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Optimising the properties of platelet reinforced composites requires the strength of the reinforcing phase to be known, however strength measurements at such small scales are difficult and therefore data is sparse. In this work the flexural strength and Weibull modulus of microscopic, alumina platelets has been measured as 5.3±1.3 GPa and 3.7 respectively, using an in-situ micro 3-point bend test. A general approach to correct for the effect of variation in sample size on the Weibull modulus is presented, and the internal structure of the platelets is revealed by TEM.

Rising levels of atmospheric CO2 are responsible for a change in the carbonate chemistry of seawater with associated pH drops (acidification) pro-jectedtoreach 0.4 units from 1950 to 2100. We investigated possible indirect effects of seawater acidification on the feeding, fecundity, and hatching success of the calanoid copepod Acartia grani, mediated by potential CO2-induced changes in the nutritional characteristics of their prey. Weused as prey the autotrophic dinoflagellate Heterocapsa sp., cultured at three distinct pH levels (control: 8.17, medium: 7.96, and low: 7.75) by bubbling pure CO2 via a computer automated system. Acartia graniadults collected fromalaboratory culture were acclimatized for 3d at food suspensions of Heterocapsa from each pH treatment (ca. 500 cells ml-1; 300 μg C l-1). Feeding and egg production rates of the preconditioned females did not differ significantly among the three Heterocapsa diets. Egg hatching success, monitored once per day for the 72 h, did not reveal significant difference among treatments. These results areinagreement with the lack of difference in the cellular stoichiometry(C: N,C: P, and N: Pratios) and fatty acid concentration and composition encountered between the three tested Heterocapsa treatments. Our findings disagree with those of other studies using distinct types of prey, suggesting that this kind of indirect influence of acidification on copepods maybe largely associated with interspecific differences among prey items with regard to their sensitivity to elevated CO2 levels. © International Council for the Exploration of the Sea 2015. All rights reserved.

This paper describes a numerical study on the instability of a brace-type seismic damper based on the out of plane yielding of the web of wide-flange steel sections (Web Plastifying Damper, WPD)The damper is intended to be installed in a framed structure as a standard diagonal brace. Under lateral forces, the damper is subjected to high axial forces, therefore its buckling instability is a matter of concern. Several finite element models representing WPDs with different axial stiffness and various geometries of their components were developed and analyzed taking into account both material and geometrical nonlinearities. The influence of several parameters defining the WPD in the load-displacement curve was examined. Furthermore, a simplified model to predict the buckling load is proposed.

The city of Lorca (Spain) was hit on May 11th 2011 by two consecutive earthquakes with 4.6 and 5.2 Mw respectively, causing casualties and important damage in buildings. Lorca is located in the south-east region of Spain and settled on the trace of the Murcia-Totana-Lorca fault. Although the magnitudes of these ground motions were not severe, the damage observed was considerable over a great amount of buildings. More than 300 of them have been demolished and many others are being retrofitted. This paper reports a field study on the damage caused by these earthquakes. The observed damage is related with the structural typology. Further, prototypes of the damaged buildings are idealized with nonlinear numerical models and their seismic behavior and proneness to damage concentration is further investigated through dynamic response analyses.

A large number of reinforced concrete (RC) frame structures built in earthquake-prone areas such as Haiti are vulnerable to strong ground motions. Structures in developing countries need low-cost seismic retrofit solutions to reduce their vulnerability. This paper investigates the feasibility of using masonry infill walls to reduce deformations and damage caused by strong ground motions in brittle and weak RC frames designed only for gravity loads. A numerical experiment was conducted in which several idealized prototypes representing RC frame structures of school buildings damaged during the Port-au-Prince earthquake (Haiti, 2010) were strengthened by adding elements representing masonry infill walls arranged in different configurations. Each configuration was characterized by the ratio Rm of the area of walls in the direction of the ground motion (in plan) installed in each story to the total floor area. The numerical representations of these idealized RC frame structures with different values of Rm were (hypothetically) subjected to three major earthquakes with peak ground accelerations of approximately 0.5g. The results of the non-linear dynamic response analyses were summarized in tentative relationships between Rm and four parameters commonly used to characterize the seismic response of structures: interstory drift, Park and Ang indexes of damage, and total amount of energy dissipated by the main frame. It was found that Rm=4% is a reasonable minimum design value for seismic retrofitting purposes in cases in which available resources are not sufficient to afford conventional retrofit measures.

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Forecasting potential geoeffectiveness of solar disturbances (in particular, of frontside full halo coronal mass ejections) is important for various practical purposes, e.g. for satellite operations, radio communications, global positioning system applications, power grid and pipeline maintenance. We analyze three frontside full halo coronal mass ejections (CMEs) that occurred in the year 2000 (close to the activity maximum of solar cycle 23), together with associated solar and heliospheric phenomena as well as their impact on the Earth?s magnetosphere. Even though all three were fast full halos (with plane of the sky speeds higher than 1100 km/s), the geomagnetic response was very different for each case. After analyzing the source regions of these halo CMEs, it was found that the halo associated with the strongest geomagnetic disturbance was the one that initiated farther away from disk center (source region at W66); while the other two CMEs originated closer to the central meridian but had weaker geomagneticresponses. Therefore, these three events do not fit into the general statistical trends that relate the location of the solar source and the corresponding geoeffectivity. We investigate possible causes of such a behavior. Non-radial direction of eruption, passage of the Earth through a leg of an interplanetary flux rope and strong compression at the eastern flank of a propagating ICME during its interaction with the ambient solar wind are found to be important factors that have a direct influence on the resulting north?south interplanetary magnetic field (IMF) component and thus on the CME geoeffectiveness. We also find indications that interaction of two CMEs could help in producing a longlasting southward IMF component. Finally, we are able to explain successfully the geomagnetic response using plasma and magnetic field in situ measurements at the L1 point. We discuss the implications of our results for operational space weather forecasting and stress the difficulties of making accurate predictions with the current knowledge and tools at hand. Fil: Rodriguez, L.. Royal Observatory of Belgium; Bélgica Fil: Zhukov, A. N.. Royal Observatory of Belgium; Bélgica Fil: Cid, C.. Universidad de Alcalá; España Fil: Cerrato, Y.. Universidad de Alcalá; España Fil: Saiz, E.. Universidad de Alcalá; España Fil: Cremades, H.. Universidad Tecnologica Nacional; Argentina Fil: Dasso, Sergio Ricardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Menvielle, M.. Centre d’Etude des Environnements Terrestre et Planetaires; Francia Fil: Aran, A.. Universidad de Barcelona; España Fil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Poedts, S.. Catholic University Leuven; Bélgica Fil: Schmieder, B.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia

International audience; On 15 May 2005, a huge interplanetary coronal mass ejection (ICME) was observed near Earth. It triggered one of the most intense geomagnetic storms of solar cycle 23 (Dstpeak = −263 nT). This structure has been associated with the two-ribbon flare, filament eruption, and coronal mass ejection originating in active region 10759 (NOAA number). We analyze here the sequence of events, from solar wind measurements (at 1 AU) and back to the Sun, to understand the origin and evolution of this geoeffective ICME. From a detailed observational study of in situ magnetic field observations and plasma parameters in the interplanetary (IP) medium and the use of appropriate models we propose an alternative interpretation of the IP observations, different to those discussed in previous studies. In our view, the IP structure is formed by two extremely close consecutive magnetic clouds (MCs) that preserve their identity during their propagation through the interplanetary medium. Consequently, we identify two solar events in Hα and EUV which occurred in the source region of the MCs. The timing between solar and IP events, as well as the orientation of the MC axes and their associated solar arcades are in good agreement. Additionally, interplanetary radio type II observations allow the tracking of the multiple structures through inner heliosphere and pin down the interaction region to be located midway between the Sun and the Earth. The chain of observations from the photosphere to interplanetary space is in agreement with this scenario. Our analysis allows the detection of the solar sources of the transients and explains the extremely fast changes of the solar wind due to the transport of two attached (though nonmerging) MCs which affect the magnetosphere.

Full Molecular Dynamics was used to simulate separately the diffusion of naked protons and H₃O⁺ hydrated protons across sulfonated polyphenyl sulfones, (sPS). The diffusion coefficient of naked protons is nearly one order of magnitude higher than that of the hydrated protons for the membranes with the lower water uptake (10%). The conductivities simulated at 300 K for the hydrated proton across membranes with water uptake 18% and 30 % are roughly similar to those both experimentally measured for the sPS4 membrane with ion exchange capacity = 1.8 eq/Kg in dry conditions and with water uptake = 24.3 %. The comparison between four sPS membranes shwon the strong dependence of conductivity with the water content into the membranes. In our study, the conductivity of sPS1 with a 3.1% water content decrease two order of magnitude respect the sPS4 with 24.3 of water content. Simulated conductivities of both naked protons and hydrated protons follow Arrhenius behavior. This work was supported by the Dirección General de Investigación Científica y Técnica (DGICYT), Grant MAT-2005-05648-C02-02, and from IMPIVA of Generalitat Valenciana through project IMCITA/2006/030 is gratefully acknowledged. The authors are also grateful to the Instituto de Tecnología Eléctrica (ITE) de la Universidad Politécnica de Valencia for the financial support.

The fixation of bone replacement implants to the hosting tissue can be improved if the implants have a bioactive surface that can precipitate hydroxyapatite in vivo. Titanium alloys, despite their desirable mechanical and nontoxic properties, are not bioactive and, therefore, do not bond directly to the bone. One of the ways to change a bioinert metallic surface is to coat it with a bioactive material. This work presents the evaluation of the fatigue behaviour by Hertzian (spherical) indentation of a glass coating on Ti6Al4V. This coating belongs to the SiO2-CaO-MgO-Na2OK2O-P2O5 system and, despite it can be used for corrosion protection, it has been specifically designed to be used as the inner layer of a bioactive bilayer coating with an outer layer of lower SiO2 content to ensure bioactivity. Hertzian monotonic tests allowed to obtain a damage sequence starting with three brittle damage events (ring, cone and radial cracking) followed by coating delamination associated to the plastic deformation of the substrate. The first brittle damage, ring cracking, was used as criteria for the evaluation of the stress-corrosion and cyclic loading cracking behaviour in air and in distilled water environments. Results showed sensitivity of the coating to degradation under both static and cyclic loadings which was considerably larger in distilled water due to the corrosion susceptibility of this glass. Delamination damage was also sensitive to Hertzian cyclic loading showing two different mechanisms depending of the maximum applied load. La fijación al tejido receptor de implantes para el reemplazo de hueso puede ser mejorada si poseen una superficie bioactiva con la capacidad de precipitar hidroxiapatita in vivo. Las aleaciones de titanio, a pesar de sus buenas propiedades mecánicas y comportamiento no-tóxico, no son bioactivas y, por tanto, no se enlazan directamente al hueso. Una de las maneras de modificar una superficie metálica bioinerte es recubriéndola con material bioactivo. En este trabajo se presenta la evaluación del comportamiento a fatiga mediante indentación hertziana (esférica) de un recubrimiento de vidrio sobre Ti6Al4V. Este recubrimiento pertenece al sistema SiO2-CaO-MgO-Na2O-K2O-P2O5 y, a pesar de que puede usarse para protección contra la corrosión, ha sido específicamente diseñado para ser utilizado como capa interna de un recubrimiento bicapa bioactivo con una capa externa de bajo contenido en SiO2 para garantizar la bioactividad. Los ensayos hertzianos monotónicos permitieron obtener una secuencia de daños comenzando con tres eventos de daño tipo frágil (agrietamiento tipo anillo, cono y radial) seguidos por la delaminación del recubrimiento asociada a la deformación plástica del substrato. El primer daño frágil, el agrietamiento tipo anillo, fue usado como criterio para la evaluación del agrietamiento por corrosión bajo tensión y por carga cíclica, en aire y agua destilada. Los resultados mostraron la sensibilidad del recubrimiento a la degradación bajo ambos tipos de carga, estática y cíclica, siendo esta degradación considerablemente mayor en agua destilada debido a la susceptibilidad del vidrio a la corrosión. La delaminación fue también sensible a la carga cíclica hertziana presentando dos mecanismos diferentes dependiendo de la máxima carga aplicada.

International audience

International audience