14,519 research outputs found
When Things Matter: A Data-Centric View of the Internet of Things
With the recent advances in radio-frequency identification (RFID), low-cost
wireless sensor devices, and Web technologies, the Internet of Things (IoT)
approach has gained momentum in connecting everyday objects to the Internet and
facilitating machine-to-human and machine-to-machine communication with the
physical world. While IoT offers the capability to connect and integrate both
digital and physical entities, enabling a whole new class of applications and
services, several significant challenges need to be addressed before these
applications and services can be fully realized. A fundamental challenge
centers around managing IoT data, typically produced in dynamic and volatile
environments, which is not only extremely large in scale and volume, but also
noisy, and continuous. This article surveys the main techniques and
state-of-the-art research efforts in IoT from data-centric perspectives,
including data stream processing, data storage models, complex event
processing, and searching in IoT. Open research issues for IoT data management
are also discussed
Rare-cell enrichment by a rapid, label-free, ultrasonic isopycnic technique for medical diagnostics
One significant challenge in medical diagnostics lies in the development of label-free methods to separate different cells within complex biological samples. Here we demonstrate a generic, low-power ultrasonic separation technique, able to enrich different cell types based upon their physical properties. For malaria, we differentiate between infected and non-infected red blood cells in a fingerprick-sized drop of blood. We are able to achieve an enrichment of circulating cells infected by the ring stage of the parasite over nonparasitized red blood cells by between two and three orders of magnitude in less than 3 seconds (enabling detection at parasitemia levels as low as 0.0005 %). In a second example, we also show that our methods can be used to enrich different cell types, concentrating Trypanosoma in blood at very low levels of infection, on disposable, low-cost chips
Kinematical & Chemical Characteristics of the Thin and Thick Disks
I discuss how the chemical abundance distributions, kinematics and age
distributions of stars in the thin and thick disks of the Galaxy can be used to
decipher the merger history of the Milky Way, a typical large galaxy. The
observational evidence points to a rather quiescent past merging history,
unusual in the context of the `consensus' cold-dark-matter cosmology favoured
from observations of structure on scales larger than individual galaxies.Comment: 12 pages, 4 figures; review at IAU Symposium 254, `The Galaxy Disk in
Cosmological Context', Copenhagen, June 2008, eds J. Andersen, J.
Bland-Hawthorn & B. Nordstro
Towards the cloudification of the social networks analytics
In the last years, with the increase of the available data from social networks and the rise of big data technologies, social data has emerged as one of the most profitable market for companies to increase their benefits. Besides, social computation scientists see such data as a vast ocean of information to study modern human societies. Nowadays, enterprises and researchers are developing their own mining tools in house, or they are outsourcing their social media mining needs to specialised companies with its consequent economical cost. In this paper, we present the first cloud computing service to facilitate the deployment of social media analytics applications to allow data practitioners to use social mining tools as a service. The main advantage of this service is the possibility to run different queries at the same time and combine their results in real time. Additionally, we also introduce twearch, a prototype to develop twitter mining algorithms as services in the cloud.Peer ReviewedPostprint (author’s final draft
Merging Rates of the First Objects and the Formation of First Mini-Filaments in Models with Massive Neutrinos
We study the effect of massive neutrinos on the formation and evolution of
the first filaments containing the first star-forming halos of mass
M~10^{6}M_sun at z~20. With the help of the extended Press-Schechter formalism,
we evaluate analytically the rates of merging of the first star-forming halos
into zero-dimensional larger halos and one-dimensional first filaments. It is
shown that as the neutrino mass fraction f_{\nu} increases, the
halo-to-filament merging rate increases while the halo-to-halo merging rate
decreases sharply. For f_{\nu}<=0.04, the halo-to-filament merging rate is
negligibly low at all filament mass scales, while for f_{\nu}>=0.07 the
halo-to-filament merging rate exceeds 0.1 at the characteristic filament mass
scale of ~10^{9}M_sun. The distribution of the redshifts at which the first
filaments ultimately collapse along their longest axes is derived and found to
have a sharp maximum at z~8. We also investigate the formation and evolution of
the second generation filaments which contain the first galaxies of mass
10^{9}M_sun at z=8 as the parent of the first generation filaments. A similar
trend is found: For f_{\nu}>= 0.07 the rate of clustering of the first galaxies
into the second-generation filaments exceeds 0.3 at the characteristic mass
scale of ~10^{11}M_sun. The longest-axis collapse of these second-generation
filaments are found to occur at z~3. The implications of our results on the
formation of massive high-z galaxies and the early metal enrichment of the
intergalactic media by supernova-driven outflows, and possibility of
constraining the neutrino mass from the mass distribution of the high-z central
blackholes are discussed.Comment: Accepted for publication in ApJ, mistakes in the calculation of the
merging rates corrected, feasibility study of constraining neutrino mass with
high-z quasar luminosity function presented, discussion improved, 7 figure
The Heavy Element Composition of Disk Instability Planets Can Range From Sub- to Super-Nebular
Transit surveys combined with Doppler data have revealed a class of gas giant
planets that are massive and highly enriched in heavy elements (e.g.,
HD149026b, GJ436b, and HAT-P-20b). It is tempting to consider these planets as
validation of core accretion plus gas capture because it is often assumed that
disk instability planets should be of nebular composition. We show in this
paper, to the contrary, that gas giants that form by disk instability can have
a variety of heavy element compositions, ranging from sub- to super-nebular
values. High levels of enrichment can be achieved through one or multiple
mechanisms, including enrichment at birth, planetesimal capture, and
differentiation plus tidal stripping. As a result, the metallicity of an
individual gas giant cannot be used to discriminate between gas giant formation
modes.Comment: Accepted by Ap
Three-Dimensional Numerical Modeling of Acoustic Trapping in Glass Capillaries
Acoustic traps are used to capture and handle suspended microparticles and
cells in microfluidic applications. A particular simple and much-used acoustic
trap consists of a commercially available, millimeter-sized, liquid-filled
glass capillary actuated by a piezoelectric transducer. Here, we present a
three-dimensional numerical model of the acoustic pressure field in the liquid
coupled to the displacement field of the glass wall, taking into account mixed
standing and traveling waves as well as absorption. The model predicts
resonance modes well suited for acoustic trapping, their frequencies and
quality factors, the magnitude of the acoustic radiation force on a single test
particle as a function of position, and the resulting acoustic retention force
of the trap. We show that the model predictions are in agreement with published
experimental results, and we discuss how improved and more stable acoustic
trapping modes might be obtained using the model as a design tool.Comment: 13 pages, 15 pdf figures, pdfLatex/Revte
The imprint of cosmological non-Gaussianities on primordial structure formation
We study via numerical N-body/SPH chemistry simulations the effects of
primordial non-Gaussianities on the formation of the first stars and galaxies,
and investigate the impact of supernova feedback in cosmologies with different
fnl. Density distributions are biased to higher values, so star formation and
the consequent feedback processes take place earlier in high-fnl models and
later in low-fnl ones. Mechanical feedback is responsible for shocking and
evacuating the gas from star forming sites earlier in the highly non-Gaussian
cases, because of the larger bias at high densities. Chemical feedback
translates into high-redshift metal filling factors that are larger by some
orders of magnitude for larger fnl, but that converge within one Gyr, for both
population III and population II-I stellar regimes. The efficient enrichment
process, though, leads to metallicities > 0.01 Zsun by redshift ~9, almost
independently from fnl. The impact of non-Gaussianities on the formation of
dark-matter haloes at high redshift is directly reflected in the properties of
the gas in these haloes, as models with larger fnl show more concentrated gas
profiles at early times. Non-Gaussian signatures in the gas behaviour are lost
after the first feedback takes place and introduces a significant degree of
turbulence and chaotic motions.Comment: 10 pages, 9 figures - accepted for publication in MNRA
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