Modificación superficial de nanotubos de carbono mediante un plasma de CO2

En el presente trabajo se estudió la funcionalización de nanotubos de carbono de pared múltiple (NTCPM) con un plasma de CO2, donde se determinó el efecto del tiempo de tratamiento por plasma sobre las propiedades de los NTCPM. Para determinar el cambio en la hibridación de los NTCPM se utilizó espectroscopia Raman y espectroscopia de infrarrojo para identificar los grupos funcionales. Adicionalmente se determinó el ángulo de contacto y se hicieron dispersiones en agua para corroborar el cambio de polaridad de los NTCPM. Se encontró que a medida que se incrementa el tiempo de exposición al plasma de CO2, se observan dos incrementos, uno en la banda de infrarrojo de 1070 cm-1 asociada al grupo C-O y otro en la relación de intensidades D/G del espectro Raman asociado a la hibridación sp3, los cuales corroboran el injerto de oxígeno en la superficie de los NTCPM

Microwave irradiation versus conventional heating assisted free-radical copolymerization in solution

Microwave (MW) irradiation has arisen as a more sustainable alternative to conventional heating (CH) for chemical reactions because it provides non-contact, volumetric equal and fast heating. However, in free-radical polymerization, the MW effect is still quite controversial, probably due to the lack of reliable, comparable experimental data of both CH and MW assisted polymerization processes. In this work, taking advantage of technically superior MW reactor design, similar temperature profiles and conditions of CH and MW assisted polymerization reactions were enabled. Copolymerization of various monomer couples with different polarity and dielectric properties was studied in solution of different organic solvents in the presence of different initiators. As a result, it was concluded that the interaction of the reaction components with the MW irradiation is essential and will determine if any effect of MW irradiation on the reaction and products occurs. On the contrary to some reported studies, for the typical monomers used in free radical polymerization studied here (acrylates, methacrylates, styrene) no difference in reaction rates, copolymer composition and properties were observed between the MWH and CH processes, independently of the solvent and initiator used. However, in the case of the presence of an organometallic monomer within the monomer couple, an observable reaction rate enhancement was obtained under MW irradiation, along with changes in the reactivity ratios and differences in the copolymer composition. This effect is considered a specific microwave effect, for the first time demonstrated in free-radical solution polymerization process and was explained by the principles of selective heating of the organometallic reaction components in solution.The authors gratefully acknowledge the financial support by NATO (SfP project G4255), Spanish Government (CTQ2016-80886-R), and Basque Government (GV IT999-16). Bertha Pérez-Martínez acknowledges the PhD fellowship No. 410922 provided by The National Council of Science and Technology (CONACyT-México).Peer reviewe

Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications

Film forming, stable hybrid latexes made of methyl metacrylate (MMA), butyl acrylate (BA) and 2-hydroxyethyl methacrylate (HEMA) copolymer reinforced with modified multiwalled carbon nanotubes (MWCNTs) were synthesized by in situ miniemulsion polymerization. The MWCNTs were pretreated by an air sonication process and stabilized by polyvinylpyrrolidone. The presence of the MWCNTs had no significant effect on the polymerization kinetics, but strongly affected the polymer characteristics (Tg and insoluble polymer fraction). The performance of the in situ composites was compared with that of the neat polymer dispersion as well as with those of the polymer/MWCNT physical blends. The in situ composites showed the presence of an additional phase likely due to the strong interaction between the polymer and MWNCTs (including grafting) that reduced the mobility of the polymer chains. As a result, a substantial increase of both the storage and the loss moduli was achieved. At 60 °C, which is above the main transition region of the polymer, the in situ composites maintained the reinforcement, whereas the blends behaved as a liquid-like material. This suggests the formation of a 3D network, in good agreement with the high content of insoluble polymer in the in situ composites

A snapshot of antimicrobial resistance in Mexico. Results from 47 centers from 20 states during a six-month period.

AIM:We aimed to assess the resistance rates of antimicrobial-resistant, in bacterial pathogens of epidemiological importance in 47 Mexican centers. MATERIAL AND METHODS:In this retrospective study, we included a stratified sample of 47 centers, covering 20 Mexican states. Selected isolates considered as potential causatives of disease collected over a 6-month period were included. Laboratories employed their usual methods to perform microbiological studies. The results were deposited into a database and analyzed with the WHONET 5.6 software. RESULTS:In this 6-month study, a total of 22,943 strains were included. Regarding Gram-negatives, carbapenem resistance was detected in ≤ 3% in Escherichia coli, 12.5% in Klebsiella sp. and Enterobacter sp., and up to 40% in Pseudomonas aeruginosa; in the latter, the resistance rate for piperacillin-tazobactam (TZP) was as high as 19.1%. In Acinetobacter sp., resistance rates for cefepime, ciprofloxacin, meropenem, and TZP were higher than 50%. Regarding Gram-positives, methicillin resistance in Staphylococcus aureus (MRSA) was as high as 21.4%, and vancomycin (VAN) resistance reached up to 21% in Enterococcus faecium. Acinetobacter sp. presented the highest multidrug resistance (53%) followed by Klebsiella sp. (22.6%) and E. coli (19.4%). CONCLUSION:The multidrug resistance of Acinetobacter sp., Klebsiella sp. and E. coli and the carbapenem resistance in specific groups of enterobacteria deserve special attention in Mexico. Vancomycin-resistant enterococci (VRE) and MRSA are common in our hospitals. Our results present valuable information for the implementation of measures to control drug resistance

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

non present