139 research outputs found
Building knowledge-based economies: research projects in knowledge management and knowledge transfer
Small and medium-sized enterprises (SMEs) are viewed as the growth engines of the new knowledgebased
economy. This new economic growth model differs from the old in significant ways, many of which
are related to the knowledge base that will be required by the SMEs. Based upon prior research a set of
factors important to the success of SMEs in a knowledge-based economy is described. Focusing on those
factors related to the knowledge base, the paper concludes with a set of research questions and brief
descriptions of three research projects on knowledge management and knowledge transfer
Stent Thrombogenicity Early in High Risk Interventional Settings is Driven by Stent Design and Deployment, and Protected by Polymer-Drug Coatings
Author Manuscript: 2012 April 5BackgroundâStent thrombosis is a lethal complication of endovascular intervention. Concern has been raised about the inherent risk associated with specific stent designs and drug-eluting coatings, yet clinical and animal support is equivocal.
Methods and ResultsâWe examined whether drug-eluting coatings are inherently thrombogenic and if the response to these materials was determined to a greater degree by stent design and deployment with custom-built stents. Drug/polymer coatings uniformly reduce rather than increase thrombogenicity relative to matched bare metal counterparts (0.65-fold; P=0.011). Thick-strutted (162 ÎŒm) stents were 1.5-fold more thrombogenic than otherwise identical thin-strutted (81 ÎŒm) devices in ex vivo flow loops (P<0.001), commensurate with 1.6-fold greater thrombus coverage 3 days after implantation in porcine coronary arteries (P=0.004). When bare metal stents were deployed in malapposed or overlapping configurations, thrombogenicity increased compared with apposed, length-matched controls (1.58-fold, P=0.001; and 2.32-fold, P<0.001). The thrombogenicity of polymer-coated stents with thin struts was lowest in all configurations and remained insensitive to incomplete deployment. Computational modelingâbased predictions of stent-induced flow derangements correlated with spatial distribution of formed clots.
ConclusionsâContrary to popular perception, drug/polymer coatings do not inherently increase acute stent clotting; they reduce thrombosis. However, strut dimensions and positioning relative to the vessel wall are critical factors in modulating stent thrombogenicity. Optimal stent geometries and surfaces, as demonstrated with thin stent struts, help reduce the potential for thrombosis despite complex stent configurations and variability in deployment
CO2 enrichment and soil type additively regulate grassland productivity
The development of a predictive understanding of how atmospheric CO2 enrichment is affecting the primary productivity of the terrestrial biosphere is among the most pressing of ecological challenges. The terrestrial biosphere absorbs c. 25% of anthropogenic carbon (C) emissions (Le Quere et al., 2018). Uncertainty in CO2 effects on ecosystem C uptake is a major constraint in the prediction of C cycling and the provisioning of productivity- related ecosystem services.
Grasslands cover c. 25% of the terrestrial area and are an important contributor to the global C balance (Sala et al., 1996). CO2 enrichment stimulates the aboveground net primary productivity (ANPP) of most water-limited grasslands by increasing plant water use efficiency (WUE; productivity per unit of transpiration; Morgan et al., 2004; Nowak et al., 2004; Fatichi et al., 2016), but grassland ANPP, as other ecosystem functions, is determined by drivers in addition to water availability which act simultaneously and often interactively with CO2 (Polley et al., 2011). CO2 enrichment usually shows greater stimulation of plant productivity when nitrogen (N) availability is relatively high (Owensby et al., 1994; Reich & Hobbie, 2013; Mueller et al., 2016), for example. Other drivers include precipitation timing (Hovenden et al., 2014), disturbance regimes (Newton et al., 2014), plant species composition (Langley & Megonigal, 2010; Fay et al., 2012; Polley et al., 2012) and soil properties (Epstein et al., 1997, 1998), including soil texture, which influences water availability to plants (Tor-Ngern et al., 2017)
CO2 enrichment and soil type additively regulate grassland productivity
The development of a predictive understanding of how atmospheric CO2 enrichment is affecting the primary productivity of the terrestrial biosphere is among the most pressing of ecological challenges. The terrestrial biosphere absorbs c. 25% of anthropogenic carbon (C) emissions (Le Quere et al., 2018). Uncertainty in CO2 effects on ecosystem C uptake is a major constraint in the prediction of C cycling and the provisioning of productivity- related ecosystem services.
Grasslands cover c. 25% of the terrestrial area and are an important contributor to the global C balance (Sala et al., 1996). CO2 enrichment stimulates the aboveground net primary productivity (ANPP) of most water-limited grasslands by increasing plant water use efficiency (WUE; productivity per unit of transpiration; Morgan et al., 2004; Nowak et al., 2004; Fatichi et al., 2016), but grassland ANPP, as other ecosystem functions, is determined by drivers in addition to water availability which act simultaneously and often interactively with CO2 (Polley et al., 2011). CO2 enrichment usually shows greater stimulation of plant productivity when nitrogen (N) availability is relatively high (Owensby et al., 1994; Reich & Hobbie, 2013; Mueller et al., 2016), for example. Other drivers include precipitation timing (Hovenden et al., 2014), disturbance regimes (Newton et al., 2014), plant species composition (Langley & Megonigal, 2010; Fay et al., 2012; Polley et al., 2012) and soil properties (Epstein et al., 1997, 1998), including soil texture, which influences water availability to plants (Tor-Ngern et al., 2017)
Where are the High Velocity Clouds in Local Group Analogs?
High-velocity clouds (HVCs) are clouds of HI seen around the Milky Way with
velocities inconsistent with Galactic rotation, have unknown distances and
masses and controversial origins. One possibility is that HVCs are associated
with the small dark matter halos seen in models of galaxy formation and
distributed at distances of 150 kpc - 1 Mpc. We report on our attempts to
detect the analogs to such putative extragalactic clouds in three groups of
galaxies similar to our own Local Group using the ATNF Parkes telescope and
Compact Array. Eleven dwarf galaxies were found, but no HI clouds lacking stars
were detected. Using the population of compact HVCs around the Milky Way as a
template, we find that our non-detection of analogs implies that they must be
clustered within 160 kpc of the Milky Way (and other galaxies) with an average
HI mass <4x10^5 M(sun) at the 95% confidence level. This is in accordance with
recent limits derived by other authors. If our groups are true analogs to the
Local Group, then this makes the original Blitz et al. and Braun & Burton
picture of HVCs residing out to 1 Mpc from the Milky Way extremely unlikely.
The total HI mass in HVCs, < 10^8 M(sun), implies that there is not a large
reservoir of neutral hydrogen waiting to be accreted onto the Milky Way. Any
substantial reservoir of baryonic matter must be mostly ionized or condensed
enough as to be undetectable.Comment: 5 pages, 2 figures, ApJ letters, in pres
Perspectives on Astrophysics Based on Atomic, Molecular, and Optical (AMO) Techniques
About two generations ago, a large part of AMO science was dominated by
experimental high energy collision studies and perturbative theoretical
methods. Since then, AMO science has undergone a transition and is now
dominated by quantum, ultracold, and ultrafast studies. But in the process, the
field has passed over the complexity that lies between these two extremes. Most
of the Universe resides in this intermediate region. We put forward that the
next frontier for AMO science is to explore the AMO complexity that describes
most of the Cosmos.Comment: White paper submission to the Decadal Assessment and Outlook Report
on Atomic, Molecular, and Optical (AMO) Science (AMO 2020
The HIPASS Catalogue - II. Completeness, Reliability, and Parameter Accuracy
The HI Parkes All Sky Survey (HIPASS) is a blind extragalactic HI 21-cm
emission line survey covering the whole southern sky from declination -90 to
+25. The HIPASS catalogue (HICAT), containing 4315 HI-selected galaxies from
the region south of declination +2, is presented in Meyer et al. (2004a, Paper
I). This paper describes in detail the completeness and reliability of HICAT,
which are calculated from the recovery rate of synthetic sources and follow-up
observations, respectively. HICAT is found to be 99 per cent complete at a peak
flux of 84 mJy and an integrated flux of 9.4 Jy km/s. The overall reliability
is 95 per cent, but rises to 99 per cent for sources with peak fluxes >58 mJy
or integrated flux > 8.2 Jy km/s. Expressions are derived for the uncertainties
on the most important HICAT parameters: peak flux, integrated flux, velocity
width, and recessional velocity. The errors on HICAT parameters are dominated
by the noise in the HIPASS data, rather than by the parametrization procedure.Comment: Accepted for publication in MNRAS. 12 pages, 11 figures. Paper with
higher resolution figures can be downloaded from http://hipass.aus-vo.or
An HI survey of six Local Group analogs: I. Survey description and the search for high-velocity clouds
We have conducted an HI 21 cm emission-line survey using the Parkes 20cm
multibeam instrument and the Australia Telescope Compact Array (ATCA) of six
loose groups of galaxies chosen to be analogs to the Local Group. The goal of
this survey is to make a census of the HI-rich galaxies and high-velocity
clouds (HVCs) within these groups and compare these populations with those in
the Local Group. The Parkes observations covered the entire volume of each
group with a rms M(HI) sensitivity of 4-10x10^5 M(sun) per 3.3 km/s channel.
All potential sources detected in the Parkes data were confirmed with ATCA
observations at ~2' resolution and the same M(sun) sensitivity. All the
confirmed sources have associated stellar counterparts; no starless HI
clouds--HVC analogs--were found in the six groups. In this paper, we present a
description of the survey parameters, its sensitivity and completeness. Using
the population of compact HVCs (CHVCs) around the Milky Way as a template
coupled with the detailed knowledge of our survey parameters, we infer that our
non-detection of CHVC analogs implies that, if similar populations exist in the
six groups studied, the CHVCs must be clustered within 90 kpc of group
galaxies, with average M(HI) < 4x10^5 M(sun) at the 95% confidence level. The
corollary is that the same must apply to Milky Way CHVCs. This is consistent
with our previous results from a smaller sample of groups, and in accordance
with recent observational and theoretical constraints from other authors. These
results confirm that there is very little neutral matter around galaxies, and
that any substantial reservoir of baryons must be in other phases.Comment: 10 pages, ApJ accepte
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
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