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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jmoneco.2007.06.002 Byline: Russell Cooper (a), John Haltiwanger (b), Jonathan L. Willis (c) Abstract: We estimate a search model to match hours, employment, vacancies and unemployment at the micro- and macrolevels. We establish a set of facts concerning the variability of unemployment and vacancies in the aggregate and the distribution of net employment growth and the comovement of hours and employment growth at the establishment level. A search model with non-convex costs of posting vacancies, establishment-level profitability shocks and a contracting framework to set hours provides a structure to understand these observations. The estimated model is able to capture both the aggregate and establishment-level facts. Author Affiliation: (a) Department of Economics, University of Texas at Austin and the NBER, Austin, TX 78712, USA (b) Department of Economics, University of Maryland and the NBER, USA (c) Research Department, Federal Reserve Bank of Kansas City, USA Article History: Received 15 September 2006; Revised 6 June 2007; Accepted 7 June 2007 Article Note: (footnote) [star] We are grateful to an anonymous referee, Robert King, Shigeru Fujita, Murat Tasci and Eran Yashiv for helpful comments. Thanks also to Stephen Nickell, Julian Messina, participants at the 2006 Swiss National Bank/JME Conference and seminar participants at the Ohio State University, Washington University of St. Louis and the Federal Reserve Banks of Chicago, Dallas, Kansas City and New York for comments and suggestions. The authors thank the NSF for financial support. The views expressed herein are solely those of the authors and do not necessarily reflect the views of the Federal Reserve Bank of Kansas City or the Federal Reserve System.

Financial collapses are analyzed from the perspective of a monetary model with multiple equilibria. The policy prescription, which increases money supply, is assessed as a possible solution to avoid financial collapses.

The contribution of learning-by-doing (LBD) mechanism in stimulating the endogenous propagation of shocks in business cycle was studied. The results showed that the LBD had the potential of creating endogenous propagation and autocorrelation function was noticed for real output growth with positive coefficients for several periods.

An extension of the Diamond-Dybvig framework was undertaken to analyze the effects of bank runs and to forecast banks' reactions to the possibility of runs. The framework revealed that banks also have the option to offer contracts that might possibly lead to runs in order to attain more profitable investment returns. The approach signified the presence of intermediaries' true liquidity role in offering new conditions for bank runs.

A standard business cycle model modified with contemporaneous and dynamic complementarities was proposed to evaluate the significance of dynamic complementarities as an antecedent of propagation in a dynamic stochastic economy. The model relies on past data from Baxter and King (1991) and issues on propagation from dynamic complementarities from Cooper and John (1988). The complementarities are seen as contributing factors that augment and produce shocks to technology and tastes.

The COSHER joint industry project involved the conduct of large scale experiments to provide release and dispersion data under well-defined conditions, studying the full bore rupture of a CO 2 dense phase high pressure underground pipeline at large scale. The data generated are useful for model development and validation as well as for better understanding of the risks due to large scale underground CO 2 pipeline ruptures. In order to simulate the depressurization of a pipeline, a 219.1 mm diameter pipeline loop was fed from both ends by a 148 m 3 reservoir of CO 2 . The rig was designed to promote outflow in the liquid phase for as long as possible. About 136 ton of CO 2 were released in 204 s. During the experiments, measurements of the fluid pressure, fluid temperature and wall temperature of the test facility were made together with measurements of the CO 2 concentration contours and temperature within the dispersing gas cloud. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of Al2O3 grown using atomic layer deposition (ALD) techniques can protect polymers from erosion by oxygen atoms. To quantify this protection, polyimide substrates with the same chemical repeat unit as Kapton® were applied to quartz crystal microbalance (QCM) sensors. Al2O3 ALD films with varying thicknesses were grown on the polyimide substrates. The ALD-coated polyimide materials were then exposed to a hyperthermal atomic-oxygen beam. The mass loss versus oxygen-atom exposure time was measured in situ by the QCM. Al2O3 ALD film thicknesses of ∼35 Å were found to protect the polymer from erosion. [Copyright &y& Elsevier]

Polyimides, particularly poly-(pyromellitic dianhydride-4,40-oxydianiline) or PMDA-ODA (Kapton-H®), are ubiquitous in the aircraft and aerospace industries, flexible printed circuits, and many other high-performance applications. For many of these applications, the polymer's stability during and after radiation damage is a serious concern. The effect of electron irradiation on the breaking of inter-molecular bonds and creation of free radicals in Kapton polyimide were studied using reactive molecular dynamics simulation with the polarizable ReaxFF method and experimentally on pristine and electron irradiated polyimide by vibrational spectroscopy, electron paramagnetic resonance, nuclear magnetic resonance, wide angle x-ray diffraction, small angle x-ray scattering, and dynamic mechanical analysis. In our simulations, the electron beam is approximated by a dense column of negatively charged particles, which is inserted at random positions in the polyimide matrix. In order to observe inter-molecular bond breaking during the time frame of the molecular simulations, each electron beam is switched on for 2 fs, causing an average energy of 21 eV per electron trajectory to be transferred to the polyimide through Coulomb interactions during the simulation. Experimentally, polyimide is aged in vacuum with a 90 keV electron beam with a maximum penetration depth greater than the material's thickness. Throughout the simulations, modifications in the chemical structure of the polyimide during and after the electron beam irradiations are monitored. During electron beam irradiation, hydrogen atoms separate from different parts of the polyimide through C–H bond cleavage. After turning off the electron beams and running a microcanonical molecular dynamics simulation for 0.5 ns, several chemical and structural rearrangements are observed in the polyimide structure. The chemical modifications mostly include ring opening and other changes to the imide rings. The computations are compared to infrared spectroscopy, electron paramagnetic resonance, nuclear magnetic resonance, x-ray scattering, and mechanical measurements on aged and pristine polyimide to both guide and validate the conclusions from the computational study. Apart from these changes in chemistry we also evaluate temperature evolution and change in mechanical response of the polyimide slab caused by electron beam exposure. Taken together, the direct measurements of the electronic, chemical, and mechanical properties of the irradiated Kapton films validate the key results of the model. Image 1 • Most of the chemical rearrangements are observed in the imide ring spots. • Cross linking of the polyimide chains is observed after electron irradiations. • Cross linking leads to higher glass transition temperature. • Electron beam irradiations cause reduced toughness and increased brittleness. [ABSTRACT FROM AUTHOR]