We have obtained spectrophotometric observations of 41 anticenter planetary nebulae (PNe) located in the disk of the Milky Way. Electron temperatures and densities, as well as chemical abundances for He, N, O, Ne, S, Cl, and Ar were determined. Incorporating these results into our existing database of PN abundances yielded a sample of 124 well-observed objects with homogeneously determined abundances extending from 0.9 to 21 kpc in galactocentric distance. We performed a detailed regression analysis which accounted for uncertainties in both oxygen abundances and radial distances in order to establish the metallicity gradient across the disk to be 12 + log(O/H) = (9.09 ± 0.05) − (0.058 ± 0.006) × R g , with R g in kpc. While we see some evidence that the gradient steepens at large galactocentric distances, more objects toward the anticenter need to be observed in order to confidently establish the true form of the metallicity gradient. We find no compelling evidence that the gradient differs between Peimbert Types I and II, nor is oxygen abundance related to the vertical distance from the galactic plane. Our gradient agrees well with analogous results for H ii regions but is steeper than the one recently published by Stanghellini & Haywood over a similar range in galactocentric distance. A second analysis using PN distances from a different source implied a flatter gradient, and we suggest that we have reached a confusion limit which can only be resolved with greatly improved distance measurements and an understanding of the natural scatter in oxygen abundances.

We have carried out a comprehensive theoretical and experimental study of electron scattering from molecular nitrogen at energies below 10.0 eV. In the theoretical component of this project we have generated differential and integral cross sections for elastic scattering and vibrational excitation in converged vibrational close-coupling calculations. In the experiments, we have measured dift'erential cross sections for these processes at scattering angles from 20' to 130 in a crossed-beam experiment at a large number of energies between 0.55 and 10 eV and, in a complementary time-of-Right experiment, total cross sections at energies between 0.08 and 10.0 eV. The measured angular distributions have been extrapolated to 0 and 180 using a procedure based on a nonlinear least-squares fit constrained by known physical properties of the e-Nz scattering matrix; numerical integration of the resulting extrapolated distributions yields integrated cross sections with almost no error beyond that inherent in the measured angular data. We find generally good agreement between the present experimental and theoretical cross section, particularly at energies near the H~r esonance near 2.39 eV. In previous studies of scattering in this region, such comparisons have been made problematical by the difhculty of ascertaining the appropriate theoretical scattering energy. We recommend here a protocol for resolving this problem for both elastic scattering and vibrational excitation.PACS number(s): 34.80.6s

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Benefit transfer is increasingly being used by decision makers as a way of estimating environmental values suitable for use in benefit cost analysis. However, recent studies examining the validity of benefit transfer of passive use values estimated using contingent valuation have rejected the hypothesis of convergent validity. In this article, we demonstrate the usage of a form of conjoint analysis known as choice modeling for benefit transfer. Choice modeling has been touted as being particularly suitable for benefit transfer because it is possible to allow for differences in environmental quality and socioeconomic characteristics when transferring benefit estimates. We demonstrate that choice modeling is suitable for benefit transfer, particularly when the transfers involve implicit prices. Second, we examine the circumstances in which benefit transfer of choice modeling derived value estimates is likely to be most valid. Two split sample tests were undertaken to achieve this objective. The evidence from these tests indicates that transfers across different case study sites are likely to be subject to less error than those across different populations. Copyright 2002, Oxford University Press.

This paper explores the performance effects of Human Resource Management (HRM) practices in seventy-four Chinese small and medium sized enterprises (SMEs). Four high performance HRM practices are identified: performance-based pay, participatory decision making, free market selection, and performance evaluation. Regression analysis results support the conventional idea that the adoption of HRM practices generates better HRM outcomes and, in turn, better HRM outcomes contribute positively to firm performance. However, not all HRM practices, and their effects, led to improved SME performance. Among the Chinese SMEs investigated, a high level of employee commitment was identified as being the key HRM outcome for enhancing performance.

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Engaging the public about mitigating or adapting to climate change threats poses significant challenges for scientists, policy makers, and others responsible for developing communication strategies. In response to these challenges, interest is growing in audience segmentation as a possible strategy to develop more effective communications that are tailored and targeted to subgroups of the public who share similar values, beliefs, behaviors, and/or policy preferences about climate change. In this article, we provide a brief historical overview of audience segmentation and its applications to marketing, health, politics, and most recently climate change. We then critically evaluate several conceptual arguments about whether segmentation is an appropriate strategy for climate change communications, review key methodological considerations associated with conducting segmentation analyses, and make several recommendations about best practice. We conclude that, in principle, audience segmentation and targeted messaging are potentially valuable tools for enhancing climate change communication. But, in practice, there are conceptual and methodological complexities of which practitioners and consumers should be aware when conducting and interpreting the results of segmentation studies. In addition, more research is required, particularly related to tailoring and targeting messages to identified segments, before these strategies can be considered to have a sufficient evidence base to warrant widespread adoption. This article is categorized under: Perceptions, Behavior, and Communication of Climate Change > Perceptions of Climate Change

The ‘two-term’ approximation (representation of the electron distribution by the first two terms of an expansion in spherical harmonics in velocity space) continues to occupy a central role in the low-temperature plasma physics literature, in spite of the mass of evidence illustrating its inadequacy in the swarm (free diffusion) limit for many molecular gases. Part of the problem lies in the failure of many authors to specify quantitatively what they mean when they say that the two-term approximation is ‘acceptable’. Thus for example, an error of 10% in transport coefficients may well be acceptable in many plasma applications, but for analysis of highly accurate swarm experiments to compare with ab initio and beam-derived cross-sections, 0.1% or less is required, making ‘multi-term’ analysis mandatory. While reconciliation of the swarm and plasma literature along the lines of two different accuracy regimes may thus be possible, we dispute claims that the two-term approximation is generally satisfactory for inversion of swarm experiment data to obtain electron impact cross-sections. The unsatisfactory nature of other assumptions implicit in much of the modern plasma kinetic theory literature is also discussed.