Concept, modeling, and performance prediction of a low-cost, large deformable mirror

While it is attractive to integrate a deformable mirror (DM) for adaptive optics (AO) into the telescope itself rather than using relay optics within an instrument, the resulting large DM can be expensive, particularly for extremely large telescopes. A low-cost approach for building a large DM is to use voice-coil actuators connected to the back of the DM through suction cups. Use of such inexpensive voice-coil actuators leads to a poorly damped system with many structural modes within the desired bandwidth. Control of the mirror dynamics using electro-mechanical sensors is thus required for integration within an AO system. We introduce a distributed control approach, and we show that the “inner” back sensor control loop does not need to function at low frequencies, leading to significant cost reduction for the sensors. Incorporating realistic models of low-cost actuators and sensors together with an atmospheric seeing model, we demonstrate that the low-cost mirror strategy is feasible within a closed-loop AO system

Financing Direct Democracy: Revisiting the Research on Campaign Spending and Citizen Initiatives

The conventional view in the direct democracy literature is that spending against a measure is more effective than spending in favor of a measure, but the empirical results underlying this conclusion have been questioned by recent research. We argue that the conventional finding is driven by the endogenous nature of campaign spending: initiative proponents spend more when their ballot measure is likely to fail. We address this endogeneity by using an instrumental variables approach to analyze a comprehensive dataset of ballot propositions in California from 1976 to 2004. We find that both support and opposition spending on citizen initiatives have strong, statistically significant, and countervailing effects. We confirm this finding by looking at time series data from early polling on a subset of these measures. Both analyses show that spending in favor of citizen initiatives substantially increases their chances of passage, just as opposition spending decreases this likelihood

A Comparison between Political Claims Analysis and Discourse Network Analysis: The Case of Software Patents in the European Union

The study of policy discourse comprises actor-centered and content-oriented approaches. We attempt to close the gap between the two kinds of approaches by introducing a new methodology for the analysis of political discourse called Discourse Network Analysis. It is based on social network analysis and qualitative content analysis and takes an entirely relational perspective. Political discourse can be analyzed in a dynamic way, and the approach makes previously unobservable cleavage lines and alignments measurable at the actor level, at the level of the contents of a discourse, and a combined layer. We compare discourse network analysis with political claims analysis, a competing method, and apply both methods to the European-level discourse on software patents. Our results demonstrate how an anti-softwarepatent coalition was mobilized and how it gained control over important frames, while the well-organized pro-software-patent discourse coalition was not able to gain sovereignty over the discourse.Software Patents, Intellectual Property Rights, Discourse Network Analysis, Social Network Analysis, Political Discourse, Policy Networks, Public Policy Analysis, Social Movements, Political Claims Analysis

Politics 2.0: the Multifaceted Effect of Broadband Internet on Political Participation

We investigate the causal impact of broadband Internet on political participation using data from Italy. We show that this impact varies across different forms of political engagement and over time. Initially, broadband had a negative effect on turnout in national elections, driven by increased abstention of ideologically extreme voters. Meanwhile, however, broadband fostered other forms of online and offline participation. Over time, the negative effect was reverted due to the emergence of new political entrepreneurs who used the Internet to convert the initial “exit” back into “voice”. Overall, these nuanced effects underscore the general equilibrium dynamic induced by the Internet

Distributed Control of Large Deformable Mirrors

While it is attractive to integrate a deformable mirror (DM) for adaptive optics (AO) into the telescope itself rather than using relay optics within an instrument, the resulting large DM can be expensive, particularly for extremely large telescopes. A low-cost approach for building a large DM is to use voice-coil actuators, and rely on feedback from mechanical sensors to improve the dynamic response of the mirror sufficiently so that it can be used in a standard AO control system. The use of inexpensive voice-coil actuators results in many lightly- damped structural resonances within the desired control bandwidth. We present a robust control approach for this problem, and demonstrate performance in a closed-loop AO simulation, incorporating realistic models of low-cost actuators and sensors. The first contribution is to demonstrate that high-bandwidth active damping can be robustly implemented even with non-collocated sensors, by relying on the "acoustic limit" of the structure where the modal bandwidth exceeds the modal spacing. Next we introduce a novel local control approach, which significantly improves the high spatial frequency performance relative to collocated position control, but without the robustness challenges associated with a global control approach. The combination of these "inner" control loops results in DM command response that is demonstrated to be sufficient for integration within an AO system

Discrimination of Timbre in Early Auditory Responses of the Human Brain

The issue of how differences in timbre are represented in the neural response still has not been well addressed, particularly with regard to the relevant brain mechanisms. Here we employ phasing and clipping of tones to produce auditory stimuli differing to describe the multidimensional nature of timbre. We investigated the auditory response and sensory gating as well, using by magnetoencephalography (MEG).Thirty-five healthy subjects without hearing deficit participated in the experiments. Two different or same tones in timbre were presented through conditioning (S1) – testing (S2) paradigm as a pair with an interval of 500 ms. As a result, the magnitudes of auditory M50 and M100 responses were different with timbre in both hemispheres. This result might support that timbre, at least by phasing and clipping, is discriminated in the auditory early processing. The second response in a pair affected by S1 in the consecutive stimuli occurred in M100 of the left hemisphere, whereas both M50 and M100 responses to S2 only in the right hemisphere reflected whether two stimuli in a pair were the same or not. Both M50 and M100 magnitudes were different with the presenting order (S1 vs. S2) for both same and different conditions in the both hemispheres.Our results demonstrate that the auditory response depends on timbre characteristics. Moreover, it was revealed that the auditory sensory gating is determined not by the stimulus that directly evokes the response, but rather by whether or not the two stimuli are identical in timbre

Measuring Externalities in Program Evaluation

Impact evaluations of development programmes usually focus on a comparison of participants with a control group. However, if the programme generates externalities for non-participants such an approach will capture only part of the programme's impact. Based on a unique large-scale quantitative survey we estimate the direct as well as the spillover effects of a womena's empowerment programme in rural India on child immunization and school enrolment. The survey covers both participants and non-participants living in programme villages, as well as respondents in control villages where the programme is not yet active. We account for participation selection bias using instrumental variables. The control villages allow us to test the exclusion restriction and provide us with an effective control group to analyze programme impact. We find both direct effects and significant spillovers on non-participants. The impact of interventions might be substantially underestimated if such external effects were not taken into account