Spatio-temporal Brain Dynamics Mediating Post-error Behavioral Adjustments.

Optimal behavior relies on flexible adaptation to environmental requirements, notably based on the detection of errors. The impact of error detection on subsequent behavior typically manifests as a slowing down of RTs following errors. Precisely how errors impact the processing of subsequent stimuli and in turn shape behavior remains unresolved. To address these questions, we used an auditory spatial go/no-go task where continual feedback informed participants of whether they were too slow. We contrasted auditory-evoked potentials to left-lateralized go and right no-go stimuli as a function of performance on the preceding go stimuli, generating a 2 × 2 design with "preceding performance" (fast hit [FH], slow hit [SH]) and stimulus type (go, no-go) as within-subject factors. SH trials yielded SH trials on the following trials more often than did FHs, supporting our assumption that SHs engaged effects similar to errors. Electrophysiologically, auditory-evoked potentials modulated topographically as a function of preceding performance 80-110 msec poststimulus onset and then as a function of stimulus type at 110-140 msec, indicative of changes in the underlying brain networks. Source estimations revealed a stronger activity of prefrontal regions to stimuli after successful than error trials, followed by a stronger response of parietal areas to the no-go than go stimuli. We interpret these results in terms of a shift from a fast automatic to a slow controlled form of inhibitory control induced by the detection of errors, manifesting during low-level integration of task-relevant features of subsequent stimuli, which in turn influences response speed.

Organic material decomposition and nutrient dynamics in a mulch system enriched with leguminous trees in the Amazon

The new techniques proposed for agriculture in the Amazon region include rotational fallow systems enriched with leguminous trees and the replacement of biomass burning by mulching. Decomposition and nutrient release from mulch were studied using fine-mesh litterbags with five different leguminous species and the natural fallow vegetation as control. Samples from each treatment were analyzed for total C, N, P, K, Ca, Mg, lignin, cellulose content and soluble polyphenol at different sampling times over the course of one year. The decomposition rate constant varied with species and time. Weight loss from the decomposed litter bag material after 96 days was 30.1 % for Acacia angustissima, 32.7 % for Sclerolobium paniculatum, 33.9 % for Iinga edulis and the Fallow vegetation, 45.2 % for Acacia mangium and 63.6 % for Clitoria racemosa. Immobilization of N and P was observed in all studied treatments. Nitrogen mineralization was negatively correlated with phenol, C-to-N ratio, lignin + phenol/N ratio, and phenol/phosphorus ratios and with N content in the litterbag material. After 362 days of field incubation, an average (of all treatments), 3.3 % K, 32.2 % Ca and 22.4 % Mg remained in the mulch. Results confirm that low quality and high amount of organic C as mulch application are limiting for the quantity of energy available for microorganisms and increase the nutrient immobilization for biomass decomposition, which results in competition for nutrients with the crop plants.

Thermal activation and ATP dependence of the cytoskeleton remodeling dynamics

The cytoskeleton (CSK) is a nonequilibrium polymer network that uses hydrolyzable sources of free energy such as adenosine triphosphate (ATP) to remodel its internal structure. As in inert nonequilibrium soft materials, CSK remodeling has been associated with structural rearrangements driven by energy-activated processes. We carry out particle tracking and traction microscopy measurements of alveolar epithelial cells at various temperatures and ATP concentrations. We provide the first experimental evidence that the remodeling dynamics of the CSK is driven by structural rearrangements over free-energy barriers induced by thermally activated forces mediated by ATP. The measured activation energy of these forces is ~40kBTr (kB being the Boltzmann constant and Tr being the room temperature). Our experiments provide clues to understand the analogy between the dynamics of the living CSK and that of inert nonequilibrium soft materials.

Tax reforms and inequality: theoretical and empirical implications

In this paper we examine the effect of tax policy on the relationship between inequality and growth in a two-sector non-scale model. With non-scale models, the longrun equilibrium growth rate is determined by technological parameters and it is independent of macroeconomic policy instruments. However, this fact does not imply that fiscal policy is unimportant for long-run economic performance. It indeed has important effects on the different levels of key economic variables such as per capita stock of capital and output. Hence, although the economy grows at the same rate across steady states, the bases for economic growth may be different.The model has three essential features. First, we explicitly model skill accumulation, second, we introduce government finance into the production function, and we introduce an income tax to mirror the fiscal events of the 1980¿s and 1990¿s in the US. The fact that the non-scale model is associated with higher order dynamics enables it to replicate the distinctly non-linear nature of inequality in the US with relative ease. The results derived in this paper attract attention to the fact that the non-scale growth model does not only fit the US data well for the long-run (Jones, 1995b) but also that it possesses unique abilities in explaining short term fluctuations of the economy. It is shown that during transition the response of the relative simulated wage to changes in the tax code is rather non-monotonic, quite in accordance to the US inequality pattern in the 1980¿s and early 1990¿s.More specifically, we have analyzed in detail the dynamics following the simulation of an isolated tax decrease and an isolated tax increase. So, after a tax decrease the skill premium follows a lower trajectory than the one it would follow without a tax decrease. Hence we are able to reduce inequality for several periods after the fiscal shock. On the contrary, following a tax increase, the evolution of the skill premium remains above the trajectory carried on by the skill premium under a situation with no tax increase. Consequently, a tax increase would imply a higher level of inequality in the economy

Regional economic dynamics and convergence in the european union

Deepening in the European Union (EU) integration process has enhanced the question of economic disparities at a regional level. Theconvergence process observed until the late seventies was exhausted onwards incoincidence with important changes in the economic activity. The paper showshow these factors would have provoked a regional differenciated response that,despite being important, would have not strengthened the decrease in regionalinequalities. We use an alternative and (in our opinion) richer approach to thetraditional convergence analysis, where the evolution of the whole regionaldistribution is what matters and not that of a representative economy. Moreover,when analysing inequalities among regional economies, the geographical spaceacquire an outstanding role. Hence, we apply spatial association tests and relatethem to the convergence analysis

Industrial agglomerations and wage gradients: the Spanish economy in the interwar period

This paper gives new evidence on the relationship between integration and industrial agglomeration in the presence of scale economies, by testing directly one of the predictions that can be derived from Krugman (1991), that is, the existence of regional nominal wage gradients and its transformation following changes in trade regimes. Our case study analyzes the effects of the substitution of an open economy by a closed economy regime, exactly the opposite process studied by Hanson (1996, 1997). In Spain, during the interwar period, protectionist policies would have favored the loss of centrality of the coastal location (Barcelona) and the relative rise of central locations (such as Madrid). Our results indicate the existence of a wage gradient centered in Barcelona during the interwar period (1914-1930) and its weakening after 1925.

Unemployment dynamics and NAIRU estimates for CEECs : a univariate approach

In this paper we test for the hysteresis versus the natural rate hypothesis on the unemployment rates of the EU new members using unit root tests that account for the presence of level shifts. As a by product, the analysis proceeds to the estimation of a NAIRU measure from a univariate point of view. The paper also focuses on the precision of these NAIRU estimates studying the two sources of inaccuracy that derive from the break points estimation and the autoregressive parameters estimation. The results point to the existence of up to four structural breaks in the transition countries NAIRU that can be associated with institutional changes implementing market-oriented reforms. Moreover, the degree of persistence in unemployment varies dramatically among the individual countries depending on the stage reached in the transition process

Potencial de mercado y estructura espacial de los salarios en las regiones españolas, 1955-1995

En este artículo se examina la relación existente entre los salarios de las regiones españolas y su potencial de mercado en el período 1955-1995. Se prueba la existencia de una estructura espacial de los salarios, en la que los salarios disminuyen al alejarnos de las regiones de renta elevada. Este resultado refuerza la hipótesis de la existencia de una dinámica aglomerativa en España durante la segunda mitad del siglo XX. Sin embargo, el efecto del potencial de mercado sobre los salarios disminuye en la segunda parte del período (1975-1995). Este resultado es consistente con la apertura de una senda de dispersión en la localización de la actividad industrial a partir de mediados de los setenta

Deficit, human capital and economic growth dynamics

Long-run economic growth arouses a great interest since it can shed light on the income-path of an economy and try to explain the large differences in income we observe across countries and over time. The neoclassical model has been followed by several endogenous growth models which, contrarily to the former, seem to predict that economies with similar preferences and technological level, do not necessarily tend to converge to similar per capita income levels. This paper attempts to show a possible mechanismthrough which macroeconomic disequilibria and inefficiencies, represented by budget deficits, may hinder human capital accumulation and therefore economic growth. Using a mixed education system, deficit is characterized as a bug agent which may end up sharply reducing the resources devoted to education and training. The paper goes a step further from the literature on deficit by introducing a rich dynamic analysis of the effects of a deficit reduction on different economic aspects.Following a simple growth model and allowing for slight changes in the law of human capital accumulation, we reach a point where deficit might sharply reduce human capital accumulation. On the other hand, a deficit reduction carried on for a long time, taking that reduction as a more efficient management of the economy, may prove useful in inducing endogenous growth. Empirical evidence for a sample of countries seems to support the theoretical assumptions in the model: (1) evidence on an inverse relationship betweendeficit and human capital accumulation, (2) presence of a strongly negative associationbetween the quantity of deficit in the economy and the rate of growth. They may prove a certain role for budget deficit in economic growth

Wage curves for Spain evidence from the family budget survey

This study explores the existence of a wage curve for Spain. To quantify this relationship for the Spanish economy, we used individual datafrom the EPF 1990-1991. The results show the presence of a wage curve with an elasticity of -0.13. The availability of very detailed information on wages and unemployment has also shown that less protected labour market groups -young workers, manual workers and building sector workers- have a higher elasticity of wages to local unemployment. These results could be interpreted as a greater facility of firms in these segments to settle wages as a function ofthe unemployment rate

Size-dependent recombination dynamics in ZnO nanowires.

A deep understanding of the recombination dynamics of ZnO nanowires NWs is a natural step for a precise design of on-demand nanostructures based on this material system. In this work we investigate the influence of finite-size on the recombination dynamics of the neutral bound exciton around 3.365 eV for ZnO NWs with different diameters. We demonstrate that the lifetime of this excitonic transition decreases with increasing the surface-to-volume ratio due to a surface induced recombination process. Furthermore, we have observed two broad transitions around 3.341 and 3.314 eV, which were identified as surface states by studying the dependence of their life time and intensitiy with the NWs dimensions.

Dynamics of 14C-labeled glucose and ammonium in saline arable soils

Organic matter dynamics and nutrient availability in saline agricultural soils of the State of Guanajuato might provide information for remediation strategies. 14C labeled glucose with or without 200 mg kg-1 of NH4+-N soil was added to two clayey agricultural soils with different electrolytic conductivity (EC), i.e. 0.94 dS m-1 (low EC; LEC) and 6.72 dS m-1 (high EC; HEC), to investigate the effect of N availability and salt content on organic material decomposition. Inorganic N dynamics and production of CO2 and 14CO2 were monitored. Approximately 60 % of the glucose-14C added to LEC soil evolved as 14CO2, but only 20 % in HEC soil after the incubation period of 21 days. After one day, < 200 mg 14C was extractable from LEC soil, but > 500 mg 14C from HEC soil. No N mineralization occurred in the LEC and HEC soils and glucose addition reduced the concentrations of inorganic N in unamended soil and soil amended with NH4+-N. The NO2- and NO3- concentrations were on average higher in LEC than in HEC soil, with exception of NO2- in HEC amended with NH4+-N. It was concluded that increases in soil EC reduced mineralization of the easily decomposable C substrate and resulted in N-depleted soil.

Soil water dynamics related to the degree of compaction of two brazilian oxisols under no-tillage

Soil water properties are related to crop growth and environmental aspects and are influenced by the degree of soil compaction. The objective of this study was to determine the water infiltration and hydraulic conductivity of saturated soil under field conditions in terms of the compaction degree of two Oxisols under a no-tillage (NT). Two commercial fields were studied in the state of Rio Grande do Sul, Brazil: one a Haplortox after 14 years under NT; the other a Hapludox after seven years under NT. Maps (50 x 30 m) of the levels of mechanical penetration resistance (PR) were drawn based on the kriging method, differentiating three compaction degrees (CD): high, intermediate and low. In each CD area, the infiltration rate (initial and steady-state) and cumulative water infiltration were measured using concentric rings, with six replications, and the saturated hydraulic conductivity (K(θs)) was determined using the Guelph permeameter. Statistical evaluation was performed based on a randomized design, using the least significant difference (LSD) test and regression analysis. The steady-state infiltration rate was not influenced by the compaction degree, with mean values of 3 and 0.39 cm h-1 in the Haplortox and the Hapludox, respectively. In the Haplortox, saturated soil hydraulic conductivity was 26.76 cm h-1 at a low CD and 9.18 cm h-1 at a high CD, whereas in the Hapludox, this value was 5.16 cm h-1 and 1.19 cm h-1 for the low and high CD, respectively. The compaction degree did not affect the initial and steady-state water infiltration rate, nor the cumulative water infiltration for either soil type, although the values were higher for the Haplortox than the Hapludox.