Air cushion vehicles: A briefing

Experience and characteristics; the powering, uses, and implications of large air cushion vehicles (ACV); and the conceptual design and operation of a nuclear powered ACV freighter and supporting facilities are described

STS-26 solid rocket booster post flight structural assessment

A post flight assessment of the Space Shuttle's Solid Rocket Boosters was conducted at the John F. Kennedy Space Center in Florida after the launch of STS-26. The two boosters were inspected for structural damage and the results of this inspection are presented. Overall, the boosters were in good condition. However, there was some minor damage attributed to splash down. Some of this damage is a recurring problem. Explanations of these problems are provided

Different Motion Cues Are Used to Estimate Time-to-arrival for Frontoparallel and Loming Trajectories

Estimation of time-to-arrival for moving objects is critical to obstacle interception and avoidance, as well as to timing actions such as reaching and grasping moving objects. The source of motion information that conveys arrival time varies with the trajectory of the object raising the question of whether multiple context-dependent mechanisms are involved in this computation. To address this question we conducted a series of psychophysical studies to measure observers’ performance on time-to-arrival estimation when object trajectory was specified by angular motion (“gap closure” trajectories in the frontoparallel plane), looming (colliding trajectories, TTC) or both (passage courses, TTP). We measured performance of time-to-arrival judgments in the presence of irrelevant motion, in which a perpendicular motion vector was added to the object trajectory. Data were compared to models of expected performance based on the use of different components of optical information. Our results demonstrate that for gap closure, performance depended only on the angular motion, whereas for TTC and TTP, both angular and looming motion affected performance. This dissociation of inputs suggests that gap closures are mediated by a separate mechanism than that used for the detection of time-to-collision and time-to-passage. We show that existing models of TTC and TTP estimation make systematic errors in predicting subject performance, and suggest that a model which weights motion cues by their relative time-to-arrival provides a better account of performance

Crystallization of a Mos1 transposase-inverted-repeat DNA complex: biochemical and preliminary crystallographic analyses

A complex formed between Mos1 transposase and its inverted-repeat DNA has been crystallized. The crystals diffract to 3.25 Å resolution and exhibit monoclinic (P2(1)) symmetry, with unit-cell parameters a = 120.8, b = 85.1, c = 131.6 Å, β = 99.3°. The X-ray diffraction data display noncrystallographic twofold symmetry and characteristic dsDNA diffraction at ∼3.3 Å. Biochemical analyses confirmed the presence of DNA and full-length protein in the crystals. The relationship between the axis of noncrystallographic symmetry, the unit-cell axes and the DNA diffraction pattern are discussed. The data are consistent with the previously proposed model of the paired-ends complex containing a dimer of the transposase

Two mechanisms for optic flow and scale change processing of looming

Published in final edited form as: J Vis. ; 11(3): . doi:10.1167/11.3.5.The detection of looming, the motion of objects in depth, underlies many behavioral tasks, including the perception of self-motion and time-to-collision. A number of studies have demonstrated that one of the most important cues for looming detection is optic flow, the pattern of motion across the retina. Schrater et al. have suggested that changes in spatial frequency over time, or scale changes, may also support looming detection in the absence of optic flow (P. R. Schrater, D. C. Knill, & E. P. Simoncelli, 2001). Here we used an adaptation paradigm to determine whether the perception of looming from optic flow and scale changes is mediated by single or separate mechanisms. We show first that when the adaptation and test stimuli were the same (both optic flow or both scale change), observer performance was significantly impaired compared to a dynamic (non-motion, non-scale change) null adaptation control. Second, we found no evidence of cross-cue adaptation, either from optic flow to scale change, or vice versa. Taken together, our data suggest that optic flow and scale changes are processed by separate mechanisms, providing multiple pathways for the detection of looming.We thank Jonathan Victor and the anonymous reviewers of the paper for feedback and suggestions regarding the stimuli used here. This work was supported by NIH grant R01NS064100 to LMV. (R01NS064100 - NIH)Accepted manuscrip

Institutions, Climate Change, and the Foundations of Long-Term Policymaking

Many policy problems require taking costly action today for future benefits. Examining the case of climate change, this paper examines how two institutions—electoral rules and interest group intermediation—structure the distributional politics of climate change and as a result, drive variation in climate “policy investments” across the high-income democracies. Proportional electoral rules increase electoral safety, allowing politicians to impose short-term costs on voters. Concertation between industry and the state enables governments to compensate losers, defusing organized opposition to policy change. Moreover, the joint presence of both institutions generates complementarities that reinforce their independent effects, pushing countries onto different climate politics trajectories. Newly available data on climate policy stringency provide empirical support for the arguments. Countries with PR and interest group concertation have the highest levels of policy stringency and distribute higher costs toward consumers. The analysis points to causal mechanisms that should structure policy responses to a more general set of long-term challenges

From adaptation to climate-resilient development: What are the implications for policymakers?

Jared J. Finnegan gives an overview of The economics of climate-resilient development, a new book edited by Sam Fankhauser and Thomas K.J. McDermott, which he also contributed to. The book explores the link between adaptation to climate change and economic development. The authors hope this new edited volume can help inform adaptation policymaking and contribute to the widening literature on climate-resilient development

Development of simulation tests to assess the fate of Unilever ingredients under untreated discharge conditions

Unilever product ingredients are discharged into the environment via a number of routes, in many regions of the world there is a lack of municipal waste water treatment and the discharge of chemicals directly into the environment in the presence of untreated sewage is a major pathway. An absence of data on the behaviour of the fate and effects of chemicals under such conditions requires overly stringent and unrealistic assumptions when assessing risk (e.g. no biodegradation is assumed). Traditional risk assessment fails since water quality is compromised by pollutants associated with raw sewage (e.g. BOD and ammonia) and the relevance of the ‘standard’ risk assessment approach has thus been questioned. An alternative risk assessment model, based on the ‘impact zone’ concept, has been proposed for direct discharge conditions. In this model, chemicals are assessed in terms of their predicted environmental concentration (PEC) at the end of an impact zone, within which the ecosystem is impacted by the pollutant, free ammonia, and beyond which it is not. Linear alkylbenzene sulphonate (LAS) was used a model compound to understand the fate of materials classified as readily biodegradable in this scenario. Batch and dynamic test systems simulating conditions associated with untreated discharge, confirmed that LAS was degraded quicker than the general organics present in settled sewage and that beyond the defined ‘impact zone’ it is extensively removed. Predicted no effect concentrations (PNECs) can also be generated for chemicals on the inhibition of key microbial processes (biological oxidation and nitrification) which are essential in rivers for self purification. A variety of detergent ingredients (ranging from readily biodegradable to anti-bacterial) were investigated in short term toxicity tests. The tests produced a range PNECs and confirmed that these ingredients can show selective inhibition towards heterotrophic or autotrophic bacterial populations. All of the PNECs generated were above the PEC for these ingredients