233 research outputs found
EU-funded malaria research under the 6th and 7th Framework Programmes for research and technological development
While malaria research has traditionally been strong in Europe, targeted and sustained support for cooperative malaria research at EU level, namely through the EU's 6th and 7th Framework Programmes for research and technological development, FP6 (2002-2006) and FP7 (2007-2013), has boosted both impact and visibility of European malaria research. Most of the European malaria research community is now organized under a number of comprehensive and complementary research networks and projects, assembled around four key areas: (1) fundamental research on the malaria parasite and the disease, (2) development of new malaria drugs, (3) research and development of a malaria vaccine, and (4) research to control the malaria-transmitting mosquito vector. Considerable efforts were undertaken to ensure adequate participation of research groups from disease-endemic countries, in particular from Africa, with the long-term aim to strengthen cooperative links and research capacities in these countries. The concept of organizing European research through major strategic projects to form a "European Research Area" (ERA) was originally developed in the preparation of FP6, and ERA formation has now turned into a major EU policy objective explicitly inscribed into the Lisbon Treaty. EU-funded malaria research may serve as a showcase to demonstrate how ERA formation can successfully be implemented in a given area of science when several surrounding parameters converge to support implementation of this strategic concept: timely coincidence of political stimuli, responsive programming, a clearly defined - and well confined - area of research, and the readiness of the targeted research community who is well familiar with transnational cooperation at EU level. Major EU-funded malaria projects have evolved into thematic and organizational platforms that can collaborate with other global players. Europe may thus contribute more, and better, to addressing the global research agenda for malaria
A Magnetohydrodynamic Model for the Formation of Episodic Jets
Episodic ejection of plasma blobs have been observed in many black hole
systems. While steady, continuous jets are believed to be associated with
large-scale open magnetic fields, what causes the episodic ejection of blobs
remains unclear. Here by analogy with the coronal mass ejection on the Sun, we
propose a magnetohydrodynamical model for episodic ejections from black holes
associated with the closed magnetic fields in an accretion flow. Shear and
turbulence of the accretion flow deform the field and result in the formation
of a flux rope in the disk corona. Energy and helicity are accumulated and
stored until a threshold is reached. The system then loses its equilibrium and
the flux rope is thrust outward by the magnetic compression force in a
catastrophic way. Our calculations show that for parameters appropriate for the
black hole in our Galactic center, the plasmoid can attain relativistic speeds
in about 35 minutes.Comment: 8 pages, 2 figures; the finalized version to appear in MNRA
Practical use of variational principles for modeling water waves
This paper describes a method for deriving approximate equations for
irrotational water waves. The method is based on a 'relaxed' variational
principle, i.e., on a Lagrangian involving as many variables as possible. This
formulation is particularly suitable for the construction of approximate water
wave models, since it allows more freedom while preserving the variational
structure. The advantages of this relaxed formulation are illustrated with
various examples in shallow and deep waters, as well as arbitrary depths. Using
subordinate constraints (e.g., irrotationality or free surface impermeability)
in various combinations, several model equations are derived, some being
well-known, other being new. The models obtained are studied analytically and
exact travelling wave solutions are constructed when possible.Comment: 30 pages, 1 figure, 62 references. Other author's papers can be
downloaded at http://www.denys-dutykh.com
The unusual emission line spectrum of IZw1
Most Seyfert 1s show strong Fe II lines in their spectrum having the velocity
and width of the broad emission lines. To remove the Fe II contribution in
these objects, an accurate template is necessary. We used very high
signal-to-noise, medium resolution archive optical spectra of I Zw 1 to build
such a template.
I Zw 1 is a bright narrow-line Seyfert 1 galaxy. As such it is well suited
for a detailed analysis of its emission line spectrum. Furthermore it is known
to have a very peculiar spectrum with, in addition to the usual broad and
narrow line regions, two emission regions emitting broad and blue shifted [O
III] lines making it a peculiarly interesting object. While analysing the
spectra, we found that the narrow-line region is, unlike the NLR of most
Seyfert 1 galaxies, a very low excitation region dominated by both permitted
and forbidden Fe II lines. It is very similar to the emission spectrum of a
blob in Carinae which is a low temperature (T6 500 K),
relatively high density (N=10 cm) cloud. The Fe II lines
in this cloud are mainly due to pumping via the stellar continuum radiation
field (Verner et al. \cite{verner02}). We did not succeed in modelling the
spectrum of the broad-line region, and we suggest that a non radiative heating
mechanism increases the temperature in the excited H I region, thus providing
the necessary additional excitation of the Fe II lines. For the low-excitation
narrow-line region, we are able to settle boundaries to the physical conditions
accounting for the forbidden and permitted Fe II lines (10N cm; 10U).Comment: 16 pages, 7 figures, 10 tables, 1 ascii file, accepted in A&
X-ray observations of highly obscured 9.7 micron sources: an efficient method for selecting Compton-thick AGN ?
Spitzer/IRS has revealed many sources with very deep Si features at 9.7micron
(tau>1). We set out to investigate whether a strong Si absorption feature is a
good indicator for the presence of a heavily obscured AGN. We compile X-ray
spectroscopic observations available in the literature on the
optically-thick,tau(9.7)>1 sources from the IRAS Seyfert sample. We find that
the majority of the high-tau optically confirmed Seyferts (6/9) in this sample
are probably CT. Thus we provide direct evidence for a connection between
mid-IR optically-thick galaxies and CT AGN, with the success rate being close
to 70% in the local Universe. This is at least comparable, if not better, than
other rates obtained with photometric information in the mid to far-IR, or even
mid-IR to Xray. However, this technique cannot provide complete CT AGN
samples,ie there are many CT AGN which do not show significant Si absorption,
with the most notable example being N1068. Having assessed the validity of the
high 9.7micron technique locally, we attempt to construct a sample of candidate
CT AGN at higher redshifts. We compile a sample of 7 high-tau sources in the
GOODS and 5 in the Spitzer FLS. All these have been selected to have no PAH
features EW(6.2)<0.3 in order to maximize the probability that they are AGN. 6
out of 7 sources in the GOODS have been detected in X-rays, while for the five
FLS sources only X-ray flux upper limits are available. The high X-ray
luminosities of the detected GOODS sources corroborates that these are AGN. For
FLS, ancillary optical spectroscopy reveals hidden nuclei in two more sources.
SED fitting can support the presence of an AGN in the vast majority of sources.
We cannot derive useful X-ray spectroscopy constraints on whether these are CT.
However, the low LX/L6 ratios, suggest that at least 4 out of the 6 detected
sources in GOODS may be associated with CT AGN.Comment: 12 pages, to appear in A&A; version after language editin
On the Lx-L6micron ratio as a diagnostic for Compton-thick AGN
As the mid-IR luminosity represents a good isotropic proxy of the AGN power,
a low X-ray to mid-IR luminosity ratio is often claimed to be a reliable
indicator for selecting Compton-thick (CT) AGN. We assess the efficiency of
this diagnostic by examining the 12mu IRAS AGN sample for which high
signal-to-noise XMM observations have been recently become available. We find
that the vast majority (10/11) of the AGN that have been classified as CT on
the basis the X-ray spectroscopy by Brightman & Nandra present a low Lx/L6
luminosity ratio, i.e. lower than a few percent of the average AGN ratio which
is typical of reflection-dominated CT sources. At low Lx/L6 ratios we also find
a comparable number of AGN, most of which are heavily absorbed but not CT. This
implies that although most Compton-thick AGN present low Lx/L6 ratios, at least
in the local, Universe, the opposite is not necessarily true. Next, we extend
our analysis to higher redshifts. We perform the same analysis in the CDFS
where excellent quality chandra (4 Ms) and xmm (3 Ms) X-ray spectra are
available. We derive accurate X-ray luminosities for chandra sources using
X-ray spectral fits, as well as 6mu luminosities from SED fits. We find 8 AGN
with low Lx/L6 ratios in total, after excluding one source where the 6mu
emission primarily comes from star-formation. One of these sources has been
already demonstrated to host a CT nucleus, while for another one at a redshift
of z=1.22 we argue it is most likely CT on the basis of its combined chandra
and xmm spectrum. We find a large number of non CT contaminant with low Lx/L6
ratios. The above suggest that a low Lx/L6 ratio alone cannot ascertain the
presence of a CT AGN, albeit the majority of low Lx/L6 AGN are heavily
obscured. The two most reliable CT AGN in the high redshift Universe have high
Lx/L6 ratios, showing that this method cannot provide complete CT AGN samples.Comment: 11 pages, to appear to A&
Short-term Building Energy Model Recommendation System: A Meta-learning Approach
High-fidelity and computationally efficient energy forecasting models for building systems are needed to ensure optimal automatic operation, reduce energy consumption, and improve the building’s resilience capability to power disturbances. Various models have been developed to forecast building energy consumption. However, given buildings have different characteristics and operating conditions, model performance varies. Existing research has mainly taken a trial-and-error approach by developing multiple models and identifying the best performer for a specific building, or presumed one universal model form which is applied on different building cases. To the best of our knowledge, there does not exist a generalized system framework which can recommend appropriate models to forecast the building energy profiles based on building characteristics. To bridge this research gap, we propose a meta-learning based framework, termed Building Energy Model Recommendation System (BEMR). Based on the building’s physical features as well as statistical and time series meta-features extracted from the operational data and energy consumption data, BEMR is able to identify the most appropriate load forecasting model for each unique building. Three sets of experiments on 48 test buildings and one real building were conducted. The first experiment was to test the accuracy of BEMR when the training data and testing data cover the same condition. BEMR correctly identified the best model on 90% of the buildings. The second experiment was to test the robustness of the BEMR when the testing data is only partially covered by the training data. BEMR correctly identified the best model on 83% of the buildings. The third experiment uses a real building case to validate the proposed framework and the result shows promising applicability and extensibility. The experimental results show that BEMR is capable of adapting to a wide variety of building types ranging from a restaurant to a large office, and gives excellent performance in terms of both modeling accuracy and computational efficiency
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