What does a technology shock do? A VAR analysis with model-based sign restrictions

This paper estimates the effects of technology shocks in VAR models of the U.S., identified by imposing restrictions on the sign of impulse responses. These restrictions are consistent with the implications of a popular class of DSGE models, with both real and nominal frictions, and with sufficiently wide ranges for their parameterers. This identification strategy thus substitutes theoretically-motivated restrictions for the atheoretical assumptions on the time-series properties of the data that are key to long-run restrictions. Stochastic technology improvements persistently increase real wages, consumption, investment and output in the data; hours worked are very likely to increase, displaying a hump-shaped pattern. Contrary to most of the related VAR evidence, results are not sensitive to a number of specification assumptions, including those on the stationarity properties of variables. JEL Classification: C3, E3Bayesian VAR methods, DSGE Models, Identification, Technology shocks

What does a technology shock do? A VAR analysis with model-based sign restrictions

This paper estimates the effects of technology shocks in VAR models of the U.S., identified by imposing restrictions on the sign of impulse responses. These restrictions are consistent with the implications of a popular class of DSGE models, with both real and nominal frictions, and with sufficiently wide ranges for their parameters. This identification strategy thus substitutes theoretically-motivated restrictions for the atheoretical assumptions on the time-series properties of the data that are key to long-run restrictions. Stochastic technology improvements persistently increase real wages, consumption, investment and output in the data; hours worked are very likely to increase, displaying a hump-shaped pattern. Contrary to most of the related VAR evidence, results are not sensitive to a number of specification assumptions, including those on the stationarity properties of variables.technology shocks, DSGE models, bayesian VAR methods, identification

Reducing Power Consumption in Backbone Networks

Abstract—According to several studies, the power consumption of the Internet accounts for up to 10 % of the worldwide energy consumption, and several initiatives are being put into place to reduce the power consumption of the ICT sector in general. To this goal, we propose a novel approach to switch off network nodes and links while still guaranteeing full connectivity and maximum link utilization. After showing that the problem falls in the class of capacitated multi-commodity flow problems, and therefore it is NP-complete, we propose some heuristic algorithms to solve it. Simulation results in a realistic scenario show that it is possible to reduce the number of links and nodes currently used by up to 30 % and 50 % respectively during off-peak hours, while offering the same service quality

Power-Aware Routing and Wavelength Assignment in Optical Networks

We introduce the Power-Aware RWA problem, whose goal is to accommodate lightpaths in wavelength routing networks minimizing the power consumption. Formulation, algorithms, and results are presented, showing that significant power savings are possibl

Credit and banking in a DSGE model of the euro area

This paper studies the role of credit-supply factors in business cycle fluctuations. For this purpose, we introduce an imperfectly competitive banking sector into a DSGE model with financial frictions. Banks issue collateralized loans to both households and firms, obtain funding via deposits and accumulate capital from retained earnings. Margins charged on loans depend on bank capital-to-assets ratios and on the degree of interest rate stickiness. Bank balance-sheet constraints establish a link between the business cycle, which affects bank profits and thus capital, and the supply and cost of loans. The model is estimated with Bayesian techniques using data for the euro area. The analysis delivers the following results. First, the existence of a banking sector partially attenuates the effects of demand shocks, while it helps propagate supply shocks. Second, shocks originating in the banking sector explain the largest share of the fall of output in 2008 in the euro area, while macroeconomic shocks played a limited role. Third, an unexpected destruction of bank capital has a substantial impact on the real economy and particularly on investment.collateral constraints, banks, banking capital, sticky interest rates

Motor proteins traffic regulation by supply-demand balance of resources

In cells and in vitro assays the number of motor proteins involved in biological transport processes is far from being unlimited. The cytoskeletal binding sites are in contact with the same finite reservoir of motors (either the cytosol or the flow chamber) and hence compete for recruiting the available motors, potentially depleting the reservoir and affecting cytoskeletal transport. In this work we provide a theoretical framework to study, analytically and numerically, how motor density profiles and crowding along cytoskeletal filaments depend on the competition of motors for their binding sites. We propose two models in which finite processive motor proteins actively advance along cytoskeletal filaments and are continuously exchanged with the motor pool. We first look at homogeneous reservoirs and then examine the effects of free motor diffusion in the surrounding medium. We consider as a reference situation recent in vitro experimental setups of kinesin-8 motors binding and moving along microtubule filaments in a flow chamber. We investigate how the crowding of linear motor proteins moving on a filament can be regulated by the balance between supply (concentration of motor proteins in the flow chamber) and demand (total number of polymerised tubulin heterodimers). We present analytical results for the density profiles of bound motors, the reservoir depletion, and propose novel phase diagrams that present the formation of jams of motor proteins on the filament as a function of two tuneable experimental parameters: the motor protein concentration and the concentration of tubulins polymerized into cytoskeletal filaments. Extensive numerical simulations corroborate the analytical results for parameters in the experimental range and also address the effects of diffusion of motor proteins in the reservoir.Comment: 31 pages, 10 figure

Energy-aware Backbone Networks: a Case Study

Abstract—Power consumption of ICT is becoming more and more a sensible problem, which is of interest for both the research community, for ISPs and for the general public. In this paper we consider a real IP backbone network and a real traffic profile. We evaluate the energy cost of running it, and, speculating on the possibility of selectively turning off spare devices whose capacity is not required to transport off-peak traffic, we show that it is possible to easily achieve more than 23 % of energy saving per year, i.e., to save about 3GWh/year considering today’s power footprint of real network devices. I