436 research outputs found
Triadic closure dynamics drives scaling-laws in social multiplex networks
Social networks exhibit scaling-laws for several structural characteristics,
such as the degree distribution, the scaling of the attachment kernel, and the
clustering coefficients as a function of node degree. A detailed understanding
if and how these scaling laws are inter-related is missing so far, let alone
whether they can be understood through a common, dynamical principle. We
propose a simple model for stationary network formation and show that the three
mentioned scaling relations follow as natural consequences of triadic closure.
The validity of the model is tested on multiplex data from a well studied
massive multiplayer online game. We find that the three scaling exponents
observed in the multiplex data for the friendship, communication and trading
networks can simultaneously be explained by the model. These results suggest
that triadic closure could be identified as one of the fundamental dynamical
principles in social multiplex network formation.Comment: 5 pages, 3 figure
Instrumentational complexity of music genres and why simplicity sells
Listening habits are strongly influenced by two opposing aspects, the desire
for variety and the demand for uniformity in music. In this work we quantify
these two notions in terms of musical instrumentation and production
technologies that are typically involved in crafting popular music. We assign a
"complexity value" to each music style. A style is complex if it shows the
property of having both high variety and low uniformity in instrumentation. We
find a strong inverse relation between variety and uniformity of music styles
that is remarkably stable over the last half century. Individual styles,
however, show dramatic changes in their "complexity" during that period. Styles
like "new wave" or "disco" quickly climbed towards higher complexity in the 70s
and fell back to low complexity levels shortly afterwards, whereas styles like
"folk rock" remained at constant high complexity levels. We show that changes
in the complexity of a style are related to its number of sales and to the
number of artists contributing to that style. As a style attracts a growing
number of artists, its instrumentational variety usually increases. At the same
time the instrumentational uniformity of a style decreases, i.e. a unique
stylistic and increasingly complex expression pattern emerges. In contrast,
album sales of a given style typically increase with decreasing complexity.
This can be interpreted as music becoming increasingly formulaic once
commercial or mainstream success sets in.Comment: 17 pages, 5 figures, Supporting Informatio
Systemic trade-risk of critical resources
In the wake of the 2008 financial crisis the role of strongly interconnected
markets in fostering systemic instability has been increasingly acknowledged.
Trade networks of commodities are susceptible to deleterious cascades of supply
shocks that increase systemic trade-risks and pose a threat to geopolitical
stability. On a global and a regional level we show that supply risk, scarcity,
and price volatility of non-fuel mineral resources are intricately connected
with the structure of the world-trade network of or spanned by these resources.
On the global level we demonstrate that the scarcity of a resource, as measured
by its trade volume compared to extractable reserves, is closely related to the
susceptibility of the trade network with respect to cascading shocks. On the
regional level we find that to some extent the region-specific price volatility
and supply risk can be understood by centrality measures that capture systemic
trade-risk. The resources associated with the highest systemic trade-risk
indicators are often those that are produced as byproducts of major metals. We
identify significant shortcomings in the management of systemic trade-risk, in
particular in the EU
Spreading of diseases through comorbidity networks across life and gender
The state of health of patients is typically not characterized by a single
disease alone but by multiple (comorbid) medical conditions. These
comorbidities may depend strongly on age and gender. We propose a specific
phenomenological comorbidity network of human diseases that is based on medical
claims data of the entire population of Austria. The network is constructed
from a two-layer multiplex network, where in one layer the links represent the
conditional probability for a comorbidity, and in the other the links contain
the respective statistical significance. We show that the network undergoes
dramatic structural changes across the lifetime of patients.Disease networks
for children consist of a single, strongly inter-connected cluster. During
adolescence and adulthood further disease clusters emerge that are related to
specific classes of diseases, such as circulatory, mental, or genitourinary
disorders.For people above 65 these clusters start to merge and highly
connected hubs dominate the network. These hubs are related to hypertension,
chronic ischemic heart diseases, and chronic obstructive pulmonary diseases. We
introduce a simple diffusion model to understand the spreading of diseases on
the disease network at the population level. For the first time we are able to
show that patients predominantly develop diseases which are in close
network-proximity to disorders that they already suffer. The model explains
more than 85 % of the variance of all disease incidents in the population. The
presented methodology could be of importance for anticipating age-dependent
disease-profiles for entire populations, and for validation and of prevention
schemes.Comment: 14 pages,5 figure
To how many politicians should government be left?
The quality of governance of institutions, corporations and countries depends
on the ability of efficient decision making within the respective boards or
cabinets. Opinion formation processes within groups are size dependent. It is
often argued - as now e.g. in the discussion of the future size of the European
Commission - that decision making bodies of a size beyond 20 become strongly
inefficient. We report empirical evidence that the performance of national
governments declines with increasing membership and undergoes a qualitative
change in behavior at a particular group size. We use recent UNDP, World Bank
and CIA data on overall government efficacy, i.e. stability, the quality of
policy formulation as well as human development indices of individual countries
and relate it to the country's cabinet size. We are able to understand our
findings through a simple physical model of opinion dynamics in groups.Comment: main text 5 pages and 4 eps figures, appendi
Causal ACTH-Depot Therapy during Pregnancies following Infertility Treatment
The aim of this paper was to confirm the efficacy of adrenocorticotropin depot (ACTH-depot) therapy in pregnancies with threatened miscarriage and preterm delivery through the desired stimulation of the adrenal glands controlled by the rest of organism. The activity of hypothalamic-pituitary-adrenal axis plays a key role in pregnancy. Such naturally stimulated endogenous corticosteroid hormones are free from unwanted side effects of their synthetics analogs. Low level of maternal blood ACTH and insufficient increase of induced by hypothalamic hormones oxytocinases (cystine-β-aminopeptidases) were indication to ACTH-depot therapy (0.5âmg/week) in our consecutive prospective studies. Contrary to antenatal use of synthetic corticosteroids, there are no temporal limits of this therapy, which has to be more often recommended into clinical prevention of fetal morbidity, treatment of premature delivery, and finally elimination of the newborn's mortality caused by the neuroendocrinological gestoses
Dynamical origins of the community structure of multi-layer societies
Social structures emerge as a result of individuals managing a variety of
different of social relationships. Societies can be represented as highly
structured dynamic multiplex networks. Here we study the dynamical origins of
the specific community structures of a large-scale social multiplex network of
a human society that interacts in a virtual world of a massive multiplayer
online game. There we find substantial differences in the community structures
of different social actions, represented by the various network layers in the
multiplex. Community size distributions are either similar to a power-law or
appear to be centered around a size of 50 individuals. To understand these
observations we propose a voter model that is built around the principle of
triadic closure. It explicitly models the co-evolution of node- and
link-dynamics across different layers of the multiplex. Depending on link- and
node fluctuation rates, the model exhibits an anomalous shattered fragmentation
transition, where one layer fragments from one large component into many small
components. The observed community size distributions are in good agreement
with the predicted fragmentation in the model. We show that the empirical
pairwise similarities of network layers, in terms of link overlap and degree
correlations, practically coincide with the model. This suggests that several
detailed features of the fragmentation in societies can be traced back to the
triadic closure processes.Comment: 8 pages, 6 figure
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