Legitimidad Científica y Verdad

Con el trasfondo de algunas de las tesis principales que Lyotard plasmó en su obra La Condition Postmoderne, el presente artículo pretende ofrecer una visión de la crisis por la que atraviesa la ciencia y que afecta a la concepción, fines y funciones de la misma. La tesis que vertebra dicha visión es que la crisis actual de la ciencia es una crisis de legitimidad que dimana del escepticismo posmoderno acerca de la verdad. Un breve recorrido histórico, en donde se destaca el papel jugado por la noción de juego de lenguaje de Wittgenstein, da pie a mostrar cómo una impostura la doctrina de Popper acerca de la relación entre la verdad y la legitimación científica. Finalmente el autor defiende que la verdad universalmente válida debe recuperar su estatus como principio legitimador de la ciencia en un marco neoilustrado que preste la debida atención a las corrientes de pensamiento surgidas con la posmodernidad.

Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, HR-297, 1990

This research project was directed at laboratory and field evaluation of sodium montmorillonite clay (bentonite) as a dust palliative for limestone surfaced secondary roads. It had been postulated that the electrically charged surfaces of the clay particles could interact with the charged surfaces of the limestone and act as a bonding agent to agglomerate fine (-#200) particulates and also to band the fine particulates to larger (+#200) limestone particles. Laboratory testing using soda ash dispersed bentonite treatment of limestone fines indicated significant improvement of compressive strength and slaking characteristics. It was recommended that the project proceed to field trials and test roads were constructed in Dallas and Adair counties in Iowa. Soda ash dispersed bentonite solutions can be field mixed and applied with conventional spray distribution equipment. A maximum of 1.5% bentonite(by weight of aggregate)can be applied at one time. Higher applications would have to be staged allowing the excess moisture to evaporate between applications. Construction of higher application treatments can be accomplished by adding dry bentonite to the surfacing material and then by dry road mixing. The soda ash water solution can then be spray applied and the treated surfacing material wet mixed by motor graders to a consistency of 3 to 4 inch slump concrete. Two motor graders working in tandem can provide rapid mixing for both methods of construction. Calcium and magnesium chloride treatments are 2 to 3 times more effective in dust reduction in the short term (3-4 months) but are prone to washboarding and potholing due to maintenance restrictions. Bentonite treatment at the 2-3% level is estimated to provide a 30-40% dust reduction over the long term(18-24 months). Normal maintenance blading operations can be used on bentonite treated areas. Vehicle braking characteristics are not adversely affected up to the 3.0% treatment level. The bentonite appears to be functioning as a banding agent to bind small particulates to larger particles and is acting to agglomerate fine particles of limestone. This bonding capability appears recoverable from environmental effects of winter, and from alternating wet and dry periods. The bentonite appears to be able to interact with new applications of limestone maintenance material and maintains a dust reduction capability. Soda ash dispersed bentonite treatment is approximately 10 times more cost effective per percent dust reduction than conventional chloride treatments with respect to time. However,the disadvantage is that there is not the initial dramatic reduction in dust generation as with the chloride treatment. Although dust is reduced 30-40% after treatment there is still dust being generated and the traveling public or residents may not perceive the reduction.

Embankment Quality Phase II Final Report, TR-401, 1999

Phase II research included the following: (1) develop and evaluate alternative soil design and embankment construction specifications based on soil type, moisture, density, stability, and compaction process; (2) assess various quality control and acceptance procedures with a variety of in-situ test methods including the Dual-mass Dynamic Cone Penetrometer (DCP); and (3) develop and design rapid field soil identification methods. At the start of the research, soils were divided into cohesive and cohesionless soil types, with each category being addressed separately. Cohesionless soils were designated as having less than 36% fines content (material passing the No. 200 sieve) and cohesive soils as having greater than 36% fines content. Subsequently, soil categories were refined based not only on fines content but soil plasticity as well. Research activities included observations of fill placement, in-place moisture and density testing, and dual-mass DCP index testing on several highway embankment projects throughout Iowa. Experiments involving rubber-tired and vibratory compaction, lift thickness changes, and disk aeration were carried out for the full range of Iowa soils. By testing for soil stability the DCP was found to be a valuable field tool for quality control, whereby shortcomings from density testing (density gradients) were avoided. Furthermore, critical DCP index values were established based on soil type and compaction moisture content.

Improvement of Granular Base Course Materials with Portland Cement, Special Report, HR-99

A highway base course may be defined as a layer of granular material which lies immediately below the wearing surface of a pavement and must possess high resistance to deformation in order to withstand pressures imposed by traffic. A material commonly used for base course construction is crushed limestone. Sources of limestone, acceptable for highway bases in the state of Iowa, occur almost entirely in the Pennsylvanian, Mississippian and Devonian strata. Performance records of the latter two have been quite good, while material from the Pennsylvanian stratum has failed on numerous occasions. The study reported herein is one segment of an extensive research program on compacted crushed limestone used for flexible highway base courses. The primary goals of the total study are: 1. Determination of a suitable and realistic laboratory method of compaction. 2. Effect of gradation, and mineralogy of the fines, on shearing strength. 3. Possible improvement of the shear strength with organic and inorganic chemical stabilization additives. Although the study reported herein deals primarily with the third goal, information gathered from work on the first two was required for this investigation. The primary goal of this study was the evaluation of various factors of stability of three crushed limestones when treated with small amounts of type I Portland cement. Investigation of the untreated materials has indicated that shear strength alone is not the controlling factor for stability of crushed stone bases. Thus the following observations were made in addition to shear strength parameters, to more adequately ascertain the stability of the cement treated materials: 1. Volume change during consolidation and shear testing. 2. Pore pressure during shear. The consolidated-undrained triaxial shear test was used for determination of the above factors.

Aplicaciones del láser en odontologia

Existen diferentes tipos de láseres que pueden tener aplicación en Odontología, y éstos pueden ser utilizados con diferentes fines. El propósito de este artículo es comentar, de forma genérica, el empleo de diferentes tipos de láseres en diversos tipos de tratamientos habituales en la práctica odontológica. No todos los láseres producen los mismos efectos; tampoco un mismo láser produce el mismo efecto sobre diferentes tejidos, y, según sean los parámetros de emisión utilizados, incluso el mismo láser puede producir diferentes efectos sobre el mismo tejido. Para poder incorporar el láser a la praxis diaria, el profesional debe conocer, entre otros extremos, las indicaciones, las contraindicaciones y la forma de utilización del tipo o tipos de láseres que desee utilizar, antes de su aplicación en clínica.

Salsa Brava: nómada en Barcelona. Escenarios y métodos de estudio de un estilo musical y bailable

La salsa brava es un estilo musical que surge en Nueva York a cargo de la diáspora latinoamericana, a finales de los años 1960 y principios de 1970. Contemporáneamente a estos años la salsa viajó a ciudades latinoamericanas y, desde hace una década, su trayecto se hace, relativamente, notorio en Barcelona, entre otras ciudades de Europa. En Barcelona, la salsa brava coexiste con otros estilos salseros y se caracteriza por ser usada, festiva y de forma itinerante, en espacios concebidos para otras músicas o fines. Su nomadismo, también es notable a través del desdoblamiento que experimentan las personas que hacen parte de esta escena, incluida la propia autora de esta investigación. El motivo de este artículo es aproximarse de forma histórica, conceptual y etnográfica a diversos momentos de la trayectoria salsera brava, así como a una de sus estrategias metodológicas o bien al hecho de como una música nómada sugiere un método nómada para su estudio.

Guía sobre gestión de derechos de autor y acceso abierto en bibliotecas, servicios de documentación y archivos

A raíz de una conferencia organizada por SEDIC y realizada en Madrid sobre el acceso libre se nos pidió que reuniéramos toda la información volcada en aquel acto en un texto o una publicación. Hoy en día el movimiento de acceso libre al conocimiento y a la cultura se ha convertido en un movimiento de dimensión mundial con seguidores en diferentes sectores de la sociedad. Aquí queremos exponer una visión de este movimiento y de sus relaciones con la propiedad intelectual y las licencias para contenidos abiertos que sirva de herramienta informativa para cualquier persona interesada pero especialmente para el colectivo de bibliotecarios, archiveros y documentalistas que muchas veces son la punta de lanza de este movimiento en muchas instituciones. La propiedad intelectual o los derechos de autor han dejado de ser un tema de conversación exclusivo de los abogados o los juristas y se ha convertido en un tema de debate en la sociedad. Esperamos que esta publicación pueda ayudar a aclarar muchas dudas y pueda ayudar a todos aquellos que quieran información sobre el tema. Pero lo que más nos gustaría es poder aportar nuestro granito de arena al conocimiento libre y es por esto que esta publicación estará sujeta a una licencia que permita la reproducción, la distribución y la comunicación pública sin fines comerciales siempre que cite a los autores y la fuente de donde se ha obtenido, y se mantenga el aviso de la licencia, además se permiten hacer obras derivadas si estas se difunden con la misma licencia. En suma, este es un documento vivo en el que esperamos se vaya volcando la experiencia española en un tema tan apasionante como es la consecución del acceso libre al saber científico.

Molecular hydrogen diffusion in nanostructured amorphous silicon thin films

We study hydrogen stability and its evolution during thermal annealing in nanostructured amorphous silicon thin films. From the simultaneous measurement of heat and hydrogen desorption, we obtain the experimental evidence of molecular diffusion in these materials. In addition, we introduce a simple diffusion model which shows good agreement with the experimental data

La lectura y escritura de géneros profesionales en EpFE

Conferencia plenaria en el II CIEFE sobre algunas de las características más importantes de la educación lingüística del español para fines específicos (EpFE), así como los aspectos más particulares en contextos laborales auténticos (entornos educativo, empresarial, institucional) y algunas reflexiones sobre este ámbito relevante, creciente y desatendido de la enseñanza del español.

La Novela 53, 6 y sus precedentes inmediatos

Por ser la cuarta vidual, como corroboran las Nov. 53, 6; 74, 5 y 117, 5, una figura vinculada tanto al Derecho de familia, en concreto, a la denominada, en doctrina, cuarta marital o uxoria en su acepción penal, pues en ésta encuentra una parte importante de sus raíces, como al Derecho sucesorio; su historia y fines se entenderán mejor si se integra en la evolución de ambos sistemas. Lo dicho justifica, a mi juicio, el interés de un estudio que, como éste, se centre, por una parte, en la institución que fue el precedente histórico inmediato de la cuarta vidual y, por otra, en el análisis de la Novela que, por primera vez, reguló el derecho a la cuarta en favor del cónyuge viudo, esto es, la 53, 6.

Constraining 3-D electrical resistance tomography with GPR reflection data forimproved aquifer characterization

Surface-based ground penetrating radar (GPR) and electrical resistance tomography (ERT) are common tools for aquifer characterization, because both methods provide data that are sensitive to hydrogeologically relevant quantities. To retrieve bulk subsurface properties at high resolution, we suggest incorporating structural information derived from GPR reflection data when inverting surface ERT data. This reduces resolution limitations, which might hinder quantitative interpretations. Surface-based GPR reflection and ERT data have been recorded on an exposed gravel bar within a restored section of a previously channelized river in northeastern Switzerland to characterize an underlying gravel aquifer. The GPR reflection data acquired over an area of 240×40 m map the aquifer's thickness and two internal sub-horizontal regions with different depositional patterns. The interface between these two regions and the boundary of the aquifer with then underlying clay are incorporated in an unstructured ERT mesh. Subsequent inversions are performed without applying smoothness constraints across these boundaries. Inversion models obtained by using these structural constraints contain subtle resistivity variations within the aquifer that are hardly visible in standard inversion models as a result of strong vertical smearing in the latter. In the upper aquifer region, with high GPR coherency and horizontal layering, the resistivity is moderately high (N300 Ωm). We suggest that this region consists of sediments that were rearranged during more than a century of channelized flow. In the lower low coherency region, the GPR image reveals fluvial features (e.g., foresets) and generally more heterogeneous deposits. In this region, the resistivity is lower (~200 Ωm), which we attribute to increased amounts of fines in some of the well-sorted fluvial deposits. We also find elongated conductive anomalies that correspond to the location of river embankments that were removed in 2002.

Production of nanometric particles in radio frequency glow discharges in mixtures of silane and methane

The formation of silicon particles in rf glow discharges has attracted attention due to their effect as a contaminant during film deposition or etching. However, silicon and silicon alloy powders produced by plasma¿enhanced chemical vapor deposition (PECVD) are promising new materials for sintering ceramics, for making nanoscale filters, or for supporting catalytic surfaces. Common characteristics of these powders are their high purity and the easy control of their stoichiometry through the composition of the precursor gas mixture. Plasma parameters also influence their structure. Nanometric powders of silicon¿carbon alloys exhibiting microstructural properties such as large hydrogen content and high surface/volume ratio have been produced in a PECVD reactor using mixtures of silane and methane at low pressure (-1 Torr) and low frequency square¿wave modulated rf power (13.56 MHz). The a¿Si1¿xCx:H powders were obtained from different precursor gas mixtures, from R=0.05 to R=9, where R=[SiH4]/([SiH4]+[CH4]). The structure of the a¿Si1¿xCx:H powder was analyzed by several techniques. The particles appeared agglomerated, with a wide size distribution between 5 and 100 nm. The silane/methane gas mixture determined the vibrational features of these powders in the infrared. Silicon-hydrogen groups were present for every gas composition, whereas carbon¿hydrogen and silicon¿carbon bonds appeared in methane¿rich mixtures (R-0.6). The thermal desorption of hydrogen revealed two main evolutions at about 375 and 660¿°C that were ascribed to hydrogen bonded to silicon and carbon, respectively. The estimated hydrogen atom concentration in the sample was about 50%.

Nanoparticles in SiH4-Ar plasma: Modelling and comparison with experimental data

Experimental and theoretical investigations for growth of silicon nanoparticles (4 to 14 nm) in radio frequency discharge were carried out. Growth processes were performed with gas mixtures of SiH4 and Ar in a plasma chemical reactor at low pressure. A distinctive feature of presented kinetic model of generation and growth of nanoparticles (compared to our earlier model) is its ability to investigate small"critical" dimensions of clusters, determining the rate of particle production and taking into account the influence of SiH2 and Si2Hm dimer radicals. The experiments in the present study were extended to high pressure (≥20 Pa) and discharge power (≥40 W). Model calculations were compared to experimental measurements, investigating the dimension of silicon nanoparticles as a function of time, discharge power, gas mixture, total pressure, and gas flow.

L'argot juvenil i el codi d'escriptura al web adolescents.cat

En aquest treball s'analitza la manera d'expressar-se dels joves al fòrum del web adolescents.cat des de dos punts de vista. Per una banda, s'analitza la productivitat i recursivitat dels diversos processos de formació d'argot. Per altra banda, s'estudien les alteracions en el codi d'escriptura amb finalitats estilístiques i pràctiques.

Visión estrátegica policial ante el fenómeno de la TSH

El diseño de una estragia implica el conocimiento del problema; a qué nos enfrentamos. Y la visión estratégica de la Guardia Civil ante el fenómeno de la Trata de Seres Humanos pasa a través del Crimen Organizado. Entendemos, que en la investigación de los delitos de Trata de Seres Humanos, deben utilizarse métodos y procedimientos propios de la investigación de crimen organizado. Obviamente, hay singularidades ante las cuales la Institución se ha adaptado. TSH es, o puede ser, Crimen Organizado. También las particularidades que este tipo de delito tiene y las posibles conexiones internacionales. En la TSH, la víctima es sujeto pasivo a la vez el resultado del delito (cosificación); y por ello, el nudo gordiano de la investigación. La grandes líneas de investigación se trazan sobre el reclutamiento, el traslado, los fines de explotación o el sometimiento.