Potential GDP growth in Venezuela : a structural time series approach

Real GDP and oil prices are decomposed into common stochastic trend and cycle processes using structural time series models. Potential real GDP is represented by the level of the trend component of real GDP. The potential rate of growth of real GDP is represented by the stochastic drift element of the trend component. Cuevas finds that there is a strong association at the trend and cycle frequencies between real GDP and the real price of oil. This association is also robust in the presence of key economic policy variables. From 1970-80, when the underlying annual rate of increase of the real price of oil was 12 percent, the underlying annual rate of increase of potential GDP in Venezuela was 2.6 percent. By contrast, from 1981-2000 when the underlying rate of increase of the real price of oil was -5 percent, the underlying growth rate of potential GDP fell 1.5 percent. However, the strength of association between the underlying growth of oil prices and real GDP has fallen considerably since the early 1980s, suggesting that oil cannot be relied on as an engine for future growth in Venezuela.Environmental Economics&Policies,Climate Change,Poverty Impact Evaluation,Economic Theory&Research,Poverty Reduction Strategies,Economic Theory&Research,Environmental Economics&Policies,Energy Demand,Oil Refining&Gas Industry,Climate Change

Demand for imports in Venezuela : a structural time series approach

Using structural time series models, Cuevas estimates common stochastic trends of real GDP and imports in Venezuela from 1974-2000. The real imports trend drifts upward at almost twice the rate of growth of GDP. This highlights the powerful structural tendency toward increasing imports in Venezuela. The author also explicitly estimates common stochastic cycles, which he finds to have 5 and 17 year periods. In addition, he finds that a 1 percent real exchange rate appreciation leads to a 0.4 percent increase in imports. And in the long-run, 1 percent real GDP growth is associated with 1.7 percent real imports growth. The author also shows that the GDP elasticity of imports uniformly falls with cycle period, with the elasticity reaching 4.55 at the frequency associated with the 5-year cycle. A powerful imports responsiveness at the higher cycle frequency is associated with the recurrence of external imbalances in Venezuela.Environmental Economics&Policies,Climate Change,Consumption,Economic Theory&Research,Water Conservation,Economic Theory&Research,Environmental Economics&Policies,Macroeconomic Management,Economic Stabilization,Consumption

Theoretical study of the charge transport through C60-based single-molecule junctions

We present a theoretical study of the conductance and thermopower of single-molecule junctions based on C60 and C60-terminated molecules. We first analyze the transport properties of gold-C60-gold junctions and show that these junctions can be highly conductive (with conductances above 0.1G0, where G0 is the quantum of conductance). Moreover, we find that the thermopower in these junctions is negative due to the fact that the LUMO dominates the charge transport, and its magnitude can reach several tens of micro-V/K, depending on the contact geometry. On the other hand, we study the suitability of C60 as an anchoring group in single-molecule junctions. For this purpose, we analyze the transport through several dumbbell derivatives using C60 as anchors, and we compare the results with those obtained with thiol and amine groups. Our results show that the conductance of C60-terminated molecules is rather sensitive to the binding geometry. Moreover, the conductance of the molecules is typically reduced by the presence of the C60 anchors, which in turn makes the junctions more sensitive to the functionalization of the molecular core with appropriate side groups.Comment: 9 pages, 7 figure

Discrete moving breather collisions in a Klein-Gordon chain of oscillators

We study collision processes of moving breathers with the same frequency, traveling with opposite directions within a Klein-Gordon chain of oscillators. Two types of collisions have been analyzed: symmetric and non-symmetric, head-on collisions. For low enough frequency the outcome is strongly dependent of the dynamical states of the two colliding breathers just before the collision. For symmetric collisions, several results can be observed: breather generation, with the formation of a trapped breather and two new moving breathers; breather reflection; generation of two new moving breathers; and breather fusion bringing about a trapped breather. For non-symmetric collisions the possible results are: breather generation, with the formation of three new moving breathers; breather fusion, originating a new moving breather; breather trapping with also breather reflection; generation of two new moving breathers; and two new moving breathers traveling as a ligand state. Breather annihilation has never been observed.Comment: 19 pages, 12 figure

Field enhancement in subnanometer metallic gaps

Motivated by recent experiments [Ward et al., Nature Nanotech. 5, 732 (2010)], we present here a theoretical analysis of the optical response of sharp gold electrodes separated by a subnanometer gap. In particular, we have used classical finite difference time domain simulations to investigate the electric field distribution in these nanojunctions upon illumination. Our results show a strong confinement of the field within the gap region, resulting in a large enhancement compared to the incident field. Enhancement factors exceeding 1000 are found for interelectrode distances on the order of a few angstroms, which are fully compatible with the experimental findings. Such huge enhancements originate from the coupling of the incident light to the evanescent field of hybrid plasmons involving charge density oscillations in both electrodes.Comment: 4 pages, 3 figures, to appear in Physical Review

Measuring dopant concentrations in compensated p-type crystalline silicon via iron-acceptor pairing

We present a method for measuring the concentrations of ionized acceptors and donors in compensated p-type silicon at room temperature.Carrier lifetimemeasurements on silicon wafers that contain minute traces of iron allow the iron-acceptor pair formation rate to be determined, which in turn allows the acceptor concentration to be calculated. Coupled with an independent measurement of the resistivity and a mobility model that accounts for majority and minority impurity scatterings of charge carriers, it is then possible to also estimate the total concentration of ionized donors. The method is valid for combinations of different acceptor and donor species.D.M. is supported by an Australian Research Council fellowship. L.J.G. would like to acknowledge SenterNovem for support

Tunable plasmonic enhancement of light scattering and absorption in graphene-coated subwavelength wires

The electromagnetic response of subwavelength wires coated with a graphene monolayer illuminated by a linearly polarized plane waves is investigated. The results show that the scattering and extintion cross-sections of the coated wire can be dramatically enhanced when the incident radiation resonantly excites localized surface plasmons. The enhancements occur for p--polarized incident waves and for excitation frequencies that correspond to complex poles in the coefficients of the multipole expansion for the scattered field. By dynamically tuning the chemical potential of graphene, the spectral position of the enhancements can be chosen over a wide range.Comment: Accepted for publication in Journal of Optics 201