All sky pointing attitude control system

In a strapped-down gyroscope space vehicle attitude control system, a method and apparatus are provided for gyro drift and input axis misalignment error compensation employing a sun and a star tracker and preselected vehicle calibration maneuvers. The outputs of two-axis strapped-down gyroscopes nominally aligned with the optical axis of the sun and star trackers are measured to provide gyro drift calibration, roll, pitch and yaw axis scale factors and values corresponding to the degree of nonorthogonality between the roll axis and the pitch and yaw gyro input axes and the nonorthogonality of the roll and pitch axes relative to the yaw axis. The vehicle is then rolled and yawed through precomputed angles as modified by the calibrated data stored in a digital computer, and acquires a target without recourse to external references

Dorsal root ganglion neurons maintained in a 3D culture model exhibit similar electrophysiological properties to fresh explants

Tissue engineered culture models provide a powerful tool for neuroscience research1. They overcome limitations associated with monolayer cultures of neurons and glia by maintaining cells in a more realistic 3D spatial arrangement, and permit continuous monitoring and control of variables that cannot be achieved in animal models. Here we report the development of a system for recording electrophysiological behaviour in neurons in 3D culture

Comment on "Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars"

In their Letter [Phys. Rev. Lett. 92, 121302 (2004)] (also [Astron. Astrophys. 417, 853 (2004)]), Srianand et al. analysed optical spectra of heavy-element species in 23 absorption systems along background quasar sight-lines, reporting limits on relative variations in the fine-structure constant: da/a=(-0.06+/-0.06) x 10^{-5}. Here we demonstrate basic flaws in their analysis, using the same data and absorption profile fits, which led to spurious values of da/a and significantly underestimated uncertainties. We conclude that these data and fits offer no stringent test of previous evidence for a varying alpha. In their Reply (arXiv:0711.1742) to this Comment, Srianand et al. state or argue several points regarding their original analysis and our new analysis. We discuss these points here, dismissing all of them because they are demonstrably incorrect or because they rely on a flawed application of simple statistical arguments.Comment: 1+2 pages, 1 EPS figure. Page 1 accepted as PRL Comment on arXiv:astro-ph/0402177 . Further details available in arXiv:astro-ph/0612407 . v2: Added critical discussion of Reply from Srianand et al. (arXiv:0711.1742

A Laboratory Investigation of Compliance Behavior under Tradable Emissions Rights: Implications for Targeted Enforcement

This paper uses laboratory experiments to test the theoretical observations that both the violations of competitive risk-neutral firms and the marginal effectiveness of increased enforcement across firms are independent of differences in their abatement costs and their initial allocations of permits. This conclusion has important implications for enforcing emissions trading programs because it suggests that regulators have no justification for targeting their enforcement effort based on firm-level characteristics. Consistent with the theory, we find that subjects’ violations were independent of parametric differences in their abatement costs. However, those subjects that were predicted to buy permits tended to have higher violation levels than those who were predicted to sell permits. Despite this, we find no statistically significant evidence that the marginal effectiveness of enforcement depends on any firmspecific characteristic. We also examine the determinants of compliance behavior under fixed emissions standards. As expected, we find significant differences between compliance behavior under fixed standards and emissions trading programs.enforcement, compliance, emissions trading, permit markets, standards, commandand- control

The AIROscope pointing and stabilization system

The AIROscope pointing and stabilization system is described. The system is configured with three gimbal axes and rate integrating gyro stabilization to provide a stable platform for infrared astronomy. Error signals for on and off-axis pointing are derived from a video sensor which also drives a ground station display. Other features of the system include direct drive torque motors and electronic suspension damping. Results of analysis and simulations used to design the control loops, and a pointing error analysis are presented

An Investigation of Voluntary Discovery and Disclosure of Environmental Violations Using Laboratory Experiments

This paper uses laboratory experiments to test individual responses to policies that seek to encourage firms to voluntarily discover and disclose violations of environmental standards. We find that while it is possible to motivate a significant number of voluntary disclosures without adversely affecting environmental quality, this result is sensitive to both the fine for disclosed violations and the assumption that firms know their compliance status without cost. When firms have to expend resources to determine their compliance status, motivating a significant number of violation disclosures yields worse environmental quality. Finally, relative to conventional enforcement, disclosure polices will result in more violations being sanctioned, but fewer of these sanctions are for violations that are uncovered by the government.enforcement, compliance, environmental standards, self-reporting, self-auditing voluntary disclosure

AN EXPERIMENTAL ANALYSIS OF COMPLIANCE BEHAVIOR IN EMISSIONS TRADING PROGRAMS: SOME PRELIMINARY RESULTS

While there is a substantial body of economic theory about compliance and enforcement in emissions trading programs, and readily available information about how existing emissions trading programs are enforced, there are no empirical analyses of the determinants of compliance decisions in emissions trading programs. This paper contains preliminary results from laboratory experiments designed to examine compliance behavior in emissions trading programs.Environmental Economics and Policy,

Effect of microstructure and temperature on the erosion rates and mechanisms of modified EB PVD TBCs

Thermal barrier coatings (TBCs) have now been used in gas turbine engines for a number of decades and are now considered to be an accepted technology. As there is a constant drive to increase the turbine entry temperature, in order to increase engine efficiency, the coatings operate in increasingly hostile environments. Thus there is a constant drive to both increase the temperature capabilities of TBCs while at the same time reducing their thermal conductivities. The thermal conductivity of standard 7 wt% yttria stabilized zirconia (7YSZ) electron beam (EB) physical vapour deposited (PVD) TBCs can be reduced in two ways: the first by modification of the microstructure of the TBC and the second by addition of ternary oxides. By modifying the microstructure of the TBC such that there are more fine pores, more photon scattering centres are introduced into the coatings, which reduce the heat transfer by radiation. While ternary oxides will introduce lattice defects into the coating, which increases the phonon scattering, thus reducing the thermal conductivity via lattice vibrations. Unfortunately, both of these methods can have a negative effect on the erosion resistance of EB PVD TBCs. This paper compares the relative erosion rates of ten different EB PVD TBCs tested at 90à ° impact at room temperature and at high temperature and discusses the results in term of microstructural and temperature effects. It was found that by modifying the coating deposition, such that a low density coating with a highly â  featheredâ  microstructure formed, generally resulted in an increase in the erosion rate at room temperature. When there was a significant change between the room temperature and the high temperature erosion mechanism it was accompanied by a significant decrease in the erosion rate, while additions of dopents was found to significantly increase the erosion rate at room and high temperature. However, all the modified coatings still had a lower erosion rate than a plasma sprayed coatings. So, although, relative to a standard 7YSZ coating, the modified coatings have a lower erosion resistance, they still perform better than PS TBCs and their lower thermal conductivities could make them viable alternatives to 7YSZ for use in gas turbine en