3,856 research outputs found
Operation of EMEP ‘supersites’ in the United Kingdom. Annual report for 2008.
As part of its commitment to the UN-ECE Convention on Long-range Transboundary Air Pollution the United Kingdom operates two ‘supersites’ reporting data to the Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP).
This report provides the annual summary for 2008, the second full calendar year of operation of the first EMEP ‘supersite’ to be established in the United Kingdom. Detailed operational reports have been submitted to Defra every 3 months, with unratified data. This annual report contains a summary of the ratified data for 2008.
The EMEP ‘supersite’ is located in central southern Scotland at Auchencorth (3.2oW, 55.8oN), a remote rural moorland site ~20 km south-west of Edinburgh. Monitoring operations started formally on 1 June 2006.
In addition to measurements made specifically under this contract, the Centre for Ecology & Hydrology also acts as local site operator for measurements made under other UK monitoring networks: the Automated Urban and Rural Network (AURN), the UK Eutrophication and Acidification Network (UKEAP), the UK Hydrocarbons Network, and the UK Heavy Metals Rural Network. Some measurements were also made under the auspices of the ‘Air Pollution Deposition Processes’ contract. All these associated networks are funded by Defra.
This report summarises the measurements made between January and December 2008, and presents summary statistics on average concentrations.
The site is dominated by winds from the south-west, but wind direction data highlight potential sources of airborne pollutants (power stations, conurbations).
The average diurnal patterns of gases and particles are consistent with those expected for a remote rural site.
The frequency distributions are presented for data where there was good data capture throughout the whole period. Some components (e.g. black carbon) show log-normal frequency distributions, while other components (e.g. ozone) have more nearly normal frequency distributions.
A case study is presented for a period in June 2008, showing the influence of regional air pollutants at this remote rural site.
All the data reported under the contract are shown graphically in the Appendix
Disentangling heterogeneity in contemporary undifferentiated arthritis – A large cohort study using latent class analysis
Objectives: Undifferentiated arthritis(UA) is clinically heterogeneous and differs in outcomes ranging from spontaneous resolution to RA-development. Therefore, we hypothesized that subgroups exist within UA and we aimed to identify homogeneous groups based on clinical features, and thereafter to relate these groups to the outcomes spontaneous resolution and RA-development. These outcomes can only be studied in UA-patients in which DMARD-treatment does not influence the natural disease course; these cohorts are scarce. Methods: We studied autoantibody-negative UA-patients (not fulfilling 1987/2010 RA-criteria, no alternate diagnosis), included in the Leiden Early Arthritis Clinic between 1993 and 2006, when early DMARD-treatment in UA was infrequent. Latent class analysis was used to identify subgroups based on combinations of clinical features. Within these subgroups, test-characteristics were assessed for spontaneous resolution of arthritis and RA-development within 1 year. Results: 310 consecutive UA-patients were studied. Five classes were identified: location and number of swollen joints were most distinguishing. Classes were characterized by: 1) polyarthritis, often symmetric; 2) oligoarthritis, frequently with subacute onset; 3) wrist-monoarthritis, often with subacute onset, increased BMI and without morning stiffness; 4) small-joint monoarthritis, often without increased acute phase reactants, and 5) large-joint monoarthritis, often with subacute onset. Studying the classes in relation to the outcomes revealed that patients without spontaneous resolution (thus having persistent disease) were nearly absent in the classes characterized by monoarthritis (specificity >90%). Additionally, patients who developed RA were infrequent in monoarthritis classes (sensitivity <7%). Conclusion: Using a data-driven unsupervised approach, five subgroups within contemporary UA were identified. These have differences in the natural course of disease.</p
Anisotropic and strong negative magneto-resistance in the three-dimensional topological insulator Bi2Se3
We report on high-field angle-dependent magneto-transport measurements on
epitaxial thin films of Bi2Se3, a three-dimensional topological insulator. At
low temperature, we observe quantum oscillations that demonstrate the
simultaneous presence of bulk and surface carriers. The magneto- resistance of
Bi2Se3 is found to be highly anisotropic. In the presence of a parallel
electric and magnetic field, we observe a strong negative longitudinal
magneto-resistance that has been consid- ered as a smoking-gun for the presence
of chiral fermions in a certain class of semi-metals due to the so-called axial
anomaly. Its observation in a three-dimensional topological insulator implies
that the axial anomaly may be in fact a far more generic phenomenon than
originally thought.Comment: 6 pages, 4 figure
Utilisation of cardiac pacemakers over a 20-year period: Results from a nationwide pacemaker registry
The implantation of cardiac pacemakers has become a well-established therapy for conduction disorders and sinus node dysfunction. In many countries pacemaker registries have been initiated in order to collect information on patient characteristics, trends in numbers and the types of pacemakers used, to identify problematic devices, and for safety monitoring. For this utilisation study the Central Pacemaker Patients Registration (CPPR) from the Netherlands Pacemaker Registry Foundation (CPPR-SPRN) containing data collected for more than 20 years was used. During this period nearly 97,000 first pacemakers were implanted. Analyses show an increase in the rate of implanted devices. The change in pacemaker type from VVI to DDD, followed by biventricular stimulation, is reflected by the number of simultaneously implanted leads, which is partly a consequence of cardiac resynchronisation therapy. Our data demonstrate that indications for implantation and type of pacemaker are comparable with other European countries
Gamma-rays from Galactic Black Hole Candidates with Stochastic Particle Acceleration
We consider stochastic particle acceleration in plasmas around stellar mass
black holes to explain the emissions above 1 MeV from Galactic black hole
candidates. We show that for certain parameter regimes, electrons can overcome
Coulomb losses and be accelerated beyond the thermal distribution to form a new
population, whose distribution is broad and usually not a power law; the peak
energy of the distribution is determined by the balance between acceleration
and cooling, with particles piling up around it. Radiation by inverse Compton
scattering off the thermal (from background) and non-thermal (produced by
acceleration) particles can in principle explain the hard X-ray to gamma-ray
emissions from black hole candidates. We present model fits of Cyg X-1 and GRO
J0422 in 50 keV -- 5 MeV region observed with OSSE and COMPTEL.Comment: 2 figures, to appear in March 20 of ApJ
Memory effects induced by initial switching conditions
Initial-switching refers to the way in which the decay of an initially
confined state begins, as the barrier isolating it from the exterior is
relaxed. We study these effects in the context of Longhi's version of the
Fano-Anderson model. Most authors assume the sudden approximation where the
coupling is turned on instantaneously. We consider a finite rise time T, both
numerically and analytically. When the coupling is ramped up linearly over a
switching time T, we show that the asymptotic survival amplitude acquires a
phase T and is modulated by a factor (sin T)/T. Several other results relating
to the solution of the model are obtained. All site amplitudes have the same
decay constant during the exponential decay regime. In the asymptotic regime,
the amplitude and phase of decay oscillations depend on the initial-switching
profile, but the period does not.Comment: 12 pages, 10 figures, accepted by Phys. Rev.
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