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"Fluctuations"
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Control of switching between metastable superconducting states in delta-MoN nanowires
The superconducting state in one-dimensional nanosystems is very delicate. While fluctuations of the phase of the superconducting wave function lead to the spontaneous decay of persistent supercurrents in thin superconducting wires and nanocircuits, discrete phase-slip fluctuations can also lead to more exotic phenomena, such as the appearance of metastable superconducting states in current-bearing wires. Here we show that switching between different metastable superconducting states in δ-MoN nanowires can be very effectively manipulated by introducing small amplitude electrical noise. Furthermore, we show that deterministic switching between metastable superconducting states with different numbers of phase-slip centres can be achieved in both directions with small electrical current pulse perturbations of appropriate polarity. The observed current-controlled bi-stability is in remarkable agreement with theoretically predicted trajectories of the system switching between different limit cycle solutions of a model one-dimensional superconductor.
Journal Article
WIN induces apoptotic cell death in human colon cancer cells through a block of autophagic flux dependent on PPARgamma down-regulation
Cannabinoids have been reported to possess anti-tumorigenic activity in cancer models although their mechanism of action is not well understood. Here, we show that the synthetic cannabinoid WIN55,212-2 (WIN)-induced apoptosis in colon cancer cell lines is accompanied by endoplasmic reticulum stress induction. The formation of acidic vacuoles and the increase in LC3-II protein indicated the involvement of autophagic process which seemed to play a pro-survival role against the cytotoxic effects of the drug. However, the enhanced lysosomal membrane permeabilization (LMP) blocked the autophagic flux after the formation of autophagosomes as demonstrated by the accumulation of p62 and LC3, two markers of autophagic degradation. Data also provided evidence for a role for nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) in cannabinoid signalling. PPARγ expression, at both protein and mRNA levels, was significantly down-regulated after WIN treatment and its inhibition, either by specific antagonists or by down-regulation via gene silencing, induced effects on cell viability as well as on ER stress and autophagic markers similar to those obtained in the presence of WIN. Moreover, the observation that the increase in p62 level and the induction of LMP were also modified by PPARγ antagonists seemed to indicate that PPARγ down-regulation was crucial to determinate the block of autophagic flux, thus confirming the critical role of PPARγ in WIN action. In conclusion, at our knowledge, our results are the first to show that the reduction of PPARγ levels contributes to WIN-induced colon carcinoma cell death by blocking the pro-survival autophagic response of cells.[PUBLICATION ABSTRACT]
Journal Article
Narrative Economics
This address considers the epidemiology of narratives relevant to economic fluctuations. The human brain has always been highly tuned toward narratives, whether factual or not, to justify ongoing actions, even such basic actions as spending and investing. Stories motivate and connect activities to deeply felt values and needs. Narratives \"go viral\" and spread far, even worldwide, with economic impact. The 1920-1921 Depression, the Great Depression of the 1930s, the so-called Great Recession of 2007-2009, and the contentious political-economic situation of today are considered as the results of the popular narratives of their respective times. Though these narratives are deeply human phenomena that are difficult to study in a scientific manner, quantitative analysis may help us gain a better understanding of these epidemics in the future.
Journal Article
CREDIT-MARKET SENTIMENT AND THE BUSINESS CYCLE
Using U.S. data from 1929 to 2015, we show that elevated credit-market sentiment in year t − 2 is associated with a decline in economic activity in years t and t + 1. Underlying this result is the existence of predictable mean reversion in credit-market conditions. When credit risk is aggressively priced, spreads subsequently widen. The timing of this widening is, in turn, closely tied to the onset of a contraction in economic activity. Exploring the mechanism, we find that buoyant credit-market sentiment in year t − 2 also forecasts a change in the composition of external finance: net debt issuance falls in year t, while net equity issuance increases, consistent with the reversal in credit-market conditions leading to an inward shift in credit supply. Unlike much of the current literature on the role of financial frictions in macroeconomics, this article suggests that investor sentiment in credit markets can be an important driver of economic fluctuations.
Journal Article
Words are the New Numbers: A Newsy Coincident Index of the Business Cycle
I construct a daily business cycle index based on quarterly GDP growth and textual information contained in a daily business newspaper. The newspaper data are decomposed into time series representing news topics, while the business cycle index is estimated using the topics and a time-varying dynamic factor model where dynamic sparsity is enforced upon the factor loadings using a latent threshold mechanism. The resulting index classifies the phases of the business cycle with almost perfect accuracy and provides broad-based high-frequency information about the type of news that drive or reflect economic fluctuations. In out-of-sample nowcasting experiments, the model is competitive with forecast combination systems and expert judgment, and produces forecasts with predictive power for future revisions in GDP. Thus, news reduces noise. Supplementary materials for this article are available online.
Journal Article
Asset Pricing in the Frequency Domain: Theory and Empirics
We quantify investors' preferences over the dynamics of shocks by deriving frequency-specific risk prices that capture the price of risk of consumption fluctuations at each frequency. The frequency-specific risk prices are derived analytically for leading models. The decomposition helps measure the importance of economic fluctuations at different frequencies. We precisely quantify the meaning of \"long-run\" in the context of Epstein-Zin preferences -centuries -and measure the exact relevance of business-cycle fluctuations. Finally, we estimate frequency-specific risk prices and show that cycles longer than the business cycle -long-run risks -are significantly priced in the equity market.
Journal Article
WHAT'S NEWS IN BUSINESS CYCLES
In the context of a dynamic, stochastic, general equilibrium model, we perform classical maximum likelihood and Bayesian estimations of the contribution of anticipated shocks to business cycles in the postwar United States. Our identification approach relies on the fact that forward-looking agents react to anticipated changes in exogenous fundamentals before such changes materialize. It further allows us to distinguish changes in fundamentals by their anticipation horizon. We find that anticipated shocks account for about half of predicted aggregate fluctuations in output, consumption, investment, and employment.
Journal Article
Gross Worker Flows over the Business Cycle
We build a hybrid model of the aggregate labor market that features both standard labor supply forces and frictions in order to study the cyclical properties of gross worker flows across the three labor market states: employment, unemployment, and nonparticipation. Our parsimonious model is able to capture the hey features of the cyclical movements in gross worker flows. Despite the fact that the wage per efficiency unit is constant over time, intertemporal substitution plays an important role in shaping fluctuations in the participation rate.
Journal Article
Forty Years of Oil Price Fluctuations: Why the Price of Oil May Still Surprise Us
It has been 40 years since the oil crisis of 1973/74. This crisis has been one of the defining economic events of the 1970s and has shaped how many economists think about oil price shocks. In recent years, a large literature on the economic determinants of oil price fluctuations has emerged. Drawing on this literature, we first provide an overview of the causes of all major oil price fluctuations between 1973 and 2014. We then discuss why oil price fluctuations remain difficult to predict, despite economists’ improved understanding of oil markets. Unexpected oil price fluctuations are commonly referred to as oil price shocks. We document that, in practice, consumers, policymakers, financial market participants, and economists may have different oil price expectations, and that, what may be surprising to some, need not be equally surprising to others.
Journal Article