Road and bridge construction across gypsum karst in England

Gypsum karst problems in the Permian and Triassic sequences of England have caused difficult conditions for bridge and road construction. In Northern England, the Ripon Bypass crosses Permian strata affected by active gypsum karst and severe subsidence problems. Here, the initial borehole site investigation for the road was supplemented by resistivity tomography studies. The roadway was reinforced with two layers of tensile membrane material within the earth embankment. This will prevent dangerous catastrophic collapse, but will allow sagging to show where problems exist. The River Ure Bridge was constructed across an area of subsidence pipes filled with alluvial deposits. It was built with extra strength, larger than normal foundations. If one pier fails, the bridge is designed for adjacent arches to span the gap without collapse. The bridge piers are also fitted with electronic load monitoring to warn of failure. In the Midlands area of England, road construction over Triassic gypsum has required a phase of ground improvement on the Derby Southern Bypass. Here, the gypsum caps a hill where it was formerly mined; it dips through a karstic dissolution zone into an area of complete dissolution and collapse. The road and an associated flyover were built across these ground conditions. A major grouting program before the earthworks began treated the cavities in the mine workings and the cavernous margin of the gypsum mass. Within the karstic dissolution zone, gypsum blocks and cavities along the route were identified by conductivity and resistivity geophysical surveys, excavated and backfilled. In the areas of complete dissolution and collapse, the road foundation was strengthened with vibrated stone columns and a reinforced concrete road deck was used

Assessments as Teaching and Research Tools in an Environmental Problem-Solving Program for In-Service Teachers

This article discusses the use of a scenario-based assessment tool in two environmental geoscience in-service programs for middle school and high school teachers. This tool served both to guide instructional techniques and as a method to evaluate the success of the instructional approach. In each case, participants were assessed before the workshops to reveal misconceptions that could be addressed in program activities and afterwards to reveal shifts in their understanding of concepts and approaches. The researchers noted that this scenario-based assessment was effective in providing guidance in refining instructional techniques and as a method to evaluate the effectiveness of an instructional program. In addition, participating teachers reported significant changes in their teaching as a result of the program. Educational levels: Graduate or professional, Graduate or professional

The economics of labor adjustment: mind the gap

We study inferences about the dynamics of labor adjustment obtained by the "gap methodology" of Caballero and Engel [1993] and Caballero, Engel and Haltiwanger [1997]. In that approach, the policy function for employment growth is assumed to depend on an unobservable gap between the target and current levels of employment. Using time series observations, these studies reject the partial adjustment model and find that aggregate employment dynamics depend on the cross-sectional distribution of employment gaps. Thus, nonlinear adjustment at the plant level appears to have aggregate implications. We argue that this conclusion is not justified: these findings of nonlinearities in time series data may reflect mismeasurement of the gaps rather than the aggregation of plant-level nonlinearities.Labor supply ; Econometric models

Mind the (approximation) gap: a robustness analysis

This note continues the discussion of the results reported by Ricardo Caballero and Eduardo Engel (1993), hereafter CE, and Ricardo Caballero, Eduardo Engel, and John Haltiwanger (1997), hereafter CEH, by responding to the results reported in Christian Bayer (2008). Russell Cooper and Jonathan Willis (2004), hereafter CW, find that the aggregate nonlinearities reported in CE and CEH may be the consequence of mismeasurement of the employment gap rather than nonlinearities in plant-level adjustment. Bayer reassesses this finding in the context of the CE model in the case where static employment gaps are observed and concludes that the CW result is not robust to alternative shock processes. We concur with Bayer's assessment that the nonlinearity finding is sensitive to the aggregate profitability shock process. We argue, however, that Bayer's finding does not imply that the mismeasurement problem goes away. Instead, the nonlinearity created by mismeasurement is directly related to the level of the aggregate shock. Once the empirical specification properly incorporates the aggregate shock, the nonlinearity test is robust to alternative shock processes and confirms the results in CW. More importantly, we demonstrate that the CW findings are robust to alternative shock processes for the natural case of unobserved gaps as examined by CE and CEH.

The Cost of Labor Adjustment: Inferences from the Gap

We study labor adjustment costs. We specify a dynamic optimization problem at the plant-level, allowing for both convex and non-convex adjustment costs. We estimate the parameters of the adjustment process using an indirect inference procedure in which simulated moments are matched with data moments. For this study we use estimates of reduced-form adjustment functions obtained by the gap methodology' reported in Caballero-Engel as data moments. Contrary to evidence at the micro level in support of non-convex adjustment costs, our findings indicate that piecewise quadratic adjustment costs are sufficient to match these aggregate moments.

Coordination of expectations in the recent crisis: private actions and policy responses

Some of the events of the recent financial crisis have made clear the importance of expectations in an economy. The economic choices individuals make are often based on their expectations of what other people will do—in what economists call a “coordination game.” In such situations, changes in the beliefs of what others may do can affect the actions of individuals. A key element in such situations is that, as the collective beliefs change and individuals respond to these altered expectations, the outcome in the marketplace can change. In the recent crisis, the coordination of expectations played a key role in areas such as financial markets, the housing market, and the automobile sector. ; When the coordination of expectations results in a crisis or a panic, policymakers are the primary group with the ability to alter the expectations of individuals. By using various policy tools, policymakers can lessen the damage from the crisis. Such tools include providing guarantees and changing marketplace incentives such as interest rates and tax rates. ; Cooper and Willis develop a framework to illustrate how the coordination of expectations was instrumental in the economic and financial crisis. The framework also helps describe the actions policymakers took to limit the severity of the downturn by coordinating expectations to achieve more positive outcomes.

The Economics of Labor Adjustment: Mind the Gap

We study the inferences about labor adjustment costs obtained by the 'gap methodology' of Caballero and Engel [1993] and Caballero, Engel and Haltiwanger [1997]. In that approach, the policy function of a manufacturing plant is assumed to depend on the gap between a target and the current level of employment. Using time series observations, these studies reject the quadratic cost of adjustment model and find that aggregate employment dynamics depend on the cross sectional distribution of employment gaps. We argue that these conclusions may not be justified. Instead these findings may reflect difficulties measuring the gap. Thus it appears that the gap methodology, as currently employed, may be unable to: (i) identify the costs of labor adjustment and (ii) assess the aggregate implications of labor adjustment costs.

Dual color plasmonic pixels create a polarization controlled nano color palette

Color filters based upon nanostructured metals have garnered significant interest in recent years, having been positioned as alternatives to the organic dye-based filters which provide color selectivity in image sensors, as nonfading “printing” technologies for producing images with nanometer pixel resolution, and as ultra-high-resolution, small foot-print optical storage and encoding solutions. Here, we demonstrate a plasmonic filter set with polarization-switchable color properties, based upon arrays of asymmetric cross-shaped nanoapertures in an aluminum thin-film. Acting as individual color-emitting nanopixels, the plasmonic cavity-apertures have dual-color selectivity, transmitting one of two visible colors, controlled by the polarization of the white light incident on the rear of the pixel and tuned by varying the critical dimensions of the geometry and periodicity of the array. This structural approach to switchable optical filtering enables a single nanoaperture to encode two information states within the same physical nanoaperture, an attribute we use here to create micro image displays containing duality in their optical information states