631 research outputs found
Participatory Budgeting: Diffusion and Outcomes across the World
In this special issue of the Journal of Public Deliberation, multiple faces of Participatory Budgeting programs are revealed. The articles demonstrate that there is no standardized set of “best practices” that governments are adopting, but there are a broader set of principles that are adapted by local governments to meet local circumstances. Adopt and adapt appears to be the logic behind many PB programs
Do Quasars Lens Quasars?
If the unexpectedly high frequency of quasar pairs with very different
component redshifts is due to the lensing of a population of background quasars
by the foreground quasar, typical lens masses must be \sim10^{12}M_{\sun} and
the sum of all such quasar lenses would have to contain times the
closure density of the Universe. It then seems plausible that a very high
fraction of all \sim10^{12} M_{\sun} gravitational lenses with redshifts
contain quasars. Here I propose that these systems have evolved to
form the present population of massive galaxies with M and M
>5\times10^{11} M_{\sun}.Comment: 6 pages, aas style, ams symbols, ApJL (accepted
Colloidal Gels: Equilibrium and Non-Equilibrium Routes
We attempt a classification of different colloidal gels based on
colloid-colloid interactions. We discriminate primarily between non-equilibrium
and equilibrium routes to gelation, the former case being slaved to
thermodynamic phase separation while the latter is individuated in the
framework of competing interactions and of patchy colloids. Emphasis is put on
recent numerical simulations of colloidal gelation and their connection to
experiments. Finally we underline typical signatures of different gel types, to
be looked in more details in experiments.Comment: topical review, accepted in J. Phys. Condens. Matte
Assessment of Positron Annihilation as a Potential Non-Destructive Examination Technique
The positron annihilation technique can provide a sensitive measure of defect density in metals. In this program the technique has been used to monitor defects generated during plastic deformation by cold work or fatigue cycling. The primary goals have been 1) to assess the degree of sensitivity of the technique, 2) to correlate positron annihilation readings with observed microstructural changes to better understand the physical basis for these readings, and 3) to determine correlations between positron annihilation measurements and number of fatigue cycles. Examination of fatigued samples by transmission electron microscopy indicates some correlation between dislocation density and positron annihilation lineshape parameter (determined by the Doppler broadening technique). However, annealing studies of deformed samples indicate that positron annihilation response in 316 stainless steel is sensitive primarily to excess vacancies generated during the deformation and is less sensitive to dislocation density. Data on deformed nickel show sensitivity to both vacancies and dislocations. In general, lineshape parameter values tend to achieve a constant level at approximately 10 per cent of fatigue life
Broad P V Absorption in the BALQSO, PG 1254+047: Column Densities, Ionizations and Metal Abundances in BAL Winds
This paper discusses the detection of P V 1118,1128 and other broad
absorption lines (BALs) in archival HST spectra of the low-redshift BALQSO, PG
1254+047. The P V identification is secured by excellent redshift and profile
coincidences with the other BALs, such as C IV 1548,1550 and Si IV 1393,1403,
and by photoionization calculations showing that other lines near this
wavelength, e.g. Fe III 1123, should be much weaker than P V. The observed BAL
strengths imply that either 1) there are extreme abundance ratios such as [C/H]
>~ +1.0, [Si/H] >~ +1.8 and [P/C] >~ +2.2, or 2) at least some of the lines are
much more optically thick than they appear. I argue that the significant
presence of P V absorption indicates severe line saturation, which is disguised
in the observed (moderate-strength) BALs because the absorber does not fully
cover the continuum source(s) along our line(s) of sight. Computed optical
depths for all UV resonance lines show that the observed BALs are consistent
with solar abundances if 1) the ionization parameter is at least moderately
high, log U >~ -0.6, 2) the total hydrogen column density is log N_H(cm-2) >~
22.0, and 3) the optical depths in strong lines like C IV and O VI 1032,1038
are >~25 and >~80, respectively. These optical depths and column densities are
at least an order of magnitude larger than expected from the residual
intensities in the BAL troughs, but they are consistent with the large
absorbing columns derived from X-ray observations of BALQSOs. The outflowing
BALR, at velocities from -15,000 to -27,000 km/s in PG 1254+047, is therefore a
strong candidate for the X-ray absorber in BALQSOs.Comment: 16 pages (LaTeX) plus 8 pages of figures in one file
(pg1254_figs.ps.gz), in press with Ap
Food and water intake prior to parturition in the rat
Food and water intakes were measured in pregnant rats to determine whether parturition is preceded by significant changes in food and water intake. Three diets of different palatability and caloric value were used. Over the last 5 days of pregnancy, pregnant rats were found to ingest more calories/day than nonpregnant rats, and females with prior parturitional experience (multiparous) ingested more than virgin or primiparous females. Pregnant rats also ingested significantly greater amounts of fluid when compared to nonpregnant rats, and multiparous rats (pregnant or not) ingested greater amounts of fluid than did virgin or primiparous rats. On the last day of pregnancy, the intake of solid foods or a liquid diet did not change significantly, but the intake of either water or 5% sucrose was significantly reduced
Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots
We present seven epochs between October 1999 and November 2007 of high
resolution VLT/UVES echelle spectra of the ejecta-ring collision of SN 1987A.
The fluxes of most of the narrow lines from the unshocked gas decreased by a
factor of 2-3 during this period, consistent with the decay from the initial
ionization by the shock break-out. However, [O III] in particular shows an
increase up to day ~6800. This agrees with radiative shock models where the
pre-shocked gas is heated by the soft X-rays from the shock. The line emission
from the shocked gas increases rapidly as the shock sweeps up more gas. We find
that the neutral and high ionization lines follow the evolution of the Balmer
lines roughly, while the intermediate ionization lines evolve less rapidly. Up
to day ~6800, the optical light curves have a similar evolution to that of the
soft X-rays. The break between day 6500 and day 7000 for [O III] and [Ne III]
is likely due to recombination to lower ionization levels. Nevertheless, the
evolution of the [Fe XIV] line, as well as the lines from the lowest ionization
stages, continue to follow that of the soft X-rays, as expected. There is a
clear difference in the line profiles between the low and intermediate
ionization lines, and those from the coronal lines at the earlier epochs. This
shows that these lines arise from regions with different physical conditions,
with at least a fraction of the coronal lines coming from adiabatic shocks. At
later epochs the line widths of the low ionization lines, however, increase and
approach those of the high ionization lines of [Fe X-XIV]. The H-alpha line
profile can be traced up to ~500 km/s at the latest epoch. This is consistent
with the cooling time of shocks propagating into a density of (1-4)x10^4 cm-3.Comment: 25 Pages, 12 Figures, accepted for publication in A&
The Nucleon-Nucleon Interaction in the Chromo-Dielectric Soliton Model: Dynamics
The present work is an extension of a previous study of the nucleon-nucleon
interaction based on the chromo-dielectric soliton model. The former approach
was static, leading to an adiabatic potential. Here we perform a dynamical
study in the framework of the Generator Coordinate Method. In practice, we
derive an approximate Hill-Wheeler differential equation and obtain a local
nucleon-nucleon potential as a function of a mean generator coordinate. This
coordinate is related to an effective separation distance between the two
nucleons by a Fujiwara transformation. This latter relationship is especially
useful in studying the quark substructure of light nuclei. We investigate the
explicit contribution of the one-gluon exchange part of the six-quark
Hamiltonian to the nucleon-nucleon potential, and we find that the dynamics are
responsible for a significant part of the short-range N-N repulsion.Comment: 16 pages (REVTEX), 6 figures (uuencoded Postscript) optionally
included using epsfig.st
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I. Observations toward delta Orionis by the Interstellar Medium Absorption Profile Spectrograph
Studies of the abundances of deuterium in different astrophysical sites are
of fundamental importance to answering the question about how much deuterium
was produced during big bang nucleosynthesis and what fraction of it was
destroyed later. With this in mind, we used the Interstellar Medium Absorption
Profile Spectrograph (IMAPS) on the ORFEUS-SPAS II mission to observe at a
wavelength resolution of 4 km/s (FWHM) the L-delta and L-epsilon absorption
features produced by interstellar atomic deuterium in the spectrum of delta Ori
A. A chi-square analysis indicated that 0.96 < N(D I)< 1.45e15 cm^{-2} at a 90%
level of confidence, and the gas is at a temperature of about 6000K. To obtain
an accurate value of N(H I) needed for a determination of the atomic ratio of D
to H, we measured the L-alpha absorption features in 57 spectra of delta Ori in
the IUE archive. From our measurement of N(H I)= 1.56e20 cm^{-2}, we found that
N(D I)/N(H I)= 7.4(+1.9,-1.3)e-6 (90% confidence). Our result for D/H contrasts
with the more general finding along other lines of sight that D/H is
approximately 1.5e-5. The underabundance of D toward delta Ori A is not
accompanied by an overabundance of N or O relative to H, as one might expect if
the gas were subjected to more stellar processing than usual.Comment: 37 pages, 6 figures. Submitted to the Astrophysical Journa
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