3,251 research outputs found
The morphodynamic responses of artificial embayed beaches to storm events
The morphological changes caused by storm events in two Barcelona beaches
were recorded using video monitoring techniques during the period 2001–2006.
Changes in shoreline position and configuration and submerged bar position
and shape were analyzed during the 25 major storm events that occurred
during the study period. Beach responses to storms were grouped into three
categories: shoreline advance or retreat (including rotation), sandbar
migration and/or configuration change (linear or crescentic shape) and
formation of megacusps. This work provides examples of the differential
adaptation of both beaches to the same storm and of some unexpected
morphological responses of both beaches. The response of the beach to storm
events is not straightforward because wave conditions are not the only
relevant parameter to be considered. In particular, in such embayed beaches
it is crucial to take into account their specific morphodynamic
configuration prior to the storm
Exploring the boundaries in the analysis of large particles by single particle inductively coupled plasma mass spectrometry: application to nanoclays
The analysis of microparticles by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) requires sample introduction systems that guarantee transport efficiencies similar to those obtained with dissolved standards across the size range covered. The utilization of a nebulisation system based on a linear pass spray chamber and a micronebuliser is discussed and optimized for the introduction of large inorganic particles. Limitations caused by incomplete ionisation or the counting limit of detectors affecting particle size characterisation are also considered. The procedure developed has been applied to the characterisation of suspensions of a natural clay (kaolinite), with a thickness in the range of a few nanometers and lateral dimensions up to 1 mu m. The application of different sensitivity conditions by the modification of the ion transmission allowed us to cover the whole size range of the suspension monitoring the Al-27 isotope and achieve a quantitative mass recovery with respect to ICP-MS analysis. Finally, the migration of nanoclays (montmorillonite) from food containers and their detection by SP-ICP-MS are presented. The results have been compared to those obtained by TEM, showing that nanoclays migrated from the containers into water
The use of recovery time in timetables: rail passengers' preferences and valuation relative to travel time and delays
Recovery time in the rail industry is the additional time that is included in train timetables over and above the minimum journey time necessary often with the explicit aim of improving punctuality. Recovery time is widely used in railways in a number of countries but prior to this study there has been no investigation of the rail users’ point of view. Perceived recovery time, such as being held outside stations and prolonged stops at stations, might have some premium valuation due to the frustration caused. If perceived recovery time in train timetables does carry a premium, then the benefits of improved punctuality achieved by it will be reduced. This paper is the first to investigate passengers’ views and preferences on the use of recovery time. We summarise the findings of a large study and provide estimates of passengers’ valuations of recovery time, both relative to in-vehicle time and late time, that can be used for economic appraisal purposes. Overall, we find most passengers support the use of recovery time but the context is important. Only 13% of users disapprove of its use as a tool to reduce lateness. The estimated premia vary by demand characteristics and are significant in some contexts, although on average are of a small magnitude. The applicability of the estimates is demonstrated through the appraisal of an actual scheme in the UK. We observe that the introduction of more recovery time along with the subsequent improvement in reliability can lead to significant reductions in generalised journey time, even when recovery time carries a valuation premium. We must however strike a word of caution since we note that there were higher than expected proportions of non-traders in the survey which may have affected the results; future studies into the topic should look to minimise the proportion of non-traders. This study provides valuable and necessary first steps in this challenging topic
Supersymmetry of FRW barotropic cosmologies
Barotropic FRW cosmologies are presented from the standpoint of
nonrelativistic supersymmetry. First, we reduce the barotropic FRW system of
differential equations to simple harmonic oscillator differential equations.
Employing the factorization procedure, the solutions of the latter equations
are divided into the two classes of bosonic (nonsingular) and fermionic
(singular) cosmological solutions. We next introduce a coupling parameter
denoted by K between the two classes of solutions and obtain barotropic
cosmologies with dissipative features acting on the scale factors and spatial
curvature of the universe. The K-extended FRW equations in comoving time are
presented in explicit form in the low coupling regime. The standard barotropic
FRW cosmologies correspond to the dissipationless limit K =0Comment: 6 page
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Spanish validation of the revised depression attitude questionnaire (R-daq)
Purpose: The aim of the study was to develop and validate a Spanish version of the Revised Depression Attitude Questionnaire (R-DAQ). Methods: The R-DAQ was used as a baseline for the study. It was translated and tested to ensure the instrument was appropriate for the target population. 537 Ecuadorian healthcare professionals completed the revised Spanish version of the R-DAQ (SR-DAQ). Statistical and exploratory factor analyses were performed to examine construct validity, internal consistency, readability and floor and ceiling effects. Results: Three factors were obtained: “Professional confidence in depression care”; “Therapeutic optimism about depression”; and “Generalist perspective about depression occurrence, recognition, and management”. The internal consistency of the SR-DAQ was determined by means of Cronbach’s α coefficient, with values ranging between 0.61–0.8. The correlations with the English version reflected adequate validity. The model explained 39% of the variance. Subsequent analysis with a sample restricted to those who had received training in depression produced a model that explained 42% of the variance. Conclusion: The SR-DAQ meets the psychometric requirements for measuring depression attitude in a Spanish-speaking population and shows adequate internal consistency and validity
¿Qué herramientas proporcionan las Tecnologías de la Información y la Comunicación a la educación ambiental?
Tras una revisión exhaustiva de la literatura publicada que relaciona los campos de las Tecnologías de la Información y Comunicación (TIC) y la Educación Ambiental para la Sostenibilidad, en este trabajo planteamos un estudio y clasificación de los medios TIC que están a disposición de los educadores ambientales o profesionales de la educación para su tarea docente, en la que se nos muestran las múltiples posibilidades que se nos abren en este campo, todavía escasamente explorado.Palabras clave: TIC; Educación Ambiental; Educación para la Sostenibilidad.Which tools does information comunication technology provide to enviromental education?After an exhaustive revision of the literature published relating to the topics of Information and Communication Technologies (ICT) and Environmental Education for Sustainability, in this work we set out a study and classification of ICT media available for environmental educators or teachers for their educational tasks. After that we show the multiple possibilities that those offer us in this field, still scarcely explored.Keywords: ICT; Environmental Education; Environmental Education for Sustainability
Variaciones estacionales de parámetros reproductivos, calidad espermática y enzimas del plasma seminal en carneros texel
El objetivo del presente trabajo fue determinar el efecto de la estación del año (fotoperíodo) sobre la circunferencia escrotal (CE), peso testicular (PT), volumen testicular (VT), capacidad de servicio (CS), concentración plasmática de testosterona, características cuali-cuantitativas del semen fresco y enzimas del plasma seminal de carneros de raza Texel. El estudio se realizó en la pampa húmeda de Argentina (37°45’ S, 58°18’ O, 130 msnm). Se utilizaron seis carneros jóvenes (2 años de edad) y las determinaciones realizadas, peso vivo, CE, PT [PT=0,5533 x (L) x (A)2], VT [VT=4/3 x (n) x (L/2) x (A/2)2] (siendo L=longitud y A=ancho del testículo) y testosterona plasmática se realizaron una vez por mes. La prueba de CS se realizó dos veces por estación y la evaluación del semen se efectuó dos veces por semana durante el mes central de cada estación. Las variables fueron analizadas mediante modelos lineales mixtos para medidas repetidas en el tiempo (R Core Team). En verano (Marzo) se observaron los mayores valores (media ±EE; p<0,05) de CE (33,8±0,6 cm), PT (467,5±15,2 g) y VT (442,3±8,5 cm3). El número promedio de montas totales fue mayor (p<0,05) en invierno (21) respecto de la primavera (9). La mayor concentración plasmática de testosterona (p<0,05) fue determinada en verano (Enero=13,2±2,9 ng/ml) y la menor en invierno (Sep- tiembre=0,13±0,1 ng/ml). Eyaculados (n=192) fueron evaluados y los mejores parámetros de calidad seminal fueron determinados en otoño e invierno. Los patrones anuales de las enzimas alanina-amino-transferasa y lactato-deshidrogenasa mostraron una significativa variación estacional (p<0,05), con la más alta actividad durante la estación reproductiva. Por otro lado, las concentraciones de aspartato-amino-transferasa, gama-glutamil-transpeptidasa y fosfatasa alcalina fueron más bajas en verano. Los resultados sugieren que los carneros Texel presentan un mayor potencial reproductivo en la estación de otoño (fotoperíodo decreciente) en esta latitud
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