Monodisperse Dry Granular Flows on Inclined Planes : Role of Roughness

Recent studies have pointed out the importance of the basal friction on the dynamics of granular flows. We present experimental results on the influence of the roughness of the inclined plane on the dynamics of a monodisperse dry granular flow. We found experimentally that it exists a maximum of the friction for a given relative roughness. This maximum is shown to be independent of the angle of the slope. This behavior is observed for four planes with different bump sizes (given by the size of the beads glued on the plane) from 200 microns to 2 mm. The relative roughness corresponding to the maximum of the friction can be predicted with a geometrical model of stability of one single bead on the plane. The main parameters are the size of the bumps and the size of the flowing beads. In order to obtain a higher precision, the model also takes into account of the spacing between the bumps of the rough plane. Experimental results and model are in good agreement for all the planes we studied. Other parameters, like the sphericity of the beads, or irregularities in the thickness of the layer of glued particles, are shown to be of influence on the friction.Comment: 17 pages, 15 figures, submitted to EPJ

PHARAO Laser Source Flight Model: Design and Performances

In this paper, we describe the design and the main performances of the PHARAO laser source flight model. PHARAO is a laser cooled cesium clock specially designed for operation in space and the laser source is one of the main sub-systems. The flight model presented in this work is the first remote-controlled laser system designed for spaceborne cold atom manipulation. The main challenges arise from mechanical compatibility with space constraints, which impose a high level of compactness, a low electric power consumption, a wide range of operating temperature and a vacuum environment. We describe the main functions of the laser source and give an overview of the main technologies developed for this instrument. We present some results of the qualification process. The characteristics of the laser source flight model, and their impact on the clock performances, have been verified in operational conditions.Comment: Accepted for publication in Review of Scientific Instrument

Collective effects in spin-crossover chains with exchange interaction

The collective properties of spin-crossover chains are studied. Spin-crossover compounds contain ions with a low-spin ground state and low lying high-spin excited states and are of interest for molecular memory applications. Some of them naturally form one-dimensional chains. Elastic interaction and Ising exchange interaction are taken into account. The transfer-matrix approach is used to calculate the partition function, the fraction of ions in the high-spin state, the magnetization, susceptibility, etc., exactly. The high-spin-low-spin degree of freedom leads to collective effects not present in simple spin chains. The ground-state phase diagram is mapped out and compared to the case with Heisenberg exchange interaction. The various phases give rise to characteristic behavior at nonzero temperatures, including sharp crossovers between low- and high-temperature regimes. A Curie-Weiss law for the susceptibility is derived and the paramagnetic Curie temperature is calculated. Possible experiments to determine the exchange coupling are discussed.Comment: 9 pages, 13 color figures, published versio

The future of the Protestant Church: Estimates for Austria and for the Provinces of Burgenland, Carinthia and Vienna

Secularization and migration have substantially affected the place of the Protestant Church in the Austrian society in the last decades. The number of members has been shrinking markedly from 447 thousand members in 1971 to 278 thousand in 2018. The trend is visible across all provinces, although the magnitude is stronger in Vienna where both disaffiliation and international migration are stronger: In the capital city, the Protestant population diminished from 126 thousand to 47 thousand over the 1971-2018 period. Using population projections of membership to the Protestant Church, we look at the potential future of affiliation to the Protestant Church in Austria, and in three provinces: Burgenland, Carinthia, and Vienna from 2018 to 2048, considering different paths of fertility and disaffiliation. We also look at the impact of different scenarios regarding the composition of international migration flows on affiliation to the Protestant Church. Our findings suggest that in the absence of compensatory flows, the Protestant Church will keep shrinking unless it manages to stop disaffiliation. The projections also show that migrants, especially within mobile Europe, are a potential source of members that is at present not properly contributing to membership in Austria. According to the TREND EUROPE scenario, which is – seen from today – the most likely scenario with a continuation of declining entries and increased exits, the Protestant population in Austria would still decline from 283 thousand in 2018 to 144 thousand in 2048 (-49%). At the level of the three provinces, the decline would be faster in Vienna (-42%, from 47 to 27 thousand) than in Burgenland (-26%, from 32 to 24 thousand) and Carinthia (-37%, from 48 to 30 thousand). According to this scenario, by 2048 the Protestant population would correspond to 1.5% of the total population of Austria(1.3% in Vienna, 7.3% in Burgenland and 5.4% in Carinthia). Other scenarios reflect the potential impact of different religious composition of future migrant flows, as well as changing disaffiliation patterns. Only under the LIFT scenario, which assumes a reduction in exits by 50% and more migrants enrolling to the Protestant Church, we see an end of the haemorrhage and even an increase in the number of Protestants in Vienna

Fabrication and characterization of Eri silk fibers-based sponges for biomedical application

Cocoon-derived semi-domesticated Eri silk fibers still lack exploitation for tissue engineering applications due to their poor solubility using conventional methods. The present work explores the ability to process cocoon fibers of non-mulberry Eri silk (Samia/Philosamia ricini) into sponges through a green approach using ionic liquid (IL) â 1-buthyl-imidazolium acetate as a solvent. The formation of β-sheet structures during Eri silk/IL gelation was acquired by exposing the Eri silk/IL gels to a saturated atmosphere composed of two different solvents: (i) isopropanol/ethanol (physical stabilization) and (ii) genipin, a natural crosslinker, dissolved in ethanol (chemical crosslinking). The sponges were then obtained by freeze-drying. This approach promotes the formation of both stable and ordered non-crosslinked Eri silk fibroin matrices. Moreover, genipin-crosslinked silk fibroin sponges presenting high height recovery capacity after compression, high swelling degree and suitable mechanical properties for tissue engineering applications were produced. The incorporation of a model drug â ibuprofen â and the corresponding release study from the loaded sponges demonstrated the potential of using these matrices as effective drug delivery systems. The assessment of the biological performance of ATDC5 chondrocyte-like cells in contact with the developed sponges showed the promotion of cell adhesion and proliferation, as well as extracellular matrix production within two weeks of culture. Spongesâ intrinsic properties and biological findings open up their potential use for biomedical applications.The authors SSS, DSC, MBO, NMO acknowledge financial support from Portuguese Foundation for Science and Technology – FCT (Grants SFRH/BPD/45307/2008, SFRH/BPD/85790/2012, SFRH/BD/71396/2010 and SFRH/BD/73172/2010, respectively), ‘‘Fundo Social Europeu” – FSE, and ‘‘Programa Diferencial de Potencial Humano POPH”. This work is also financially supported by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n REGPOT-CT2012-316331-POLARIS and from Fundação para a Ciência e Tecnologia (FCT) through the project ENIGMA – PTDC/EQU-EPR/121491/2010. The laboratory work of SCK is supported by Department of Biotechnology and Indian Council of Medical Research, Govt of India. SCK and RLR acknowledge their short visits either Institutes. SCK is also grateful to 3B´ s Research Group- Biomaterials, Biodegradables and Biomimetics, University of Minho, Portugal for providing facilities during his short visit

Simulation and implementation of a piezoelectric sensor for harmonic in-situ strain monitoring

To monitor the strain in a multilayer steel/adhesive/ceramic beam structure, a 9-µmthick piezoelectric PVDF film is inserted in the adhesive joint. Two 2D finite element models of the structure with and without the film were developed using a sub-structuring procedure to reduce computational time and to refine the mesh in the thickness of the film. The models provide the harmonic displacement of the beam and the voltage across the film which is related to the strain. A prototype of the analyzed structure has been developed as well. Simulation and experimental analysis was performed and obtained results were compared. It was demonstrated that the influence of the presence of the film on the stress distribution is negligible, thus the implementation of an embedded PVDF film is a well-suited technique to monitor the strain transfer in a bonded assembl

Simulation and implementation of a piezoelectric sensor for harmonic in-situ strain monitoring

To monitor the strain in a multilayer steel/adhesive/ceramic beam structure, a 9-µmthick piezoelectric PVDF film is inserted in the adhesive joint. Two 2D finite element models of the structure with and without the film were developed using a sub-structuring procedure to reduce computational time and to refine the mesh in the thickness of the film. The models provide the harmonic displacement of the beam and the voltage across the film which is related to the strain. A prototype of the analyzed structure has been developed as well. Simulation and experimental analysis was performed and obtained results were compared. It was demonstrated that the influence of the presence of the film on the stress distribution is negligible, thus the implementation of an embedded PVDF film is a well-suited technique to monitor the strain transfer in a bonded assembl