14,127 research outputs found
Molecular Imaging of Microglial Activation in Amyotrophic Lateral Sclerosis
There is growing evidence of activated microglia and inflammatory processes in the cerebral cortex in amyotrophic lateral sclerosis (ALS). Activated microglia is characterized by increased expression of the 18 kDa translocator protein (TSPO) in the brain and may be a useful biomarker of inflammation. In this study, we evaluated neuroinflammation in ALS patients using a radioligand of TSPO, 18F-DPA-714. Ten patients with probable or definite ALS (all right-handed, without dementia, and untreated by riluzole or other medication that might bias the binding on the TSPO), were enrolled prospectively and eight healthy controls matched for age underwent a PET study. Comparison of the distribution volume ratios between both groups were performed using a Mann-Whitney’s test. Significant increase of distribution of volume ratios values corresponding to microglial activation was found in the ALS sample in primary motor, supplementary motor and temporal cortex (p = 0.009, p = 0.001 and p = 0.004, respectively). These results suggested that the cortical uptake of 18F-DPA-714 was increased in ALS patients during the ‘‘time of diagnosis’’ phase of the disease. This finding might improve our understanding of the pathophysiology of ALS and might be a surrogate marker of efficacy of treatment on microglial activation
Approximability of the Multiple Stack TSP
STSP seeks a pair of pickup and delivery tours in two distinct networks,
where the two tours are related by LIFO contraints. We address here the problem
approximability. We notably establish that asymmetric MaxSTSP and MinSTSP12 are
APX, and propose a heuristic that yields to a 1/2, 3/4 and 3/2 standard
approximation for respectively Max2STSP, Max2STSP12 and Min2STSP12
Destination image analytics through traveller-generated content
The explosion of content generated by users, in parallel with the spectacular growth of social media and the proliferation of mobile devices, is causing a paradigm shift in research. Surveys or interviews are no longer necessary to obtain users' opinions, because researchers can get this information freely on social media. In the field of tourism, online travel reviews (OTRs) hosted on travel-related websites stand out. The objective of this article is to demonstrate the usefulness of OTRs to analyse the image of a tourist destination. For this, a theoretical and methodological framework is defined, as well as metrics that allow for measuring different aspects (designative, appraisive and prescriptive) of the tourist image. The model is applied to the region of Attica (Greece) through a random sample of 300,000 TripAdvisor OTRs about attractions, activities, restaurants and hotels written in English between 2013 and 2018. The results show trends, preferences, assessments, and opinions from the demand side, which can be useful for destination managers in optimising the distribution of available resources and promoting sustainability
Investigation of Travel Behaviour of Visitors to Scotland
Tourism in Scotland is both an important and extensive land use and a major contributor to Gross Domestic Product. In 2005, it is estimated that Scotland received around 10.5 million visitors from outside Scotland. Just over 76% of the visits originated in the rest of the United Kingdom, with the remainder having an international origin. Tourism relies heavily on passenger transport both to access the destination, but also to travel around within it. However, there has been a lack of attention to the internal accessibility of Scotland from the visitor perspective. Whilst some attempts have been suggested and prioritised for facilitating tourists' travel around Scotland, such efforts are mainly undertaken by tourism organisations throughout Scotland, whose ultimate power to enable changes to transport systems is largely limited to lobbying. Moreover, without a clear picture of how accessible Scotland is internally as a destination, or of the transport demands of visitors in terms of internal accessibility, any measures taken to enhance visitor transportation remain largely uninformed. How tourists travel around Scotland, the extent to which they are reliant on public transport and the importance of existing transport provision in their travel behaviour and experience of the destination, including the areas they ultimately visit, merits further clarification. To this end, this study was commissioned by the Transport Department of The Scottish Executive to provide an overview of existing research into the travel behaviour of visitors to Scotland. The principal aim of the study was to review and collate existing sources of information on the use of transport by those visiting Scotland for leisure, recreation and business purposes. In conjunction with the objectives of the Scottish Executive, a thorough review of the literature and secondary data sources pertaining to the use of transport by visitors to Scotland for leisure, tourism and business purposes was conducted
The random subgraph model for the analysis of an ecclesiastical network in Merovingian Gaul
In the last two decades many random graph models have been proposed to
extract knowledge from networks. Most of them look for communities or, more
generally, clusters of vertices with homogeneous connection profiles. While the
first models focused on networks with binary edges only, extensions now allow
to deal with valued networks. Recently, new models were also introduced in
order to characterize connection patterns in networks through mixed
memberships. This work was motivated by the need of analyzing a historical
network where a partition of the vertices is given and where edges are typed. A
known partition is seen as a decomposition of a network into subgraphs that we
propose to model using a stochastic model with unknown latent clusters. Each
subgraph has its own mixing vector and sees its vertices associated to the
clusters. The vertices then connect with a probability depending on the
subgraphs only, while the types of edges are assumed to be sampled from the
latent clusters. A variational Bayes expectation-maximization algorithm is
proposed for inference as well as a model selection criterion for the
estimation of the cluster number. Experiments are carried out on simulated data
to assess the approach. The proposed methodology is then applied to an
ecclesiastical network in Merovingian Gaul. An R code, called Rambo,
implementing the inference algorithm is available from the authors upon
request.Comment: Published in at http://dx.doi.org/10.1214/13-AOAS691 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Dense circum-nuclear molecular gas in starburst galaxies
We present results from a study of the dense circum-nuclear molecular gas of
starburst galaxies. The study aims to investigate the interplay between
starbursts, active galactic nuclei and molecular gas. We characterise the dense
gas traced by HCN, HCO and HNC and examine its kinematics in the
circum-nuclear regions of nine starburst galaxies observed with the Australia
Telescope Compact Array. We detect HCN (10) and HCO (10) in seven
of the nine galaxies and HNC (10) in four. Approximately 7 arcsec resolution
maps of the circum-nuclear molecular gas are presented. The velocity integrated
intensity ratios, HCO (10)/HCN (10) and HNC (10)/HCN (10),
are calculated. Using these integrated intensity ratios and spatial intensity
ratio maps we identify photon dominated regions (PDRs) in NGC 1097, NGC 1365
and NGC 1808. We find no galaxy which shows the PDR signature in only one part
of the observed nuclear region. We also observe unusually strong HNC emission
in NGC 5236, but it is not strong enough to be consistent with X-ray dominated
region (XDR) chemistry. Rotation curves are derived for five of the galaxies
and dynamical mass estimates of the inner regions of three of the galaxies are
made.Comment: Accepted for publication in MNRAS, 22 December 2015. Main manuscript
is 13 pages, containing 3 figures. Also has 4 appendices of 13 pages total
containing numerous figures and details of calculation
Graphic Symbol Recognition using Graph Based Signature and Bayesian Network Classifier
We present a new approach for recognition of complex graphic symbols in
technical documents. Graphic symbol recognition is a well known challenge in
the field of document image analysis and is at heart of most graphic
recognition systems. Our method uses structural approach for symbol
representation and statistical classifier for symbol recognition. In our system
we represent symbols by their graph based signatures: a graphic symbol is
vectorized and is converted to an attributed relational graph, which is used
for computing a feature vector for the symbol. This signature corresponds to
geometry and topology of the symbol. We learn a Bayesian network to encode
joint probability distribution of symbol signatures and use it in a supervised
learning scenario for graphic symbol recognition. We have evaluated our method
on synthetically deformed and degraded images of pre-segmented 2D architectural
and electronic symbols from GREC databases and have obtained encouraging
recognition rates.Comment: 5 pages, 8 figures, Tenth International Conference on Document
Analysis and Recognition (ICDAR), IEEE Computer Society, 2009, volume 10,
1325-132
Wigner-Souriau translations and Lorentz symmetry of chiral fermions
Chiral fermions can be embedded into Souriau's massless spinning particle
model by "enslaving" the spin, viewed as a gauge constraint. The latter is not
invariant under Lorentz boosts; spin enslavement can be restored, however, by a
subsequent Wigner-Souriau (WS) translation, analogous to a compensating gauge
transformation. The combined transformation is precisely the recently uncovered
twisted boost, which we now extend to finite transformations. WS-translations
are identified with the stability group of a motion acting on the right on the
Poincare group, whereas the natural Poincare action corresponds to action on
the left. The relation to non-commutative mechanics is explained.Comment: v3: a new Section explaining the relation to non-commutativity is
added. 14 pages, 2 figure
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