Mechanical reliability of dental grade zirconia after laser patterning

The aim of this work is to test the mechanical properties of dental zirconia surfaces patterned with Nd:YAG laser interference (¿¿=¿532¿nm and 10¿ns pulse). The laser treatment produces an alteration of the topography, engraving a periodic striped pattern. Laser-material interaction results mainly in thermal effects producing microcracking, phase transformation and texturization. The role of such microstructural modifications and collateral damage on the integrity and mechanical performances has been assessed. Laser patterned discs of zirconia doped with 3% mol yttria (3Y-TZP) have been tested before and after a thermal treatment to anneal residual stresses and revert phase transformation. Both groups of samples behave in a similar manner, excluding residual stresses and phase transformation from the origin of properties modification. Result show that laser patterning induces a minor decrease in mechanical properties and surface integrity of 3Y-TZP surfaces. The biaxial strength decreases as a consequence of the damage induced by laser patterning. Fractographic observations identify preexisting defects enlarged by local laser interaction as the fracture origins. The Hardness and Young modulus of treated surfaces tested with nanoindentation also decrease slightly after laser treatment and this may be attributed to laser-induced microcracking.Peer ReviewedPreprin

Hábitos de sueño y problemas relacionados con el sueño en adolescentes: relación con el rendimiento escolar

ObjetivoConocer la prevalencia de trastornos de sueño en los adolescentes. Describir los hábitos de sueño de los adolescentes y su relación con los trastornos del sueño y los factores asociados. Conocer la relación entre los trastornos del sueño y/o los hábitos de sueño inadecuados con el rendimiento escolar.DiseñoEstudio observacional, descriptivo y transversal.EmplazamientoInstitutos de enseñanza secundaria obligatoria (ESO) de la ciudad de Cuenca.ParticipantesUn total de 1.293 alumnos escolarizados en primero y cuarto cursos de ESO.Mediciones principalesHábitos de sueño en días lectivos y fines de semana y prevalencia de trastornos del sueño medidos mediante un cuestionario estructurado con preguntas abiertas y cerradas, autoadministrado y anónimo. Se determinó el rendimiento escolar de los alumnos y su relación con los hábitos y trastornos de sueño.ResultadosDe los 1.293 alumnos matriculados, completaron la encuesta 1.155 (89,33%), 537 (45,9%) chicos y 618 (54,1%) chicas, con una media de edad de 14 años (rango, 11-18 años). Los días laborables se acuestan en promedio a las 23.17 y se levantan a las 7.46 (tiempo medio, 8 h y 18 min) y los fines de semana se acuestan a la 1.02 y se levantan a las 10.42 (tiempo medio, 9 h y 40 min). El 45,4% declara dormir mal la noche del domingo al lunes. El promedio de asignaturas suspendidas es mayor en los adolescentes con queja de sueño (2,28 frente a 1,91; p = 0,04), los que se levantan cansados (2,17 frente a 1,97; p = 0,048) y los que tienen somnolencia diurnal (2,17 frente a 1,75; p = 0,004).ConclusionesEl horario escolar conlleva deuda de sueño durante la semana que se recupera parcialmente el fin de semana. En los fines de semana se produce una rotura en los hábitos de sueño de los adolescentes. Los adolescentes con problemas relacionados con el sueño muestran peor rendimiento escolar.ObjectiveTo determine the prevalence of sleep disorders in adolescence.To describe sleeping habits of adolescents in relation to sleep disorders and associated factors. To determine the relation between sleep disorders/inappropiate sleeping habits and school performance.DesignObservational, descriptive, crosssectional study.SettingSecondary school of Cuenca (city in Spain).Participants1293 school children of first and fourth curses of secondary education.Main measuresStructured questionnaire with opened and closed questions on sleeping habits during weekdays and at weekends and sleep disorders to be answered by the adolescents anonymously and on their own. Student's school performance with relation with to sleeping habits and sleep disorders were determined.Results1155 students out of 1293 (response rate 89.33%) answered the questionnaire, 537 (45.9%) boys and 618 (54.1%) girls, 14 years old on average (between 11-18 years). On weekdays students went to bed at 23.17 h and got up at 7.46 h (average sleeping time =8 hours and 18 minutes). At weekends they went to bed at 1.02 h and got up at 10.42 h (average sleeping time =9 hours and 40 minutes). 45.4% of students said to sleep badly on Sunday night's.On average the number of subjects failed in class is higher with adolescents who complain about sleep (2.28 vs 1.91; P=.04), who are tired at waking up time (2.17 vs 1.97; P=.048) and who have morning sleepiness (2.17 vs 1.75; P=.004).ConclusionsSchools hours cause deficitsleeping time during weekdays which is partly made up for at weekend. At weekends there is an interruption of the adolescent's sleeping habits. School performance of adolescents with sleep disorders is lower

Seasonal variation of zooplankton and environmental conditions along a transect in the Gulf of Cádiz

This study presents seasonal variation in the zooplankton composition of the Gulf of Cádiz was studied between 2001 and 2012. Samples were collected three times per year, in the spring, summer and autumn at three stations situated along a transect perpendicular to the coast. The total zooplankton abundance during the summer was higher than in the spring and autumn. Zooplankton community is characterized by a seasonal cycle mirroring similar cycles in the physical environment. Differences in community composition were also found along the transect, particularly between the coastal station, under the influence of the Guadalquivir River, and the outer station, characterized by oceanic conditions. This study is the first description of the seasonal and spatial variation of this marine component of the Gulf of Cádi

Elastic properties of B-C-N films grown by N2-reactive sputtering from boron carbide targets

The following article appeared in Journal of Applied Physics 114.21 (2013): 213508 and may be found at http://scitation.aip.org/content/aip/journal/jap/114/21/10.1063/1.4837655Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B4C target and N2 as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.This work has been supported by Spanish MINECO under contracts MAT2009-08786 and MAT2012-37276- C03-01 as well as by the Madrid Regional Government though contract S2009/MAT-1756

Anodic oxidation of titanium for implants and prothesis: processing characterization and potential improvement of osteointegration

Among all biomaterials used for bone replacement, it is recognized that both commercially pure titanium (Ti c.p.) and Ti6Al4V alloy are the materials that show the best in vivo performance due to their excellent balance between mechanical, physical-chemical and biofunctional properties. However, one of its main drawbacks, which compromise the service reliability of the implants and its osteointegration capacity, is the thin film of fibrous tissue around the implant due to the bioinert behaviour of titanium. One of the alternatives more studied to improve the titanium osteointegration is the surface modification through the control of the roughness parameters within a specific range which is recognized that improve the osteoblasts adhesion. In this work is investigated the influence of different electrochemical processing conditions for surface modification of c.p. Ti, in their microstructural, morphological, topographical and mechanical properties, as well as in their biological behaviour. The electrochemical anodizing treatment was performed by using different electrolytes based on phosphoric acid (H3PO4), sulphuric acid (H2SO4) with a fluoride salt; and the Focused Ion Beam (FIB) technique, normally named as Nanolab, was used for the microstructural, chemical and morphological characterization, as well as the confocal laser microscopy technique which also served for roughness measurements. The mechanical response of the anodic layers was evaluated through the using of a scratch tester which showed the critical loads for the coating damages. The characterization results showed that both, concentrations and electrolyte species, clearly influenced the morphological and topographical features, as well as the chemical composition of the anodic layer. By using the FIB was possible to detect nanopores within both the surface and the bulk of the coating. Some of the conditions generated a very special coating morphology which promoted a better osteoblasts adhesion. Contrary to what it was a priory expected, all anodic coatings showed high critical loads for damages during scratch test, despite their high porosity, which could be related with some defects coalescence mechanism that allows dissipating the high stress concentration applied during the test.Postprint (published version