1,263 research outputs found
Tourniquet Test for Dengue Diagnosis: Systematic Review and Meta-analysis of Diagnostic Test Accuracy.
BACKGROUND: Dengue fever is a ubiquitous arboviral infection in tropical and sub-tropical regions, whose incidence has increased over recent decades. In the absence of a rapid point of care test, the clinical diagnosis of dengue is complex. The World Health Organisation has outlined diagnostic criteria for making the diagnosis of dengue infection, which includes the use of the tourniquet test (TT). PURPOSE: To assess the quality of the evidence supporting the use of the TT and perform a diagnostic accuracy meta-analysis comparing the TT to antibody response measured by ELISA. DATA SOURCES: A comprehensive literature search was conducted in the following databases to April, 2016: MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials, BIOSIS, Web of Science, SCOPUS. STUDY SELECTION: Studies comparing the diagnostic accuracy of the tourniquet test with ELISA for the diagnosis of dengue were included. DATA EXTRACTION: Two independent authors extracted data using a standardized form. DATA SYNTHESIS: A total of 16 studies with 28,739 participants were included in the meta-analysis. Pooled sensitivity for dengue diagnosis by TT was 58% (95% Confidence Interval (CI), 43%-71%) and the specificity was 71% (95% CI, 60%-80%). In the subgroup analysis sensitivity for non-severe dengue diagnosis was 55% (95% CI, 52%-59%) and the specificity was 63% (95% CI, 60%-66%), whilst sensitivity for dengue hemorrhagic fever diagnosis was 62% (95% CI, 53%-71%) and the specificity was 60% (95% CI, 48%-70%). Receiver-operator characteristics demonstrated a test accuracy (AUC) of 0.70 (95% CI, 0.66-0.74). CONCLUSION: The tourniquet test is widely used in resource poor settings despite currently available evidence demonstrating only a marginal benefit in making a diagnosis of dengue infection alone. REGISTRATION: The protocol for this systematic review was registered at PROSPERO: CRD42015020323
Battery energy storage systems for the electricity grid: UK research facilities
Grid-connected battery energy storage systems with fast
acting control are a key technology for improving power
network stability and increasing the penetration of renewable
generation. This paper describes two battery energy storage
research facilities connected to the UK electricity grid. Their
performance is detailed, along with hardware results, and a
number of grid support services are demonstrated, again with
results presented. The facility operated by The University of
Manchester is rated at 236kVA, 180kWh, and connected to
the 400V campus power network, The University of Sheffield
operates a 2MVA, 1MWh facility connected to an 11kV
distribution network
Can invasions occur without change? A comparison of G-matrices and selection in the peach-potato aphid, Myzus persicae
Most evolutionary research on biological invasions has focused on changes seen between the native and invaded range for a particular species. However, it is likely that species that live in human-modified habitats in their native range might have evolved specific adaptations to those environments, which increase the likelihood of establishment and spread in similar human-altered environments. From a quantitative genetic perspective, this hypothesis suggests that both native and introduced populations should reside at or near the same adaptive peak. Therefore, we should observe no overall changes in the G (genetic variance–covariance) matrices between native and introduced ranges, and stabilizing selection on fitness-related traits in all populations. We tested these predictions comparing three populations of the worldwide pest Myzus persicae from the Middle East (native range) and the UK and Chile (separately introduced ranges). In general, our results provide mixed support for this idea, but further comparisons of other species are needed. In particular, we found that there has been some limited evolution in the studied traits, with the Middle East population differing from the UK and Chilean populations. This was reflected in the structure of the G-matrices, in which Chile differed from both UK and Middle East populations. Furthermore, the amount of genetic variation was massively reduced in Chile in comparison with UK and Middle East populations. Finally, we found no detectable selection on any trait in the three populations, but clones from the introduced ranges started to reproduce later, were smaller, had smaller offspring, and had lower reproductive fitness than clones from the native range
On the formation of sand ramps: A case study from the Mojave Desert
Sand ramps are dune-scale sedimentary accumulations found at mountain fronts and consist of a combination of aeolian sands and the deposits of other geomorphological processes associated with hillslope and fluvial activity. Their complexity and their construction by wind, water and mass movement means that sand ramps potentially hold a very rich store of palaeoenvironmental information. However, before this potential can be realised a full understanding of their formation is necessary. This paper aims to provide a better understanding of the principal factors influencing the development of sand ramps. It reviews the stratigraphic, chronometric and sedimentological evidence relating to the past development of sand ramps, focussing particularly on Soldier Mountain sand ramp in the Mojave Desert, as well as using observations of the modern movement of slope material to elucidate the formation of stone horizons within sand ramps.
Findings show that sand ramps cannot easily be interpreted in terms of a simple model of fluctuating palaeoenvironmental phases from aeolian dominated to soil/fluvial dominated episodes. They accumulate quickly (perhaps in < 5 ka), probably in a single phase before becoming relict. Based on the evidence from Soldier Mountain, they appear strongly controlled by a ‘window of opportunity’ when sediment supply is plentiful and cease to develop when this sediment supply diminishes and/or the accommodation space is filled up. Contemporary observations of stone movement both on rock and sandy sloping surfaces in the Mojave region indicate movement rates in the order of 0.6 and 11 mm yr− 1, which is insufficiently fast to explain how stone horizons could have been moved across and been incorporated into sand ramps on multiple occasions. Stone horizons found within the aeolian sediments lack evidence for soil development and are interpreted as very short-term events in which small streams moved and splayed discontinuous stone horizons across the sand ramp surface before aeolian deposition resumed. Surface stone horizons may form by creep from mountain slope sources across sand ramps but require enhanced speed compared to measured rates of runoff creep. We propose the mechanism of fluvio-aeolian creep. Our study suggests that current models of alternating aeolian and colluvial deposition within sand ramps, their palaeoenvironmental significance and indeed how sand ramps are distinguished from other dune forms require amendment
A completely self-contained cryogen-free dilution refrigerator, the TritonDR™
Oxford Instruments have developed a new dilution refrigerator for ultralow temperatures down to below
35 mK. The TritonDRTM system is a continuous cryogenic cycle dilution refrigerator. The refrigerator is
driven by a closed cycle cryocooler and hence requires no liquid cryogens. The system has a dedicated electronic
control unit and software that provides full control of operation
Exchange coupling in CaMnO and LaMnO: configuration interaction and the coupling mechanism
The equilibrium structure and exchange constants of CaMnO and LaMnO
have been investigated using total energy unrestricted Hartree-Fock (UHF) and
localised orbital configuration interaction (CI) calculations on the bulk
compounds and MnO and MnO clusters. The
predicted structure and exchange constants for CaMnO are in reasonable
agreement with estimates based on its N\'eel temperature. A series of
calculations on LaMnO in the cubic perovskite structure shows that a
Hamiltonian with independent orbital ordering and exchange terms accounts for
the total energies of cubic LaMnO with various spin and orbital orderings.
Computed exchange constants depend on orbital ordering. UHF calculations tend
to underestimate exchange constants in LaMnO, but have the correct sign
when compared with values obtained by neutron scattering; exchange constants
obtained from CI calculations are in good agreement with neutron scattering
data provided the Madelung potential of the cluster is appropriate. Cluster CI
calculations reveal a strong dependence of exchange constants on Mn d e
orbital populations in both compounds. CI wave functions are analysed in order
to determine which exchange processes are important in exchange coupling in
CaMnO and LaMnO.Comment: 25 pages and 9 postscript figure
Minimal Flavour Violation Waiting for Precise Measurements of Delta M_s, S_{psi phi}, A^s_SL, |V_ub|, gamma and B^0_{s,d} -> mu+ mu-
We emphasize that the recent measurements of the B^0_s - bar B^0_s mass
difference Delta M_s by the CDF and D0 collaborations offer an important model
independent test of minimal flavour violation (MFV). The improved measurements
of the angle gamma in the unitarity triangle and of |V_ub| from tree level
decays, combined with future accurate measurements of Delta M_s, S_{psi K_S},
S_{psi phi}, Br(B_{d,s} -> mu+ mu-), Br(B -> X_{d,s} nu bar nu), Br(K+ -> pi+
nu bar nu) and Br(K_L -> pi^0 nu bar nu) and improved values of the relevant
non-perturbative parameters, will allow to test the MFV hypothesis in a model
independent manner to a high accuracy. In particular, the difference between
the reference unitarity triangle obtained from tree level processes and the
universal unitarity triangle (UUT) in MFV models would signal either new
flavour violating interactions and/or new local operators that are suppressed
in MFV models with low tan(beta), with the former best tested through S_{psi
phi} and K_L -> pi^0 nu bar nu. A brief discussion of non-MFV scenarios is also
given. In this context we identify in the recent literature a relative sign
error between Standard Model and new physics contributions to S_{psi phi}, that
has an impact on the correlation between S_{psi phi} and A^s_SL. We point out
that the ratios S_{psi phi}/A^s_SL and (Delta M_s)/(Delta Gamma_s) will allow
to determine (Delta M_s)/(Delta M_s)^SM. Similar proposals for the
determination of (Delta M_d)/(Delta M_d)^SM are also given.Comment: 22 pages, 8 figures, 1 table. Extended discussion of the correlation
between S_{psi phi} and A^s_SL and new proposals to determine Delta
M_q/(Delta M_q)^SM from future measurements, with respect to the first
version. Minor changes and few references adde
Dynamics of Robertson-Walker spacetimes with diffusion
We study the dynamics of spatially homogeneous and isotropic spacetimes containing a fluid undergoing microscopic velocity diffusion in a cosmological scalar field. After deriving a few exact solutions of the equations, we continue by analyzing the qualitative behavior of general solutions. To this purpose we recast the equations in the form of a two dimensional dynamical system and perform a global analysis of the flow. Among the admissible behaviors, we find solutions that are asymptotically de-Sitter both in the past and future time directions and which undergo accelerated expansion at all times.Fundação para a Ciência e a Tecnologia (FCT
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