1,381 research outputs found
Exorcising Malthusian ghosts: Vaccinating the Nexus to advance integrated water, energy and food resource resilience
Water-Energy-Food (WEF) Nexus interactions vary from seemingly negative and intractable wicked problems to opportunities for enhanced sustainability. The aim of this paper is to review the current state of understanding on WEF resource interactions and to provide a roadmap to enhance integrated resource management. A qualitative perspective based on expert insight and experience was supported by a more quantitative systematic analysis of the literature to define Nexus interactions, describe the nature of different challenges, and explore the factors that influence them. We found that Nexus challenges, and associated interactions (e.g. trade-offs and synergies), vary with complexity and spatial and temporal scale, and biases in research and culture act as barriers to progress. An interdisciplinary approach is needed to develop technical solutions employed through the use of orchestrated shocks (e.g. historic analogues, predictive modelling, experimentation, and scenario planning) to âVaccinate the Nexusâ and improve system resilience. To achieve this, multidisciplinary capability should be developed to solve interdisciplinary challenges, while protecting specialism. It is recognised that through embracing complexity and âNexus (or Systems) Thinkingâ, future integration of resource management may be facilitated through holistic education, informed by interdisciplinary research, and ingrained in cross-sector policy and governance
Detecting gravitational waves from precessing binaries of spinning compact objects: Adiabatic limit
Black-hole (BH) binaries with single-BH masses m=5--20 Msun, moving on
quasicircular orbits, are among the most promising sources for first-generation
ground-based gravitational-wave (GW) detectors. Until now, the development of
data-analysis techniques to detect GWs from these sources has been focused
mostly on nonspinning BHs. The data-analysis problem for the spinning case is
complicated by the necessity to model the precession-induced modulations of the
GW signal, and by the large number of parameters needed to characterize the
system, including the initial directions of the spins, and the position and
orientation of the binary with respect to the GW detector. In this paper we
consider binaries of maximally spinning BHs, and we work in the
adiabatic-inspiral regime to build families of modulated detection templates
that (i) are functions of very few physical and phenomenological parameters,
(ii) model remarkably well the dynamical and precessional effects on the GW
signal, with fitting factors on average >~ 0.97, but (iii) might require
increasing the detection thresholds, offsetting at least partially the gains in
the fitting factors. Our detection-template families are quite promising also
for the case of neutron-star--black-hole binaries, with fitting factors on
average ~ 0.93. For these binaries we also suggest (but do not test) a further
template family, which would produce essentially exact waveforms written
directly in terms of the physical spin parameters.Comment: 38 pages, 16 figures, RevTeX4. Final PRD version. Lingering typos
corrected. Small corrections to GW flux terms as per Blanchet et al., PRD 71,
129902(E)-129904(E) (2005
The Effect of Sample Handling on Cross Sectional HIV Incidence Testing Results
To determine if mishandling prior to testing would make a sample from a chronically infected subject appear recently infected when tested by cross-sectional HIV incidence assays.Serum samples from 31 subjects with chronic HIV infection were tested. Samples were subjected to different handling conditions, including incubation at 4 °C, 25 °C and 37 °C, for 1, 3, 7 or 15 days prior to testing. Samples were also subjected to 1,3, 7 and 15 freeze-thaw cycles prior to testing. Samples were tested using the BED capture enzyme immuno assay (BED-CEIA), Vironostika-less sensitive (V-LS), and an avidity assay using the Genetic Systems HIV-1/HIV-2 plus O EIA (avidity assay).Compared to the sample that was not subjected to any mishandling conditions, for the BED-CEIA, V-LS and avidity assay, there was no significant change in test results for samples incubated at 4 °C or 25 °C prior to testing. No impact on test results occurred after 15 freeze-thaw cycles. A decrease in assay results was observed when samples were held for 3 days or longer at 37 °C prior to testing.Samples can be subjected up to 15 freeze-thaw cycles without affecting the results the BED-CEIA, Vironostika-LS, or avidity assays. Storing samples at 4 °C or 25 °C for up to fifteen days prior to testing had no impact on test results. However, storing samples at 37°C for three or more days did affect results obtained with these assays
Non-Linear Evolution of the r-Modes in Neutron Stars
The evolution of a neutron-star r-mode driven unstable by gravitational
radiation (GR) is studied here using numerical solutions of the full non-linear
fluid equations. The amplitude of the mode grows to order unity before strong
shocks develop which quickly damp the mode. In this simulation the star loses
about 40% of its initial angular momentum and 50% of its rotational kinetic
energy before the mode is damped. The non-linear evolution causes the fluid to
develop strong differential rotation which is concentrated near the surface and
especially near the poles of the star.Comment: 4 pages, 7 eps figures, revtex; revised, typos correcte
Numerical evolutions of nonlinear r-modes in neutron stars
Nonlinear evolution of the gravitational radiation (GR) driven instability in
the r-modes of neutron stars is studied by full numerical 3D hydrodynamical
simulations. The growth of the r-mode instability is found to be limited by the
formation of shocks and breaking waves when the dimensionless amplitude of the
mode grows to about three in value. This maximum mode amplitude is shown by
numerical tests to be rather insensitive to the strength of the GR driving
force. Upper limits on the strengths of possible nonlinear mode--mode coupling
are inferred. Previously unpublished details of the numerical techniques used
are presented, and the results of numerous calibration runs are discussed.Comment: RevTeX 4, 17 pages, 26 figures. Slightly revised. To be published in
PRD (April 2002
Isothermal Amplification Using a Chemical Heating Device for Point-of-Care Detection of HIV-1
Background: To date, the use of traditional nucleic acid amplification tests (NAAT) for detection of HIV-1 DNA or RNA has been restricted to laboratory settings due to time, equipment, and technical expertise requirements. The availability of a rapid NAAT with applicability for resource-limited or point-of-care (POC) settings would fill a great need in HIV diagnostics, allowing for timely diagnosis or confirmation of infection status, as well as facilitating the diagnosis of acute infection, screening and evaluation of infants born to HIV-infected mothers. Isothermal amplification methods, such as reversetranscription, loop-mediated isothermal amplification (RT-LAMP), exhibit characteristics that are ideal for POC settings, since they are typically quicker, easier to perform, and allow for integration into low-tech, portable heating devices. Methodology/Significant Findings: In this study, we evaluated the HIV-1 RT-LAMP assay using portable, non-instrumented nucleic acid amplification (NINA) heating devices that generate heat from the exothermic reaction of calcium oxide and water. The NINA heating devices exhibited stable temperatures throughout the amplification reaction and consistent amplification results between three separate devices and a thermalcycler. The performance of the NINA heaters was validated using whole blood specimens from HIV-1 infected patients. Conclusion: The RT-LAMP isothermal amplification method used in conjunction with a chemical heating device provides
Clinical Presentation and Angiographic Characteristics of Saphenous Vein Graft Failure After Stenting Insights From the SOS (Stenting Of Saphenous Vein Grafts) Trial
ObjectivesWe sought to compare the clinical presentation and angiographic patterns of saphenous vein graft (SVG) failure after stenting with a paclitaxel-eluting stent (PES) versus a similar bare-metal stent (BMS).BackgroundThe mode of SVG failure after stenting has been poorly characterized.MethodsThe SOS (Stenting Of Saphenous Vein Grafts) trial enrolled 80 patients with 112 lesions in 88 SVGs who were randomized to a BMS or PES. Angiographic follow-up at 12 months was available in 83% of the patients.ResultsBinary angiographic restenosis occurred in 51% (24 of 47) of BMS-treated lesions versus 9% (4 of 43) of PES-treated lesions (p < 0.0001). Graft occlusion occurred in 9 of the 21 SVGs (43%) that failed in the BMS group and in 2 of 4 SVGs (50%) that failed in the PES group. SVG failure after stenting presented as an acute coronary syndrome in 10 of the 24 patients (42%) (7 of those 10 patients presented with nonâST-segment elevation acute myocardial infarction), stable angina in 9 (37%) patients, and without symptoms in 5 (21%) patients. Of the 19 patients (with 20 grafts) who developed symptomatic graft failure, repeat SVG revascularization was successfully performed in all 13 (100%) subtotally obstructed SVGs but was attempted (and successful) in only 1 of 7 (14%) occluded SVGs. Revascularization of a native coronary artery was performed in an additional 4 of 7 (57%) symptomatic patients with an occluded SVG.ConclusionsSVG failure after stenting often presents as acute myocardial infarction and with SVG occlusion. Compared with BMS, PES reduce SVG failure
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
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