Ions at the air-water interface: An end to one hundred year old mystery?

Availability of highly reactive halogen ions at the surface of aerosols has tremendous implications for the atmospheric chemistry. Yet neither simulations, experiments, nor existing theories are able to provide a fully consistent description of the electrolyte-air interface. In this paper a new theory is proposed which allows us to explicitly calculate the ionic density profiles, the surface tension, and the electrostatic potential difference across the solution-air interface. Predictions of the theory are compared to experiments and are found to be in excellent agreement. The theory also sheds new light on one of the oldest puzzles of physical chemistry -- the Hofmeister effect

Dynamic Bayesian smooth transition autoregressive models applied to hourly electricity load in southern Brazil

Dynamic Bayesian Smooth Transition Autoregressive (DBSTAR) models are proposed for nonlinear autoregressive time series processes as alternative to both the classical Smooth Transition Autoregressive (STAR) models of Chan and Tong (1986) and the Bayesian Simulation STAR (BSTAR) models of Lopes and Salazar (2005). Unlike those, DBSTAR models are sequential polynomial dynamic analytical models suitable for inherently non-stationary time series with non-linear characteristics such as asymmetric cycles. As they are analytical, they also avoid potential computational problems associated with BSTAR models and allow fast sequential estimation of parameters. Two types of DBSTAR models are defined here based on the method adopted to approximate the transition function of their autoregressive components, namely the Taylor and the B-splines DBSTAR models. A harmonic version of those models, that accounted for the cyclical component explicitly in a flexible yet parsimonious way, were applied to the well-known series of annual Canadian lynx trappings and showed improved fitting when compared to both the classical STAR and the BSTAR models. Another application to a long series of hourly electricity loading in southern Brazil, covering the period of the South-African Football World Cup in June 2010, illustrates the short-term forecasting accuracy of fast computing harmonic DBSTAR models that account for various characteristics such as periodic behaviour (both within-the-day and within-the-week) and average temperature

Inflation and Welfare in Long-Run Equilibrium with Firm Dynamics

We analyze the welfare cost of inflation in a model with cash-in-advance constraints and an endogenous distribution of establishments' productivities. Inflation distorts aggregate productivity through firm entry dynamics. The model is calibrated to the United States economy and the long-run equilibrium properties are compared at low and high inflation. We find that, when the period over which the cash-in-advance constraint is binding is one quarter, an annual inflation rate of 10 percent leads to a decrease in the steady-state average productivity of roughly 0.5 percent compared to the optimum's steady-state. This decrease in productivity is not innocuous: it leads to a doubling of the welfare cost of inflation.firm dynamics, productivity, inflation, welfare