820 research outputs found
Landscape scenic values. Protection and management from a spatial planning perspective
The aesthetic dimension distinguishes the concept of “landscape” from other concepts such as “environment” and “territory”, and is a recurrent justification for conserving both natural and cultural landscapes. However, scenic beauty remains particularly difficult to define and protect under specific regulations. Moreover, the topic is seldom dealt with in spatial planning literature and practice. This lack of a systematic approach severely limits the capacity of public administrations to protect and enhance scenic resources. The paper highlights the need for further research into technical tools and suggests a number of perspectives which call for international collaboration. As a worked example of how planning can deal with scenic resources, an Italian case is illustrated, the Piedmont Region’s “Guidelines for the analysis, protection and enhancement of the landscape scenic characters”. The guidelines focus on the protection of visual relationships, which connect designated heritage assets and outstanding features with their settings and the area as a whole. The implementation measures within the planning regulatory system are discussed, as well as the role of different actors, planning levels and phases
On the Wilson-Bappu relationship in the Mg II k line
An investigation is carried out on the Wilson-Bappu effect in the Mg II k
line at 2796.34 A. The work is based on a selection of 230 stars observed by
both the IUE and HIPPARCOS satellites, covering a wide range of spectral type
and absolute visual magnitudes. The Wilson-Bappu relationship here provided is
considered to represent an improvement over previous recent results for the
considerably larger data sample used as well as for a proper consideration of
the measurement errors. No evidence has been found for a possible dependence of
the WB effect on stellar metallicity and effective temperature.Comment: 8 pages, 8 figures Accepted for publication on A&
A study of the Mg II 2796.34 A emission line in late--type normal, and RS CVn stars
We carry out an analysis of the Mg II 2796.34 A emission line in RS CVn stars
and make a comparison with the normal stars studied in a previous paper (Paper
I). The sample of RS CVn stars consists of 34 objects with known HIPPARCOS
parallaxes and observed at high resolution with IUE. We confirm that RS CVn
stars tend to possess wider Mg II lines than normal stars having the same
absolute visual magnitude. However, we could not find any correlation between
the logarithmic line width log Wo and the absolute visual magnitude Mv (the
Wilson--Bappu relationship) for these active stars, contrary to the case of
normal stars addressed in Paper I. On the contrary, we find that a strong
correlation exists in the (Mv, log L) plane (L is the absolute flux in the
line). In this plane, normal and RS CVn stars are distributed along two nearly
parallel straight lines with RS CVn stars being systematically brighter by
about 1 dex. Such a diagram provides an interesting tool to discriminate active
from normal stars. We finally analyse the distribution of RS CVn and of normal
stars in the (log L, log Wo) plane, and find a strong linear correlation for
normal stars, which can be used for distance determinations.Comment: 10 pages, 7 figures, latex, to be published in A&
Challenges in landscape planning: the rural-urban interface
Peri-urban, and rur-urban categories emerged in the last decades. Functional linkages and conflicts between urban and rural areas can be found in peri-urban areas. Recent policies by UN, OECD, EU aim at creating 'Rural-Urban Partnerships’ as an integrated approach to economic development, by strengthening national and regional development planning. The paper discuss how landscape planning can offer spatial solutions in metropolitan areas, with particular reference to the concept of Green Infrastructure, and illustrate a range of implementation tools. A case study in Japan, Nishi-Tokyo, provide further insights on actual challenges for conserving urban farmlands in metropolitan areas and shrinking cities
The evolution of ultraviolet emission lines from the circumstellar material surrounding SN 1987A
The presence of narrow high-temperature emission lines from nitrogen-rich gas
close to SN 1987A has been the principal observational constraint on the evolu-
tionary status of the supernova's progenitor. A new analysis of the complete
five-year set of low and high resolution IUE ultraviolet spectra of SN 1987A
(1987.2--1992.3) provide fluxes for the N V 1240, N IV] 1486, He II 1640, OIII]
1665, NIII] 1751, and CIII] 1908 lines with significantly reduced random and
systematic errors and reveals significant short-term fluctuations in the light
curves. The N V, N IV] and N III] lines turn on sequentially over 15 to 20 days
and show a progression from high to low ionization potential, implying an ioni-
zation gradient in the emitting region. The line emission turns on suddenly at
83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches
peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)E{17} cm and
inclination of 41.0+/-3.9 is derived from these times, assuming a circular
ring. The probable role of resonant scattering in the N V light curve
introduces systematic errors that leads us to exclude this line from the timing
analysis. A new nebular analysis yields improved CNO abundance ratios
N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in
our previous paper. From the late-time behavior of the light curves we find
that the emission origi- nates from progressively lower density gas. We
estimate the emitting mass near maximum (roughly 400 days) to be roughly
4.7E{-2} solar masses, assuming a filling factor of unity and an electron
density of 2.6E4 cm^{-3}. These results are discussed in the context of current
models for the emission and hydrodynamics of the ring.Comment: 38 pages, AASTeX v.4.0, 13 Postscript figures; ApJ, in pres
The C IV Doublet Ratio Intensity Effect in Symbiotic Stars
The first successful high-resolution ultraviolet spectra in the λλ 1200-2000 wavelength range of the symbiotic variable R Aquarii and its nebular Jet were obtained in 1987 July with the International Ultraviolet Explorer (IUE). The line profile structure of the C IV λλ1548, 1550 doublet in the jet indicates multicomponent velocity structure from an optically thin emitting gas. The C IV doublet profiles in the compact H II region engulfing the Mira and hot companion binary also suggest multicomponent structure, in which the radial velocities range up to ~ -100 km s^- 1. The value of the doublet intensity ratio in the R Aqr H II region is I(λ1548)/ I(λ1550) ~0.6, which is less than the optically thick limit of unity, an effect which has also been observed in other similar symbiotic stars such as RX Pup. In the case of RX Pup, however, the C IV doublet intensity ratio was I(λ1548)/I(λ1550) ~0.6 during an enhanced phase of UV and optical emission, but became larger, acquiring a value ~1, as the star declined in light over a 5 yr period. The anomalous behavior of the C IV doublet intensities, which. we refer to as the C IV Doublet Ratio Intensity Effect, may provide an important tool for studying the spatial structure and temporal nature of winds in symbiotic stars
Un processo per la qualitĂ paesaggistica
Il saggio sintetizza il processo metodologico proposto come esito della ricerca PRIN "Scenari di paesaggio nel piano urbanistico locale".
La ricerca muove dalla constatazione della mancanza di modelli di riferimento, nel nostro paese, per il trattamento degli aspetti paesaggistici a livello locale, e in particolare negli strumenti urbanistici comunali, e della difficoltĂ nell'adeguamento ai nuovi piani paesaggistici regionali.
Si sviluppa ed illustra, attraverso un caso studio, un processo di analisi, valutazione dello stato e delle dinamiche, proposta di scenari progettuali, valutazione degli stessi scenari e coinvolgimento delle popolazioni nelle scelte.
Il processo presenta alcune proposte di innovazione ed è concretamente illustrato nei diversi passaggi
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