264 resultados para Sustainability transitions


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Upland Scotland contains some of Britain’s most prized areas of natural heritage value. However, although such areas may appear both ‘wild’ and ‘remote’, these are typically working landscapes which symbolise the interdependence of nature and society. The complexity of this relationship means that management responses will need to address a multitude of potentially conflicting priorities whilst at the same time ensuring that sufficient social and institutional capital exists to allow for the promotion of landscape integrity. The introduction of national parks to Scotland in the form of the National Parks (Scotland) Act 2000 allows for a high-level of protection for designated areas in upland Scotland. Yet, whilst the recent Act outlines the statutory purpose and direction national parks should take, it allows a significant degree of flexibility in theway in which the Actmay be implemented. This level of discretion allows for significant local distinctiveness within the model but also raises questions about the potential effectiveness of chosen responses. In order to assess the potential implications of a model rooted in self-determination,we provide a case study review of the institutional basis of the Cairngorms National Park along with an assessment of the strategic character of the first National Park Plan. It is argued that whilst the Cairngorms National Park Authority has developed a significant level of stakeholder engagement, the authority may struggle to bridge the policy-implementation gap. Although a number of shortcomings are identified, particular concerns relate to the potential mismatch between strategic ambition and local level capacity.

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Aims.
In this paper we report calculations for energy levels, radiative rates, and electron impact excitation rates for transitions in O vii.
Methods.
The grasp (general-purpose relativistic atomic structure package) is adopted for calculating energy levels and radiative
rates. For determining the collision strengths and subsequently the excitation rates, the Dirac atomic R-matrix code (darc) and the
flexible atomic code (fac) are used.
Results.
Oscillator strengths, radiative rates, and line strengths are reported for all E1, E2, M1, and M2 transitions among the lowest
49 levels of O vii. Collision strengths have been averaged over a Maxwellian velocity distribution, and the resulting effective collision
strengths are reported over a wide temperature range below 2 × 106 K. Additionally, lifetimes are also listed for all levels.
Key words.

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Aims. In this paper we report calculations for energy levels and radiative rates for transitions in Ni XIX.

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Aims. In this paper we report calculations for energy levels and radiative rates for transitions in Fe IX.

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Electron impact excitation collision strengths are required for the analysis and interpretation of stellar observations. This calculation aims to provide fine structure effective collision strengths for the Ni XVII ion using a method which includes contributions from resonances. A DARC calculation has been performed, involving 37 J pi states. The effective collision strengths are calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. The non-zero effective collision strengths for transitions between the fine structure levels are given for electron temperatures (T(e)) in the range log(10) T(e)(K) = 4.5 - 8.5. Data for several transitions from the ground state are discussed in this paper.

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In this paper. we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of Fe II. We consider specifically the optically allowed lines for transitions from the 3d(6)4s and 3d(7) even parity configuration states to the 3d(6)4p odd parity configuration levels. The parallel suite of Breit-Pauli codes are utilized to compute the collision cross-sections where relativistic effects are included explicitly in both the target and the scattering approximation. A total of 100 LS or 262-jj levels formed from the basis configurations 3d(6)4s, 3d(7) and 3d(6)4p were included in the wave-function representation of the target, including all doublet. quartet and sextet terms. The Maxwellian averaged effective collision strengths are computed across a wide range of electron temperatures from 100 to 100,000 K, temperatures of importance in astrophysical and plasma applications. A detailed comparison is made with previous works and significant differences were found to occur for some of the transitions considered. We conclude that in order to obtain converged collision strengths and effective collision strengths for these allowed transitions it is necessary to include contributions from partial waves up to L = 50 explicitly in the calculation, and in addition, account for contributions from even higher partial waves through a "top up" procedure.

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Context. Considerable demand exists for electron excitation data for Ni ii, since lines from this abundant ion are observed in a wide variety of laboratory and astrophysical spectra. The accurate theoretical determination of these data can present a significant challenge however, due to complications arising from the presence of an open 3d-shell in the description of the target ion. Aims. In this work we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact ex- citation of Ni ii. Attention is concentrated on the 153 forbidden fine-structure transitions between the energetically lowest 18 levels of Ni ii. Effective collision strengths have been evaluated at 27 individual electron temperatures ranging from 30–100 000 K. To our knowledge this is the most extensive theoretical collisional study carried out on this ion to date.Methods. The parallel R-matrix package RMATRX II has recently been extended to allow for the inclusion of relativistic effects. This suite of codes has been utilised in the present work in conjunction with PSTGF to evaluate collision strengths and effective collision strengths for all of the low-lying forbidden fine-structure transitions. The following basis configurations were included in the target model – 3d9 , 3d8 4s, 3d8 4p, 3d7 4s2 and 3d7 4s4p – giving rise to a sophisticated 295 j j-level, 1930 coupled channel scattering problem. Results. Comprehensive comparisons are made between the present collisional data and those obtained from earlier theoretical evaluations. While the effective collision strengths agree well for some transitions, significant discrepancies exist for others.

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Context. Absorption or emission lines of Cr II are observed in a wide variety of astrophysical spectra and accurate atomic data are urgently needed to interpret these lines. Many of these data are impossible to measure experimentally and a full theoretical treatment is the only means by which these data can be obtained.

Aims. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of Cr II for forbidden transitions among the lowest-lying 74 fine-structure levels. Effective collision strengths have been computed for 18 individual electron temperatures of astrophysical importance, ranging from 2000-100 000 K.

Methods. The parallel suite of R-matrix packages, RMATRX II, which has recently been extended to allow for the inclusion of relativistic effects, has been used in the present work to compute the collision strengths and effective collision strengths for electron-impact excitation of Cr II. We concentrate in this publication on low-lying forbidden lines among the lowest 74 jj fine-structure levels with configurations 3d(5) and 3d(4)4s, although atomic data has been evaluated for all 39 060 transitions among the 280 jj levels of configurations 3d(5), 3d(4)4s and 3d(4)4p. This work constitutes the largest evaluation ever performed for this ion involving 1932 coupled channels.

Results. Collision and effective collision strengths are presented for all transitions among the lowest 74 J pi states of Cr II and comparisons made with the work of Bautista et al. (2009). While the effective collision strengths agree well for some transitions, significant discrepancies exist for others. We believe that the present atomic data represents the most accurate, most sophisticated and most complete data set for electron-impact excitation of Cr II and we would recommend them to astrophysicists and plasma physicists in their application work. We would expect that the effective collision strengths presented for the important low-lying forbidden lines are accurate to within 15%.