A new distinction between two kinds of state constraints is introduced and proved important for solving the Ramiication Problem in Reasoning about Actions. Steady constraints never, not even for an instant, cease to being in force. As such they give rise to truly instantaneous indirect eeects of actions. Stabilizing state constraints, on the other hand, may be suspended for a short period of ti...

This essay presents a theoretical description of the superradiance phenomenon, in which both the quantal and the classical aspects are discussed. Starting from the simple two-level atom-small sample Dicke model, we successively introduce various complications inherent to a realistic superradiance experiment: effects of Van der Waals interaction between the atoms, propagation and diffraction of ...

There is good evidence that morbidity and mortality increase for young persons (YP) following the move from paediatric to adult services. Studies show that effective transition between paediatric and adult care improves long-term outcomes. Many of the issues faced by young people across subspecialties with a long-term condition are generic. This article sets out some of the obstacles that have ...

We describe a method for converting the problem of computing steady-state probabilities of a continuous-time Markov chain into the problem of computing absorption probabilities for a related chain. The construction enables us to apply compositional techniques for computing absorption probabilities that we have previously developed for probabilistic I/O automata to be used for computing certain ...

When roads are clear, traffic proceeds as a continuous flow of cars; if the road is blocked, everything comes to a standstill. However, anyone stuck in the office rush knows life is more complex—traffic tends to move in waves, often slowing down to an annoying stop-andgo. Traffic congestion also makes life difficult for electrons in nanodevices. We tend to think of charge carriers as experienci...

Electrophoretic image displays (EPIDs) are a very promising solution in the search for low-power, paper like reflective displays. While the technology is already mature, little is known about the internal physical properties. In this paper, we will describe which elements contribute to the charge transport and give an explanation of the steady state current. The contribution of the surfactant m...

We present the results of a detailed study of energy correlations at steady state for a 1-D model of coupled energy and matter transport. Our aim is to discover — via theoretical arguments, conjectures, and numerical simulations — how spatial covariances scale with system size, their relations to local thermodynamic quantities, and the randomizing effects of heat baths. Among our findings are t...

Steady plane flow under gravity of a symmetric ice sheet resting on a horizontal rigid bed, subject to surface accumulation and ablation, basal drainage, and basal sliding according to a shear-tractionvelocity power law, is treated . The surface accumulation is taken to depend on height, and the drainage and sliding coefficient also depend on the height of overlying ice. The ice is described as...

Observations indicate that mass accretion rates onto low-mass protostars are generally lower than the rates of infall to their disks; this suggests that much of the protostellar mass must be accreted during rare, short outbursts of rapid accretion. We explore when protostellar disk accretion is likely to be highly variable. While constant α disks can in principle adjust their accretion rates to...

Assistant Professor, Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, N.Y. 14850 The shear resistance of slipping surfaces at fixed normal stress is given by r = r( v,state). Here V = slip velocity, dependence on «state" is equivalent to functional dependence with fading memory on prior V(t), and ar( v,state) /iJV>O. We establish linear stability conditions for stead...