Análisis multiescala de indicadores arqueológicos de Tlajinga, Teotihuacan (México). Desde la percepción remota a la microscopía.

El barrio de Tlajinga es un área ubicada al sur de la ciudad de Teotihuacán, Estado de México, que preserva materiales prehispánicos diseminados en distintas zonas del terreno, así como estructuras arqueológicas enterradas. Las partículas del suelo, al mezclarse con materiales arqueológicos tales como piedra, estuco, cerámica y fragmentos de murales, enriquecen el suelo principalmente con carbonato de calcio, lo que contribuye al aumento de la reflectancia en distintas zonas del terreno, principalmente en zonas donde había estructuras arqueológicas. Este fenómeno es registrado desde un nivel sinóptico por los sensores remotos actuales, con mayor resolución espectral, espacial y radiométrica, correlacionándose a una menor es-cala con la espectrorradiometría y la micromorfología de los suelos. De esta forma se identificaron algunos mine-rales presentes en los pisos y muros, principalmente el estuco arqueológico, ahora transformado en pequeñas partículas de carbonato de calcio. La fluorescencia (FRX) y difracción de rayos X (DRX) complementaron los resultados de la percepcción remota, la espectrorradiometría y la micromorfología, identificando la composición elemental de las partículas del suelo y los minerales asociados, de la que sobresale el carbonato de calcio, un compuesto muy importante utilizado para el recubrimiento de pisos y edificios durante la época teotihuacana.The Tlajinga Barrio is a domestic area situated in the south of Teotihuacan, Estado de México, where preserves original surface materials as well as buried archaeological structures are preserved. Original soil particles mixed with archaeological materials such as stone, stucco, ceramics, and mural fragments enrich the soil mainly with calcium carbonate, contributing to the increase in reflectance in different areas of the terrain, mainly in nearby areas where there were archaeological structures. This is recorded from a synoptic level by the modern remote sensors, with higher spectral, spatial, and radiometric resolution, correlating it to a smaller scale with soil micromorphology analysis. In this way, some minerals present in the floors and walls were identified, mainly the archaeological stucco now transformed into small particles of calcium carbonate. X-ray fluorescence (XFRF) and X-ray diffraction (XRD) complemented the results of remote sensing, spectrometry and micromorphology, identifying the elemental composition of soil particles and associated minerals, mainly calcium carbonate, that were used live in coatings on floors and buildings during the Teotihuacan era.Published versio

Hydrogen-wettability alteration of Indiana limestone in the presence of organic acids and nanofluid

This study focuses on the wettability alteration (changing from a hydrophobic state to a hydrophilic state) of Indiana limestone for hydrogen (H2) geological storage. We examine the effect of hexanoic acid C6, lauric acid C12, and stearic acid C18, on the wettability of Indiana limestone at ambient (298 K and 0.1 MPa) and reservoir (323 K and 8.27 MPa) conditions. The effects of silica nanofluids (silica with deionized water) at various concentrations (0.1 wt%, 0.25 wt%, and 0.5 wt%) on the wettability reversal of stearic-aged samples were tested at ambient and reservoir conditions. The results revealed increased H2-wetness (hydrophobicity) of the rock exposed to these organic acids in reservoir conditions. However, this hydrophobicity significantly decreased with the nanofluid treatment of the stearic-aged samples. This wettability reversal may increase the H2 storage capacity and containment security and lead to successful large-scale geological storage operations if H2 residual trapping is minimized

Flotation of Chromium Ions from Simulated Wastewater Using Air Microbubbles

   A microbubble air flotation technique was used to remove chromium ions from simulated wastewater (e.g. water used for electroplating, textiles, paints and pigments, and tanning leather). Experimental parameters were investigated to analyze the flotation process and determine the removal efficiency. These parameters included the location of the sampling port from the bottom of the column, where the diffuser is located to the top of flotation column (30, 60, and 90 cm), the type of surfactant (anionic, SDS, or cationic, CTAB) and its concentration (5, 10, 15, and 20 mg/L), the pH of the initial solution (3, 5, 7, 9, and 11), the initial contaminant concentration (10, 20, 30, and 40 mg/L), the gas flow rate (0.1, 0.2, 0.3, and 0.5 L/min), and the contact time (5, 10, 15, 20, 25, 30, and 35 min). The experimental results revealed that the highest removal efficiency (95%) was achieved in 20 min with a pH of 7, a flow rate of air 0.5 L/min, an SDS surfactant concentration of 15 mg/L, and a pollutant concentration of 30 mg/L at a sampling port height of 30 cm. The use of microbubbles in comparison to normal bubbles, resulted in a 56% improvement of the removal efficiency. The flotation process follows a first-order kinetics

Dynamic Wetting and Dewetting: Comparison of Experiment with Theories

The dynamics wetting/dewetting of a metal surface by distilled water drop was studied experimentally. The advancing and receding dynamic contact angles were obtained as a function of a contact line speed. The hydrodynamic and molecular-kinetic models have been applied to the experimental data to interpret the obtained results. The independent variables of the molecular-kinetic and hydrodynamic models, and the determination coefficient were determined by fitting procedure. The receding contact angles are found to be fitted better to the wetting models in comparison with the advancing dynamic contact angles

Wettability and corrosion of [NTf2] anion-based ionic liquids on steel and PVD (TiN, CrN, ZrN) coatings

Thewetting and corrosion behavior of three bis(trifluoromethylsulfonyl)imide-based ionic liquids: 1-Dodecyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide [C12MIM][NTf2], tributylmethylammonium bis(trifluoromethylsulfonyl)imide [N4441][NTf2] and methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [N1888][NTf2] are tested in this research. The surface tension was measured for temperatures of 293–353 K resulting in the expected linearly decreasing behavior with temperature increase. In addition, contact angle measurements were made on AISI 52100 steel and three coatings (TiN, CrN and ZrN) obtained by PVD technique, finding the regular behavior in hydrophobic (non-polar) systems: high contact angles led to high surface tensions. Complementary parameters like spreading parameter and polarity fraction were calculated to enhance the wetting evaluation of these ionic liquids. [N1888][NTf2]/TiN resulted as the best IL-surface combination for a good wettability, due to the higher dispersion of the charge on the large size cation in this IL and the higher values of total and polar component of the surface free energy for this coating. Finally, SEM-EDS analysis determined that [N1888][NTf2]/ZrN was the best option in order to avoid corrosion problems. The evaporation of water, present as impurity in the ionic liquids, was found the main reason because of corrosion did not occur in the tests carried out at 100 °C

Molecular level studies of polymer behaviors at the water interface using sum frequency generation vibrational spectroscopy

Industrial plastics, biomedical polymers and numerous other polymeric systems are contacted with water for everyday functions and after disposal. Probing the interfacial molecular interactions between widely used polymers and water yields valuable information that can be extrapolated to macroscopic polymer/water interfacial behaviors so scientists can better understand polymer bio‐compatibility, hygroscopic tendencies and improve upon beneficial polymer behavior in water. There is an ongoing concerted effort to elucidate the molecular level behaviors of polymers in water by using sum frequency generation vibrational spectroscopy (SFG). SFG stands out for its utility in probing buried interfaces in situ and in real time without disrupting interfacial chemistry. Included in this review are SFG water interfacial studies performed on poly(methacrylate) and (acrylate)s, poly(dimethyl siloxane)s, poly(ethylene glycol)s, poly(electrolyte)s and other polymer types. The driving forces behind common water/polymer interfacial molecular features will be discussed as well as unique molecular reorientation phenomena and resulting macroscopic behaviors from microscopic polymer rearrangement. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 Macroscopic polymer surface properties such as hydrophilicity, biocompatibility, and structural stability in water may be extrapolated from microscopic behaviors of polymer functional groups. Sum frequency generation vibrational spectroscopy (SFG) has been used to directly probe polymer molecular vibrational modes at the water interface, revealing functional group orientation changes, movement trends, and ordering at polymer surfaces. This review covers a variety of SFG studies of polymer water interactions performed in the preceding decade to the present.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96247/1/23221_ftp.pd

Surface tension, interfacial tension and contact angles of ionic liquids

Ionic liquids combine the properties of molten salts (they are liquids composed predominantly of ions) and organic liquids (a variety of chemical bonds and interactions are relevant). Their unique properties have attracted significant attention over the last decade. Their interfacial properties are now coming under scrutiny because (i) they are important for their performance in specific applications and also because (ii) they provide an opportunity to study diverse chemical systems under vacuum. Recent examples from the literature are used to illustrate what is currently known. The surface tension, interfacial tension and wettability of ionic liquids resemble these of polar molecular organic liquids. It is physically clear there is a relation between surface tension and molecular structure but only general trends have been identified so far. Structural studies of the free surface of ionic liquids (e.g. with surface spectroscopy) are possible and reveal unique information about the interfacial molecular orientation. The amount of empirical data available is growing rapidly and elements of systematisation are beginning to appear. © 2011 Elsevier Ltd

The molecular-kinetic approach to wetting dynamics: Achievements and limitations

The molecular-kinetic theory (MKT) of dynamic wetting was formulated almost 50 years ago. It explains the dependence of the dynamic contact angle on the speed of a moving meniscus by estimating the non-hydrodynamic dissipation in the contact line. Over the years it has been refined to account explicitly for the influence of (bulk) fluid viscosity and it has been applied successfully to both solid-liquid-vapour and solid-liquid-liquid systems. The free energy barrier for surface diffusion has been related to the energy of adhesion. The MKT provides a qualitative explanation for most effects in dynamic wetting. The theory is simple, flexible, and it is widely used to rationalize the physics of wetting dynamics and fit experimental data (dynamic contact angle versus contact line speed). The MKT predicts an intermediate wettability as optimal for high-speed coating as well as the maximum speeds of wetting and dewetting. Nevertheless, the values of the molecular parameters derived from experimental data tend to be scattered and not particularly reliable. This review outlines the main achievements and limitations of the MKT and highlights some common cases of misinterpretation

Electrowetting: Electrocapillarity, saturation, and dynamics

Electrowetting is an electrocapillary phenomenon, i.e. the surface charge generated at the solid-liquid interface through an external voltage improves the wettability in the system. The Young-Lippmann equation provides the simplest thermodynamic framework and describes electrowetting adequately. Saturation, i.e. the reduced or nullified effectiveness of the external voltage below a threshold contact angle value, was and remains the most controversial issue in the physics of electrowetting. A simple estimation of the limits of validity of the Young model is obtained by setting the solid-liquid interfacial tension to zero. This approach predicts acceptably the change in electrowetting mechanism but not the minimal value of the contact angle achievable during electrowetting. The mechanism of saturation is, in all probability, related to charge injection into the dielectric layer insulating the working electrode but physical details are scarce. Surface force and spectroscopic techniques should be deployed in order to improve our understanding of the surface charging of insulators immersed in conductive liquids. Electrowetting in solid-liquid-liquid systems is generally more effective and robust. Electrowetting offers new ways of studying the dynamics of liquid movement as it allows selective changes in the wettability of the system