4,031 research outputs found
Optimal Tradeoff Between Exposed and Hidden Nodes in Large Wireless Networks
Wireless networks equipped with the CSMA protocol are subject to collisions
due to interference. For a given interference range we investigate the tradeoff
between collisions (hidden nodes) and unused capacity (exposed nodes). We show
that the sensing range that maximizes throughput critically depends on the
activation rate of nodes. For infinite line networks, we prove the existence of
a threshold: When the activation rate is below this threshold the optimal
sensing range is small (to maximize spatial reuse). When the activation rate is
above the threshold the optimal sensing range is just large enough to preclude
all collisions. Simulations suggest that this threshold policy extends to more
complex linear and non-linear topologies
The Dirichlet Obstruction in AdS/CFT
The obstruction for a perturbative reconstruction of the five-dimensional
bulk metric starting from the four-dimensional metric at the boundary,that is,
the Dirichlet problem, is computed in dimensions and some
comments are made on its general structure and, in particular, on its
relationship with the conformal anomaly, which we compute in dimension .Comment: 13 pages, references added (this paper supersedes hep-th/0206140, "A
Note on the Bach Tensor in AdS/CFT", which has been withdrawn
Primary Papillary Serous Carcinoma of the Peritoneum: A Case of Complete Remission of Bulky Peritoneal Disease After Chemotherapy
Peritoneal papillary serous carcinoma is a rare tumor that involves the surface of the pelvic and/or abdominal peritoneum. Long-term survival among patients with this tumor has been rare. Most patients with this cancer have been treated with debulking surgery and postoperative chemotherapy. A case of incompletely resected peritoneal papillary serous carcinoma with a complete response to cisplatin-based chemotherapy is reported. Subsequent laparotomy revealed no residual tumor. This case suggests that primary chemotherapy may be successful in treating unresectable primary papillary serous tumors of the peritoneum
Fish Allergy:Fishing for Novel Diagnostic and Therapeutic Options
Fish allergy is one of the most common food allergies. The currently recommended treatment commonly consists of avoiding all fish species. Recent literature suggests that these recommendations are overprotective for the majority of fish-allergic patients. This review summarizes recent findings and provides practical information regarding management of fish allergy in the individual patient. After precise history taking supported by additional specific IgE measurements and/or skin prick tests, fish-allergic patients can generally be categorized into the following clinical clusters: (A) poly-sensitized patients reacting to all fish species due to their sensitization to the panallergen β-parvalbumin, (B) mono-sensitized patients with selective reactions to individual fish species only, and (C) oligo-sensitized patients reacting to several specific fish. A number of allergens including parvalbumin, enolase, and aldolase can be involved. Depending on the specific cluster the patient belongs to, oral food challenges for one or more fish species can be performed with the aim to provide safe alternatives for consumption. This way, several alternative fish species can be identified for mono- and oligo-sensitized patients that can safely be consumed. Notably, even poly-sensitized patients generally tolerate fish species low in β-parvalbumin such as tuna and mackerel, particularly when processed. Taken together, allergological evaluation of patients with a documented fish allergy should be strongly considered, as it will allow the majority of patients to safely reintroduce one or more fish species
A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372
Aims: We present the first in-depth study of the kinematic properties and
derive the structural parameters of NGC 4372 based on the fit of a Plummer
profile and a rotating, physical model. We explore the link between internal
rotation to different cluster properties and together with similar studies of
more GCs, we put these in the context of globular cluster formation and
evolution. Methods: We present radial velocities for 131 cluster member stars
measured from high-resolution FLAMES/GIRAFFE observations. Their membership to
the GC is additionally confirmed from precise metallicity estimates. Using this
kinematic data set we build a velocity dispersion profile and a systemic
rotation curve. Additionally, we obtain an elliptical number density profile of
NGC 4372 based on optical images using a MCMC fitting algorithm. From this we
derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and
e=0.08+/-0.01. Finally, we give a physical interpretation of the observed
morphological and kinematic properties of this GC by fitting an axisymmetric,
differentially rotating, dynamical model. Results: Our results show that NGC
4372 has an unusually high ratio of rotation amplitude to velocity dispersion
(1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two
other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild
flattening of NGC 4372 in the direction of its rotation. Given its old age,
this suggests that the flattening is indeed caused by the systemic rotation
rather than tidal interactions with the Galaxy. Additionally, we estimate the
dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical
model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3
M_Sun/L_Sun, representative of an old, purely stellar population.Comment: Accepted for publication in A&A, 12 pages, 14 figures, 2 table
Assessing synergies and trade-offs of diverging Paris-compliant mitigation strategies with long-term SDG objectives
The Sustainable Development Goals (SDGs) and the Paris Agreement are the two transformative agendas, which set the benchmarks for nations to address urgent social, economic and environmental challenges. Aside from setting long-term goals, the pathways followed by nations will involve a series of synergies and trade-offs both between and within these agendas. Since it will not be possible to optimise across the 17 SDGs while simultaneously transitioning to low-carbon societies, it will be necessary to implement policies to address the most critical aspects of the agendas and understand the implications for the other dimensions. Here, we rely on a modelling exercise to analyse the long-term implications of a variety of Paris-compliant mitigation strategies suggested in the recent scientific literature on multiple dimensions of the SDG Agenda. The strategies included rely on technological solutions such as renewable energy deployment or carbon capture and storage, nature-based solutions such as afforestation and behavioural changes in the demand side. Results for a selection of energy-environment SDGs suggest that some mitigation pathways could have negative implications on food and water prices, forest cover and increase pressure on water resources depending on the strategy followed, while renewable energy shares, household energy costs, ambient air pollution and yield impacts could be improved simultaneously while reducing greenhouse gas emissions. Overall, results indicate that promoting changes in the demand side could be beneficial to limit potential trade-offs
Analytical and experimental characterization of a miniature calorimetric sensor in pulsatile flow
The behaviour of a miniature calorimetric sensor, which is under
consideration for catheter-based coronary artery flow assessment, is
investigated in both steady and pulsatile tube flow. The sensor is composed of
a heating element operated at constant power, and two thermopiles that measure
flow-induced temperature differences over the sensor surface.
An analytical sensor model is developed, which includes axial heat conduction
in the fluid and a simple representation of the solid wall, assuming a
quasi-steady sensor response to the pulsatile flow. To reduce the mathematical
problem, described by a two-dimensional advection-diffusion equation, a
spectral method is applied. A Fourier transform is then used to solve the
resulting set of ordinary differential equations and an analytical expression
for the fluid temperature is found. To validate the analytical model,
experiments with the sensor mounted in a tube have been performed in steady and
pulsatile water flow with various amplitudes and Strouhal numbers. Experimental
results are generally in good agreement with theory and show a quasi-steady
sensor response in the coronary flow regime. The model can therefore be used to
optimize the sensor design for coronary flow assessment
The Fornax Deep Survey with VST. VIII. Connecting the accretion history with the cluster density
This work is based on deep multi-band (g, r, i) data from the Fornax Deep
Survey with VST. We analyse the surface brightness profiles of the 19 bright
ETGs inside the virial radius of the Fornax cluster. The main aim of this work
is to identify signatures of accretion onto galaxies by studying the presence
of outer stellar halos, and understand their nature and occurrence. Our
analysis also provides a new and accurate estimate of the intra-cluster light
inside the virial radius of Fornax. We performed multi-component fits to the
azimuthally averaged surface brightness profiles available for all sample
galaxies. This allows to quantify the relative weight of all components in the
galaxy structure that contribute to the total light. In addition, we derived
the average g-i colours in each component identified by the fit, as well as the
azimuthally averaged g-i colour profiles, to correlate them with the stellar
mass of each galaxy and the location inside the cluster. We find that in the
most massive and reddest ETGs the fraction of light in, probably accreted,
halos is much larger than in the other galaxies. Less-massive galaxies have an
accreted mass fraction lower than 30%, bluer colours and reside in the
low-density regions of the cluster. Inside the virial radius of the cluster,
the total luminosity of the intra-cluster light, compared with the total
luminosity of all cluster members, is about 34%. Inside the Fornax cluster
there is a clear correlation between the amount of accreted material in the
stellar halos of galaxies and the density of the environment in which those
galaxies reside. By comparing this quantity with theoretical predictions and
previous observational estimates, there is a clear indication that the driving
factor for the accretion process is the total stellar mass of the galaxy, in
agreement with the hierarchical accretion scenario.Comment: 18 pages, 10 figures. Accepted for publication in A&
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