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Search Results: 1 - 10 of 413089 matches for " Nella M. Vargas-Barbosa "
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Electrochemical Capacitance DNA Sensing at Hairpin-Modified Au Electrodes
Joel Rivera-Gandía,Maria del Mar Maldonado,Yarimar De La Torre-Meléndez,Edwin O. Ortiz-Quiles,Nella M. Vargas-Barbosa,Carlos R. Cabrera
Journal of Sensors , 2011, DOI: 10.1155/2011/735279
Abstract: An interfacial capacitance measurement electrochemical technique has been used for the sensing of self-assembled DNA hairpin probes (M. tuberculosis and B. anthracis) attached to Au electrodes. The double-layer capacitance ( ) was determined with electrochemical perturbations from 0.2?V to 0.5?V versus Ag/AgCl at a Au/M. tuberculosis DNA hairpin probe at surface coverage Au electrodes. The capacitance study was done at pH 7, which was necessary to maintain the M. tuberculosis and B. anthracis DNA probes closed during the electrochemical perturbation. Detailed experimental analysis carried out by repetitively switching the electrochemical potential between 0.2 and 0.5?V (versus Ag/AgCl) strongly supports the use of capacitance measurements as a tool to detect the hybridization of DNA targets. A large change in the capacitance deference between 0.2 and 0.5?V was observed in the DNA hybridization process. Therefore, no fluorophores or secondary transducers were necessary to sense a DNA target for both DNA hairpins. 1. Introduction The behavior of DNA attached onto metallic and nonmetallic surfaces via self-assembly with various chemistries (e.g., Au-S) may have applications in biomedical devices. For example, single-stranded DNA (ssDNA) self-assembled on a metallic interface such as gold [1, 2] or on nonmetals such as carbon nanotubes [3] and diamond [4–6] has potential use in DNA microarrays [7]. In addition, detection of DNA hybridization has been possible with techniques using different types of reporting, including fluorescence [8–11], chronocoulometry [12–14], surface plasmon resonance (SPR) [15, 16], colloidal labeling [17–19], and polarization modulation infrared reflection absorption spectroscopy [20]. Electroactive molecules can also be used to monitor the electron transfer mechanism during the hybridization process [21]. Here, we present a nonfaradaic electrochemical method based on capacitive measurement to sense DNA hairpin modification and hybridization. A nucleic acid probe has been developed to recognize specific DNA targets in solution [22]. These probes, called molecular beacons, are DNA hairpins with a fluorophore-quencher pair, which is completely unable to fluoresce when the two components are in close proximity (i.e., closed molecular beacon). When the molecular beacon spontaneously changes its conformation (like during hybridization), the fluorophore attached to one end of the molecule is no longer quenched as the quencher moves away. The capacity of this DNA hairpin has shown to discriminate between alleles with high specificity when
Predictors of Red Fox (Vulpes vulpes) Helminth Parasite Diversity in the Provinces of Spain
Barbosa, A.M.,Segovia, J.M.,Vargas, J.M.,Torres, J.
Wildlife Biology in Practice , 2005,
Abstract: We analysed the viscera of 321 red foxes collected over the last 30 years in 34 of the 47 provinces of peninsular Spain, and identified their helminth parasites. We measured parasite diversity in each sampled province using four diversity indices: Species richness, Margalef's species richness index, Shannon's species diversity index, and inverse Simpson's index. In order to find geographical, environmental, and/or human-related predictors of fox parasite diversity, we recorded 45 variables related to topography, climate, lithology, habitat heterogeneity, land use, spatial situation, human activity, sampling effort, and fox presence probability (obtained after environmental modelling of fox distribution). We then performed a stepwise linear regression of each diversity index on these variables, to find a minimal subset of statistically significant variables that account for the variation in each diversity index. We found that most parasite diversity indices increase with the mean distance to urban centres, or in other words, foxes in more rural provinces have a more diverse helminth fauna. Sampling effort and fox presence probability (probably related to fox density) also appeared as conditioning variables for some indices, as well as soil permeability (related with water availability). We then extrapolated the models to predict these fox parasite diversity indices in non-sampled provinces and have a view of their geographical trends.
Phylogeographic Triangulation: Using Predator-Prey-Parasite Interactions to Infer Population History from Partial Genetic Information
A. Márcia Barbosa, Guillermo Thode, Raimundo Real, Carlos Feliu, J. Mario Vargas
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050877
Abstract: Phylogeographic studies, which infer population history and dispersal movements from intra-specific spatial genetic variation, require expensive and time-consuming analyses that are not always feasible, especially in the case of rare or endangered species. On the other hand, comparative phylogeography of species involved in close biotic interactions may show congruent patterns depending on the specificity of the relationship. Consequently, the phylogeography of a parasite that needs two hosts to complete its life cycle should reflect population history traits of both hosts. Population movements evidenced by the parasite’s phylogeography that are not reflected in the phylogeography of one of these hosts may thus be attributed to the other host. Using the wild rabbit (Oryctolagus cuniculus) and a parasitic tapeworm (Taenia pisiformis) as an example, we propose comparing the phylogeography of easily available organisms such as game species and their specific heteroxenous parasites to infer population movements of definitive host/predator species, independently of performing genetic analyses on the latter. This may be an interesting approach for indirectly studying the history of species whose phylogeography is difficult to analyse directly.
FAST HUG in an ICU at a private hospital in Brasília: checklist and the eighth evaluation item
GB Magnan, RS Vargas, LF Lins, KR Mendon?a, M Barbosa, PR Rocha, MO Maia
Critical Care , 2009, DOI: 10.1186/cc7803
Abstract: To expose the shortcomings found during the FAST HUG application, and to show results obtained with the eighth item of the FAST HUG mnemonic: S – Skin.A descriptive study, based on institutional data, was carried out in the adult ICU of a private hospital. It was performed from 2 to 27 June 2008, except on weekends. Three hundred and twenty-three patients were involved. The checklist was carried out during the afternoons by the head nurse, or the assistant nurse of the unit. In order to do this job, a spreadsheet was elaborated to control data, updated every week. This spreadsheet provided graphics for a more objective control of the results obtained. The idea was exposed to the team, during a training program, and so we started the activities.For 20 days of the checklist, 323 patients were evaluated for the eight items. The real shortcomings most frequently found were related to thromboembolic prophylaxis (85%) and glucose control (90%). These shortcomings were immediately evaluated and, depending on this analysis, this item would go on or not, according to the patient's clinical situation. The shortcomings found were tracked just as they were detected, and their cause would be discussed in a multidisciplinary group, and a solution was found. If the item was not observed, it would be written down but not treated as a real shortcoming. The changes in medial prescription were done immediately. In cases where the patient did not show a favorable situation for the utilization of thromboembolic prophylaxis (bleeding, presurgical, among others), it would be treated as a nonreal shortcoming. The same was done for glucose control. We realized that after 4 weeks using this instrument there was a small reduction of shortcomings in glucose control (Figure 1), and a discrete raise in thromboembolic prophylaxis (Figure 2). From this point we reviewed the checklist, in order to provide a field to write down real shortcomings, so that they are given more relevance and treatment,
Desarrollo y validación de una metodología analítica por HPLC para la cuantificación de fenobarbital en una suspensión extemporánea
Morantes,Marcela; Vargas,Mónica; Figueroa,Fanny S; Sierra,Noralba; Barbosa,Helber;
Revista Colombiana de Ciencias Químico - Farmacéuticas , 2010,
Abstract: in this article we present the data obtained during the development, standardization and validation of a high performance liquid chromatography method for the quantification of phenobarbital in an extemporaneous suspension using butobarbital as internal standard. the chromatographic method uses a uv detector with diode array (dad) as detection system, as mobile phase a mixture of h3po4 0.1% in methanol and h3po4 to 0.1% in water (48:52) and column chromatography c18 stabilized at 35 °c. the validated methodology was selective, linear, precise and accurate. the linearity was evaluated for concentrations between 4.8 and 24 mcg/ml. the developed methodology was used to carry out the study of stability of an extemporaneous suspension of phenobarbital used in the clinic country for the treatment of convulsions in pediatric patients.
Flowsheet optimization of a lubricant base oil hydrotreatment process
Medeiros J. L.,Barbosa L. C.,Vargas F. M.,Araújo O. Q. F.
Brazilian Journal of Chemical Engineering , 2004,
Abstract: Unsaturated, nitrogenated and sulfured compounds may reach undesirable levels in lubricant base oils, requiring hydrotreatment (HDT) at high temperatures and pressures. HDT processes are well known for their high capital and operational costs due to the use of hydrogen, compressors and multistage heterogeneous reactors. Process costs are thus highly dependent on the applied conditions. An oversized process entails unnecessary costs and capital investment. On the other hand, mild reaction conditions lead to unspecified products. This work analyzes the process using a compositional modeling and a kinetic framework developed previously (Barbosa et al., 2002) for the HDT of lubricant base oils. The industrial reactor is rigorously modeled on an adiabatic and multistage configuration. For the remaining equipment in the flowsheet, we adopt shortcut models for compressors and exchangers. The process is then optimized in terms of its variables subject to product specification constraints.
Flowsheet optimization of a lubricant base oil hydrotreatment process
Medeiros, J. L.;Barbosa, L. C.;Vargas, F. M.;Araújo, O. Q. F.;Silva, R. M. F.;
Brazilian Journal of Chemical Engineering , 2004, DOI: 10.1590/S0104-66322004000200022
Abstract: unsaturated, nitrogenated and sulfured compounds may reach undesirable levels in lubricant base oils, requiring hydrotreatment (hdt) at high temperatures and pressures. hdt processes are well known for their high capital and operational costs due to the use of hydrogen, compressors and multistage heterogeneous reactors. process costs are thus highly dependent on the applied conditions. an oversized process entails unnecessary costs and capital investment. on the other hand, mild reaction conditions lead to unspecified products. this work analyzes the process using a compositional modeling and a kinetic framework developed previously (barbosa et al., 2002) for the hdt of lubricant base oils. the industrial reactor is rigorously modeled on an adiabatic and multistage configuration. for the remaining equipment in the flowsheet, we adopt shortcut models for compressors and exchangers. the process is then optimized in terms of its variables subject to product specification constraints.
Statistical properties of the LEDA redshift database
L. Amendola,H. Di Nella,M. Montuori,F. Sylos Labini
Physics , 1997,
Abstract: We present the statistical properties of large scale galaxy distribution in the LEDA redshift database. This catalog contains more than 40,000 redshifts over all the sky. We find that LEDA, although seriously affected by incompleteness, shows quite stable statistical properties. In particular, we have considered the behaviour of the two points correlation function and of the power spectrum of the density fluctuations, and we have done several tests to check whether the incompleteness of the catalog affect these statistical quantities. Our conclusion is that galaxy distribution in this catalog has fractal properties up to the distance 200 Mpc with D = 2.1 \pm 0.2, with no sign towards homogeneity: this result is statistically stable. We analyze also the properties of the angular distributions, finding a complete agreement with the results obtained in redshift space. Finally, we compare these results with those obtained in other redshift surveys, finding that this sample well reproduces the properties of galaxy distribution found in the different catalogs.
Rese a de Tesis de Maestría: Qué le agrega la Educación Física al juego? La búsqueda del saber jugar.
Nella, Jorge
Lúdicamente , 2012,
Abstract: El presente trabajo intenta identificar la diferencia entre jugar fuera y dentro de la escuela, principalmente en las clases de Educación Física. En este sentido la tesis no se pregunta acerca de qué es el juego, sino más bien desde una mirada foucaultiana interroga sobre por qué jugamos como jugamos, o cómo hemos llegado a jugar de una manera y sobre todo, cómo tenemos que orientar nuestra vista como jugador dentro de una clase de Educación Física. Así, el aporte de este trabajo es argumentar que ante aquellas experiencias "objetivas" del mundo exterior, donde uno aprende los significados y sentido de los juegos, los ni os/alumnos adquieren al mismo tiempo por la intervención del profesor, experiencias donde uno aprende el sentido de ser jugador y lo que significa ser un jugador.
Scientific correspondence in the archive of the General Directorate of Agriculture under the Ministry of Agriculture Industry and Commerce
Nella Eramo
Annals of Geophysics , 2009, DOI: 10.4401/ag-4615
Abstract: The archive, which testifies the activity of the offices dedicated to geological studies and to the collection of meteorological investigations from 1870 to 1895, contains important files of scientific correspondence. The latter includes letters from scientists, members of the councils, committees and research commissions established under the Ministry of Agriculture Industry and Commerce, as well as correspondence of technicians who were charged with particular duties by the administration, like Nicola Maraglia, general director for Agriculture, and Felice Giordano, director of the Service of the Mines. They are rich in news, opinions, observations and reports portraying scientific events and personalities of the time. As an example, some documents concerning the following topics are illustrated: the origins of the Central Office of Meteorology and the role of Giovanni Cantoni the establishment of a service for the systematic collection of data about seismic phenomena, by Michele Stefano De Rossi; the activity of the Geodynamic Commission; the project by Giulio Grablowitz for the constructionof the observatory of Ischia.
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