340 research outputs found
Landscape Loopholes: Moments for Change
Social-ecological systems are breaking down at local, regional, and global scales, and sustainability seems an increasingly distant aspiration. Social harmony and economic systems are connected to ecological systems and climate, in multiple complex ways, at many scales. Adapting research practice to match integration opportunities within social-ecological systems could contribute foresight capabilities emerging from landscape change studies, which can be coupled with emerging policy transformation opportunities. The shaping of landscapes by human imagination and physical action creates meaningful contexts for building sustainability. However, the policy landscape is often dominated by circularity and âlock-inâ to unsustainable pathways that are hard to escape. Moments for change emerge through timely convergence of circumstances, within a landscape context, that provide a window of opportunityâa âlandscape loopholeââthrough which the transformation to more sustainable social-ecological relationships might be achieved. Creating future options redundancy (FOR) plans, a variety of possible pathways and alternative landscape futures within the characteristics and capacity of a region, could facilitate policy shifts and adaptive capacity, and reduce risk through reflexive future options. The convergence of circumstances providing loophole opportunities to escape existing lock-in might be understood, and even predicted, by closely coupling landscape sciences and policy research
Hepatic Bile Acid Reuptake in the Rat Depends on Bile Acid Conjugation but Not on Agonistic Properties towards FXR and TGR5
HST Snapshot Survey of Post-AGB Objects
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB
objects are shown. The aim of the survey is to complement existing HST images
of PPN and to connect various types of nebulosities with physical and chemical
properties of their central stars. Nebulosities are detected in 15 of 33
sources. Images and photometric and geometric measurements are presented. For
sources with nebulosities we see a morphological bifurcation into two groups,
DUPLEX and SOLE, as previous studies have found. We find further support to the
previous results suggesting that this dichotomy is caused by a difference in
optical thickness of the dust shell. The remaining 18 sources are classified as
stellar post-AGB objects, because our observations indicate a lack of
nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE
based on their infrared colors. The cause of the differences among the groups
are investigated. We discuss some evidence suggesting that high progenitor-mass
AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass
AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources
probably have low mass progenitors and do not seem to develop nebulosities
during the post-AGB phase and therefore do not become planetary nebulae.Comment: 21 pages, 11 figure
Self-assembled photosystem-I biophotovoltaics on nanostructured TiO2 and ZnO
The abundant pigment-protein membrane complex photosystem-I (PS-I) is at the heart of the Earthâs energy cycle. It is the central molecule in the âZ-schemeâ of photosynthesis, converting sunlight into the chemical energy of life. Commandeering this intricately organized photosynthetic nanocircuitry and re-wiring it to produce electricity carries the promise of inexpensive and environmentally friendly solar power. We here report that dry PS-I stabilized by surfactant peptides functioned as both the light-harvester and charge separator in solar cells self-assembled on nanostructured semiconductors. Contrary to previous attempts at biophotovoltaics requiring elaborate surface chemistries, thin film deposition, and illumination concentrated into narrow wavelength ranges the devices described here are straightforward and inexpensive to fabricate and perform well under standard sunlight yielding open circuit photovoltage of 0.5â
V, fill factor of 71%, electrical power density of 81â
”W/cm2 and photocurrent density of 362â
”A/cm2, over four orders of magnitude higher than any photosystem-based biophotovoltaic to date
Optical spectrum of the post-AGB star HD56126 in the region 4010-8790 AA
We studied in detail the optical spectrum of the post-AGB star HD56126
(IRAS07134+1005). We use high resolution spectra (R=25000 and 60000) obtained
with the echelle spectrographs of the 6-m telescope. About one and a half
thousand absorptions of neutral atoms and ions, absorption bands of C_2, CN,
and CH molecules, and interstellar bands (DIBs) are identified in the 4010 to
8790 AA wavelength region, and the depths and radial velocities of these
spectral features are measured. Differences are revealed between the variations
of the radial velocities measured from spectral features of different
excitation. In addition to the well-known variability of the Halpha profile, we
found variations in the profiles of a number of FeII, YII, and BaII lines. We
also produce an atlas of the spectrum of HD56126 and its comparison staralpha
Per. The full version of the atlas is available in electronic form from
Web-address: http://www.sao.ru/hq/ssl/Atlas/Atlas.htmlComment: 42 pages, 6 figure
Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars
We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z ~ 3, with predictions to z = 7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio
Pulsations and Long-Term Light Variability of Three Candidates to Protoplanetary Nebulae
We present new photometric data and analysis of the long-duration UBV
photoelectric observations for three candidates to protoplanetary objects -
F-supergiants with IR-excesses located at large galactic latitudes, IRAS
18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All three stars have revealed
quasiperiodic low-amplitude variabilities caused by pulsations observed against
the long-term trends of brightnesses. For IRAS 18095+2704=V887 Her we have
found a pulsation period of 109 days and a linear trend of brightness under the
constant colours if being averaged over the year timescale. The light curve of
IRAS 19386+0155=V1648 Aql over 2000-2008 can be approximated by a wave with a
main period of 102 days which is modulated by close frequency, with a period of
98 days, that results in brightness oscillations with a variable amplitude.
V1648 Aql has also shown synchronous reddening together with a persistent rise
of brightness in the V-band. IRAS 19500-1709=V5112 Sgr experiences irregular
pulsations with the periods of 39 and 47 days. The long-term component of the
variability of V5112 Sgr may be related to the binary character of this star.Comment: 11 pages, 6 figures, accepted for publication in Pis'ma Astron. Z
The evolutionary status of the semiregular variable QYSge
Repeated spectroscopic observations made with the 6m telescope of yielded new
data on the radial-velocity variability of the anomalous yellow supergiant
QYSge. The strongest and most peculiar feature in its spectrum is the complex
profile of NaI D lines, which contains a narrow and a very wide emission
components. The wide emission component can be seen to extend from -170 to +120
km/s, and at its central part it is cut by an absorption feature, which, in
turn, is split into two subcomponents by a narrow (16km/s at r=2.5) emission
peak. An analysis of all the Vr values leads us to adopt for the star a
systemic velocity of Vr=-21.1 km/s, which corresponds to the position of the
narrow emission component of NaI. The locations of emission-line features of
NaI D lines are invariable, which point to their formation in regions that are
external to the supergiant's photosphere. Differential line shifts of about
10km/s are revealed. The absorption lines in the spectrum of QYSge have a
substantial width of FWHM~45 km/s. The method of model atmospheres is used to
determine the following parameters: Teff=6250K, lg g=2.0, and microturbulence
Vt=4.5km/s. The metallicity of the star is found to be somewhat higher than the
solar one with an average overabundance of iron-peak elements of [Met/H]=+0.20.
The star is found to be slightly overabundant in carbon and nitrogen,
[C/Fe]=+0.25, [N/Fe]=+0.27. The alpha-process elements Mg, Si, and Ca are
slightly overabundant [alpha/H]=+0.12. The strong sodium excess, [Na/Fe]=+0.75,
is likely to be due to the dredge-up of the matter processed in the NeNa cycle.
Heavy elements of the s-process are underabundant relative to the Sun. On the
whole, the observed properties of QYSge do not give grounds for including this
star into the group of RCrB or RVTau-type type objects.Comment: 29 pages, 8 figures, 4 tables; accepted by Astrophys. Bulleti
Two close large quasar groups of size ⌠350 Mpc at
The Clowes & Campusano large quasar group (LQG) atâinline imageâhas been re-examined using the quasar data from the DR7QSO catalogue of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR7QSO data, the western, northern and southern boundaries of the LQG remain essentially the same, but an extension eastwards of âŒ2° is indicated. In the DR7QSO data, the LQG has 34 members, withâinline image. A new group of 38 members is indicated atâinline imageâand within âŒ2bsl000640 of the Clowes & Campusano LQG. The characteristic sizes of these two LQGs, âŒ350â400 Mpc, appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology. In addition to their intrinsic interest, these two LQGs provide locations in which to investigate early large-scale structure in galaxies and to identify high-zâclusters. A method is presented for assessing the statistical significance and overdensity of groups found by linkage of points
Dust temperature and density profiles of AGB and post-AGB stars from mid-infrared observations
First mid-infrared images of a sample of AGB and post-AGB carbon stars (V
Hya, IRC +10216, CIT 6 and Roberts 22) obtained at La Silla Observatory (ESO,
Chile) are reported. CIT 6 presents a cometary-like feature clearly seen in the
9.7m image, Roberts 22 shows an envelope slightly elongated in the
north-east direction while images of V Hya and IRC+10216 are roughly
spherically symmetric. Using inversion technique, the dust emissivity was
derived from the observed intensity profiles, allowing a determination of the
grain temperature and density distributions inside the envelope for these
stars. Dust masses and mass-loss rates were estimated for V Hya and IRC +10216.
Our results are comparable to those obtained in previous studies if dust grains
have dimensions in the range 0.01 - 0.2 m. Color maps suggest the
presence of temperature inhomogeneities in the central regions of the dust
envelopes. In the case of V Hya, an eccentric hot point, which direction
coincides with the jet previously seen in [SII] emission, suggest that we are
observing a material ejected in a previous mass-loss event. Bipolar lobes are
clearly seen in the color maps of Roberts 22 and IRC +10216.Comment: accepted for publication in Astronomy and Astrophysic
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