Productivity and Economic Growth: the Case of Chile

After a decade and a half of economic growth above 7% per year, the Chilean economy has been growing at rates below 3% during the last five years. In this article we suggest that in order to produce a new surge in economic growth, Chile needs a productivity shock arising from economic policy initiatives aimed at improving economic efficiency and institutions. Although Chile has a good record in both, it is still possible to have an upgrade. We run a cross section regression in which the dependent variable is total factor productivity. We conclude that modest changes in the country’s policies and institutions may increase Chile’s rate of growth in 1.5 percent points.

Conflicting accounts of λ-definability

© 2016 A function on some domain is λ-definable if the corresponding function of λ-terms is so definable. However, the correspondence is parametrized by a representation of the domain. Often there is a natural choice of representation, but when the domain consists of λ-terms then they can be represented by either themselves or by the Church numeral of their Gödel number. This choice determines whether or not all computable functions are λ-definable

Phase partition of gaseous hexane and surface hydrophobicity of Fusarium solani when grown in liquid and solid media with hexanol and hexane

The filamentous fungus, Fusarium solani, was grown in liquid and solid culture with glucose, glycerol, 1-hexanol and n-hexane. The partition coefficient with gaseous hexane (HPC) in the biomass was lower when grown in liquid medium with 1-hexanol (0.4) than with glycerol (0.8) or glucose (1) The HPC for surface growth were 0.2 for 1-hexanol, 0.5 for glycerol, 0.6 for glucose, and 0.2 for F. solani biomass obtained from a biofilter fed with gaseous n-hexane. These values show a 200-fold increase in n-hexane solubility when compared to water (HPC = 42). Lower HPC values can be partially explained by increased lipid accumulation with 1-hexanol, 10.5% (w/w) than with glycerol (8.5% w/w) or glucose (7.1% w/w). The diameter of the hyphae diminished from 3 μm to 2 μm when F. solani was grown on solid media with gaseous n-hexane thereby doubling the surface area for gaseous substrate exchange. The surface hydrophobicity of the mycelia increased consistently with more hydrophobic substrates and the contact angle of a drop of water on the mycelial mat was 113° when grown on n-hexane as compared to 75° with glucose. The fungus thus adapts to hydrophobic conditions and these changes may explain the higher uptake of gaseous hydrophobic substances by fungi in biofilters

Bio-inspired Tensegrity Soft Modular Robots

In this paper, we introduce a design principle to develop novel soft modular robots based on tensegrity structures and inspired by the cytoskeleton of living cells. We describe a novel strategy to realize tensegrity structures using planar manufacturing techniques, such as 3D printing. We use this strategy to develop icosahedron tensegrity structures with programmable variable stiffness that can deform in a three-dimensional space. We also describe a tendon-driven contraction mechanism to actively control the deformation of the tensegrity mod-ules. Finally, we validate the approach in a modular locomotory worm as a proof of concept.Comment: 12 pages, 7 figures, submitted to Living Machine conference 201

Optically probing symmetry breaking in the chiral magnet Cu2OSeO3

We report on the linear optical properties of the chiral magnet Cu2OSeO3, specifically associated with the absence of inversion symmetry, the chiral crystallographic structure, and magnetic order. Through spectroscopic ellipsometry, we observe local crystal-field excitations below the charge-transfer gap. These crystal-field excitations are optically allowed due to the lack of inversion symmetry at the Cu sites. Optical polarization rotation measurements were used to study the structural chirality and magnetic order. The temperature dependence of the natural optical rotation, originating in the chiral crystal structure, provides evidence for a finite magneto-electric effect in the helimagnetic phase. We find a large magneto-optical susceptibility on the order of V(540nm)~10^4 rad/(T*m) in the helimagnetic phase and a maximum Faraday rotation of ~165deg/mm in the ferrimagnetic phase. The large value of V can be explained by considering spin cluster formation and the relative ease of domain reorientation in this metamagnetic material. The magneto-optical activity allows us to map the magnetic phase diagram, including the skyrmion lattice phase. In addition to this, we probe and discuss the nature of the various magnetic phase transitions in Cu2OSeO3.Comment: 9 pages, 10 figure

Feature selection for chemical sensor arrays using mutual information

We address the problem of feature selection for classifying a diverse set of chemicals using an array of metal oxide sensors. Our aim is to evaluate a filter approach to feature selection with reference to previous work, which used a wrapper approach on the same data set, and established best features and upper bounds on classification performance. We selected feature sets that exhibit the maximal mutual information with the identity of the chemicals. The selected features closely match those found to perform well in the previous study using a wrapper approach to conduct an exhaustive search of all permitted feature combinations. By comparing the classification performance of support vector machines (using features selected by mutual information) with the performance observed in the previous study, we found that while our approach does not always give the maximum possible classification performance, it always selects features that achieve classification performance approaching the optimum obtained by exhaustive search. We performed further classification using the selected feature set with some common classifiers and found that, for the selected features, Bayesian Networks gave the best performance. Finally, we compared the observed classification performances with the performance of classifiers using randomly selected features. We found that the selected features consistently outperformed randomly selected features for all tested classifiers. The mutual information filter approach is therefore a computationally efficient method for selecting near optimal features for chemical sensor arrays

Global instability by runaway collisions in nuclear stellar clusters: Numerical tests of a route for massive black hole formation

The centers of galaxies host nuclear stellar clusters, supermassive black holes, or both, but the origin of this dichotomy is still a mystery. Nuclear stellar clusters are the densest stellar system of the Universe, so they are ideal places for runaway collisions to occur. In these dense clusters it is possible that global instability occurs, triggered by collisions and mergers forming a massive black hole. Here we test a new mechanism to form massive black holes through runaway stellar collisions in nuclear stellar clusters, performing N-body simulations using the code nbody6++gpu. Our idealized models show that there is a critical mass where collisions become very efficient making it possible to form massive black holes in nuclear stellar clusters. The most massive objects reach masses of the order of $10^4-10^5\rm~ M_\odot$. We find that our highest black hole formation efficiency is up to $50\%$ of the stellar mass at the end of the simulation. In real astrophysical systems, the critical mass scale for this transition is expected to occur in stellar clusters of $10^7-10^9\rm~M_\odot$, implying the formation of quite massive central objects.Comment: 11 pages, 6 figure