Viscoelastic repetitive creep and recovery in bituminous materials

Abstract Repetitive creep and recovery tests in bituminous materials- asphalt and asphalt paving mix are studied at high service temperatures. The non-exponential- stretched exponential type of continuous retardation spectrum is defined and used for the calculation of creep compliance function in repetitive shear and tensile creep and recovery experiments and also in the wheel tracking test on asphalt paving mix. It is shown that the used model, with only five adjustable parameters, can describe the test quite well. The model is also adequate for the description of the composite compliance function constructed from the linear viscoelastic data and the apparently nonlinear compliance function obtained in the wheel tracking test, for asphalt paving mix

Observations of nonlinear internal waves at a persistent coastal upwelling front

We collected high-resolution observations of nonlinear internal waves (NLIWs) at a persistent upwelling front in the shallow coastal environment (~20 m) of northern Monterey Bay, CA. The coastal upwelling front forms between recently upwelled waters and warmer stratified waters that are trapped in the bay (upwelling shadow). The front propagates up and down the coast in the along-shore direction as a buoyant plume front due to modulation by strong diurnal wind forcing. The evolution of the coastal upwelling front, and the subsequent modulation of background environmental conditions, is examined using both individual events and composite day averages. We demonstrate that regional-scale upwelling and local diurnal wind forcing are key components controlling local stratification and the formation of internal wave guides that allow for high-frequency internal wave activity. Finally, we discuss the ability of theoretical models to describe particularly large-amplitude internal waves that exist in the presence of a strong background shear and test a fully nonlinear model (i.e., the Dubreil–Jacotin–Long equation)

Nonlinear interfacial waves in a constant-vorticity planar flow over variable depth

Exact Lagrangian in compact form is derived for planar internal waves in a two-fluid system with a relatively small density jump (the Boussinesq limit taking place in real oceanic conditions), in the presence of a background shear current of constant vorticity, and over arbitrary bottom profile. Long-wave asymptotic approximations of higher orders are derived from the exact Hamiltonian functional in a remarkably simple way, for two different parametrizations of the interface shape.Comment: revtex, 4.5 pages, minor corrections, summary added, accepted to JETP Letter

Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule

N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor's ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system

Mobile Criminals, Immobile Crime: The Efficiency of Decentralized Crime Deterrence

In this paper we examine a class of local crimes that involve perfectly mobile criminals, and perfectly immobile criminal opportunities. We focus on local non-rival crime deterrence that is more efficient against criminals pursuing domestic crimes than criminals pursuing crimes elsewhere. In a standard case of sincerely delegated politicians and zero transfers to other districts, we show that centralized deterrence unambiguously dominates the decentralized deterrence. With strategic delegation and voluntary in-kind transfers, the tradeoff is exactly the opposite: Decentralization achieves the social optimum, whereas cooperative centralization overprovides for enforcement. This is robust to various cost-sharing modes. We also examine the effects of the growing interdependence of districts, stemming from criminals' increasing opportunities to strategically displace. Contrary to the supposition in Oates's decentralization theorem, increasing interdependence makes centralization less desirable

The Decentralization Tradeoff for Complementary Spillovers

We examine a symmetric two-district setting with spillovers of local public spending where a spill-in from the foreign spending is not a substitute, but a complement to domestic spending. Specifically, we assume production of two district-specific public goods out of two complementary district-specific inputs. We compare equilibria in non-cooperative decentralization and cooperative centralization for different spillovers, complementarities and cost-division rules, and control for the effects of strategic delegation and the feasibility of voluntary contributions to the input in the foreign district. We find that centralization welfare-dominates decentralization in most institutional settings and for a wide range of parameters, yet we can also identify necessary and sufficient conditions for decentralization to welfare-dominate centralization. The setup features three novelties: In the absence of transfers, welfare in decentralization increases in spillovers, strategic delegation in decentralization improves welfare, and centralized provision may be non-monotonic in spillovers

Local Government Efficiency: Evidence from the Czech Municipalities

We measure cost efficiency of 202 Czech municipalities of extended scope in period 2003-2008. The study is the first application of overall efficiency measurement of the local governments in the new EU member states, and the second in post-communist countries. We measure government efficiency through established quantitative and qualitative indicators of the provision of education, cultural facilities, infrastructure and other local services. First, we employ non-parametric approach of the data envelopment analysis and adjust the efficiency scores by bootstrapping. Second, we employ the stochastic frontier analysis and control for effects of various demographic, economic, and political variables. We compare scores under our preferred specification, i.e. pseudo-translog time-variant stochastic-frontier analysis with determinants, with alternative scores. The determinants that robustly increase inefficiency are population size, distance to the regional center, share of university-educated citizens, capital expenditures, subsidies per capita, and the share of self-generated revenues. Concerning political variables, increase in party concentration and the voters' involvement increases efficiency, and local council with a lower share of left-wing representatives also tend to be more efficient. We interpret determinants both as indicators of slack, non-discretionary inputs, and unobservable outputs. The analysis is conducted also for the period 1994-1996, where political variables appear to influence inefficiency in a structurally different way. From comparison of the two periods, we obtain that small municipalities improve efficiency significantly more that large municipalities