Microscopic origin of granular ratcheting

Numerical simulations of assemblies of grains under cyclic loading exhibit ``granular ratcheting'': a small net deformation occurs with each cycle, leading to a linear accumulation of deformation with cycle number. We show that this is due to a curious property of the most frequently used models of the particle-particle interaction: namely, that the potential energy stored in contacts is path-dependent. There exist closed paths that change the stored energy, even if the particles remain in contact and do not slide. An alternative method for calculating the tangential force removes granular ratcheting.Comment: 13 pages, 18 figure

Symmetry breaking and clustering in a vibrated granular gas with several macroscopically connected compartments

The spontaneous symmetry breaking in a vibro-fluidized low-density granular gas in three connected compartments is investigated. When the total number of particles in the system becomes large enough, particles distribute themselves unequally among the three compartments. Particles tend to concentrate in one of the compartments, the other two having the (relatively small) same average number of particles. A hydrodynamical model that accurately predicts the bifurcation diagram of the system is presented. The theory can be easily extended to the case of an arbitrary number of connected compartments

The PDFLattice2017 workshop: a summary report

The workshop on Parton Distributions and Lattice Calculations in the LHC era (PDFLattice2017) was hosted at Balliol College, Oxford (UK), from 22$^{\rm nd}$ to 24$^{\rm th}$ March 2017. The workshop brought together the lattice-QCD and the global-fit physicists who devote their efforts to determine the parton distribution functions (PDFs) of the proton. The goals were to make the two communities more familiar between each other, review developments from both sides, and set precision targets for lattice calculations so that they can contribute, together with the forthcoming experimental input, to the next generation of PDF determinations. This contribution summarises the relevant outcome of the workshop, in anticipation of a thorough white paper.Comment: 5 pages, 1 figure, contribution to the proceedings of the XXV Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2017

Dendrimers and Dendritic Polymers as Anti-infective Agents: New Antimicrobial Strategies for Therapeutic Drugs

24 páginas, 24 figuras, 6 tablas, abreviaturasNearly 3 decades ago, a dendritic structure was stepwise synthesized for the first time as a new type of molecules with promising applications. During years a huge effort has been devoted to implement the synthetic skills concerning the synthesis of these molecules and especially, new methods for purification and characterization of these compounds that are in the nanoscale range. The chemical manipulation of the surface and inner core of dendrimers were strategically used to allow a tailor-made control of physical-chemical properties and to discover new applications in material science and biomedicine. Although several examples have been reported in the literature describing applications of functionalized dendrimers and acclaiming a key role of these molecules, very scarce examples are actually close to the market. This review summarizes the state of the art of dendrimers and dendritic polymers as anti-infective agents, with a special focus on the strategies to block receptors used by pathogens for attachment, cell entry and dissemination. These nanometre size molecules are very attractive compounds as new drugs easily to be manipulated to improve their activity and scope. This is already a very active area of research, where we are involved, with interesting potential as demonstrated by the Phase I clinical trial of a functionalized dendrimer with real possibilities to reach the market soon. The success of this compound should provoke an enormous stimulus to scientists working in this area as well as in the industrial companies for investment in this topic.We would like to thank Instituto de Salud Carlos III (Spain Ministry of Health) projects PI030093 (J.R.) and PI030300 (R.D.) for financial support.Peer reviewe

Constraints on hidden gravitons from fifth-force experiments and stellar energy loss

We study different phenomenological signatures associated with new spin-2 particles. These new degrees of freedom, that we call hidden gravitons, arise in different high-energy theories such as extra-dimensional models or extensions of General Relativity. At low energies, hidden gravitons can be generally described by the Fierz-Pauli Lagrangian. Their phenomenology is parameterized by two dimensionful constants: their mass and their coupling strength. In this work, we analyze two different sets of constraints. On the one hand, we study potential deviations from the inverse-square law on solar-system and laboratory scales. To extend the constraints to scales where the laboratory probes are not competitive, we also study consequences on astrophysical objects. We analyze in detail the processes that may take place in stellar interiors and lead to emission of hidden gravitons, acting like an additional source of energy loss.Comment: 15 pages, 7 figure