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OALib Journal期刊

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Solid-Surface Fluorescence Determination of Samarium(III) Using an Eosin-o-Phenanthroline-HTAB System: Application to Water and Sediment Samples  [PDF]
Juan Manuel Pérez Iglesias, César Américo Almeida, María Carolina Talio
Open Access Library Journal (OALib Journal) , 2026, DOI: 10.4236/oalib.1115866
Abstract: Samarium is a technologically relevant rare earth element whose trace determination in aquatic systems requires sensitive and accessible analytical alternatives. A solid-surface fluorescence method was developed for Sm(III) using eosin, o-phenanthroline, hexadecyltrimethylammonium bromide (HTAB), and cellulose filter paper as the retention and measurement substrate. Experimental variables, including pH, reagent volumes, and the order of addition, were optimized. The selected sequence was eosin → o-phenanthroline → Sm(III) → HTAB → phosphate buffer, at pH 6.5. The retained system was measured at excitation/emission wavelengths of 525/645 nm. Fluorescence intensity was linear from 1.31 to 375.9 ng∙L−1, with R2 = 0.9967. The calculated limits of detection and quantification were 0.39 and 1.31 ng∙L−1, respectively. No significant interference was observed for the investigated species at the tested molar ratios. Recoveries were 92.71% - 105.42% in natural waters and 99.50% - 100.43% in sediment extracts. Sm(III) was detected in six of ten water samples, while acid-extractable Sm concentrations in sediments ranged from 509.76 to 1218.68 µg∙kg−1. The aqueous fluorescence step avoided organic solvents and used small sample aliquots, low reagent concentrations, a cellulose support, and conventional instrumentation. These results demonstrate a simple and sensitive approach for Sm(III) screening in aquatic environmental samples, with potential advantages from a green analytical chemistry perspective that should be confirmed through formal assessment.
Recidiva local después de la prostatectomía radical y radioterapia de rescate
Ojea Calvo,Antonio; Pérez Rodríguez,Alberto; Domínguez Freire,Fernando; Alonso Rodrigo,Arturo; Rodríguez Iglesias,Benito; Benavente Delgado,Juan; Barros Rodríguez,José Manuel; González Pi？eiro,Ana; Otero García,Milagros; Mu？oz Garzón,Víctor;
Archivos Espa？oles de Urología (Ed. impresa) , 2005, DOI: 10.4321/S0004-06142005000100004
Abstract: objetive: to evaluate the efficacy of radiotherapy to the prostatic bed in patients with biochemical recurrence prostate cancer after radical prostatectomy. methods: we analyse the outcomes of 292 patients who underwent radical prostatectomy for localized prostate cancer t1-t2 between january 1992 and june 2003, with an average folow-up of 36 months (range 6 months to 12 years). we detected biochemical recurrence (psa > 0.20 ng/ml) in 75(26%) patients. 75 patients with biochemical recurrence, 9 (12 %) were diagnosed of local recurrence by the following criteria: a) first psa obtained 6 weeks after radical prostatectomy < 0.20 ng/ml. b) time to biochemical recurrence > 6 months. c) prostate specific antigen doubling time > 6 months. d) prostate specific antigen velocity after radical prostatectomy < 0.75 ng/ml/year. e) prostate specific antigen level after radical prostatectomy < 2.5 ng/ml. the 9 patients diagnosed of local recurrence received an average dose of 56.42 gy to the prostate bed. results: of all 9 patients with local recurrence, 8(88.8%) have complete response with a mean followup of 30 months (12-36 months). the time between the radiotherapy and the response, in patients with complete response, was lower than 3 months in 7 patients and 12 months in 1 patient. significant adverse effects associated to radiotherapy were not observed. conclusions: salvage radiotherapy may be beneficial in selected patients with local recurrence. the characteristics of prostate specific antigen elevation are useful in distinguishing men with local recurrence from those with distant metastases.
Arqueofauna del Nororiente de Cuba
Lourdes Pérez Iglesias,Juan Guarch Rodríguez
Cuba Arqueológica : Revista Digital de Arqueología de Cuba y el Caribe , 2011,
Abstract: La región nororiental de Cuba, que abarca el norte de los territorios de las provincias Las Tunas, Holguín y Guantánamo, posee un potencial arqueológico de alrededor de 220 sitios, de ellos se posee información zooarqueológica de 35 localidades. Esta información se ha reunido en un sistema de información geográfica(SIG) denominado Arqueofauna del Nororiente de Cuba, que permite el manejo de los datos a través de entradas como: nombre del sitio, coordenadas, provincia, municipio, categoría, filiación, lista de taxones presentes (Moluscos, Crustáceos, Peces, Reptiles, Aves, Mamíferos), número de especies respectiva a cada taxón, fechado del sitio, persona y fecha en que fue trabajado. Este levantamiento zooarqueológico ofrece además, una aproximación del uso de los recursos faunísticos por parte de las comunidades aborígenes, en esta área geográfica, así como datos sobre el uso de especies extintas, variaciones en la distribución de especies en el pasado, cuestión tratada en el presente trabajo.
Generación de nuevos significados, mediante la metonimia, en el parlache
Pérez Sánchez,Juan Manuel;
íkala, Revista de Lenguaje y Cultura , 2009,
Abstract: taking into consideration the impact that semantic change has on slang, we analyse the role metonymy plays as a mechanism for generating new meanings in the youth slang of medellín (colombia), also known as parlache. as a starting point, the concepts ''slang'' and ''metonymy'' are delimited. following these clarifications, a sample of twelve argotic meanings generated through metonymic processes of existing units is analysed. the results obtained after the analysis evidence tendencies in the use of certain types of metonymy within the sample. likewise, tendencies in the choice of source concepts seem to be based on universal cognitive principles such as ''typical over non-typical,'' ''bodily over mental,'' and ''concrete over abstract,'' among others.
On the Theory of Self-Adjoint Extensions of the Laplace-Beltrami Operator, Quadratic Forms and Symmetry
Juan Manuel Pérez-Pardo
Mathematics , 2013,
Abstract: The main objective of this dissertation is to analyse thoroughly the construction of self-adjoint extensions of the Laplace-Beltrami operator defined on a compact Riemannian manifold with boundary and the role that quadratic forms play to describe them. Moreover, we want to emphasise the role that quadratic forms can play in the description of quantum systems. A characterisation of the self-adjoint extensions of the Laplace-Beltrami operator in terms of unitary operators acting on the Hilbert space at the boundary is given. Using this description we are able to characterise a wide class of self-adjoint extensions that go beyond the usual ones, i.e. Dirichlet, Neumann, Robin,.. and that are semi-bounded below. A numerical scheme to compute the eigenvalues and eigenvectors in any dimension is proposed and its convergence is proved. The role of invariance under the action of symmetry groups is analysed in the general context of the theory of self-adjoint extensions of symmetric operators and in the context of closed quadratic forms. The self-adjoint extensions possessing the same invariance than the symmetric operator that they extend are characterised in the most abstract setting. The case of the Laplace-Beltrami operator is analysed also in this case. Finally, a way to generalise Kato's representation theorem for not semi-bounded, closed quadratic forms is proposed.
The African Atlantic islands in maritime history during the Ancien Régime
Juan Manuel Santana-Pérez
- , 2018, DOI: 10.1177/0843871418803301
Abstract: This paper aims at describing and explaining certain common characteristics that have endured in the African Atlantic islands by virtue of the fact that these islands depend on centres of authority located at considerable distances away. Their location on linking routes to three continents led to the first globalization since the world economic shifts of the 16th century. The islands have sometimes been described metaphorically as a bridge, but we prefer to speak of maritime doors. These islands have been an entrance and exit for goods, people, culture, and ideas, opened or closed, depending on your point of view, through the modern age as European penetration spread. It includes the archipelagos of the Middle Atlantic, the cases of Madeira, the Canaries, Cape Verde, S？o Tomé, and Principe, and the Guinea Islands of Bioko, Corisco, and Annobon
Determination of Radioactive Contaminant 137Cs (Fission Product) and Comparison with Natural 40K Present in Mexican Strawberries  [PDF]
Fridda Concepción Fuentes Gama, Juan Manuel Navarrete Tejero, Alejandro Ramírez Chávez, Miguel ángel Zú？iga Pérez
Journal of Geoscience and Environment Protection (GEP) , 2022, DOI: 10.4236/gep.2022.107015
Abstract: Several previous papers have been published about radioactive contamination in Mexican soil, marine sediments and foodstuffs. Ever since, results have been according to expectation, mainly consisting of natural isotopes in small concentration. Continuous research leads with the surprising finding of fission product 137Cs (t1/2 = 30 years) in strawberries produced in different states, about 2000 km away from each other. Never before, such contaminant has been observed in foodstuffs, produced in this country. The aim of this work is to report the presence of 137Cs in Mexican strawberries and compare the activity of such contaminant with the natural radioactivity of 40K (t1/2 = 1.28 × 109 years), through gamma spectrometry. Eventually, the specific activity of 137Cs observed in samples FM4, FM5 and FBC is respectively 0.7, 0.8 and 0.3 Bq/kg. The limits established in CODEX-STAN-193-1995 for 137Cs are 1000 Bq/kg, so all samples meet the recommendation. It’s presence now
Avances en la clínica de las adicciones: el rol del aprendizaje y la dopamina
Pérez F,Juan Manuel; Orellana V,Gricel;
Revista médica de Chile , 2007, DOI: 10.4067/S0034-98872007000300015
Abstract: there are two parallel explanatory models for addictions. one is the homeostatic model, that explains tolerance and the abstinence syndrome. tolerance and abstinence are reversible phenomena that mask sensitization. these appear more commonly with the continued use of drugs, and are based in the up-regulation of cyclic amp. the other is the plasticity model, that explains sensitization and compulsive use of drugs or addiction. addiction is probably irreversible, underlies tolerance, appears more frequently with intermittent use of drugs, and is based in learning and memory mechanisms. both are boldly linked to environmental and behavioral elements. in the plasticity model, dopamine (da) has an outstanding role. its phasic discharge is a temporal reward prediction error marker. it is the prediction error that generates learning. all the addictive drugs provoke a very strong increase of phasic da discharge in some cerebral nuclei by direct or indirect paths. this increase is interpreted by cerebral circuits as prediction errors that generate learning behaviors. pavlovian and operating type learning is involved. it is clinically observed as the prominence of environmental cues that are related to drug consumption, and the appearance of behaviors directed to the search and use of drugs, that are mainly involuntary and triggered by these cues. pleasure (primary reinforcement) plays a role in this model, only in the initial stages of addiction. understanding this double parallel model allows to design therapeutic interventions directed towards a conscious control of involuntary, environmental and affective cues that trigger drug search and use
Designación del neotipo de Brachycolus dusmeti Gómez-Menor, 1950, syn. nov. de Brevicoryne brassicae (Linnaeus, 1758) (Hemiptera, Aphididae, Macrosiphini)
Pérez Hidalgo, Nicolás,Nieto Nafría, Juan Manuel
Graellsia , 2004,
Abstract: Not available No disponible
Caracterizando a los consumidores en los mercados de consumo de alta frecuencia
Juan Carlos Gáquez Abab,Manuel Sánchez Pérez
Universia Business Review , 2007,
Abstract: Los mercados de consumo de alta frecuencia presentan rasgos particulares en cuanto a la diversidad de estrategias de precio, constantes promociones en precio, publicidad masiva o estrategias de marca que hacen que la identificación de segmentos sea especialmente interesante para la empresa. En el presente trabajo se lleva a cabo un análisis de segmentación sobre datos de panel que pretende identificar cuántos segmentos existen y describir cuál es su comportamiento en relación a variables como el precio o las promociones de ventas.
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