RESUMO
Understanding and mastering the mechanical properties of metallic nanoparticles is crucial for their use in a wide range of applications. In this context, atomic-scale (molecular dynamics) and continuous (finite elements) calculations is used to investigate in details gold nanoparticles under deformation. By combining these two approaches, it is shown that the elastic properties of such nano-objects are driven by their size but, above all, by their shape. This outcome is achieved by introducing a descriptor in the analysis of the results enabling to distinguish among the different nanoparticle shapes studied in the present work. In addition, other transition-metal nanoparticles are considered (copper and platinum) using the aforementioned approach. The same strong dependence of the elastic properties with the shape is revealed, thus highlighting the universal character of the achievements.
RESUMO
Intrinsic dislocation mechanisms in the vicinity of free surfaces of an almost FIB damage-free single crystal Ni sample have been quantitatively investigated owing to a novel sample preparation method combining twin-jet electro-polishing, in-situ TEM heating and FIB. The results reveal that the small-scale plasticity is mainly controlled by the conversion of few tangled dislocations, still present after heating, into stable single arm sources (SASs) as well as by the successive operation of these sources. Strain hardening resulting from the operation of an individual SAS is reported and attributed to the decrease of the length of the source. Moreover, the impact of the shortening of the dislocation source on the intermittent plastic flow, characteristic of SASs, is discussed. These findings provide essential information for the understanding of the regime of 'dislocation source' controlled plasticity and the related mechanical size effect.
RESUMO
The aim of this study is to assess social, personality and behaviors of alcoholics using Virtual Reality (VR). Specifically, we defined a VR protocol using the free NeuroVR software -- (http://www.neurovr.org) -- to investigate the following factors: drinking behaviors, intrapersonal factors (Emotional Management and Self Esteem) and environmental factors (Relational Competences and Social Pressure). In this preliminary study we evaluated the difference between assessment methods by comparing the VR assessment protocol with the SCID - Structured Clinical Interview for DSM-IV Axis I Disorders - in a sample of 20 alcohol-dependent individuals (10 experimental group + 10 control group) entering a non-pharmacological outpatient treatment. The data, obtained using both qualitative and quantitative analyses, confirm the possibility of using the VR protocol in the assessment of alcohol-dependent patients: the therapist obtains more critical data about behaviors and attitudes in less time. Further, the VR group reported a significant improvement in the motivation for change after the assessment protocol, not found in the SCID group: apparently, the experiential approach required by VR makes the patient more active and involved in the processes of introspection and change. A wider sample and a multicentric trial are now needed to confirm these results.
