Harnessing Greenhouse Gases Absorption by Doped Fullerenes with Externally Oriented Electric Field

In this work, a theoretical investigation of the effects caused by the doping of C₂₀ with silicon (Si) atom as well as the adsorption of CO, CO₂ and N₂ gases to C₂₀ and C₁₉Si fullerenes was carried out. In concordance with previous studies, it was found that the choice of the doping site can control the structural, electronic, and energetic characteristics of the C₁₉Si system. The ability of C₂₀ and C₁₉Si to adsorb CO, CO₂ and N₂ gas molecules was evaluated. In order to modulate the process of adsorption of these chemical species to C₁₉Si, an externally oriented electric field was included in the theoretical calculations. It was observed that C₁₉Si is highly selective with respect to CO adsorption. Upon the increase of the electric field intensity the adsorption energy was magnified correspondingly and that the interaction between CO and C₁₉Si changes in nature from a physical adsorption to a partial covalent character interaction.     

Visibility Graph Analysis of Reservoir-Triggered Seismicity: The Case of Song Tranh 2 Hydropower,Vietnam

In this study, the visibility graph analysis of seismicity triggered by Song Tranh 2 hydropower (Vietnam) is performed. The relationship between the seismic (the Gutenberg–Richter b-value) and topological (the k–M slope) parameters of seismicity is analysed. Our findings indicate that the relationship between the Gutenberg–Richter b-value and the k–M slope of the investigated seismicity is in agreement with that characterising the tectonic seismicity. The results obtained from analysing the reservoir-triggered seismicity of Song Tranh 2 area could contribute to better characterisation of the relationship between the seismological and topological parameters of seismicity, strengthening the universal character of the relationship between the b-value and the k–M slope.     

Duguetia pycnastera Sandwith (Annonaceae) Leaf Essential Oil Inhibits HepG2 Cell Growth In Vitro and In Vivo

Duguetia pycnastera Sandwith (Annonaceae) is a tropical tree that can be found in the Guyanas, Bolivia, Venezuela, and Brazil. In Brazil, it is popularly known as “ata”, “envira”, “envira-preta”, and “envira-surucucu”. In the present work, we investigated the in vitro and in vivo HepG2 cell growth inhibition capacity of D. pycnastera leaf essential oil (EO). The chemical composition of the EO was determined by GC–MS and GC–FID analyses. The alamar blue assay was used to examine the in vitro cytotoxicity of EO in cancer cell lines and non-cancerous cells. In EO-treated HepG2 cells, DNA fragmentation was measured by flow cytometry. The in vivo antitumor activity of the EO was assessed in C.B-17 SCID mice xenografted with HepG2 cells treated with the EO at a dosage of 40 mg/kg. Chemical composition analysis displayed the sesquiterpenes α-gurjunene (26.83%), bicyclogermacrene (24.90%), germacrene D (15.35%), and spathulenol (12.97%) as the main EO constituents. The EO exhibited cytotoxicity, with IC₅₀ values ranging from 3.28 to 39.39 μg/mL in the cancer cell lines SCC4 and CAL27, respectively. The cytotoxic activity of the EO in non-cancerous cells revealed IC₅₀ values of 16.57, 21.28, and >50 μg/mL for MRC-5, PBMC, and BJ cells, respectively. An increase of the fragmented DNA content was observed in EO-treated HepG2 cells. In vivo, EO displayed tumor mass inhibition activity by 47.76%. These findings imply that D. pycnastera leaf EO may have anti-liver cancer properties.     

Visible-Light Promoted Intramolecular para-Cycloadditions on Simple Aromatics

Dearomative cycloadditions are a powerful tool to access a large chemical space exploiting simple and ubiquitous building blocks. The energetic burden due to the loss of aromaticity has however greatly limited their synthetic potential. We devised a general intramolecular method that overcomes these limitations thanks to the photosensitization of allenamides. The visible-light-promoted process gives complex [2.2.2]-(hetero)-bicyclooctadienes at room temperature, likely through the stabilization of transient (bi)radicals by naphthalene. The reaction tolerates several valuable functionalities, offering a convenient handle for a myriad of applications, including original isoindoles and metal complexes.     

Flame surface modification of polyethylene sheets

High density polyethylene sheets 2 mm thick were flame treated to modify the surface properties. Sheets treated using a flame with air to gas (methane) ratio ∼ 10:1 at different distances between the inner cone tip of the flame and the polymer surface were investigated. Grafting of selected monomers as maleic anhydride, acrylamide and glycidyl methacrylate was attempted by flame treatment of sheets covered with a monomer layer. Good grafting results were obtained with acrylamide and maleic anhydride. The surface temperature-time dependence during the flame treatment was measured with a high resolution thermocouple. Scanning Electron Microscopy (SEM) allowed evidencing a modified thickness of about 120 μ. The chemical surface modification was studied by X ray Photoelectron Spectroscopy (XPS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT). The hydroxyl, carbonyl and carboxyl content was measured after derivatization with reagents containing an elemental tag to facilitate XPS analysis of surface functional groups. In comparison to the untreated polyethylene, wetting tension and contact angle of the flamed materials showed a strong variation. This variation was almost independent of the distance between the flame and the polymer surface. Adhesion between treated polyethylene and a polyurethane adhesive was determined using T-peel test measurements. High adhesion levels were found with flame treated polyethylene at 5 mm distance. XPS results indicate that when adhesion is high, the hydroxyl is in excess compared to the other measured functions, i.e. carbonyl and carboxyl species.     

Molecular dynamics simulation of semirigid polymers

The chain rigidity of poly(p-hydroxybenzoate) was estimated through the theoretical evaluation of its persistence length (L_p). A non-Brownian molecular dynamics (MD) simulation of an isolated chain with 20 monomeric units was performed. The sampled conformational population was analyzed and the orientational correlation function between monomeric units along the chain was calculated. An algorithm based on the worm-like chain model was applied to evaluate the persistence length. The results were compared with those obtained from equilibrium models like the freely-rotating-chain and the rotational-matrix method with fluctuations. Equilibrium models give different results depending on the degree of accuracy used in describing the monomeric unit. The inclusion of thermal fluctuations is crucial to obtain realistic results. These coincide with those given by MD simulation when only nearest-neighbour orientational correlations are taken into account: inclusion of higher-order correlation terms leads to lower values of the persistence length. The origin of this discrepancy was investigated. The MD simulation results are characterized by an overrepresentation of conformations with a short end-to-end distance resulting from an anomalous energy concentration in the first bending mode of the chain. In analogy with previous simulation results from systems characterized by a week coupling amoung their degrees of freedom, failure in the energy equipartition is proposed as a likely explanation of the anomalous dynamical behaviour.