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Se evaluó el desempeño de la influencia de la ceniza de bagazo de caña (CBC) como filler en mezclas de concreto autocompactante (CAC), adicionado en un 0%, 5%, 10%, 15%, 20% y 25% con respecto al peso de cemento. La caracterización de la ceniza se realizó mediante FTIR, FRX y DRX. Las propiedades de trabajabilidad del CAC fueron determinadas mediante ensayos de flujo de asentamiento, anillo J, caja en L, embudo V, Índice de Estabilidad Visual y resistencia a la compresión. De acuerdo con los resultados, los porcentajes de 10 al 20% en las mezclas de CAC obtuvieron un desempeño satisfactorio, evidenciando parámetros de trabajabilidad y resistencia a la compresión sobresalientes comparados con trabajos similares a los publicados en la literatura.

Se evaluó el riesgo por corrosión del acero en concreto, utilizando sensores galvánicos internos de acero al carbono/acero inoxidable y un electrodo externo de Cu/CuSO4. Los sensores se utilizaron para monitorear los potenciales y corrientes de macrocelda de probetas prismáticas de concreto reforzado con relaciones agua-cemento de 0.4 y 0.6, inmersas en solución de NaCl al 5% durante 18 meses. Los resultados de los potenciales mostraron buena correlación entre los dos electrodos de referencia, pudiendo evaluar la corrosión del sistema. Además, la técnica de ruido electroquímico respalda el efecto por iones cloruro. Por lo tanto, los sensores galvánicos pueden considerarse para su implementación en el monitoreo y evaluación del estado de riesgo por corrosión en estructuras de concreto reforzado.

El desarrollo de la Ciencia, Tecnología e Innovación (CTI) se ha convertido en un factor primordial para el crecimiento económico de un país. El presente artículo busca mostrar la importancia de las políticas públicas de inversión para la CTI, en la conformación del campo científico y en las trayectorias profesionales de los investigadores adscritos al Sistema Nacional de Investigadores (SNI) del área VIII-Ingenierías y Desarrollo Tecnológico en Chiapas, una entidad en el Sureste de México. Se trata de una investigación documental que empleó criterios de selección y de exclusión, como la temporalidad de los documentos y la metodología empleada por mencionar algunos, así se obtuvieron documentos rectores y fuentes secundarias significativas que ofrecieron información relevante. Los resultados revelaron que la aplicación de las políticas públicas de inversión en CTI se realiza de manera desigual en las diferentes entidades de México, lo que ha provocado que Chiapas no haya alcanzado los niveles de desarrollo deseables. Se concluye que las políticas públicas de inversión son relevantes, ya que se han convertido en la oportunidad de adquirir las herramientas necesarias para que los investigadores de Chiapas sigan desarrollando sus trabajos.

Chiapas es una entidad que históricamente se ha ubicado en la periferia de las oportunidades, lo que ha provocado que el desarrollo de investigaciones se convierta en un reto para los académicos e investigadores de dicha región ya que son los que tienen que resistir las dificultades relacionadas al contexto de la entidad. El presente estudio tuvo como objetivo recuperar la percepción sobre el concepto de resiliencia que los académicos e investigadores del Sistema Nacional de Investigadores (SNI) del área VIIIIngenierías y desarrollo tecnológico poseen para sobreponerse a las adversidades. El área VIII es la menos apoyada, y, por lo tanto, ofrece mayores factores de estrés para sujetos de esta investigación. A través de entrevistas en profundidad aplicadas a cuatro investigadores de universidades públicas en Chiapas se plantearon tres categorías (actitudes, valores y socioemocional). Se concluye que la categoría de “actitudes” juega un papel fundamental para superar los factores de estrés., Chiapas is an entity that historically has been located on the periphery of opportunities, which has caused the development of research to become a challenge for academics and researchers of this region, since they are the ones who have to resist the difficulties related to the context of the entity. The objective of this study was to recover the perception of the concept of resilience that academics and researchers of the National System of Researchers (SNI) of the VIII-Engineering Area possess to overcome adversity. Area VIII is the least supported and therefore offers the greatest stressors for subjects of this research. Through in-depth interviews applied to four researchers from public universities in Chiapas, three categories were proposed (attitudes, values and socio-emotional). It is concluded that the category of “attitudes” plays a fundamental role in overcoming stressors.

This work presents the hydrologic estimations of the hydraulic underground arched culvert channel (UACC) in Sabinal Basin, Chiapas, Mexico and the hydrological problems associated with it, such as the erosion phenomenon and abrasion cavity formation in it. On the other hand, the maximum flows that the UACC could transport were analyzed, concluding that it no longer has the hydraulic capacity to transport the flow rate associated to return periods equal to or greater than five years and that maximum permissible velocity UACC’s bottom is 3 m/s.

We present a simple but accurate correlation between an experimental characterization and a simple analytical prediction of a wave propagation induced by the impact of a pendulum in a box filled with fine sand; this research is based on optical measurements and was carried out using the digital image correlation technique to determine the motion on the surface of the box visually observed by the reflection of the laser. We suggest that the reaction to the impact in the body will be similar to an equivalent damped mass-spring system, obtaining an average error of $3.67208$ x$10^{-4}$.

Most public universities in Latin America and Mexico lack laboratories for measuring sediment transport or to do academic activities. The Research Center of the engineering faculty of Chiapas state university (UNACH by its acronym in Spanish) designed a portable prismatic channel for teaching and researching the sediment transportation in rivers. This paper presents the method to measure river sand transportation in a laboratory channel with a mobile bottom and presents the results of twenty-seven experiments done in the portable channel, using nine different slope inclinations and 27 flow and water speed values. The three main results are the following: 1) The construction of the channel with variable slopes, to experiment and measure sediment transportation. 2) A method developed for measuring the volume of sediment in a laboratory. 3) In a channel with a bottom slope of 0.071, a water flow of 2 l/s and a water speed of 1.77 m/s, the volume of transported sediment was 0.015 m3; in a channel with a bottom slope of 0.44, a water flow of 2 l/s and a water speed of 0.788 m/s, the volume of transported sediment was 0.006 m3; in a channel with the bottom slope of 0.024, a water flow of 2 l/s and a water speed of 0.62 m/s, the transported sediment was 0 m3.

Alkali-Silica reaction (ASR) is a physicochemical process that can deteriorate concrete and is a recurring engineering problem. In this study three different cylindrical samples affected by ASR were prepared: a plain mortar and two composite mortars containing fibers (polypropylene and a polymer hybrid), which were analyzed at the microtomography (μCT) beamline 8.3.2 at the Advanced Light Source (ALS). In general, three different features were observed during the 136 day observation period: (1) aggregate dissolution, (2) crack propagation from inside the aggregate, through the cement matrix, and at the ITZ, and (3) the alkali-silica gel filling cracks and voids. In addition, accelerated mortar bar tests were utilized to observe ASR's expansive effect in the plain and composite mortars, and the fibers' ability to restrain expansion due to ASR.

This paper investigates the atomic and nano-scale structures of a 50-year-old hydrated alite paste. Imaged by TEM, the outer product C–S–H fibers are composed of particles that are 1.5–2 nm thick and several tens of nanometers long. 29Si NMR shows 47.9% Q1 and 52.1% Q2, with a mean SiO4 tetrahedron chain length (MCL) of 4.18, indicating a limited degree of polymerization after 50 years' hydration. A Scanning Transmission X-ray Microscopy (STXM) study was conducted on this late-age paste and a 1.5 year old hydrated C3S solution. Near Edge X-ray Absorption Fine Structure (NEXAFS) at Ca L3,2-edge indicates that Ca2 + in C–S–H is in an irregular symmetric coordination, which agrees more with the atomic structure of tobermorite than that of jennite. At Si K-edge, multi-scattering phenomenon is sensitive to the degree of polymerization, which has the potential to unveil the structure of the SiO44 − tetrahedron chain.

Calcium silicate hydrates (C-S-H), the primary binding phase in concrete, is the most prominent physiochemical factor controlling the mechanical and chemical properties in the production of concrete. This paper reports the local-binding structure and morphological details of C-S-H as determined by high-resolution X-ray spectromicroscopy. Hydrated tricalcium silicate (C3S) was used to determine the properties and role of the outer products (Op) of C3S. C-S-H with different molar ratios of Ca/Si, were synthesized (Syn-CSH) to quantitatively evaluate the effect of silicate polymerization on Ca L and Si K edge of C-S-H. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy of Syn-CSH showed no variation in peak positions and energy separation for CaLIII, II edge for the Ca/Si ratios investigated. Compared to Syn-CSH, C3S, when hydrated for 17 d, had a similar local structure around Ca. Si K edge NEXAFS analysis on Syn-CSH showed a tendency for the peak positions of both the Si K edge and the peak induced by multiple scattering to shift to higher energy levels. The results also indicated that the distance between the two peaks increased with a decrease of the Ca/Si ratio in Syn-CSH. Silicate polymerization influenced the multiple scattering of distant shell atoms more than the binding energy of the core atoms. Op of C3S had a uniform and higher degree of silicate polymerization compared to the core area. The results imply that Op reduces the hydration process of C3S into the core area thereby playing a key role on the properties of concrete upon formation.

Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (μCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber – the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowed visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.

© 2016 by the author. The understanding and control of early hydration of tricalcium silicate (C3S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C3S at an early stage of hydration. In situ C3S hydration in a wet cell, beginning with induction (~1 h) and acceleration (~4 h) periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period after 15 h of curing. Analysis of the near-edge X-ray absorption fine structure showed that the Ca binding energy and energy splitting of C3S changed rapidly in the early age of hydration and exhibited values similar to calcium silicate hydrate (C-S-H). The formation of C-S-H nanoseeds in the C3S solution and the development of a fibrillar C-S-H morphology on the C3S surface were visualized. Following this, silicate polymerization accompanied by C-S-H precipitation produced chemical shifts in the peaks of the main Si K edge and in multiple scattering. However, the silicate polymerization process did not significantly affect the Ca binding energy of C-S-H.

El río Sabinal atraviesa, de poniente a oriente, la ciudad de Tuxtla Gutiérrez, Chiapas, con una longitud aproximada de 12 km. Este río tiene 21 afluentes y con el paso de los años y el crecimiento poblacional, la zona federal del río y sus afluentes fue invadido por la mancha urbana. Actualmente cuatro afluentes embovedados representan un alto riesgo para la población que se ubica adjunta o sobre estas estructuras, porque algunas de ellas tienen más de 50 años sin recibir mantenimiento y además están sometidas a la agresividad ambiental interna, producto de los gases que emanan de las aguas negras como: sulfuros de hidrógeno, metano y amoniaco principalmente, esto sumado al bióxido de carbono, oxígeno y nitrógeno presentes en la atmósfera que junto a la humedad y temperatura contribuyen a su deterioro acelerado. En este artículo se presenta el análisis de la inspección visual, integrando aspectos de deterioro de materiales asociados a los posibles daños estructurales, además de los resultados obtenidos con pruebas electroquímicas y químicas puntuales para la evaluación por corrosión del elemento estructural de concreto reforzado interno que atraviesa el embovedado. Es posible concluir que las estructuras que conforman el embovedado se encuentran con patologías diversas, clasificadas desde daños comunes como eflorescencias, zonas blandas y hongos en materiales de mampostería de ladrillo y piedra. En algunas zonas recubiertas con materiales de concreto reforzado, se observaron agrietamientos, coqueras, eflorescencias, lixiviación de sales cristalizadas, infiltraciones y escurrimientos en la masa del concreto, hasta daños severos como reventones, desprendimientos parciales del concreto, corrosión generalizada y pérdida total, en ciertos puntos, del acero de refuerzo principal de la estructura. Esta degradación es activa y constante, de acuerdo a los parámetros electroquímicos evaluados; por lo tanto, podría afectar su eficiencia ante solicitaciones estáticas o dinámicas, así como la durabilidad de los elementos evaluados.

FT30 type thin film composite membranes used for reverse osmosis water purification are very difficult to analyze. With the remarkably thin polyamide layer and surface modification of the polymers now being reported, a new analytical technique is needed to determine the surface structure and chemical distribution in the active layer. In this study we show that scanning transmission X-ray microscopy (STXM) can be used to determine the spatial distribution of polyamide and polysulfone and we report on the detection of an unexpected new phase. The new phase was identified as a homopolymer of the meta-phenylene diamine (MPD) that forms in MPD solutions and can be incorporated into the discrimination layer during the interfacial reaction with the TMC to produce a mixed polyamide polyMPD layer. The detection of this second phase was only made possible by STXM. At the levels detected in membranes in this study (less than 8%) the second phase had no effect on the flux or salt passage of the membranes, however at higher levels a change in the membrane properties most likely would occur and the quantity of the polyMPD present should be eliminated or controlled.

The polarization dependence (linear dichroism) of the C 1s X-ray absorption spectrum of individual multi-walled carbon nanotubes (MWCNTs) is measured using scanning transmission X-ray microscopy. A very strong dichroic effect is found in the C 1s --> pi* transition, with almost complete disappearance of this transition when the electric-field (E)-vector is aligned parallel to high-quality (low-defect) MWCNTs and maximum intensity when the E-vector is orthogonal to the tube axis. In contrast, there is very little dichroism in the C 1s --> sigma* transitions. The origin of this polarization effect is explained. The magnitude of the polarization dependence is found to differ in MWCNTs synthesized by different methods (arc discharge versus chemical vapor deposition). This is ascribed to differences in densities of sp(2)-type defects. The potential for use of this signal to characterize defects in single-carbon-nanotube devices is discussed.

Scanning transmission X-ray microscopy (STXM) has been used to probe the electronic structure of individual multiwall carbon nanotubes by chemical mapping at the nanoscale. Carbon 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of individual structures are shown to be able to differentiate carbon nanotubes from onionlike carbon nanoparticles and to differentiate nanotubes synthesized by different growth methods. Imaging of the very same region by both STXM and transmission electron microscopy is shown to be a very useful and complementary approach.

The intrinsic variation in the near-edge X-ray absorption fine structure (NEXAFS) spectra of peptides and proteins provide an opportunity to identify and map them in various biological environments, without additional labeling. In principle, with sufficiently accurate spectra, peptides (50 amino acids) or proteins with unusual sequences (e.g., cysteine- or methionine-rich) should be differentiable from other proteins, since the NEXAFS spectrum of each amino acid is distinct. To evaluate the potential for this approach, we have developed X-SpecSim, a tool for quantitatively predicting the C, N, and O 1s NEXAFS spectra of peptides and proteins from their sequences. Here we present the methodology for predicting such spectra, along with tests of its precision using comparisons to the spectra of various proteins and peptides. The C 1s, N 1s, and O 1s spectra of two novel antimicrobial peptides, Indolicidin (ILPWKWPWWPWRR-NH2) and Sub6 (RWWKIWVIRWWR-NH2), as well as human serum albumin and fibrinogen are reported and interpreted. The ability to identify, differentiate, and quantitatively map an antimicrobial peptide against a background of protein is demonstrated by a scanning transmission X-ray microscopy study of a mixture of albumin and sub6.

In this paper, design and characterization of a pH optical fiber sensor with pH sensitive dye is described. The sensor is prepared by fixing the doped plastic fiber on a fused ortosilica block surface with blue bromophenol. The surface charge of silica and the refractive index, which plays an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 5.0 and 7.0. The advantage of this sensor is that, only 2 cm of doped fiber is enough to measure the pH of a fluid in real time. The time response of the sensor reported in the present study is approximately 10 s.

We are reporting the fabrication of a very efficient electron source using millimeter-long and highly crystalline carbon nanotubes. These devices start to emit electrons at fields as low as 0.17 V/mu m and reach threshold emission at 0.24 V/mu m. In addition, these electron sources are very stable and can achieve a peak current density of 750 mA cm(-2) at only 0.45 V/mu m . In order to demonstrate intense election beam generation, these devices were used to produce visible light by cathodoluminescence. Finally, density functional theory calculations were used to rationalize the measured electronic field emission properties in open carbon nanotubes of different lengths. The modeling establishes a clear correlation between length and field enhancement factor.

We prepare optrodes of fiber optic plastic with sol-gel technique. Suitable concentration of carbone nanotubes (CNTs), phenol red, bromophenol blue and cresol red, design optrodes with fiber optic plastic. The surface charge of silica and the refractive index, which play an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 3 and 9.

Nonlinear effects are consequence of interaction of height intensities of energy with the matter. Self-diffraction is nonlinear effect and rings are produced. We analyzed the increase of rings due to changes in intensity of CW Ar laser that modify the nonlinear refractive index. The Carbon Nanotubes (CNTs) were dispersed on different solvents: a) water, b) ethanol, c) isoprophanol, and d) acetone. The concentrations were 10ml:1mg in all samples. The dependence between power and concentration of CNTs is shown.

A novel miniature rotation device used in conjunction with a scanning transmission x-ray microscope is described. It provides convenient in situ sample rotation to enable measurements of linear dichroism at high spatial resolution. The design, fabrication, and mechanical characterization are presented. This device has been used to generate quantitative maps of the spatial distribution of the orientation of proteins in several different spider and silkworm silks. Specifically, quantitative maps of the dichroic signal at the C 1s-->pi* (amide) transition in longitudinal sections of the silk fibers give information about the spatial orientation, degree of alignment, and spatial distribution of protein peptide bonds. A new approach for analyzing the dichroic signal to extract orientation distributions, in addition to magnitudes of aligned components, is presented and illustrated with results from Nephila clavipes dragline spider silk measured using the in situ rotation device.

Design and characterization of a pH optical fiber sensor with a pH sensitive dye is described in this paper. TEOS (Tetra-ethyl-Orto-Silicate) was used to dope a plastic optical fiber, which will be used as the optical probe (OPTRODE). The sensor is prepared by fixing the doped plastic fiber on a fused ortosilica block surface with blue bromophenol. The fiber surface charged with silica modified the refractive index, which plays an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. The fiber transmittance is used to measure the pH of a solution or a fluid in a range between 4 and 7; such signal is captured by a photodetector and processed with a LabView program. The advantage of this system is that, 2cm of doped fiber are enough to measure the pH of a fluid in real time. The time response of the se nsor reported in the present study is approximately 10s. Keywords: Doped fiber, Optical fiber Sensor; pH sensor; Sol-Gel. 1. INTRODUCTION Many industrial sectors have as a need a distributed measurements system for chemical parameters. Early detection and location of water or fluids filtration, for example, could prevent premature damage to cables in both communications and power distribution ducts, in foods industry, biological systems, etc.[1-2]. The detection of some parameters, such pH decreasing to the value of 10, can be a good indicator of potential corrosion of reinforcing tensors in civil engineering structures which are on earth, underground or under water conditions. The definition of pH is the concentr ation of hydrogen ions in liquids. If the pH value is between 0 and 7, are called acids. If the pH values between 7 and 14 are called bases. For pH = 7 the substances are called neutrals, for example pure water, where is very important monitoring for our health. Some biological systems have ionic groups which electrical charge depends on pH concentration; this pH value depends on the balance between the O-H and H. Ther efore, pH is sensitive to the ions concentration in

A.P. Hitchcock,* D. Hernandez-Cruz,* J.J. Dynes,* M.-E. Rousseau,** M. Pezolet** * Dept. of Chemistry, McMaster University, Hamilton, ON, L8S 4M1, Canada. ** Departement de Chimie, Universite Laval, Ste Foy, QC, G1K 7P4,Canada The X-ray absorption signal in synchrotron based soft X-ray scanning transmission X-ray microscopy (STXM) is providing quantitative maps of chemical species in many samples, under a wide range of environments (wet, variable temperature, pH, stress, electrochemical control, etc). State-of-the art zone plates provide a spatial resolution of 15 nm [1], while 35 nm resolution is achieved routinely in STXMs at the Advanced Light Source (ALS) and at the National Synchrotron Light Source (NSLS) [2]. With appropriate software [3], sequences of images recorded over a range of photon energies spanning one or more core excitation edges can be inverted by multivariate statistical analysis methods [4] or by pixel-by-pixel spectral fitting to generate quantitative chemical component maps.

The alignment of β-sheets within spider dragline silk fibers is an important factor in their tensile strength and extensibility. We are using linear dichroism of the C 1s → π*amide transition measured using scanning transmission X-ray microscopy (STXM) to generate quantitative maps of the orientation parameters with 30 nm spatial resolution. Here we have extended these measurements from dry samples to samples with partial or full hydration. A device for monitoring and controlling the humidity of a sample in the STXM is described and used to measure the effect of saturated humidity on a section of N. clavipes dragline spider silk. The microstructure and distributions of molecular orientation change considerably with hydration in ways consistent with the supercontraction observed in free standing dragline spider silk. The STXM results are compared to infrared and Raman microscopy results.