Latin America in the Rearview Mirror

Latin American countries are the only Western countries that are poor and that aren't gaining ground on the United States. This paper evaluates why Latin America has not replicated Western economic success. We find that this failure is primarily due to TFP differences. Latin America's TFP gap is not plausibly accounted for by human capital differences, but rather reflects inefficient production. We argue that competitive barriers are a promising channel for understanding low Latin TFP. We document that Latin America has many more international and domestic competitive barriers than do Western and successful East Asian countries. We also document a number of microeconomic cases in Latin America in which large reductions in competitive barriers increase productivity to Western levels.

Latin America in the rearview mirror

Latin American countries are the only Western countries that are poor and that aren't gaining ground on the United States. This paper evaluates why Latin America has not replicated Western economic success. We find that this failure is primarily due to TFP differences. Latin America's TFP gap is not plausibly accounted for by human capital differences, but rather reflects inefficient production. We argue that competitive barriers are a promising channel for understanding low Latin TFP. We document that Latin America has many more international and domestic competitive barriers than do Western and successful East Asian countries. We also document a number of microeconomic cases in Latin America in which large reductions in competitive barriers increase productivity to Western levels.Latin America - Economic conditions

Morfological and Chemical Study of CNx Thin Films Grown by PLD at Different Pressures

En este trabajo presentamos los efectos de la presión en la morfología y enlaces químicos de películas delgadas de nitruro de crabono (CNx ), crecidas mediante la técnica de depósito por láser pulsado (PLD). Las películas de CNx se crecieron sobre substratos de silicio (100) al ablacionar un blanco de grafito pirolítico de pureza 99.999 %, en una atmósfera de gas de nitrógeno. El láser utilizado fue un Nd:YAG (λ = 1064 nm y energía = 500 mJ) a una fluencia de 10 J/cm2 . La caracterización de las películas se realizó por microscopia electrónica de barrido (SEM), por microscopia de fuerza atómica (AFM) y mediante espectroscopia infrarroja por transformada de Fourier (FTIR). Las imágenes SEM y AFM muestran una superficie uniforme y suave; además, el análisis AFM, muestra que la rugosidad disminuye con el aumento de la presión encontrando en la película producida a 13.33 Pa, un mínimo de rugosidad de 2.5 nm, con un tamaño de grano de 22.3 nm. Con FTIR se identificaron enlaces simples C-N, dobles C=N y triples C≡N cerca de las frecuencias 1100 cm-1 , 1500 cm-1 y 2200 cm-1 .In this work, we show the pressure effects on morphology and chemical bonding of carbon nitride (CNx ) thin films grown by pulsed laser deposition (PLD). CNx thin films were grown on Si (100) from a graphitic pirolitic target (99.999 % of purity), in nitrogen atmosphere. The graphite target was ablated by Nd:YAG laser (λ = 1064 nm and energy = 500 mJ) with laser fluence of 10 J/cm2 . The films were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). SEM and AFM analysis show a smooth surface. AFM shows that roughness decreases with increasing pressure with a minimum of the roughness of 2.5 nm and grain size of 22.3 nm. FTIR analisys show C-N, C=N and C≡N bonds near at 1100 cm-1 , 1500 cm-1 y 2200 cm-1 frequencies.Fil: Gallego Cano, Jorge Luis. Universidad Tecnológica de Pereira; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Riascos, Henry. Universidad Tecnológica de Pereira; ColombiaFil: Ipaz, L.. Universidad del Valle. Fundación Samanea; Colombi

Temporal visitation patterns of points of interest in cities on a planetary scale: a network science and machine learning approach

We aim to study the temporal patterns of activity in points of interest of cities around the world. In order to do so, we use the data provided by the online location-based social network Foursquare, where users make check-ins that indicate points of interest in the city. The data set comprises more than 90 million check-ins in 632 cities of 87 countries in 5 continents. We analyzed more than 11 million points of interest including all sorts of places: airports, restaurants, parks, hospitals, and many others. With this information, we obtained spatial and temporal patterns of activities for each city. We quantify similarities and differences of these patterns for all the cities involved and construct a network connecting pairs of cities. The links of this network indicate the similarity of temporal visitation patterns of points of interest between cities and is quantified with the Kullback-Leibler divergence between two distributions. Then, we obtained the community structure of this network and the geographic distribution of these communities worldwide. For comparison, we also use a Machine Learning algorithm - unsupervised agglomerative clustering - to obtain clusters or communities of cities with similar patterns. The main result is that both approaches give the same classification of five communities belonging to five different continents worldwide. This suggests that temporal patterns of activity can be universal, with some geographical, historical, and cultural variations, on a planetary scale.Comment: 18 pages, 7 figure

Evolution of transport under cumulative damage in metro systems

One dominant aspect of cities is transport and massive passenger mobilization which remains a challenge with the increasing demand on the public as cities grow. In addition, public transport infrastructure suffers from traffic congestion and deterioration, reducing its efficiency. In this paper, we study the capacity of transport in 33 worldwide metro systems under the accumulation of damage. We explore the gradual reduction of functionality in these systems associated with damage that occurs stochastically. The global transport of each network is modeled as the diffusive movement of Markovian random walkers on networks considering the capacity of transport of each link, where these links are susceptible to damage. Monte Carlo simulations of this process in metro networks show the evolution of the functionality of the system under damage considering all the complexity in the transportation structure. This information allows us to compare and classify the effect of damage in metro systems. Our findings provide a general framework for the characterization of the capacity to maintain the transport under failure in different systems described by networks.Comment: 9 pages; 4 figure

Long-Range Navigation on Complex Networks using L\'evy Random Walks

We introduce a strategy of navigation in undirected networks, including regular, random, and complex networks, that is inspired by L\'evy random walks, generalizing previous navigation rules. We obtained exact expressions for the stationary probability distribution, the occupation probability, the mean first passage time, and the average time to reach a node on the network. We found that the long-range navigation using the L\'evy random walk strategy, compared with the normal random walk strategy, is more efficient at reducing the time to cover the network. The dynamical effect of using the L\'evy walk strategy is to transform a large-world network into a small world. Our exact results provide a general framework that connects two important fields: L\'evy navigation strategies and dynamics on complex networks.Comment: 6 pages, 3 figure

Películas delgadas de zn1-xmnxo

A continuación se realiza una revisión bibliográfica de trabajos de investigación efectuados sobre películas delgadas de óxido de zinc dopadas con manganeso (Zn1-xMnxO). Las propiedades, especialmente las magnéticas, dependen de las técnicas de crecimiento. Realizamos en este trabajo una revisión de las técnicas de síntesis de Zn1-xMnxO más comunes, principalmente del método de Deposición por láser pulsado. Así mismo esbozaremos las propiedades más relevantes de estas películas y finalmente mencionaremos las técnicas para la medición de estas propiedades