1,035 research outputs found
Negative ion Time Projection Chamber operation with SF at nearly atmospheric pressure
We present measurements of drift velocities and mobilities of some innovative
negative ion gas mixtures at nearly atmospheric pressure based on SF as
electronegative capture agent and of pure SF at various pressures,
performed with the NITEC detector. NITEC is a Time Projection Chamber with 5 cm
drift distance readout by a GEMPix, a triple thin GEMs coupled to a
Quad-Timepix chip, directly sensitive to the deposited charge on each of the 55
55 m pixel. Our results contribute to expanding the knowledge
on the innovative use of SF as negative ion gas and extend to triple thin
GEMs the possibility of negative ion operation for the first time. Above all,
our findings show the feasibility of negative ion operation with
He:CF:SF at 610 Torr, opening extremely interesting possibility for
next generation directional Dark Matter detectors at 1 bar
Complex-network analysis of combinatorial spaces: The NK landscape case
We propose a network characterization of combinatorial fitness landscapes by
adapting the notion of inherent networks proposed for energy surfaces. We use
the well-known family of NK landscapes as an example. In our case the inherent
network is the graph whose vertices represent the local maxima in the
landscape, and the edges account for the transition probabilities between their
corresponding basins of attraction. We exhaustively extracted such networks on
representative NK landscape instances, and performed a statistical
characterization of their properties. We found that most of these network
properties are related to the search difficulty on the underlying NK landscapes
with varying values of K.Comment: arXiv admin note: substantial text overlap with arXiv:0810.3492,
arXiv:0810.348
The Swiss board directors network in 2009
We study the networks formed by the directors of the most important Swiss boards and the boards themselves for the year 2009. The networks are obtained by projection from the original bipartite graph. We highlight a number of important statistical features of those networks such as degree distribution, weight distribution, and several centrality measures as well as their interrelationships. While similar statistics were already known for other board systems, and are comparable here, we have extended the study with a careful investigation of director and board centrality, a k-core analysis, and a simulation of the speed of information propagation and its relationships with the topological aspects of the network such as clustering and link weight and betweenness. The overall picture that emerges is one in which the topological structure of the Swiss board and director networks has evolved in such a way that special actors and links between actors play a fundamental role in the flow of information among distant parts of the network. This is shown in particular by the centrality measures and by the simulation of a simple epidemic process on the directors networ
Social Dilemmas and Cooperation in Complex Networks
In this paper we extend the investigation of cooperation in some classical
evolutionary games on populations were the network of interactions among
individuals is of the scale-free type. We show that the update rule, the payoff
computation and, to some extent the timing of the operations, have a marked
influence on the transient dynamics and on the amount of cooperation that can
be established at equilibrium. We also study the dynamical behavior of the
populations and their evolutionary stability.Comment: 12 pages, 7 figures. to appea
Critical Cooperation Range to Improve Spatial Network Robustness
A robust worldwide air-transportation network (WAN) is one that minimizes the
number of stranded passengers under a sequence of airport closures. Building on
top of this realistic example, here we address how spatial network robustness
can profit from cooperation between local actors. We swap a series of links
within a certain distance, a cooperation range, while following typical
constraints of spatially embedded networks. We find that the network robustness
is only improved above a critical cooperation range. Such improvement can be
described in the framework of a continuum transition, where the critical
exponents depend on the spatial correlation of connected nodes. For the WAN we
show that, except for Australia, all continental networks fall into the same
universality class. Practical implications of this result are also discussed
Light Ion Accelerating Line (L3IA): Test Experiment at ILIL-PW
The construction of a novel Laser driven Light Ions Acceleration Line(L3IA)
is progressing rapidly towards the operation, following the recent upgrade of
the ILIL-PW laser facility. The Line was designed following the pilot
experimental activity carried out earlier at the same facility to define design
parameters and to identify main components including target control and
diagnostic equipment, also in combination with the numerical simulations for
the optimization of laser and target parameters. A preliminary set of data was
acquired following the successful commissioning of the laser system >100 TW
upgrade. Data include output from a range of different ion detectors and
optical diagnostics installed for qualification of the laser-target
interaction. An overview of the results is given along with a description of
the relevant upgraded laser facility and features.Comment: 6 pages, 7 figures, 18 references, presented at the EAAC 201
Relationship between prolactin plasma levels and white matter volume in women with multiple sclerosis
BACKGROUND:
The role of prolactin (PRL) on tissue injury and repair mechanisms in multiple sclerosis (MS) remains unclear. The aim of this work was to investigate the relationship between PRL plasma levels and brain damage as measured by magnetic resonance imaging (MRI).
METHODS:
We employed a chemiluminescence immunoassay for measuring plasma levels of PRL. We used a 1.5 T scanner to acquire images and Jim 4.0 and SIENAX software to analyse them.
RESULTS:
We included 106 women with relapsing remitting (RR) MS and stable disease in the last two months. There was no difference in PRL plasma levels between patients with and without gadolinium enhancement on MRI. PRL plasma levels correlated with white matter volume (WMV) (rho = 0.284, p = 0.014) but not with grey matter volume (GMV). Moreover, PRL levels predicted changes in WMV (Beta: 984, p = 0.034).
CONCLUSIONS:
Our data of a positive association between PRL serum levels and WMV support the role of PRL in promoting myelin repair as documented in animal models of demyelination. The lack of an increase of PRL in the presence of gadolinium enhancement, contrasts with the view considering this hormone as an immune-stimulating and detrimental factor in the inflammatory process associated with MS
Post-operative morbidity following pancreatic duct occlusion without anastomosis after pancreaticoduodenectomy: a systematic review and meta-analysis
Background: Pancreatic duct occlusion (PDO) without anastomosis is a technique proposed to mitigate the clinical consequences of postoperative pancreatic fistulas (POPF) after pancreaticoduodenectomy. The aim of this study was to appraise the morbidity following PDO through a systematic review and meta-analysis. Methods: A systematic search of MEDLINE, Embase, and Web Of Science identified studies reporting outcomes of PDO following pancreaticoduodenectomy. Pooled prevalence rates of postoperative complications and mortality were computed using random-effect modeling. Meta-regression analyses were performed to examine the impact of moderators on the overall estimates. Results: Sixteen studies involving 1000 patients were included. Pooled postoperative mortality was 2.7%. A POPF was reported in 29.7% of the patients. Clinically relevant POPFs occurred in 13.5% of the patients, while intra-abdominal abscess and haemorrhages occurred in 6.7% and 5.5% of the patients, respectively. Re-operation was necessary in 7.6% of the patients. Postoperatively new onset diabetes occurred in 15.8% of patients, more frequently after the use of chemical substances for PDO (p = 0.003). Conclusions: PDO is associated with significant morbidity including new onset of post-operative diabetes. The risk of new onset post-operative diabetes is associated with the use of chemical substance for PDO. Further evidence is needed to evaluate the potential benefits of PDO in patients at high risk of POPF
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