A Novel 2D Folding Technique for Enhancing Fermi Surface Signatures in the Momentum Density: Application to Compton Scattering Data from an Al-3at%Li Disordered Alloy

We present a novel technique for enhancing Fermi surface (FS) signatures in the 2D distribution obtained after the 3D momentum density in a crystal is projected along a specific direction in momentum space. These results are useful for investigating fermiology via high resolution Compton scattering and positron annihilation spectroscopies. We focus on the particular case of the (110) projection in an fcc crystal where the standard approach based on the use of the Lock-Crisp-West (LCW) folding theorem fails to give a clear FS image due to the strong overlap with FS images obtained through projection from higher Brillouin zones. We show how these superposed FS images can be disentangled by using a selected set of reciprocal lattice vectors in the folding process. The applicability of our partial folding scheme is illustrated by considering Compton spectra from an Al-3at%Li disordered alloy single crystal. For this purpose, high resolution Compton profiles along nine directions in the (110) plane were measured. Corresponding highly accurate theoretical profiles in Al-3at%Li were computed within the local density approximation (LDA)-based Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) first-principles framework. A good level of overall accord between theory and experiment is obtained, some expected discrepancies reflecting electron correlation effects notwithstanding, and the partial folding scheme is shown to yield a clear FS image in the (110) plane in Al-3%Li.Comment: 24 pages, 8 figures, to appear in Phys. Rev.

Model study of adsorbed metallic quantum dots: Na on Cu(111)

We model electronic properties of the second monolayer Na adatom islands (quantum dots) on the Cu(111) surface covered homogeneously by the first Na monolayer. An axially-symmetric three-dimensional jellium model, taking into account the effects due to the first Na monolayer and the Cu substrate, has been developed. The electronic structure is solved within the local-density approximation of the density-functional theory using a real-space multigrid method. The model enables the study of systems consisting of thousands of Na-atoms. The results for the local density of states are compared with differential conductance ($dI/dV$) spectra and constant current topographs from Scanning Tunneling Microscopy.Comment: 10 pages, 8 figures. For better quality figures, download http://www.fyslab.hut.fi/~tto/cylart1.pd

Multiscale modelling for fusion and fission materials: the M4F project

The M4F project brings together the fusion and fission materials communities working on the prediction of radiation damage production and evolution and its effects on the mechanical behaviour of irradiated ferritic/martensitic (F/M) steels. It is a multidisciplinary project in which several different experimental and computational materials science tools are integrated to understand and model the complex phenomena associated with the formation and evolution of irradiation induced defects and their effects on the macroscopic behaviour of the target materials. In particular the project focuses on two specific aspects: (1) To develop physical understanding and predictive models of the origin and consequences of localised deformation under irradiation in F/M steels; (2) To develop good practices and possibly advance towards the definition of protocols for the use of ion irradiation as a tool to evaluate radiation effects on materials. Nineteen modelling codes across different scales are being used and developed and an experimental validation programme based on the examination of materials irradiated with neutrons and ions is being carried out. The project enters now its 4th year and is close to delivering high-quality results. This paper overviews the work performed so far within the project, highlighting its impact for fission and fusion materials science.This work has received funding from the Euratom research and training programme 2014-2018 under grant agreement No. 755039 (M4F project)

Estudo da interação polímero/cartilagem/osso utilizando poli (ácido lático-co-ácido glicólico) e poli (p-dioxanona) em condilo femural de coelhos Study of polymer/cartilage/bone interaction using poly(lactic acid-co-glycolic acid) and poly (p-dioxanona) in femoral condyle of rabbits

Os dispositivos biorreabsorvíveis são alternativas para fixação interna das fraturas. Durante o tratamento estes dispositivos mantêm a fixação e degradam-se gradualmente não necessitando de uma cirurgia de remoção, reduzindo o custo de tratamento quando comparadas aos dispositivos metálicos. O objetivo desse trabalho foi estudar a interação polímero/tecido utilizando pinos de PLGA e PDS após implantes em coelhos Nova Zelândia. Separou-se os animais em 3 grupos os quais foram sacrificados após 3, 6 e 12 semanas de implantação e o material obtido foi submetido à análise histológica. As análises histológicas com implantes de PLGA mostraram após 3 semanas a formação de um tecido com características mesenquimatosas e com 12 semanas a formação de uma estrutura óssea madura. Já nos implantes de PDS de 3 semanas houve uma maior invasão de tecido mesenquimal comparado ao PLGA e após 12 semanas, ocorreu uma degradação avançada, com tecido proliferativo mesenquimal e ósseo. Assim, concluiu-se que ocorreram resultados positivos à resposta tecidual/implante e foi relevante a observação da ausência de células responsáveis pela resposta inflamatória. As análises demonstraram que o copolímero de PLGA apresentou propriedades osteoindutivas mais adequadas que os de PDS, apresentando biocompatibilidade aceitável para aplicação ortopédica.<br>Bioresorbable devices are alternatives for internal fixation. During the treatment, those devices maintain the fixation, degrade gradually and eliminate the need for a remove surgery, decreasing the treatment cost when compared with metallic devices. The aim of this work was to study the interaction polymer/tissue interaction using pins of PLGA and PDS implanted in New Zealand rabbits. The animals were separated in 3 groups which were sacrificed after 3, 6 and 12 weeks after implantation, and the obtained material was submitted to histological analysis. Histological analysis with PLGA implants showed after 3 weeks, the growth of a tissue with mesenchimal characteristics, after 3 weeks, with formation of mature bone aready after 12 weeks. PDS implants after 3 weeks showed a bigger invasion of mesenchimal tissue compared to PLGA and after 12 weeks an advanced degradation occurred, with proliferation of mesenchimal and bone tissue formation. It is concluded that the results are highly positive, with the relevant absence of cells responsible for inflammatory response. Analysis showed that the copolymer PLGA has better ostoinductive properties than PDS, showing biocompatibility acceptable for orthopedics application