The Human Right to Science and Foundational Technologies

Feeney et al. (2018) make a valid argument for restrictions on the exclusivity of foundational technologies such as CRISPR. The issue of balancing intellectual property right with access to scientific and technological advancements is certainly not new. In our commentary, we argue that the human right to science offers a more concrete basis for governments to balance their competing commitments in promoting scientific development on the one hand, and ensuring benefit-sharing on the other, in ways that advance social justice under non-ideal conditions

Corrections to local scale invariance in the non-equilibrium dynamics of critical systems: numerical evidences

Local scale invariance (LSI) has been recently proposed as a possible extension of the dynamical scaling in systems at the critical point and during phase ordering. LSI has been applied inter alia to provide predictions for the scaling properties of the response function of non-equilibrium critical systems in the aging regime following a quench from the high-temperature phase to the critical point. These predictions have been confirmed by Monte Carlo simulations and analytical results for some specific models, but they are in disagreement with field-theoretical predictions. By means of Monte Carlo simulations of the critical two- and three-dimensional Ising model with Glauber dynamics, we study the intermediate integrated response, finding deviations from the corresponding LSI predictions that are in qualitative agreement with the field-theoretical computations. This result casts some doubts on the general applicability of LSI to critical dynamics.Comment: 4 pages, 2 figures, minor changes, version to appear in Phys. Rev. B as a Rapid Communicatio

The development and evaluation of an alternative powder prepregging technique for use with LaRC-TPI/graphite composites

An alternative powder prepregging method for use with LaRC-TPI (a thermoplastic polyimide)/graphite composites is investigated. The alternative method incorporates the idea of moistening the fiber prior to powder coating. Details of the processing parameters are given and discussed. The material was subsequently laminated into small coupons which were evaluated for processing defects using electron microscopy. After the initial evaluation of the material, no major processing defects were encountered but there appeared to be an interfacial adhesion problem. As a result, prepregging efforts were extended to include an additional fiber system, XAS, and a semicrystalline form of the matrix. The semicrystalline form of the matrix was the result of a complex heat treating cycle. Using scanning electron microscopy (SEM), the fiber/matrix adhesion was evaluated in these systems relative to the amorphous/XAS coupons. Based on these results, amorphous and semicrystalline/AS-4 and XAS materials were prepregged and laminated for transverse tensile testing. The results of these tests are presented, and in an effort to obtain more information on the effect of the matrix, remaining semicrystalline transverse tensile coupons were transformed back to the amorphous state and tested. The mechanical properties of the transformed coupons returned to the values observed for the original amorphous coupons, and the interfacial adhesion, as observed by SEM, was better than in any previous sample

FDTD analysis of the tunneling and growing exponential in a pair of epsilon-negative and mu-negative slabs

Pairing together material slabs with opposite signs for the real parts of their constitutive parameters has been shown to lead to interesting and unconventional properties that are not otherwise observable for single slabs. One such case was demonstrated analytically for the conjugate (i.e., complementary) pairing of infinite planar slabs of epsilon-negative (ENG) and mu-negative (MNG) media [A. Alu, and N. Engheta, IEEE Trans. Antennas Prop., 51, 2558 (2003)]. There it was shown that when these two slabs are juxtaposed and excited by an incident plane wave, resonance, complete tunneling, total transparency and reconstruction of evanescent waves may occur in the steady-state regime under a monochromatic excitation, even though each of the two slabs by itself is essentially opaque to the incoming radiation. This may lead to virtual imagers with sub-wavelength resolution and other anomalous phenomena overcoming the physical limit of diffraction. Here we explore how a transient sinusoidal signal that starts at t = 0 interacts with such an ENG-MNG pair of finite size using an FDTD technique. Multiple reflections and transmissions at each interface are shown to build up to the eventual steady state response of the pair, and during this process one can observe how the growing exponential phenomenon may actually occur inside this bilayer.Comment: 14 pages, 9 figures, submitted to Phys Rev

Benchmarks for testing community detection algorithms on directed and weighted graphs with overlapping communities

Many complex networks display a mesoscopic structure with groups of nodes sharing many links with the other nodes in their group and comparatively few with nodes of different groups. This feature is known as community structure and encodes precious information about the organization and the function of the nodes. Many algorithms have been proposed but it is not yet clear how they should be tested. Recently we have proposed a general class of undirected and unweighted benchmark graphs, with heterogenous distributions of node degree and community size. An increasing attention has been recently devoted to develop algorithms able to consider the direction and the weight of the links, which require suitable benchmark graphs for testing. In this paper we extend the basic ideas behind our previous benchmark to generate directed and weighted networks with built-in community structure. We also consider the possibility that nodes belong to more communities, a feature occurring in real systems, like, e. g., social networks. As a practical application, we show how modularity optimization performs on our new benchmark.Comment: 9 pages, 13 figures. Final version published in Physical Review E. The code to create the benchmark graphs can be freely downloaded from http://santo.fortunato.googlepages.com/inthepress

Galactic Archaeology with TESS: Prospects for Testing the Star Formation History in the Solar Neighbourhood

A period of quenching between the formation of the thick and thin disks of the Milky Way has been recently proposed to explain the observed age-[{\alpha}/Fe] distribution of stars in the solar neighbourhood. However, robust constraints on stellar ages are currently available for only a limited number of stars. The all-sky survey TESS (Transiting Exoplanet Survey Satellite) will observe the brightest stars in the sky and thus can be used to investigate the age distributions of stars in these components of the Galaxy via asteroseismology, where previously this has been difficult using other techniques. The aim of this preliminary study was to determine whether TESS will be able to provide evidence for quenching periods during the star formation history of the Milky Way. Using a population synthesis code, we produced populations based on various stellar formation history models and limited the analysis to red-giant-branch stars. We investigated the mass-Galactic-disk-height distributions, where stellar mass was used as an age proxy, to test for whether periods of quenching can be observed by TESS. We found that even with the addition of 15% noise to the inferred masses, it will be possible for TESS to find evidence for/against quenching periods suggested in the literature (e.g. between 7 and 9 Gyr ago), therefore providing stringent constraints on the formation and evolution of the Milky Way.Comment: 4 pages, 3 figures, proceedings of "Seismology of the Sun and the Distant Stars 2016", Mario J. P. F. G. Monteiro, Margarida S. Cunha, Joao Miguel T. Ferreira editor

Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses

We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles which readily permit variation of sample packing fraction. At each packing fraction, the particle displacement covariance matrix is measured and used to extract the vibrational spectrum of the "shadow" colloidal glass (i.e., the particle network with the same geometry and interactions as the sample colloid but absent damping). Rearrangements are induced by successive, small reductions in packing fraction. The experimental results suggest that low-frequency quasi-localized phonon modes in colloidal glasses, i.e., modes that present low energy barriers for system rearrangements, are spatially correlated with rearrangements in this thermal system

Microscopic activity patterns in the Naming Game

The models of statistical physics used to study collective phenomena in some interdisciplinary contexts, such as social dynamics and opinion spreading, do not consider the effects of the memory on individual decision processes. On the contrary, in the Naming Game, a recently proposed model of Language formation, each agent chooses a particular state, or opinion, by means of a memory-based negotiation process, during which a variable number of states is collected and kept in memory. In this perspective, the statistical features of the number of states collected by the agents becomes a relevant quantity to understand the dynamics of the model, and the influence of topological properties on memory-based models. By means of a master equation approach, we analyze the internal agent dynamics of Naming Game in populations embedded on networks, finding that it strongly depends on very general topological properties of the system (e.g. average and fluctuations of the degree). However, the influence of topological properties on the microscopic individual dynamics is a general phenomenon that should characterize all those social interactions that can be modeled by memory-based negotiation processes.Comment: submitted to J. Phys.

Spectrum and Franck-Condon factors of interacting suspended single-wall carbon nanotubes

A low energy theory of suspended carbon nanotube quantum dots in weak tunnelling coupling with metallic leads is presented. The focus is put on the dependence of the spectrum and the Franck-Condon factors on the geometry of the junction including several vibronic modes. The relative size and the relative position of the dot and its associated vibrons strongly influence the electromechanical properties of the system. A detailed analysis of the complete parameters space reveals different regimes: in the short vibron regime the tunnelling of an electron into the nanotube generates a plasmon-vibron excitation while in the long vibron regime polaron excitations dominate the scenario. The small, position dependent Franck-Condon couplings of the small vibron regime convert into uniform, large couplings in the long vibron regime. Selection rules for the excitations of the different plasmon-vibron modes via electronic tunnelling events are also derived.Comment: 23 pages, 8 figures, new version according to the published on

Prescription-induced jump distributions in multiplicative Poisson processes

Generalized Langevin equations (GLE) with multiplicative white Poisson noise pose the usual prescription dilemma leading to different evolution equations (master equations) for the probability distribution. Contrary to the case of multiplicative gaussian white noise, the Stratonovich prescription does not correspond to the well known mid-point (or any other intermediate) prescription. By introducing an inertial term in the GLE we show that the Ito and Stratonovich prescriptions naturally arise depending on two time scales, the one induced by the inertial term and the other determined by the jump event. We also show that when the multiplicative noise is linear in the random variable one prescription can be made equivalent to the other by a suitable transformation in the jump probability distribution. We apply these results to a recently proposed stochastic model describing the dynamics of primary soil salinization, in which the salt mass balance within the soil root zone requires the analysis of different prescriptions arising from the resulting stochastic differential equation forced by multiplicative white Poisson noise whose features are tailored to the characters of the daily precipitation. A method is finally suggested to infer the most appropriate prescription from the data