binding protein 4-hydroxyphenylpyruvate dioxygenase (HPPD). The EO of specimen A was characterized by β-eudesmol (22.83%), (E)-caryophyllene (14.61%), and γ-eudesmol (13.87%), while compounds 1,8-cineole (8.64%), (E)-caryophyllene (5.86%), δ-cadinene (5.78%), and palustrol (4.97%) characterize the chemical profile of specimen B’s EOs, and specimen C had α-cadinol (9.03%), δ-cadinene (8.01%), and (E)-caryophyllene (6.74%) as the majority. The phytotoxic potential of the EOs was observed in the receptor species M. pudica with percentages of inhibition of 30%, and 33.33% for specimens B and C, respectively. The EOs’ antioxidant in DPPH^• was 0.79 ± 0.08 and 0.83 ± 0.02 mM for specimens A and B, respectively. In the TEAC, was 0.07 ± 0.02 mM for specimen A and 0.12 ± 0.06 mM for specimen B. In the results of the in silico study, we observed that the van der Waals and hydrophobic interactions of the alkyl and pi-alkyl types were the main interactions responsible for the formation of the receptor–ligand complex.     

The hydroboration-oxidation of the isomeric trimethylsilylcyclo- hexenes and the isomeric trimethylsilylcyclopentenes.

The isomeric trimethylsilyl substituted cyclohexenes, 1-trimethylsilylcyclohexene, 3-trimethylsilylcyclohexene, and 4-trimethylsilylcyclohexene and the analogous trimethylsilyl substituted cyclopentenes, 1-trimethylsilylcyclopentene, 3-trimethylsilylcyclopentene and 4-trimethylsilylcyclopentene have been hydroborated and oxidized under kinetic and thermodynamic conditions. The hydroborating agents used were borane and thexylborane in THF. The products of these reactions show a dependence on temperature and the hydroborating agent used and are a result of a rather facile migration of the boron atom around the ring. Some synthetically useful reactions are discussed as are the structures of various trimethylsilyl substituted cyclohexanols and cyclopentanols.     

Exploring the first-shell and second-shell structures arising in the microsolvation of Li+ by rare gases

An evolutionary algorithm was used to search for the low-energy structures of Li⁺Ar_n and Li⁺Kr_n (n = 1 − 14). Two functions were used to describe the interaction potential at the CCSD(T)/aug-cc-pVQZ level of theory: one is based on a sum of all pair potentials, whereas the other includes three-body interactions. In general, the global minimum structures are similar for both Li⁺Ar_n and Li⁺Kr_n. Modifications in the octahedral structure of the first solvation shell lead to a high-energy penalty. Conversely, the second solvation shell shows a panoply of minima with similar energies that are likely to be interconverted. Post-optimization at the MP2 level confirmed that, for n = 2 and 3, one has to include three-body terms in the potential to reproduce the low-energy structures. Additionally, MP2 calculations indicate that energy reorder of the global minimum structure observed for Li⁺Kr₈ is related to the Kr₃ Axilrod-Teller-Muto term included in the potential.     

Implementing quantum gates on oriented optical isomers

Optical enantiomers are proposed to encode molecular two-qubit information processing. Using sequences of pairs of nonresonant optimally polarized pulses, different schemes to implement quantum gates, and to prepare entangled states, are described. We discuss the role of the entanglement phase and the robustness of the pulse sequences which depend on the area theorem. Finally, possible scenarios to generalize the schemes to n-qubit systems are suggested.     

Activation of methane by the iron dimer cation. A theoretical study

A detailed investigation of the reaction mechanisms underlying the observed reactivity of the iron dimer cation with respect to methane has been performed by density functional hybrid (B3LYP) and nonhybrid (BPW91) calculations. Minima and transition states have been fully optimized and characterized along the potential energy surfaces leading to three different exit channels for both the ground and the first excited states of the dimer. A comparison with our previous work covering the reactivity of the Fe(+) monomer was made to underline similarities and differences of the reaction mechanisms. Results show that geometric arrangements corresponding to bridged positions of the ligands with respect to iron atoms are always favored and stabilize intermediates, transition states and products, facilitating their formation. Binding energies of reaction products have been computed and compared with experimental measurements, and ELF analysis of the bond has been performed to rationalize trends as a function of the structure.     

Upper bounds to atomic electron densities in position and momentum spaces

Modified functions r ^–(r) and p ^–(p) of the spherically averaged electron densities (r) in position space and (p) in momentum space are found to be convex (i.e., the second derivatives are nonnegative everywhere) for all the 103 ground-state atoms from hydrogen (atomic number Z=1) to lawrencium (Z=103), if the parameters are chosen to be 0.6 and 1.4. The convex property of r ^–(r) and p ^–(p) is used to derive upper bounds to the density functions (r) and (p) in terms of their radial moments r ^s and p ^s or frequency moments ^t and ^t . In most cases, the present bounds are shown to be more general and more accurate than those reported in the literature.