535 research outputs found
Tomorrow / music by H. Leopold Spitalny; words by Walter Hirsch and Monte Wilhite
Cover: a photo of Gene Austin; Publisher: Forster Music Publisher (Chicago)https://egrove.olemiss.edu/sharris_d/1091/thumbnail.jp
Spectral variability of quasars from multi-epoch photometric data in the Sloan Digital Sky Survey Stripe 82
We present a new approach to analysing the dependence of quasar variability
on rest-frame wavelengths. We exploited the spectral archive of the Sloan
Digital Sky Survey (SDSS) to create a sample of more than 9000 quasars in the
Stripe 82. The quasar catalogue was matched with the Light Motion Curve
Catalogue for SDSS Stripe 82 and individual first-order structure functions
were computed. The structure functions are used to create a variability
indicator that is related to the same intrinsic timescales for all quasars (1
to 2 yr in the rest frame). We study the variability ratios for adjacent SDSS
filter bands as a function of redshift. While variability is almost always
stronger in the bluer passband compared to the redder, the variability ratio
depends on whether strong emission lines contribute to either one band or the
other. The variability ratio-redshift relations resemble the corresponding
colour index-redshift relations. From the comparison with Monte Carlo
simulations of variable quasar spectra we find that the observed variability
ratio-redshift relations are closely fitted assuming that (a) the r.m.s.
fluctuation of the quasar continuum follows a power law-dependence on the
intrinsic wavelength with an exponent -2 (i.e., bluer when brighter) and (b)
the variability of the emission line flux is only about 10% of that of the
underlying continuum. These results, based upon the photometry of more than
8000 quasars, confirm the previous findings by Wilhite et al. (2005) from 315
quasars with repeated SDSS spectroscopy. Finally, we find that quasars with
unusual spectra and weak emission lines tend to have less variability than
conventional quasars. This trend is opposite to what is expected from the
dilution effect of variability due to line emission and may be indicative of
high Eddington ratios in these unconventinal quasars.Comment: Accepted for publication in Astronomy and Astrophysic
Characteristic QSO Accretion Disk Temperatures from Spectroscopic Continuum Variability
Using Sloan Digital Sky Survey (SDSS) quasar spectra taken at multiple
epochs, we find that the composite flux density differences in the rest frame
wavelength range 1300-6000 AA can be fit by a standard thermal accretion disk
model where the accretion rate has changed from one epoch to the next (without
considering additional continuum emission components). The fit to the composite
residual has two free parameters: a normalizing constant and the average
characteristic temperature . In turn the characteristic temperature
is dependent on the ratio of the mass accretion rate to the square of the black
hole mass. We therefore conclude that most of the UV/optical variability may be
due to processes involving the disk, and thus that a significant fraction of
the UV/optical spectrum may come directly from the disk.Comment: 31 pages, 8 figure
Energy performance contracting (EPC): a suitable mechanism for achieving energy savings in housing cooperatives? Results from a Norwegian pilot project
The barriers to energy savings in institutions and private homes are well known and include people’s lack of interest, awareness, knowledge and human and financial capacity. Experiences made in several countries show that EPC—energy performance contracting—may be used for overcoming many of these barriers. A typical EPC project is delivered by an energy service company (ESCO) and the contract is accompanied with a guarantee for energy savings. EPC is increasingly taken in use in the professional market (firms and the public sector), but is less common in the residential sector market. It has been suggested that there are several barriers for using EPC in the domestic sector such as the uncertainty involved in estimating forthcoming reductions in private consumption. In this paper, we present the results from a pilot project on the use of EPC in a housing cooperative in Oslo. The project was initiated and observed by the researchers. The research followed a transdisciplinary methodology in that it was conducted by both researcher and practitioner (co-authors) in close collaboration with members of the housing cooperative and the ESCOs, who also contributed to the interpretation of results. We document the process in terms of why the Board decided to join the EPC pilot, the call for offers from ESCOs who guaranteed that purchased annual energy would be reduced by one third, the responses to and negotiations of the offer from the ESCO who became contracted in the initial phase and up to the moment when the General Assembly finally decided to not invest in the proposed energy saving measures. We find that the residents not only had limited interest in energy savings but also lacked confidence in the EPC process. This contributed to the outcome. We discuss the findings in relation to the barriers to using EPC among housing cooperatives. We highlight the need for more knowledge about the client side for understanding how barriers may be overcome. Three specific recommendations for how EPC may successfully be employed among housing cooperatives are suggested as follows: (i) include refurbishment and not only energy savings in the EPC, (ii) identify the residents’ needs in an early phase and (iii) communicate the EPC principle to the residents throughout the process
Thrombopoietin: A Novel Bone Healing Agent
poster abstractCritical-size defects in bones do not heal spontaneously and usually require the use of grafts.
Unfortunately, grafts have several limitations. To improve bone formation, many clinicians now use bone
morphogenetic proteins (BMP), particularly in spinal fusion, fracture healing, and in critical-size defect
regeneration. However, multiple side effects of BMP treatment have been uncovered including increased
incidence of cancer. Thus, there is great interest in alternatives that allow for safe and effective bone
regeneration. Here we show the ability of thrombopoietin (TPO), the main megakaryocyte growth factor,
to heal critical-size femoral defects rodents. 5mm or 4mm segmental defects were created in the femur of
Long Evans rats or C57BL/6 mice, respectively. The defects were filled with a novel bioabsorbable
scaffold which was loaded with recombinant human TPO, BMP-2, or saline, and held stable by a
retrograde 1.6 mm intramedullary Kirschner wire (rats) or 23G needle (mice). Xrays were taken every 3
weeks in rats and weekly in mice. Animal were sacrificed at 15 weeks, at which time micro-computed
tomography (μCT) and histological analyses were performed. The results observed in mice and rats were
similar. The saline control group did not show bridging callus at any time. Both the BMP-2 and TPO
groups healed the defect, although bridging callus was evident at earlier times in the BMP-2 groups.
However, the TPO groups showed a much more remodeled and physiologic contour on both Xray and
μCT. μCT and histological analysis confirms that compared to BMP-2, TPO-treated specimens have a
thicker cortex but smaller diameter and smoother contour. TPO appears to restore the original bone
contour by stimulating osteoblastogenesis, allowing for periosteal bridging and stabilization to occur,
while simultaneously stimulating osteoclast formation. Thus, TPO may serve as a novel bone healing
agent
Measuring Lensing Magnification of Quasars by Large Scale Structure using the Variability-Luminosity Relation
We introduce a technique to measure gravitational lensing magnification using
the variability of type I quasars. Quasars' variability amplitudes and
luminosities are tightly correlated, on average. Magnification due to
gravitational lensing increases the quasars' apparent luminosity, while leaving
the variability amplitude unchanged. Therefore, the mean magnification of an
ensemble of quasars can be measured through the mean shift in the
variability-luminosity relation. As a proof of principle, we use this technique
to measure the magnification of quasars spectroscopically identified in the
Sloan Digital Sky Survey, due to gravitational lensing by galaxy clusters in
the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using
the DeepSky pipeline, provides variability data for the sources. We measure the
average quasar magnification as a function of scaled distance (r/R200) from the
nearest cluster; our measurements are consistent with expectations assuming NFW
cluster profiles, particularly after accounting for the known uncertainty in
the clusters' centers. Variability-based lensing measurements are a valuable
complement to shape-based techniques because their systematic errors are very
different, and also because the variability measurements are amenable to
photometric errors of a few percent and to depths seen in current wide-field
surveys. Given the data volume expected from current and upcoming surveys, this
new technique has the potential to be competitive with weak lensing shear
measurements of large scale structure.Comment: Accepted for publication in Ap
Performance assessment of aero-assisted orbital transfer vehicles
Aero-assisted orbital transfer vehicles are analyzed. The aerodynamic characteristics over the flight profile and three- and six-degree-of-freedom performance analyses were determined. The important results, to date, are: (1) the aerodynamic preliminary analysis system, an interactive computer program, used to predict the aerodynamics (performance, stability, and control) for these vehicles; (2) the performance capability, e.g., maximum inclination change, maximum heating rate, and maximum sensed acceleration, can be determined using continuum aerodynamics only; (3) guidance schemes can be developed that allow for errors in atmospheric density prediction, mispredicted trim angle of attack, and off-nominal atmospheric interface conditions, even for vehicles with a low lift-to-drag ratio; and (4) multiple pass trajectories can be used to reduce the maximum heating rate
Cold chains in Hanoi and Bangkok:changing systems of provision and practice
We know that patterns of domestic consumption are situated within broader systems of provision and that home appliances like the fridge freezer bridge between practices of cooking, shopping and eating, on the one hand, and increasingly global systems of food production, distribution and diet on the other. In analysing uses of fridge freezers in Hanoi and Bangkok as expressions, in microcosm, of complex and evolving processes of urbanisation and food provisioning this paper provides new insight into how specific configurations, dependencies and patterns of consumption take hold and how they vary and change. Our analysis of systems and practices in flux has the dual function of showing how household strategies reflect and contribute to more extensive transformations, and of demonstrating how these are shaped by ongoing tensions and relations between new and established forms of urban food supply and associated concepts of freshness and safety. The result is a subtle account of the multiple routes through which consumer ‘needs’ evolve
Quantifying the impact of climate change on drought regimes using the Standardised Precipitation Index
The study presents a methodology to characterise short- or long-term drought events, designed to aid understanding of how climate change may affect future risk. An indicator of drought magnitude, combining parameters of duration, spatial extent and intensity, is presented based on the Standardised Precipitation Index (SPI). The SPI is applied to observed (1955–2003) and projected (2003–2050) precipitation data from the Community Integrated Assessment System (CIAS). Potential consequences of climate change on drought regimes in Australia, Brazil, China, Ethiopia, India, Spain, Portugal and the USA are quantified. Uncertainty is assessed by emulating a range of global circulation models to project climate change. Further uncertainty is addressed through the use of a high-emission scenario and a low stabilisation scenario representing a stringent mitigation policy. Climate change was shown to have a larger effect on the duration and magnitude of long-term droughts, and Australia, Brazil, Spain, Portugal and the USA were highlighted as being particularly vulnerable to multi-year drought events, with the potential for drought magnitude to exceed historical experience. The study highlights the characteristics of drought which may be more sensitive under climate change. For example, on average, short-term droughts in the USA do not become more intense but are projected to increase in duration. Importantly, the stringent mitigation scenario had limited effect on drought regimes in the first half of the twenty-first century, showing that adaptation to drought risk will be vital in these regions
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