Evidence for product-specific active sites on oxide-derived Cu catalysts for electrochemical CO2 reduction

Carbon dioxide electroreduction in aqueous media using Cu catalysts can generate many different C2 and C3 products, which leads to the question whether all products are generated from the same types of active sites or if product-specific active sites are responsible for certain products. Here, by reducing mixtures of 13CO and 12CO2, we show that oxide-derived Cu catalysts have three different types of active sites for C–C coupled products, one that produces ethanol and acetate, another that produces ethylene and yet another that produces 1-propanol. In contrast, we do not find evidence of product-specific sites on polycrystalline Cu and oriented (100) and (111) Cu surfaces. Analysis of the isotopic composition of the products leads to the prediction that the adsorption energy of *COOH (the product of the first step of CO2 reduction) may be a descriptor for the product selectivity of a given active site. These new insights should enable highly selective catalysts to be developed

Cultural Diversity and Economic Growth: Evidence from the US during the Age of Mass Migration

We exploit the large inflow of immigrants to the US during the 1870-1920 period to examine the effects that changes in the cultural composition of the population of US counties had on output growth. We construct measures of fractionalization and polarization to distinguish between the different effects of cultural diversity. Our main finding is that increases in cultural fractionalization significantly increased output, while increases in cultural polarization significantly decreased output. We address the issue of identifying the causal effect of cultural diversity on output growth using the supply-push component of immigrant inflows as an instrumental variable.cultural diversity, economic growth, historical development, immigration

The Accuracy and Efficiency of the Consensus Forecasts: A Further Application and Extension of the Pooled Approach

In this paper we analyze the macroeconomic forecasts of the Consensus Forecasts for 12 countries over the period from 1996 to 2006 regarding bias and information efficiency. A pooled approach is employed which permits the evaluation of all forecasts for each target variable over 24 horizons simultaneously. It is shown how the pooled approach needs to be adjusted in order to accommodate the forecasting scheme of the Consensus Forecasts. Furthermore, the pooled approach is extended by a sequential test with the purpose of detecting the critical horizon after which the forecast should be regarded as biased. Moreover, heteroscedasticity in the form of year-specific variances of macroeconomic shocks is taken into account. The results show that in the analyzed period which was characterized by pronounced macroeconomic shocks, several countries show biased forecasts, especially with forecasts covering more than 12 months. In addition, information efficiency has to be rejected in almost all cases. --business cycle forecasting,forecast evaluation,Consensus Forecasts

A Subband-Based SVM Front-End for Robust ASR

This work proposes a novel support vector machine (SVM) based robust automatic speech recognition (ASR) front-end that operates on an ensemble of the subband components of high-dimensional acoustic waveforms. The key issues of selecting the appropriate SVM kernels for classification in frequency subbands and the combination of individual subband classifiers using ensemble methods are addressed. The proposed front-end is compared with state-of-the-art ASR front-ends in terms of robustness to additive noise and linear filtering. Experiments performed on the TIMIT phoneme classification task demonstrate the benefits of the proposed subband based SVM front-end: it outperforms the standard cepstral front-end in the presence of noise and linear filtering for signal-to-noise ratio (SNR) below 12-dB. A combination of the proposed front-end with a conventional front-end such as MFCC yields further improvements over the individual front ends across the full range of noise levels