On the recent slowdown in productivity growth in advanced economies

After two and a half decades of prosperous postwar development, western industrialised countries recently experienced a slowdown of economic growth and productivity advance together with an increase in the rates of inflation and unemployment. The deep recession of 1974/75 has uncovered fundamental structural weaknesses; since then, the advanced economies have not regained the momentum of the 1960s. In this paper, we shall attempt to contribute to a better understanding of this malaise. But as our comparative advantage is not in growth-accounting and as we do not believe that we can single out one or two specific causes, we shall merely aim at forming an idea (perhaps only a rather vague one) which might be further developed into a paradigm or research programme (in Lakatos? sense).

Optical anisotropy induced by ion bombardment of Ag(001)

Grazing incidence ion bombardment results in the formation of nanoripples that induce an anisotropic optical reflection The evolution of the reflectance anisotropy has been monitored in situ with reflectance anisotropy spectroscopy. The Rayleigh-Rice theory (RRT) has been used to analyze the optical spectra quantitatively and provides the evolution of the average ripple period and root-mean-squared surface roughness. After an incipient phase, both the increase in the periodicity and the roughness vary roughly with the square root of the sputter time. Additional high-resolution low-energy electron diffraction (HR-LEED) measurements have been performed to characterize details of the average structure created by ion bombardment

Kondo model in nonequilibrium: Interplay between voltage, temperature, and crossover from weak to strong coupling

We consider an open quantum system in contact with fermionic metallic reservoirs in a nonequilibrium setup. For the case of spin, orbital or potential fluctuations, we present a systematic formulation of real-time renormalization group at finite temperature, where the complex Fourier variable of an effective Liouvillian is used as flow parameter. We derive a universal set of differential equations free of divergencies written as a systematic power series in terms of the frequency-independent two-point vertex only, and solve it in different truncation orders by using a universal set of boundary conditions. We apply the formalism to the description of the weak to strong coupling crossover of the isotropic spin-1/2 nonequilibrium Kondo model at zero magnetic field. From the temperature and voltage dependence of the conductance in different energy regimes we determine various characteristic low-energy scales and compare their universal ratio to known results. For a fixed finite bias voltage larger than the Kondo temperature, we find that the temperature-dependence of the differential conductance exhibits non-monotonic behavior in the form of a peak structure. We show that the peak position and peak width scale linearly with the applied voltage over many orders of magnitude in units of the Kondo temperature. Finally, we compare our calculations with recent experiments.Comment: 48 pages, 10 figure

TinkerCell: Modular CAD Tool for Synthetic Biology

Synthetic biology brings together concepts and techniques from engineering and biology. In this field, computer-aided design (CAD) is necessary in order to bridge the gap between computational modeling and biological data. An application named TinkerCell has been created in order to serve as a CAD tool for synthetic biology. TinkerCell is a visual modeling tool that supports a hierarchy of biological parts. Each part in this hierarchy consists of a set of attributes that define the part, such as sequence or rate constants. Models that are constructed using these parts can be analyzed using various C and Python programs that are hosted by TinkerCell via an extensive C and Python API. TinkerCell supports the notion of a module, which are networks with interfaces. Such modules can be connected to each other, forming larger modular networks. Because TinkerCell associates parameters and equations in a model with their respective part, parts can be loaded from databases along with their parameters and rate equations. The modular network design can be used to exchange modules as well as test the concept of modularity in biological systems. The flexible modeling framework along with the C and Python API allows TinkerCell to serve as a host to numerous third-party algorithms. TinkerCell is a free and open-source project under the Berkeley Software Distribution license. Downloads, documentation, and tutorials are available at www.tinkercell.com.Comment: 23 pages, 20 figure

Numerical methods for the unsteady incompressible Navier-Stokes equations and their application to the Direct Numerical Simulation of turbulent flows

Two new methods for the efficient parallel computation of the unsteady incompressible Navier-Stokes equations are presented. Such efficient methods are desired for large scale parallel computations of unsteady turbulent flows such as Direct Numerical Simulations (DNS). The performance of the new methods has a distinct advantage over the artificial compressibility method, in that the methods exhibit robust convergence for a variety of flow problems without extensive need for tuning computational parameters. These methods and others have been implemented in a computer program designed for massively parallel computer architectures, written by the author and used to obtain all results in this work. A DNS of a film-cooling jet is performed in order to evaluate the accuracy of the modeled expressions in the k-e turbulence model. Using the results of the DNS, the terms in the exact and modeled k-e equations are computed. These terms are examined to see where the models fail for these flows. DNS budgets for k and dissipation in a film cooling jet flow are presented to provide turbulence modelers with information as to where the models used to replace the exact k-e equations need improvement for this particular type of flow. A DNS of a pulsed jet is performed to analyze the effect of external pulsing on the flow structures and the resulting mixing of the jet with the crossflow. As the problem is inherently unsteady, the key to the successful prediction of such flows is the ability to resolve the dynamics of all important flow structures resulting from the interaction of the unsteady pulsed jet with the crossflow. In the present work massless particles are released into the flow at various locations. These particles are colored by their seed locations and residence time, greatly aiding the understanding of the dynamics of the flow. A new origin for the formation of the wake vortices has been discovered for both pulsed and unpulsed jets. Pulsing is shown to drastically change the jet spreading and penetration and to increase the mixing of the jet with the crossflow. A significant asymmetry affecting primarily the wake vortices has been found for certain cases

Building drawings with patterns of processed stereotyped motifs

1982 Spring.To view the abstract, please see the full text of the document

Surrealism in Chicago

Includes bibliographic references.12/16/ 81

Where The Dreamy Susquehanna Flows

https://digitalcommons.library.umaine.edu/mmb-vp/5366/thumbnail.jp