1,554 research outputs found
An Environmental-Economic Measure of Sustainable Development
A central issue in the study of sustainable development is the interplay of growth and sacrifice in a dynamic economy. This paper investigates the relationship among current consumption, growth, and sustained consumption in two canonical, stylized economies and in a more general context. It is found that the maximin value measures what is sustainable and provides the limit to growth. Maximin value is interpreted as an environmental-economic carrying capacity and current consumption or utility as an environmental-economic footprint. The time derivative of maximin value is interpreted as net investment in sustainability improvement. It is called durable savings to distinguish it from genuine savings, usually computed with discounted utilitarian prices.sustained development, growth, maximin, sustainability indicator
Chains of rotational tori and filamentary structures close to high multiplicity periodic orbits in a 3D galactic potential
This paper discusses phase space structures encountered in the neighborhood
of periodic orbits with high order multiplicity in a 3D autonomous Hamiltonian
system with a potential of galactic type. We consider 4D spaces of section and
we use the method of color and rotation [Patsis and Zachilas 1994] in order to
visualize them. As examples we use the case of two orbits, one 2-periodic and
one 7-periodic. We investigate the structure of multiple tori around them in
the 4D surface of section and in addition we study the orbital behavior in the
neighborhood of the corresponding simple unstable periodic orbits. By
considering initially a few consequents in the neighborhood of the orbits in
both cases we find a structure in the space of section, which is in direct
correspondence with what is observed in a resonance zone of a 2D autonomous
Hamiltonian system. However, in our 3D case we have instead of stability
islands rotational tori, while the chaotic zone connecting the points of the
unstable periodic orbit is replaced by filaments extending in 4D following a
smooth color variation. For more intersections, the consequents of the orbit
which started in the neighborhood of the unstable periodic orbit, diffuse in
phase space and form a cloud that occupies a large volume surrounding the
region containing the rotational tori. In this cloud the colors of the points
are mixed. The same structures have been observed in the neighborhood of all
m-periodic orbits we have examined in the system. This indicates a generic
behavior.Comment: 12 pages,22 figures, Accepted for publication in the International
Journal of Bifurcation and Chao
Disc galaxies with multiple triaxial structures. II. JHK surface photometry and numerical simulations
We present detailed JHK surface photometry with ellipse fits of 13 galaxies
selected from previous optical observations as likely candidates for having a
secondary bar or a triaxial bulge within the primary bar. We have found 7
double-barred galaxies, 3 double-barred galaxies with an additional
intermediate structure with twisted isophotes, and 3 galaxies with a bar and
central twisted isophotes. A global analysis of the structural parameter
characteristics in the I- and K-bands is presented. Various numerical models of
galaxies with bars within bars are also analysed using the ellipse fitting
technique and compared to the observations. A thorough review of the possible
hypotheses able to explain this phenomenon is given with emphasis on the most
likely ones.Comment: 12 pages, AATEX. Accepted for publication in A&A. Large color
postscript figures omitted (Figs. 1), figures 2-9 included; gzip'ed
postscript files of the paper and Figs. 1 available via anonymous ftp at
ftp://obsftp.unige.ch/pub/fri/aasjhk/ , files fri_aasjhk.ps.gz and ngc*.ps.g
Near-infrared probing of embedded structures in starburst and Seyfert galaxies
Surface photometry in the J and K' bands of 15 southern Seyfert or starburst
galaxies is presented. The detailed central morphology and structural
properties of these objects were analyzed by fitting ellipses to isophotes. New
central peculiar structures have been identified like, for instance, three
double-barred systems (ESO 215-G031; ESO 320-G030; ESO 443-G017), one object
with a nested nuclear spiral structure at the center of a primary bar (NGC
5135), one object with a nuclear bar without evidence of a large-scale bar (NGC
4941), and one galaxy with a likely dissolved secondary bar within a primary
one (ESO 508-G005). The J-K' radial profile proved to be reasonably well linked
with the presence of a starburst, but not with the Seyfert activity. For
significant starbursts, the central J-K' value is 0.3-1.5 magnitude larger than
the disc one.Comment: 19 pages, 10 figures, accepted for publication in A&A
Basal ryanodine receptor activity suppresses autophagic flux
The inositol 1,4,5-trisphosphate receptors (IP3Rs) and intracellular Ca2+ signaling are critically involved in regulating different steps of autophagy, a lysosomal degradation pathway. The ryanodine receptors (RyR), intracellular Ca2+-release channels mainly expressed in excitable cell types including muscle and neurons, have however not yet been extensively studied in relation to autophagy. Yet, aberrant expression and excessive activity of RyRs in these tissues has been implicated in the onset of several diseases including Alzheimer’s disease, where impaired autophagy regulation contributes to the pathology. In this study, we determined whether pharmacological RyR inhibition could modulate autophagic flux in ectopic RyR-expressing models, like HEK293 cells and in cell types that endogenously express RyRs, like C2C12 myoblasts and primary hippocampal neurons. Importantly, RyR3 overexpression in HEK293 cells impaired the autophagic flux. Conversely, in all cell models tested, pharmacological inhibition of endogenous or ectopically expressed RyRs, using dantrolene or ryanodine, augmented autophagic flux by increasing lysosomal turn-over (number of autophagosomes and autolysosomes measured as mCherry-LC3 punctae/cell increased from 70.37 ± 7.81 in control HEK RyR3 cells to 111.18 ± 7.72 and 98.14 ± 7.31 after dantrolene and ryanodine treatments, respectively). Moreover, in differentiated C2C12 cells, transmission electron microscopy demonstrated that dantrolene treatment decreased the number of early autophagic vacuoles from 5.9 ± 2.97 to 1.8 ± 1.03 per cellular cross section. The modulation of the autophagic flux could be linked to the functional inhibition of RyR channels as both RyR inhibitors efficiently diminished the number of cells showing spontaneous RyR3 activity in the HEK293 cell model (from 41.14% ± 2.12 in control cells to 18.70% ± 2.25 and 9.74% ± 2.67 after dantrolene and ryanodine treatments, respectively). In conclusion, basal RyR-mediated Ca2+-release events suppress autophagic flux at the level of the lysosomes
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