1,923 research outputs found
Determinación de la Huella Ecológica Personal como Estrategia para la Adquisición de Patrones de Consumo Sostenibles UNCP 2014
El propósito de la presente investigación fue definir el efecto de la estrategia de determinación de la Huella Ecológica Personal sobre la adquisición de patrones de consumo sostenibles en estudiantes de la Facultad de Economía de la Universidad Nacional del Centro del Perú, habiéndose seleccionado una muestra de 48 estudiantes distribuidos en dos secciones (A con 21 y B con 27 estudiantes), matriculados en la asignatura de Economía Ambiental y de los Recursos Naturales. Se utilizó un diseño de investigación cuasi-experimental con grupo control con pre y post test en grupos intactos. La sección A fue seleccionada aleatoriamente como grupo control y la sección B como grupo experimental, con quienes se desarrolló el Manual del Consumidor Responsable. Se efectuó un contraste de hipótesis de diferencia de medias con muestras independientes para la prueba de entrada y otra en la prueba de salida, encontrando que, en general, los estudiantes mejoran sus patrones de consumo, haciéndolos sostenibles, luego de aplicado el módulo de aprendizaje a un nivel de significancia de α = .05. La huella ecológica promedio para la prueba de entrada se estimó en 1.13 ha, disminuyendo para la prueba de salida a 0.898 ha. Luego de transcurridos seis meses se aplicó el cuestionario de seguimiento, encontrando que los estudiantes aún mantienen como tendencia la disminución de su huella ecológica estimada en 0.996 ha, mayor que la prueba de salida y menor que la prueba de entrada. El instrumento que se aplicó para medir la huella ecológica fue el test para patrones de consumo sostenibles
Anergy in self-directed B lymphocytes from a statistical mechanics perspective
The ability of the adaptive immune system to discriminate between self and
non-self mainly stems from the ontogenic clonal-deletion of lymphocytes
expressing strong binding affinity with self-peptides. However, some
self-directed lymphocytes may evade selection and still be harmless due to a
mechanism called clonal anergy. As for B lymphocytes, two major explanations
for anergy developed over three decades: according to "Varela theory", it stems
from a proper orchestration of the whole B-repertoire, in such a way that
self-reactive clones, due to intensive interactions and feed-back from other
clones, display more inertia to mount a response. On the other hand, according
to the `two-signal model", which has prevailed nowadays, self-reacting cells
are not stimulated by helper lymphocytes and the absence of such signaling
yields anergy. The first result we present, achieved through disordered
statistical mechanics, shows that helper cells do not prompt the activation and
proliferation of a certain sub-group of B cells, which turn out to be just
those broadly interacting, hence it merges the two approaches as a whole (in
particular, Varela theory is then contained into the two-signal model). As a
second result, we outline a minimal topological architecture for the B-world,
where highly connected clones are self-directed as a natural consequence of an
ontogenetic learning; this provides a mathematical framework to Varela
perspective. As a consequence of these two achievements, clonal deletion and
clonal anergy can be seen as two inter-playing aspects of the same phenomenon
too
Topological properties of hierarchical networks
Hierarchical networks are attracting a renewal interest for modelling the
organization of a number of biological systems and for tackling the complexity
of statistical mechanical models beyond mean-field limitations. Here we
consider the Dyson hierarchical construction for ferromagnets, neural networks
and spin-glasses, recently analyzed from a statistical-mechanics perspective,
and we focus on the topological properties of the underlying structures. In
particular, we find that such structures are weighted graphs that exhibit high
degree of clustering and of modularity, with small spectral gap; the robustness
of such features with respect to link removal is also studied. These outcomes
are then discussed and related to the statistical mechanics scenario in full
consistency. Lastly, we look at these weighted graphs as Markov chains and we
show that in the limit of infinite size, the emergence of ergodicity breakdown
for the stochastic process mirrors the emergence of meta-stabilities in the
corresponding statistical mechanical analysis
Meta-stable states in the hierarchical Dyson model drive parallel processing in the hierarchical Hopfield network
In this paper we introduce and investigate the statistical mechanics of
hierarchical neural networks: First, we approach these systems \`a la Mattis,
by thinking at the Dyson model as a single-pattern hierarchical neural network
and we discuss the stability of different retrievable states as predicted by
the related self-consistencies obtained from a mean-field bound and from a
bound that bypasses the mean-field limitation. The latter is worked out by
properly reabsorbing fluctuations of the magnetization related to higher levels
of the hierarchy into effective fields for the lower levels. Remarkably, mixing
Amit's ansatz technique (to select candidate retrievable states) with the
interpolation procedure (to solve for the free energy of these states) we prove
that (due to gauge symmetry) the Dyson model accomplishes both serial and
parallel processing. One step forward, we extend this scenario toward multiple
stored patterns by implementing the Hebb prescription for learning within the
couplings. This results in an Hopfield-like networks constrained on a
hierarchical topology, for which, restricting to the low storage regime (where
the number of patterns grows at most logarithmical with the amount of neurons),
we prove the existence of the thermodynamic limit for the free energy and we
give an explicit expression of its mean field bound and of the related improved
boun
Hierarchical neural networks perform both serial and parallel processing
In this work we study a Hebbian neural network, where neurons are arranged
according to a hierarchical architecture such that their couplings scale with
their reciprocal distance. As a full statistical mechanics solution is not yet
available, after a streamlined introduction to the state of the art via that
route, the problem is consistently approached through signal- to-noise
technique and extensive numerical simulations. Focusing on the low-storage
regime, where the amount of stored patterns grows at most logarithmical with
the system size, we prove that these non-mean-field Hopfield-like networks
display a richer phase diagram than their classical counterparts. In
particular, these networks are able to perform serial processing (i.e. retrieve
one pattern at a time through a complete rearrangement of the whole ensemble of
neurons) as well as parallel processing (i.e. retrieve several patterns
simultaneously, delegating the management of diff erent patterns to diverse
communities that build network). The tune between the two regimes is given by
the rate of the coupling decay and by the level of noise affecting the system.
The price to pay for those remarkable capabilities lies in a network's capacity
smaller than the mean field counterpart, thus yielding a new budget principle:
the wider the multitasking capabilities, the lower the network load and
viceversa. This may have important implications in our understanding of
biological complexity
Marcos Del Cano, Ana María (coord.). Derechos humanos y trabajo social, Madrid: Universitas, 2013.
Recensión del libro Marcos Del Cano, Ana María. Derechos humanos en el ámbito del trabajo social, Madrid:Universitas, 2013
From Dyson to Hopfield: Processing on hierarchical networks
We consider statistical-mechanical models for spin systems built on
hierarchical structures, which provide a simple example of non-mean-field
framework. We show that the coupling decay with spin distance can give rise to
peculiar features and phase diagrams much richer that their mean-field
counterpart. In particular, we consider the Dyson model, mimicking
ferromagnetism in lattices, and we prove the existence of a number of
meta-stabilities, beyond the ordered state, which get stable in the
thermodynamic limit. Such a feature is retained when the hierarchical structure
is coupled with the Hebb rule for learning, hence mimicking the modular
architecture of neurons, and gives rise to an associative network able to
perform both as a serial processor as well as a parallel processor, depending
crucially on the external stimuli and on the rate of interaction decay with
distance; however, those emergent multitasking features reduce the network
capacity with respect to the mean-field counterpart. The analysis is
accomplished through statistical mechanics, graph theory, signal-to-noise
technique and numerical simulations in full consistency. Our results shed light
on the biological complexity shown by real networks, and suggest future
directions for understanding more realistic models
Historiadores y arbitristas
Balance de la historiografía de los arbitristas de la monarquía española desde el siglo XVIII y propuesta de reinterpretación en la óptica de una historia cultural de lo políticoBilan de l'historiographie des donneurs d'avis en Espagne depuis le XVIIIe siècle et proposition de relecture dans l'optique d'une histoire culturelle du politique
- …