Plastic behaviour of CuAl 2

The plastic behaviour of CuAl 2 was studied by compression testing of single crystals and polycrystals in the temperature range 300–575 °C. While single crystals were grown from the melt by the Bridgeman technique, ingot and powder metallurgy routes were adopted for polycrystalline specimens. In addition to exploring their flow behaviour, the deformation mechanism was assessed through thermal activation analysis. It was observed that CuAl 2 failed in a brittle manner in compression below 375 °C and its ductility improved progressively with temperature. The brittle-ductile transition (BDT) temperature was influenced by the initial dislocation density but not by the grain size. The strong temperature dependence of flow stress and grain size strengthening effect as per the Hall-Petch relation, were dominant up to nearly the melting temperature of CuAl 2 . The measured activation parameters for deformation suggest that the Peierls mechanism is rate controlling over the investigated temperature range.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44716/1/10853_2005_Article_BF01119763.pd

Advancing the understanding of treponemal disease in the past and present

Syphilis was perceived to be a new disease in Europe in the late 15th century, igniting a debate about its origin that continues today in anthropological, historical, and medical circles. We move beyond this age-old debate using an interdisciplinary approach that tackles broader questions to advance the understanding of treponemal infection (syphilis, yaws, bejel, and pinta). How did the causative organism(s) and humans co-evolve? How did the related diseases caused by Treponema pallidum emerge in different parts of the world and affect people across both time and space? How are T. pallidum subspecies related to the treponeme causing pinta? The current state of scholarship in specific areas is reviewed with recommendations made to stimulate future work. Understanding treponemal biology, genetic relationships, epidemiology, and clinical manifestations is crucial for vaccine development today and for investigating the distribution of infection in both modern and past populations. Paleopathologists must improve diagnostic criteria and use a standard approach for recording skeletal lesions on archaeological human remains. Adequate contextualization of cultural and environmental conditions is necessary, including site dating and justification for any corrections made for marine or freshwater reservoir effects. Biogeochemical analyses may assess aquatic contributions to diet, physiological changes arising from treponemal disease and its treatments (e.g., mercury), or residential mobility of those affected. Shifting the focus from point of origin to investigating who is affected (e.g., by age/sex or socioeconomic status) and disease distribution (e.g., coastal/ inland, rural/urban) will advance our understanding of the treponemal disease and its impact on people through time

rf-sputtering of PMNT thin films

We report on the realization of relaxor ferroelectric thin films by rf magnetron sputtering deposition. We investigated fabrication of films in the solid solution of PMN (Pb(Mg1/3Nb2/3)O3) with PT (PbTiO3). This material is the most studied among the relaxor ferroelectric family for applications in the field of microelectronics and microsystems. We chose the composition with 30% of PT, close to the morphotropic phase boundary between relaxor and normal ferroelectric behavior which exhibits good piezoelectric properties suited to actuators. We have grown the films in a cold deposition process. The substrates used were Si/SiO2 coated by Ti/Pt electrodes. This allowed to synthesize pyrochlore-free PMNT ceramic thin films at temperatures between 450 and 675°C in a postdeposition conventional annealing. We performed dielectric and ferroelectric characterizations of the films with Pt upper electrodes. Dielectric constant was measured as a function of temperature (up to 155°C) and frequency (1 kHz ~ 1 MHz). We obtained relative dielectric constant of the order of 1500. Relaxor behavior and ferroelectric properties are evidenced and are shown to be enhanced by annealing temperature

Thin film in-plane actuator: Assessment of monolayer and bilayer mechanical output

This article shows that in an in-plane configuration a thin film and a bulk actuators deliver the same amount of mechanical power under the same voltage. This opens the possibility to reach more powerful actuators while keeping the same geometric dimensions by simply stacking these films. It also demonstrates that the effective transverse-plane piezoelectric coefficient is constant with electric field which is a crucial result for this actuator