Zeta potential of a natural clayey sandstone saturated with carbonated NaCl solutions at supercritical CO2 conditions

The zeta potential is a measure of electric potential at the mineral-electrolyte interfaces. The zeta potential of natural sandstones depends on mineralogy, electrolyte pH, concentration, composition, amount of dissolved CO2, and temperature. We report for the first time the zeta potential measured on clayey sandstone comprising quartz, kaolinite, illite, albite and microcline saturated with NaCl solutions at supercritical CO2 conditions. Our results demonstrate that zeta potentials in clayey sandstone samples at supercritical CO2 conditions are significantly different from similar measurements conducted under ambient conditions and from those obtained with clean sandstones. Supercritical CO2 zeta potential remains negative but is influenced by clays and feldspars due to their significant presence and exposure to large pores, which yields less negative zeta potential compared to quartz, under identical conditions. Our results have significant implications to natural subsurface systems such as CO2 geo-sequestration sites, aquifers, geothermal sources and hydrocarbon reservoirs

Optical and Infrared Photometry of the Nearby Type Ia Supernovae 1999ee, 2000bh, 2000ca, and 2001ba

We present near infrared photometry of the Type Ia supernova 1999ee; also, optical and infrared photometry of the Type Ia SNe 2000bh, 2000ca, and 2001ba. For SNe 1999ee and 2000bh we present the first-ever SN photometry at 1.035 microns (the Y-band). We present K-corrections which transform the infrared photometry in the observer's frame to the supernova rest frame. Using our infrared K-corrections and stretch factors derived from optical photometry, we construct JHK templates which can be used to determine the apparent magnitudes at maximum if one has some data in the window -12 to +10 d with respect to T(B_max). Following up previous work on the uniformity of V minus IR loci of Type Ia supernovae of mid-range decline rates, we present unreddened loci for slow decliners. We also discuss evidence for a continuous change of color at a given epoch as a function of decline rate.Comment: 53 pages, 14 figures, to be published in the March 2004 issue of the Astronomical Journa

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Dise\uf1o de un Modulo Instruccional de Productos y Servicios para el Modelo Educativo de Central Banco Universal, Basado en la Teor\ueda del Aprendizaje Acelerado

El presente trabajo tiene como objetivo dise\uf1ar un M\uf3dulo lnstruccional de Productos y Servicios para el modelo educativo de Central Banco Universal basado en la teor\ueda del Aprendizaje Acelerado. Este tipo de investigaci\uf3n es un Proyecto Factible, donde se dise\uf1aron tres (3) fases: Diagn\uf3stico, Factibilidad y Dise\uf1o. Para el dise\uf1o de la propuesta, se utiliz\uf3 la revisi\uf3n bibliogr\ue1fica para obtener informaci\uf3n que fortalecer\ue1 el conocimiento sobre la teor\ueda a emplear y las bases y fundamentos de los dise\uf1os instruccionales y los modelos educativos para establecer los lineamientos al momento de dise\uf1ar la propuesta. Se entrevistara a los Gerentes de las Agencias de Barquisimeto para definir las necesidades de la Audiencia, y al personal de la Vicepresidencia Ejecutiva de Capital Humano. Se tom\uf3 el total de la poblaci\uf3n que corresponde a las Agencias las cuales son 11 y 3 personas de Capital Humano as\ued como cuatro (4) facilitadores de la Empresa PCO\u92s Intemacional. Los resultados obtenidos fueron altamente positivos para el dise\uf1o de la propuesta por lo que recomend\uf3 poner en pr\ue1ctica a corto plazo la propuesta

Habranthus neumannii (Amaryllidaceae), a new species from Argentina

Se describe e ilustra H. neumannii, una nueva especie de Habranthus que habita pastizales en el noroeste de Argentina. Esta nueva especie recuerda en tamaño a Habranthus salinarum, pero puede ser fácilmente distinguible por sus hojas verde oscuro, flores blanco-rosadas con la base amarillo-amarronada, por el perigonio angostamente infundibuliforme y el estilo más corto. Se incluye una clave para identificar las especies del género que habitan la provincia de Jujuy

Zeta potential of a natural clayey sandstone saturated with carbonated NaCl solutions at supercritical CO2 conditions

Open Access via the Wiley Agreement Miftah Hidayat was supported by the Aberdeen-Curtin PhD studentship. David Vega-Maza is funded by the Spanish Ministry of Science, Innovation and Universities (“Beatriz Galindo Senior” fellowship BEAGAL18/00259). Abbie McLaughlin from School of Natural and Computing Sciences and John Still from the School of Geoscience, University of Aberdeen are acknowledged for their assistance in the XRD and SEM analyses.Peer reviewedPublisher PD

Zeta potential of CO-rich aqueous solutions in contact with intact sandstone sample at temperatures of 23 °C and 40 °C and pressures up to 10.0 MPa

Despite the broad range of interest and applications, controls on the electric surface charge and the zeta potential of silica in contact with aqueous solutions saturated with dissolved CO at conditions relevant to natural systems, remains unreported. There have been no published zeta potential measurements conducted in such systems at equilibrium, hence the effect of composition, pH, temperature and pressure remains unknown. We describe a novel methodology developed for the streaming potential measurements under these conditions, and report zeta potential values for the first time obtained with Fontainebleau sandstone core sample saturated with carbonated NaCl, NaSO, CaCl and MgCl solutions under equilibrium conditions at pressures up to 10 MPa and temperatures up to 40 °C. The results demonstrate that pH of solutions is the only control on the zeta potential, while temperature, CO pressure and salt type affect pH values. We report three empirical relationships that describe the pH dependence of the zeta potential for: i) dead (partial CO pressure of 10 atm) NaCl/NaSO, ii) dead CaCl/MgCl solutions, and iii) for all live (fully saturated with dissolved CO) solutions. The proposed new relationships provide essential insights into interfacial electrochemical properties of silica-water systems at conditions relevant to CO geological storage

Predictive surface complexation model of the calcite-aqueous solution interface: The impact of high concentration and complex composition of brines

Electrochemical interactions at calcite-water interface are characterized by the zeta potential and play an important role in many subsurface applications. In this work we report a new physically meaningful surface complexation model that is proven to be efficient in predicting calcite-water zeta potentials for a wide range of experimental conditions. Our model uses a two-stage optimization for matching experimental observations. First, equilibrium constants are optimized, and the Stern layer capacitance is optimized in the second stage. The model is applied to a variety of experimental sets that correspond to intact natural limestones saturated with equilibrated solutions of low-to-high salinity, and crushed Iceland Spar sample saturated with NaCl at non-equilibrium conditions. The proposed linear correlation of the Stern layer capacitance with the ionic strength is the main novel contribution to our surface complexation model without which high salinity experiments cannot be modelled. Our model is fully predictive given accurately known conditions. Therefore, the reported parameters and modelling protocol are of significant importance for improving our understanding of the complex calcite-water interfacial interactions. The findings provide a robust tool to predict electrochemical properties of calcite-water interfaces, which are essential for many subsurface applications including hydrology, geothermal resources, CO2 sequestration and hydrocarbon recovery