Reduction of the Casimir force using aerogels

By using silicon oxide based aerogels we show numerically that the Casimir force can be reduced several orders of magnitude, making its effect negligible in nanodevices. This decrease in the Casimir force is also present even when the aerogels are deposited on metallic substrates. To calculate the Casimir force we model the dielectric function of silicon oxide aerogels using an effective medium dielectric function such as the Clausius-Mossotti approximation. The results show that both the porosity of the aerogel and its thickness can be use as control parameters to reduce the magnitude of the Casimir force.Comment: to appear J. Appl. Phy

Pull-in control due to Casimir forces using external magnetic fields

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.Comment: accepted for publication in App. Phys. Let

MPI+OpenMP tasking scalability for the simulation of the human brain

The simulation of the behavior of the Human Brain is one of the most ambitious challenges today with a non-end of important applications. We can find many different initiatives in the USA, Europe and Japan which attempt to achieve such a challenging target. In this work we focus on the most important European initiative (Human Brain Project) and on one of the tools (Arbor). This tool simulates the spikes triggered in a neuronal network by computing the voltage capacitance on the neurons' morphology, being one of the most precise simulators today. In the present work, we have evaluated the use of MPI+OpenMP tasking on top of the Arbor simulator. In this paper, we present the main characteristics of the Arbor tool and how these can be efficiently managed by using MPI+OpenMP tasking. We prove that this approach is able to achieve a good scaling even when computing a relatively low workload (number of neurons) per node using up to 32 nodes. Our target consists of achieving not only a highly scalable implementation based on MPI, but also to develop a tool with a high degree of abstraction without losing control and performance by using MPI+OpenMP tasking.We would like to apreciate the valuable feedback and help provided by Benjamin Cumming and Alexander Peyser. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 720270 (HBP SGA1 and HBP SGA2), from the Spanish Ministry of Economy and Competitiveness under the project Computacion de Altas Prestaciones VII (TIN2015- ´ 65316-P) and the Departament d’Innovacio, Universitats i ´ Empresa de la Generalitat de Catalunya, under project MPEXPAR: Models de Programacio i Entorns d’Execuci ´ o Paral ´ ·lels (2014-SGR-1051). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska Curie grand agreement No.749516Peer ReviewedPostprint (author version

Neocosmospora keratoplastica, a relevant human fusarial pathogen is found to be associated with wilt and root rot of Muskmelon and Watermelon crops in Spain: epidemiological and molecular evidences

[EN] Some taxa of the Fusarium solani species complex (FSSC) have been associated with clinical infections in humans and plant diseases. Among the several fusaria that cause relevant mycoses in cucurbits in Spain, Neocosmospora keratoplastica is described for the first time as responsible for wilt and root rot in both watermelon and melon crops in producing areas of Valencia and Alicante provinces. Due to the ecological and systematic complexity of the group, with described clinical forms and plant pathogens practically indistinguishable from each other, both pathological evidences (including artificial inoculation bioassays) and molecular methods (multilocus phylogeny based on ITS, TEF-1 alpha, and RPB2 regions) are provided to confirm this finding, since the presence of this soil-borne pathogen could have been probably underestimated in cucurbits-producing areas of Spain.This work was supported by the by the Spanish Ministerio de Ciencia, Innovacion y Universidades grants AGL2017-85563-C2 (1-R and 2-R) (cofunded with FEDER funds) and by the PROMETEO project 2017/078 (to promote excellence groups) by the Conselleria d'Educacio, Investigacio, Cultura i Esports (Generalitat Valenciana).González, V.; García-Martínez, S.; Flores-León, A.; Ruiz, JJ.; Picó Sirvent, MB.; Garcés-Claver, A. (2020). Neocosmospora keratoplastica, a relevant human fusarial pathogen is found to be associated with wilt and root rot of Muskmelon and Watermelon crops in Spain: epidemiological and molecular evidences. European Journal of Plant Pathology. 156(4):1189-1196. https://doi.org/10.1007/s10658-020-01931-z118911961564Cabral, C. S., Melo, M. P., Fonseca, M. E. N., Boiteux, L. S., & Reis, A. (2016). A root rot of chickpea caused by isolates of the Fusarium solani species complex in Brazil. Plant Disease, 100, 2171. https://doi.org/10.1094/PDIS-05-15-0571-PDN.Chehri, K., Salleh, B., & Zakaria, L. (2015). Morphological and phylogenetic analysis of Fusarium solani species complex in Malaysia. Microbial Ecology, 69, 457–471.Chitrampalan, P., & Nelson Jr., B. (2015). Multilocus phylogeny reveals an association of agriculturally important Fusarium solani species complex (FSSC) 11, and clinically important FSSC 5 and FSSC 3 + 4 with soybean roots in the north central United States. 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Fusarium solani species complex isolates conspecific with Fusarium solani f. sp. cucurbitae race 2 from naturally infected human and plant tissue and environmental sources are equally virulent on plants, grow at 37° C and are interfertile. Environmental Microbiology, 9, 2189–2199.O’Donnell, K. (2000). Molecular phylogeny of the Nectria haematococca–Fusarium solani species complex. Mycologia, 92, 919–938.O’Donnell, K., Kistler, H. C., Cigelnik, E., & Ploetz, R. C. (1998). Multiple evolutionary origins of the fungus causing Panama disease of banana: concordant evidence from nuclear and mitochondrial gene genealogies. Proceedings of the National Academy of Sciences of the United States of America, 95, 2044–2049.O’Donnell, K., Sutton, D. A., Fothergill, A., McCarthy, D., Rinaldi, M. G., Brandt, M. E., et al. (2008). Molecular phylogenetic diversity, multilocus haplotype nomenclature, and in vitro antifungal resistance within the Fusarium solani species complex. Journal of Clinical Microbiology, 46, 2477–2490.O’Donnell, K., Sutton, D. A., Wiederholt, N., Robert, V. A. R. G., Crous, P. W., & Geiser, D. M. (2016). Veterinary Fusarioses within the United States. Journal of Clinical Microbiology, 54, 2813–2819.Reeb, V., Lutztoni, F., & Roux, C. (2004). Contribution of RPB2 to multilocus phylogenetic studies of the euascomycetes (Pezizomycotina, Fungi) with special emphasis on the lichen-forming Acarosporaceae and evolution of polyspory. Molecular Phylogenetics and Evolution, 32, 1036–1060.Rentería-Martínez, M. E., Guerra-Camacho, M. A., Ochoa-Meza, A., Moreno-Salazar, S. F., Varela-Romero, A., Gutiérrez-Millán, L. E., & Meza-Moller, A. C. (2018). Multilocus phylogenetic analysis of fungal complex associated with root rot watermelon in Sonora, Mexico. Mexican Journal of Phytopathology, 36, 1–23. https://doi.org/10.18781/R.MEX.FIT.1710-1.Sandoval-Denis, M., & Crous, P. W. (2018). Removing chaos from confusion: assigning names to common human and animal pathogens in Neocosmospora. Persoonia, 41, 109–129.Sandoval-Denis, M., Lombard, L., & Crous, P. W. (2019). Back to the roots: a reappraisal of Neocosmospora. Persoonia, 43, 90–185.Sarmiento-Ramírez, J. M., Abella-Pérez, E., Phillott, A. D., Sim, J., van West, P., Martín, M. P., Marco, A., & Diéguez-Uribeondo, J. (2014). Global distribution of two fungal pathogens threatening endangered sea turtles. PLoS ONE, 9, e85853. https://doi.org/10.1371/journal.pone.0085853.Shaffer, J. P., U’Ren, J. M., Gallery, R. E., Baltrus, D. A., & Arnold, A. E. (2017). An endohyphal bacterium (Chitinophaga, bacteroidetes) alters carbon source use by Fusarium keratoplasticum (F. solani species complex, Nectriaceae). Frontiers in Microbiology, 8, 350.Short, D. P. G., O'Donnell, K., Thrane, U., Nielsen, K. F., Zhang, N., Juba, J. H., & Geiser, D. M. (2013). 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Microscopic origin of the conducting channels in metallic atomic-size contacts

We present a theoretical approach which allows to determine the number and orbital character of the conducting channels in metallic atomic contacts. We show how the conducting channels arise from the atomic orbitals having a significant contribution to the bands around the Fermi level. Our theory predicts that the number of conducting channels with non negligible transmission is 3 for Al and 5 for Nb one-atom contacts, in agreement with recent experiments. These results are shown to be robust with respect to disorder. The experimental values of the channels transmissions lie within the calculated distributions.Comment: 11 pages, 4 ps-figures. Submitted to Phys. Rev. Let

Spectral representation of the Casimir Force Between a Sphere and a Substrate

We calculate the Casimir force in the non-retarded limit between a spherical nanoparticle and a substrate, and we found that high-multipolar contributions are very important when the sphere is very close to the substrate. We show that the highly inhomegenous electromagnetic field induced by the presence of the substrate, can enhance the Casimir force by orders of magnitude, compared with the classical dipolar approximation.Comment: 5 page + 4 figures. Submitted to Phys. Rev. Let

Casimir-like tunneling-induced electronic forces

We study the quantum forces that act between two nearby conductors due to electronic tunneling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunneling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in J. Phys.

Casimir torque between corrugated metallic plates

We consider two parallel corrugated plates and show that a Casimir torque arises when the corrugation directions are not aligned. We follow the scattering approach and calculate the Casimir energy up to second order in the corrugation amplitudes, taking into account nonspecular reflections, polarization mixing and the finite conductivity of the metals. We compare our results with the proximity force approximation, which overestimates the torque by a factor 2 when taking the conditions that optimize the effect. We argue that the Casimir torque could be measured for separation distances as large as 1 $\mu{\rm m}.$Comment: 7 pages, 3 figures, contribution to QFEXT07 proceeding

Computation of Casimir forces for dielectrics or intrinsic semiconductors based on the Boltzmann transport equation

The interaction between drifting carriers and traveling electromagnetic waves is considered within the context of the classical Boltzmann transport equation to compute the Casimir-Lifshitz force between media with small density of charge carriers, including dielectrics and intrinsic semiconductors. We expand upon our previous work [Phys. Rev. Lett. {\bf 101}, 163203 (2008)] and derive in some detail the frequency-dependent reflection amplitudes in this theory and compute the corresponding Casimir free energy for a parallel plate configuration. We critically discuss the the issue of verification of the Nernst theorem of thermodynamics in Casimir physics, and explicity show that our theory satisfies that theorem. Finally, we show how the theory of drifting carriers connects to previous computations of Casimir forces using spatial dispersion for the material boundaries.Comment: 9 pages, 2 figures; Contribution to Proceedings of "60 Years of the Casimir Effect", Brasilia, June 200

Three novel mutations in the CFTR gene identified in Galician patients

AbstractWe report three novel CFTR missense mutations detected in Spanish patients from Galicia (North West of Spain). In the first case, a patient homozygous for a novel S1045Y mutation died due to pulmonary problems. In the other two cases, both heterozygous for novel mutations combined with the F508del mutation, clinical symptoms were different depending on the mutation, detected as M595I and A107V