A ''critical'' tracking task for man-machine research related to the operators effective delay time. Part II - Experimental effects of system input spectra, control stick stiffness, and controlled element order

Closed-loop compensatory tracking for measuring operator delay time in control actio

All the Conditions of Effective Foreign Aid

The conclusion that foreign aid will promote economic growth only when allocated towards good policy regimes has been the subject of considerable debate. Aid effectiveness researchers have variously sought to falsify this result or to find other individual conditions of aid effectiveness. However, economic theory suggests that any factor which influences the expected returns to investment may influence the effect of aid on growth even when aid is partly diverted to consumption. To investigate this hypothesis, �all� of the hypothesized conditions of aid effectiveness are individually tested in a cross-country growth specification. From these tests the most significant and robust individual interactions are simultaneously modeled, thereby deriving multiple conditions of aid effectiveness. The paper concludes that aid is more effective in economies experiencing economic shocks or recovering from war, and less effective in countries which are geographically disadvantaged or at war. We also find a previously unidentified condition of aid ineffectiveness: the inflow of foreign direct investment. This finding renews a justified interest in the policy-aid-growth nexus, insofar as domestic policy determines the distribution of aid and FDI flows, which appear to act as substitutes in the growth process.

Persistence of a pinch in a pipe

The response of low-dimensional solid objects combines geometry and physics in unusual ways, exemplified in structures of great utility such as a thin-walled tube that is ubiquitous in nature and technology. Here we provide a particularly surprising consequence of this confluence of geometry and physics in tubular structures: the anomalously large persistence of a localized pinch in an elastic pipe whose effect decays very slowly as an oscillatory exponential with a persistence length that diverges as the thickness of the tube vanishes, which we confirm experimentally. The result is more a consequence of geometry than material properties, and is thus equally applicable to carbon nanotubes as it is to oil pipelines.Comment: 6 pages, 3 figure

Adaptive Non-Inferiority Margins under Observable Non-Constancy

A central assumption in the design and conduct of non-inferiority trials is that the active-control therapy will have the same degree of effectiveness in the planned non-inferiority trial as it had in the prior placebo-controlled trials used to define the non-inferiority margin. This is referred to as the `constancy\u27 assumption. If the constancy assumption fails, the chosen non-inferiority margin is not valid and the study runs the risk of approving an inferior product or failing to approve a beneficial product. The constancy assumption cannot be validated in a trial without a placebo arm, and it is unlikely ever to be met completely. However, it is often the case that there exist strong, measurable predictors of constancy, such as dosing and adherence, and such predictors can be used to identify situations where the constancy assumption will likely fail. Here we propose a method for using measurable predictors of active-control effectiveness to specify non-inferiority margins targeted to the planned study population, and further use these predictors to adapt the non-inferiority margin at the end of the study. Population-specific margins can help avoid violations of the constancy assumption, and adaptive margins can help adjust for violations that will inevitably occur in real clinical trials, while at the same time maintain pre-specified levels of type I error and power