74,906 research outputs found
Crossmodal content binding in information-processing architectures
Operating in a physical context, an intelligent robot faces two fundamental problems. First, it needs to combine information from its different sensors to form a representation of the environment that is more complete than any of its sensors on its own could provide. Second, it needs to combine high-level representations (such as those for planning and dialogue) with its sensory information, to ensure that the interpretations of these symbolic representations are grounded in the situated context. Previous approaches to this problem have used techniques such as (low-level) information fusion, ontological reasoning, and (high-level) concept learning. This paper presents a framework in which these, and other approaches, can be combined to form a shared representation of the current state of the robot in relation to its environment and other agents. Preliminary results from an implemented system are presented to illustrate how the framework supports behaviours commonly required of an intelligent robot
Equilibrium and stability of neutrino lumps as TOV solutions
We report about stability conditions for static, spherically symmetric
objects that share the essential features of mass varying neutrinos in
cosmological scenarios. Compact structures of particles with variable mass are
held together preponderantly by an attractive force mediated by a background
scalar field. Their corresponding conditions for equilibrium and stability are
given in terms of the ratio between the total mass-energy and the spherical
lump radius, . We show that the mass varying mechanism leading to lump
formation can modify the cosmological predictions for the cosmological neutrino
mass limits. Our study comprises Tolman-Oppenheimer-Volkoff solutions of
relativistic objects with non-uniform energy densities. The results leave open
some questions concerning stable regular solutions that, to an external
observer, very closely reproduce the preliminary conditions to form
Schwarzschild black holes.Comment: 20 pages, 5 figure
Scenarios and research issues for a network of information
This paper describes ideas and items of work within the
framework of the EU-funded 4WARD project. We present
scenarios where the current host-centric approach to infor-
mation storage and retrieval is ill-suited for and explain
how a new networking paradigm emerges, by adopting the
information-centric network architecture approach, which
we call Network of Information (NetInf). NetInf capital-
izes on a proposed identifier/locator split and allows users
to create, distribute, and retrieve information using a com-
mon infrastructure without tying data to particular hosts.
NetInf introduces the concepts of information and data ob-
jects. Data objects correspond to the particular bits and
bytes of a digital object, such as text file, a specific encod-
ing of a song or a video. Information objects can be used
to identify other objects irrespective of their particular dig-
ital representation. After discussing the benefits of such an
indirection, we consider the impact of NetInf with respect
to naming and governance in the Future Internet. Finally,
we provide an outlook on the research scope of NetInf along
with items for future work
On Classification with Bags, Groups and Sets
Many classification problems can be difficult to formulate directly in terms
of the traditional supervised setting, where both training and test samples are
individual feature vectors. There are cases in which samples are better
described by sets of feature vectors, that labels are only available for sets
rather than individual samples, or, if individual labels are available, that
these are not independent. To better deal with such problems, several
extensions of supervised learning have been proposed, where either training
and/or test objects are sets of feature vectors. However, having been proposed
rather independently of each other, their mutual similarities and differences
have hitherto not been mapped out. In this work, we provide an overview of such
learning scenarios, propose a taxonomy to illustrate the relationships between
them, and discuss directions for further research in these areas
Low-Mass Binary Induced Outflows from Asymptotic Giant Branch Stars
A significant fraction of planetary nebulae (PNe) and proto-planetary nebulae
(PPNe) exhibit aspherical, axisymmetric structures, many of which are highly
collimated. The origin of these structures is not entirely understood, however
recent evidence suggests that many observed PNe harbor binary systems, which
may play a role in their shaping. In an effort to understand how binaries may
produce such asymmetries, we study the effect of low-mass (< 0.3 M_sun)
companions (planets, brown dwarfs and low-mass main sequence stars) embedded
into the envelope of a 3.0 M_sun star during three epochs of its evolution (Red
Giant Branch, Asymptotic Giant Branch (AGB), interpulse AGB). We find that
common envelope evolution can lead to three qualitatively different
consequences: (i) direct ejection of envelope material resulting in a
predominately equatorial outflow, (ii) spin-up of the envelope resulting in the
possibility of powering an explosive dynamo driven jet and (iii) tidal
shredding of the companion into a disc which facilitates a disc driven jet. We
study how these features depend on the secondary's mass and discuss
observational consequences.Comment: 24 pages, 6 figures, submitted to MNRA
Model mass spectrometric study of competitive interactions of antimicrobial bisquaternary ammonium drugs and aspirin with membrane phospholipids
The aim of the study is to reveal molecular mechanisms of possible activity modulation of antimicrobial bis-quaternary ammonium compounds (BQAC) and aspirin (ASP) through noncovalent competitive complexation under their combined introduction into the model systems with membrane phospholipids. Methods. Binary and triple systems containing either decamethoxinum or ethonium, or thionium and aspirin, as well as dipalmitoyl-phosphatidylcholine (DPPC) have been investigated by electrospray ionization mass spectrometry. Results. Basing on the analysis of associates recorded in the mass spectra, the types of nonocovalent complexes formed in the systems studied were determined and the supposed role of the complexation in the BQAC and ASP activity modulation was discussed. The formation of associates of BQAC dications with ASP anion is considered as one of the possible ways of deactivation of ionic forms of the medications. The formation of stable complexes of BQAC with DPPC and ASP with DPPC in binary systems as well as the complexes distribution in triple-components systems BQAC:ASP:DPPC point to the existence of competition between drugs of these two types for the binding to DPPC. Conclusions. The results obtained point to the competitive complexation in the model molecular systems containing the BQAC, aspirin and membrane phospholipids. The observed phenomenon testifies to the possibility of modulating the activity of bisquaternary antimicrobial agents and aspirin under their combined usage, due to the competition between the drugs for binding to the target membrane phospholipid molecules and also due to the formation of stable noncovalent complexes between BQAC and ASP
Solution Path Clustering with Adaptive Concave Penalty
Fast accumulation of large amounts of complex data has created a need for
more sophisticated statistical methodologies to discover interesting patterns
and better extract information from these data. The large scale of the data
often results in challenging high-dimensional estimation problems where only a
minority of the data shows specific grouping patterns. To address these
emerging challenges, we develop a new clustering methodology that introduces
the idea of a regularization path into unsupervised learning. A regularization
path for a clustering problem is created by varying the degree of sparsity
constraint that is imposed on the differences between objects via the minimax
concave penalty with adaptive tuning parameters. Instead of providing a single
solution represented by a cluster assignment for each object, the method
produces a short sequence of solutions that determines not only the cluster
assignment but also a corresponding number of clusters for each solution. The
optimization of the penalized loss function is carried out through an MM
algorithm with block coordinate descent. The advantages of this clustering
algorithm compared to other existing methods are as follows: it does not
require the input of the number of clusters; it is capable of simultaneously
separating irrelevant or noisy observations that show no grouping pattern,
which can greatly improve data interpretation; it is a general methodology that
can be applied to many clustering problems. We test this method on various
simulated datasets and on gene expression data, where it shows better or
competitive performance compared against several clustering methods.Comment: 36 page
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