Colloidal stability of graphene in aqueous medium: a theoretical approach through molecular dynamics.

CONTEXT: Graphene has been used as reinforcement of polymeric nanocomposites to increase mechanical and electrical properties. Recently, graphene suspensions have been used for the development of nanofluids in automotive applications, where improvements in convection heat transfer coefficients and pressure drops have been reported. However, dispersions of graphene sheets in a polymeric matrix as well as in a solvent medium are difficult to achieve; that is because Van der Waals, [Formula: see text] and Coulombic interactions cause agglomerations. Surface chemical modifications have been considered as viable options to improve the graphene integration. In this work, we studied the colloidal stability of aqueous solutions of graphene sheets functionalized with (i) carboxylic groups, (ii) 3-amino-propyl tri-ethoxy silane (amphiphilic behavior), (iii) graphene oxide, and (iv) pristine graphene. Results show that the lower sedimentation velocity corresponds to the graphene functionalized with carboxylic groups, which presents the higher colloidal stability. However, the amphiphilic group enhances the interaction energy between graphene and the solvent; we believe that there is a threshold percentage of functionalization that improves the colloidal stability of graphene. METHOD: Transport properties of graphene solutions were estimated by using Non-Equilibrium Molecular Dynamics simulations to generate Poiseuille flow in an NVT ensemble. Simulations were developed in the LAMMPS code. The COMPASS Force Field was used for the graphene systems and the TIP3P for the water molecules. Bonds and angles of hydrogen atoms were kept rigid by using the shake algorithm. The molecular models were built through MedeA and visualized with the Ovito software.

Effect of PEG grafting density on surface properties of polyurethane substrata and the viability of osteoblast and fibroblast cells.

The surface of Tecoflex SG-80A Polyurethane (PU) films was modified by grafting polyethylene glycol (PEG) chains at three different molar amounts (0.05, 0.10, and 0.15 mmol). The resulting substrata were characterized by FTIR-ATR, TGA, AFM, SEM and contact angle to assess the surface modifications occurred during the grafting reactions. Osteoblasts and fibroblasts were cultured with PU extracts for 24 h, and their cell viability and morphology were evaluated by CellTiterBlue assay, Crystal Violet staining and Live/Dead assay. FTIR and TGA results indicated that PEG chains were successfully grafted onto PU surfaces, specifically in the hard segment of PU forming allophanate groups as the PEG grafting density increased. SEM and AFM images suggest that PU substrata were partially covered by PEG, increasing the dispersive and basic components of the PU surface energy. It was found that extracts from PEG-grafted polyurethanes increased the osteoblast viability, although fibroblasts viability remained constant regardless PEG grafting density; in spite of this both cells presented a more spread morphology at the lower PEG grafting density. Our results showed that surface energy of PU substrata can be tuned by PEG grafting density; also, the PEG leached tends to increase the pH of culture medium which leads to a higher viability of osteoblasts; nevertheless, PEG grafting density should be optimized to promote a healthy cell morphology as alterations in its morphology were detected at higher concentrations. Graphical abstract.

A wide-ranging Pseudomonas aeruginosa PeptideAtlas build: A useful proteomic resource for a versatile pathogen.

Pseudomonas aeruginosa is an important opportunistic human pathogen with high prevalence in nosocomial infections. This microorganism is a good model for understanding biological processes such as the quorum-sensing response, the metabolic integration of virulence, the mechanisms of global regulation of bacterial physiology, and the evolution of antibiotic resistance. Till now, P. aeruginosa proteomic data, although available in several on-line repositories, were dispersed and difficult to access. In the present work, proteomes of the PAO1 strain grown under different conditions and from diverse cellular compartments have been joined to build the Pseudomonas PeptideAtlas. This resource is a comprehensive mass spectrometry-derived peptide and inferred protein database with 71.3% coverage of the total predicted proteome of P. aeruginosa PAO1, the highest coverage among bacterial PeptideAtlas datasets. The proteins included cover 89% of metabolic proteins, 72% of proteins involved in genetic information processing, 83% of proteins responsible for environmental information processing, more than 88% of the ones related to quorum sensing and biofilm formation, and 89% of proteins responsible for antimicrobial resistance. It exemplifies a necessary tool for targeted proteomics studies, system-wide observations, and cross-species observational studies. The manuscript describes the building of the PeptideAtlas and the contribution of the different proteomic data used. SIGNIFICANCE: Pseudomonas aeruginosa is among the most versatile human bacterial pathogens. Studies of its proteome are very important as they can reveal virulence factors and mechanisms of antibiotic resistance. The construction of a proteomic resource such as the PeptideAtlas enables targeted proteomics studies, system-wide observations, and cross-species observational studies.

Kinetic Control of the Li0.9Mn1.6Ni0.4O4 Spinel Structure with Enhanced Electrochemical Performance.

The development of more sustainable societies has become an urgent goal worldwide. Electrical batteries are currently seen as one of the most important energy storage technologies for the development of decarbonized societies. However, many lithium-ion battery manufacturers currently utilize cobalt, a toxic and hazardous mineral, in their batteries. Lithium-deficient manganese nickel oxide spinels are considered promising candidates owing to their high potential and environmental friendliness. Their electrochemical performance highly depends on their average and local structures, such as phase purities, lattice parameters, and cation sites. Thus, a synthesis protocol should be designed to control these structural parameters to improve their electrochemical performance. In this study, we controlled the average and local structures of Li0.9Mn1.6Ni0.4O4 spinels obtained by co-precipitation by optimizing their cooling rates. High-resolution techniques, including transmission electron microscopy, synchrotron X-ray diffraction, and Auger-composition analysis combined with density functional theory calculations, X-ray absorption spectroscopy, and electrochemical analysis, were used to understand the average and local structural variations and their effects on the electrochemical properties. As a result, the control of oxygen diffusion at different cooling rates can promote the rearrangement of the structure, resulting in a cation-disordered spinel with minimal variations in lattice parameters and composition. Excellent electrochemical properties were noted in the cation-disordered spinel with high crystallinity and a slightly oxygen-rich surface produced via optimized cooling rates.

Effects of palm biodiesel and blends of biodiesel with organic acids on metals.

This paper presents the corrosion behavior studies of five metallic materials used in auto part manufacturing exposed to pure palm biodiesel (B100) and palm biodiesel mixed with acidic species commonly found in biodiesel. Samples of AISI-SAE 1005 carbon steel, AISI-SAE 304 stainless steel, tin, aluminum and copper were exposed to a temperature of 45 °C for 12 months. The highest corrosion rates were present in totally immersed copper (B100-acetic acid blend) and in carbon steel (B100-oleic acid blend). The most corrosive blends for the metallic materials were B100-linoleic acid, B100-oleic acid and B100-acetic acid. The efficacy of two corrosion inhibitors, ethylenediamine (EDA) and tert-butylamine (TBA) increased as a function of exposure time. The characterization tests allowed the detection of different species, in the products of steel corrosion, associated with, lepidocrocite, ferrihydrite, magnetite, and some iron carbonates. In turn, cuprite, malachite, azurite, and some copper carbonates were found on the copper samples. Such corrosion products formed protective layers on the surface of the metals, which is reflected in a decrease in corrosion rates over time.

Effect of Type and Concentration of Nanoclay on the Mechanical and Physicochemical Properties of Bis-GMA/TTEGDMA Dental Resins.

Bis-GMA/TTEGDMA-based resin composites were prepared with two different types of nanoclays: an organically modified laminar clay (Cloisite® 30B, montmorillonite, MMT) and a microfibrous clay (palygorskite, PLG). Their physicochemical and mechanical properties were then determined. Both MMT and PLG nanoclays were added into monomer mixture (1:1 ratio) at different loading levels (0, 2, 4, 6, 8 and 10 wt.%), and the resulting composites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and mechanical testing (bending and compressive properties). Thermal properties, depth of cure and water absorption were not greatly affected by the type of nanoclay, while the mechanical properties of dental resin composites depended on both the variety and concentration of nanoclay. In this regard, composites containing MMT displayed higher mechanical strength (both flexural and compression) than those resins prepared with PLG due to a poor nanoclay dispersion as revealed by SEM. Solubility of the composites was dependent not only on nanoclay-type but also the mineral concentration. Dental composites fulfilled the minimum depth cure and solubility criteria set by the ISO 4049 standard. In contrast, the minimum bending strength (50 MPa) established by the international standard was only satisfied by the dental resins containing MMT. Based on these results, composites containing either MMT or PLG (at low filler contents) are potentially suitable for use in dental restorative resins, although those prepared with MMT displayed better results.

Effect of the reaction medium on the characteristics of silanized titanium dioxide particles: Differences obtained in the Zeta potential data and infrared spectra.

In this document we present the differences in the Zeta potential and in the Infrared spectra data obtained from the characterization of silanized titanium dioxide particles, using two different solvents as reaction media: ethanol and toluene. Also, we provide micrographs of transmission electron microscopy in order to show morphological differences between the analyzed samples.

Effect of chemical modification of titanium dioxide surface with dicarboxylic acid on the crystalline parameters and rheology behavior in polypropylene composites.

In this document, we present the effect of the surface modification of titanium dioxide particles with dicarboxylic acid on the rheological behavior of isotactic polypropylene composites. In addition to evaluating the effect of this type of modified fillers on the crystalline parameters such as long period, crystalline thickness and amorphous thickness, comparing it with unmodified fillers and pure polymer.

Newly developed Learning and Verbal Memory Test (TAMV-I): Normative data for Spanish-speaking pediatric population.

OBJECTIVE: To generate normative data for the Learning and Verbal Memory Test (TAMV-I) in Spanish-speaking pediatric populations. METHOD: The sample consisted of 4,373 healthy children from nine countries in Latin America (Chile, Cuba, Ecuador, Guatemala, Honduras, Mexico, Paraguay, Peru, and Puerto Rico) and Spain. Each participant was administered the TAMV-I as part of a larger neuropsychological battery. Free recall, memory delay and recognition scores were normed using multiple linear regressions and standard deviations of residual values. Age, age2, sex, and mean level of parental education (MLPE) were included as predictors in the analyses. RESULTS: The final multiple linear regression models indicated main effects for age on all scores, such that scores increased linearly as a function of age. Age2 had a significant effect in all countries except Cuba, and Puerto Rico for free recall score; a significant effect for memory delay score in all countries except Cuba and Puerto Rico; and a significant effect for recognition score in in all countries except Guatemala, Honduras, and Puerto Rico. Models showed an effect for MLPE in Chile (free recall), Honduras (free recall), Mexico (free recall), Puerto Rico (free recall, memory delay, and recognition), and Spain (free recall and memory delay). Sex affected free recall score for Cuba, Ecuador, Guatemala, Mexico, Paraguay, Peru, and Spain, memory delay score for all countries except Chile, Paraguay, and Puerto Rico, and recognition score for Ecuador, Mexico, Peru, and Spain, with girls scoring higher than boys. CONCLUSIONS: This is the largest Spanish-speaking pediatric normative study in the world, and it will allow neuropsychologists from these countries to have a more accurate way to interpret the TAMV-I with pediatric populations.

[Analysis of the characteristics of patients with bladder cancer diagnosed of multiple neoplasms in the health district of León (Spain)]. / Análisis de las características de los pacientes con cáncer vesical diagnosticados de neoplasias múltiples en el área sanitaria de León.

OBJECTIVE: We analyzed the characteristics of the patients with bladder neoplasms who developed a multiple malignant primary neoplasm (MMPN) in the health district of León, the impact on survival and the prognostic variables. MATERIAL AND METHODS: We have used the data from the Tumor Registry of the Hospital of León and selected all those patients who were diagnosed of a bladder tumor between 1993 and 2002. They were classified into two groups: the first with 71 patients with MMPN and a second group with 159 patients with single bladder tumors diagnosed between 1996 and 1997. RESULTS: Incidence of MMPN was of 7.1 percent. More than half of the patients had familial oncologic background. The second most frequently diagnosed neoplasms were urologic, followed by gastrointestinal and respiratory. Survival of patients with MMPN was 21 percent lower than single neoplasms. Variables with prognosis significance were the stage of the second neoplasm, diagnosis of a second urologic neoplasm and surgery treatment for the second tumor. CONCLUSIONS: MMPN in patients with bladder tumors are frequent in our geographic area. The high frequency of familial oncologic antecedents in these patients suggest a genetic background. Prognosis of MMPN patients is worse than single tumors patients, but no differences were observed regarding prognosis in patients with synchronous or metachronous MMPN.

Cáncer colo-rectal multicéntrico (CCRM) en el área sanitaria de León / Multicentric colo-rectal cancer (MSCC) in the health district of León

Objetivos: Analizar las características de los pacientes diagnosticados de CCRM en el área sanitariade León, el impacto sobre la supervivencia y las posibles variables pronósticas.Material y métodos: Utilizando los datos del Registro de Tumores del Hospital de León se hananalizado las características de aquellos pacientes con tumores colo-rectales diagnosticados entre 1993y 2002, clasificándolos dos grupos: el primero constituido por 74 pacientes diagnosticados de CCRMy el segundo formado por 1342 pacientes con tumores únicos diagnosticados en el bienio 1996-1997.Resultados: La frecuencia de CCRM fue del 2,7%. La edad de los pacientes con CCRM fue 2años mayor con respecto a la de los pacientes con neoplasias únicas, con una elevada proporción(38%) de antecedentes familiares oncológicos en familiares de primer grado. No se observaron diferenciassignificativas en cuanto a la localización y el estadio del primer tumor colo-rectal con respectoal grupo de tumores únicos. La supervivencia de los pacientes con CCRM metacrónico fue netamenteinferior, posiblemente en relación con un mayor número de segundas neoplasias diagnosticadas en estadiostempranos en los pacientes con CCRM sincrónico. Las variables que influyeron en el pronósticofueron la edad, el sexo, y el padecimiento de un CCRM sincrónico o metacrónico.Conclusiones: El CCRM es una entidad frecuente en nuestro medio. La tasa de antecedentes familiaresoncológicos en estos pacientes es muy elevada. No se encontraron diferencias significativasen cuanto al pronóstico de estos pacientes respecto al de los pacientes con neoplasias únicas

Purpose: We analyze the characteristics of patients with multicentric colo-rectal cancer (MCRC)in the health district of León, the impact on survival, and the prognostic variables.Material and methods: : Using the data from the Hospital de León Tumour Registry, weanalyzed the characteristics of all the patients diagnosed of having colo-rectal tumours between 1993and 2002. The patients were classified in two groups: one of them composed by 74 patients with MCRC,and the other formed by 1342 patients diagnosed in 1996 and 1997 of having single colo-rectal tumours.Results: The observed frequency of MCRC corresponded to 2.7 percent of the whole cases. Theage of the MCRC patients was 2 years higher than that of the patients with single neoplasms, andshowed a higher familial oncologic history, that was present in 38 percent of the cases. No differenceswere observed for location and stage of the first appeared colo-rectal neoplasm. The survival of thepatients developing metachronous MCRC was lower than for those with synchronous disease,possibly due to the higher number of the second neoplasms appearing in these patients at early stages.Prognostic values were age, sex, and metachronous or synchronous type of disease.Conclusions: MCRC is a frequent entity. The frequency of familial oncologic history is veryhigh. No significant differences were seen in relation to prognosis between single and multiple colorectalcancer

Multiple malignant primary neoplasms in patients with gatric neoplasms in the health district of León.

OBJECTIVES: We analyzed the characteristics of patients with gastric tumors diagnosed with multiple malignant primary neoplasm (MMPN) in the Health District of León. MATERIAL AND METHODS: Using the information in the Tumor Registry at León Hospital patients selected were those with gastric neoplasms diagnosed between 1993 and 2002. A follow-up was performed until December 31, 2004, and the characteristics of patients diagnosed with a second neoplasm were analyzed. RESULTS: MMPN prevalence was 1,96%; 56% of patients had a history of cancer in first-degree relatives. The most frequent second neoplasms were digestive (26%) and urologic (21%); 87% of patients were diagnosed with a second neoplasm within the first two years. No significative differences in survival were observed among patients with synchronous or metachronous MMPN. CONCLUSIONS: MMPN in patients with gastric neoplasms is a relevant problem. While external carcinogenic agents could act as promoters in the development of second neoplasms, these patients seem to have a genetic background favoring the development of MMPN. Secondary prevention is the best measure to avoid MMPN development.

Mujer de 83 años con anemia crónica, ictericia y esplenomegalia / An 83-year-old women with chronic anemia, jaundice, and splenomegaly

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