Seonghoon Kim

Improved TNT detoxification by starch addition in a nitrogen-fixing Methylophilus-dominant aerobic microbial consortium

In this study, a novel aerobic microbial consortium for the complete detoxification of 2,4,6-trinitrotoluene (TNT) was developed using starch as a slow-releasing carbon source under nitrogen-fixing conditions. Aerobic TNT biodegradation coupled with microbial growth was effectively stimulated by the co-addition of starch and TNT under nitrogen-fixing conditions. The addition of starch with TNT led to TNT mineralization via ring cleavage without accumulation of any toxic by-products, indicating improved TNT detoxification by the co-addition of starch and TNT. Pyrosequencing targeting the bacterial 16S rRNA gene suggested that Methylophilus and Pseudoxanthomonas population were significantly stimulated by the co-addition of starch and TNT and that the Methylophilus population became predominant in the consortium. Together with our previous study regarding starch-stimulated RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) degradation (Khan et al., J. Hazard. Mater. 287 (2015) 243-251), this work suggests that the co-addition of starch with a target explosive is an effective way to stimulate aerobic explosive degradation under nitrogen-fixing conditions for enhancing explosive detoxification.

Delayed Overshooting: It's an 80s Puzzle

We re-investigate the delayed overshooting puzzle. We find that delayed overshooting is primarily a phenomenon of the 1980s when the Fed was under the chairmanship of Paul Volcker. Related findings are as follows: (1) Uncovered interest parity fails to hold during the Volcker era and tends to hold in the other periods considered. (2) US monetary policy shocks have substantial impacts on exchange rate variations but misleadingly appear to have small impacts when monetary policy regimes are pooled. In brief, we confirm Dornbusch’s overshooting hypothesis.

A Risk Map of Markups: Why We Observe Mixed Behaviors of Markups

This paper proposes an explanation for mixed evidence on the behaviors of markups. The key mechanism consists of two complementary channels of risk internalization that arise when firms face uninsurable business risks. One channel is based on passive risk consideration, through which firms raise prices to abide by riskier business thereby associating higher production with higher prices. The other channel is based on active risk management, through which firms lower prices to handle riskier business thereby associating higher production with lower prices. The relative responsiveness of the two channels to a shock depends on each firm’s fundamental characteristics and leads to a sharp division of markup cyclicality across sectors.

Profits in (Partial) Equilibrium and (General) Disequilibrium

In a many-sector production economy where each sectors output is used as input for every sector, a general equilibrium implies zero profit for everyone, whereas one market in excess demand implies positive profits for all others in their partial equilibrium. If more than one market is stuck in excess demand, every market allows positive profits.

Risk Channels of Pricing and Production: A Model of Inertial Prices and Cyclical Markups

We consider a firm who faces business risk due to stochastic goods market outcomes and identify two risk channels of pricing and production. One channel is based on the passive risk consideration, through which the producer raises prices to abide by riskier business and thereby associates higher production with higher prices. The other channel is based on the idea of active risk management, through which the producer lowers prices to handle riskier business and thereby associates higher production with lower prices. We bring the two risk channels together towards an alternative theory of inertial prices and cyclical markups: (i) prices exhibit inertial behaviour relative to output variation, (ii) predicted movements of markups are in accordance with the mixed evidence of countercyclical and procyclical variations, and (iii) cyclical behaviours of markups differ across sectors.