WHEN PRICES MISS THE MARK: METHODS FOR VALUING ENVIRONMENTAL CHANGE

Environmental Economics and Policy,

A VLBA Search for a Stimulated Recombination Line from the Accretion Region in NGC1275

The radio source 3C84, in NGC1275, has a two sided structure on parsec scales. The northern feature, presumed to be associated with a jet moving away from the Earth, shows strong evidence for free-free absorption. The ionized gas responsible for that absorption would be a source of detectable stimulated recombination line emission for a wide range of physical conditions. The VLBA has been used to search for the H65$\alpha$ hydrogen recombination line. The line is only expected to be seen against the northern feature which contains a small fraction of the total radio flux density. This spatial discrimination significantly aids the search for a weak line. No line was seen, with upper limits of roughly 15% of the continuum over a velocity range of 1486 km/s with resolutions up to 6.6 km/s. In the absence of a strong radiation field, this would imply that the free-free absorbing gas has a wide velocity width, is moving rapidly relative to the systemic velocity, or is concentrated in a thin, high density structure. All of these possibilities are reasonably likely close to an AGN. However, in the intense radiation environment of the AGN, even considering only the radiation we actually observe passing through the free-free absorbing gas, the non-detection is probably assured by a combination of saturation and radiation damping.Comment: 14 pages with 4 postscript figures. Accepted for publication in the April 2003 Astronomical Journa

Understanding the different rotational behaviors of 252^{252}No and 254^{254}No

Total Routhian surface calculations have been performed to investigate rapidly rotating transfermium nuclei, the heaviest nuclei accessible by detailed spectroscopy experiments. The observed fast alignment in $^{252}$No and slow alignment in $^{254}$No are well reproduced by the calculations incorporating high-order deformations. The different rotational behaviors of $^{252}$No and $^{254}$No can be understood for the first time in terms of $\beta_6$ deformation that decreases the energies of the $\nu j_{15/2}$ intruder orbitals below the N=152 gap. Our investigations reveal the importance of high-order deformation in describing not only the multi-quasiparticle states but also the rotational spectra, both providing probes of the single-particle structure concerning the expected doubly-magic superheavy nuclei.Comment: 5 pages, 4 figures, the version accepted for publication in Phys. Rev.

Aircraft flight test trajectory control

Two design techniques for linear flight test trajectory controllers (FTTCs) are described: Eigenstructure assignment and the minimum error excitation technique. The two techniques are used to design FTTCs for an F-15 aircraft model for eight different maneuvers at thirty different flight conditions. An evaluation of the FTTCs is presented

Modelling the impact of referral guideline changes for mild dyskaryosis on colposcopy services in England

Objectives: This model examines the effects of changing referral strategies within the established structure of NHS cervical screening driven colposcopy practice. It considers the effects of the new strategy on colposcopy workload, patient waiting times, and associated costs and health benefits. Methods: By postal survey, the current operational strategies of colposcopy services were established by questionnaire with respect to referral practices and management protocols. After first-cut piloting, and utilising published and original research, a Markovian model was constructed, and the impact of the new strategy was determined on colposcopy workload and patient waiting times for three hypothetical clinic types. Expected costs and benefits of the new policy were assessed through the adaptation of a previous ScHARR cervical screening model. Results: Clinic workload is expected to increase by between 21% and 35% within three years of the policy change, depending on clinic efficiency in other areas; the majority of this impact would be seen within the first year. It is predicted that particularly inefficient clinics would struggle to meet the existing waiting time requirements for women referred with low-grade disease, owing to the increased level of workload seen throughout the patient pathway as a result of the implementation of the new policy. The impact of the new policy can, however, be mitigated through improving the efficiency of existing clinics, by altering policies relating to surveillance of low grade disease, post-treatment follow-up, treatment policy (whether or not treatment is performed at the initial colposcopy visit), and through adherence to national guidelines. A cost-effectiveness analysis using the ScHARR liquid-based cytology model suggests that the policy change is likely to be have a cost per quality-adjusted lifeyear gained of between £1,400 and £5,500 per quality-adjusted life-year gained (excluding the costs of follow-up), which would be deemed acceptable to organisations such as the National Institute for Health and Clinical Excellence