351 research outputs found
Investigating the interplay between fundamentals of national research systems: performance, investments and international collaborations
We discuss, at the macro-level of nations, the contribution of research
funding and rate of international collaboration to research performance, with
important implications for the science of science policy. In particular, we
cross-correlate suitable measures of these quantities with a
scientometric-based assessment of scientific success, studying both the average
performance of nations and their temporal dynamics in the space defined by
these variables during the last decade. We find significant differences among
nations in terms of efficiency in turning (financial) input into
bibliometrically measurable output, and we confirm that growth of international
collaboration positively correlate with scientific success, with significant
benefits brought by EU integration policies. Various geo-cultural clusters of
nations naturally emerge from our analysis. We critically discuss the possible
factors that potentially determine the observed patterns
How the Taxonomy of Products Drives the Economic Development of Countries
We introduce an algorithm able to reconstruct the relevant network structure
on which the time evolution of country-product bipartite networks takes place.
The significant links are obtained by selecting the largest values of the
projected matrix. We first perform a number of tests of this filtering
procedure on synthetic cases and a toy model. Then we analyze the bipartite
network constituted by countries and exported products, using two databases for
a total of almost 50 years. It is then possible to build a hierarchically
directed network, in which the taxonomy of products emerges in a natural way.
We study the influence of the structure of this taxonomy network on countries'
development; in particular, guided by an example taken from the
industrialization of South Korea, we link the structure of the taxonomy network
to the empirical temporal connections between product activations, finding that
the most relevant edges for countries' development are the ones suggested by
our network. These results suggest paths in the product space which are easier
to achieve, and so can drive countries' policies in the industrialization
process.Comment: 16 pages, 8 figure
On the convergence of the Fitness-Complexity Algorithm
We investigate the convergence properties of an algorithm which has been
recently proposed to measure the competitiveness of countries and the quality
of their exported products. These quantities are called respectively Fitness F
and Complexity Q. The algorithm was originally based on the adjacency matrix M
of the bipartite network connecting countries with the products they export,
but can be applied to any bipartite network. The structure of the adjacency
matrix turns to be essential to determine which countries and products converge
to non zero values of F and Q. Also the speed of convergence to zero depends on
the matrix structure. A major role is played by the shape of the ordered matrix
and, in particular, only those matrices whose diagonal does not cross the empty
part are guaranteed to have non zero values as outputs when the algorithm
reaches the fixed point. We prove this result analytically for simplified
structures of the matrix, and numerically for real cases. Finally, we propose
some practical indications to take into account our results when the algorithm
is applied.Comment: 13 pages, 8 figure
Liquidity crises on different time scales
We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales
The complex dynamics of products and its asymptotic properties
We analyse global export data within the Economic Complexity framework. We
couple the new economic dimension Complexity, which captures how sophisticated
products are, with an index called logPRODY, a measure of the income of the
respective exporters. Products' aggregate motion is treated as a 2-dimensional
dynamical system in the Complexity-logPRODY plane. We find that this motion can
be explained by a quantitative model involving the competition on the markets,
that can be mapped as a scalar field on the Complexity-logPRODY plane and acts
in a way akin to a potential. This explains the movement of products towards
areas of the plane in which the competition is higher. We analyse market
composition in more detail, finding that for most products it tends, over time,
to a characteristic configuration, which depends on the Complexity of the
products. This market configuration, which we called asymptotic, is
characterized by higher levels of competition.Comment: 20 pages, 5 figures, supporting information. This paper was published
on PLOS One on May 17, 201
Collaboration between a human group and artificial intelligence can improve prediction of multiple sclerosis course. A proof-of-principle study
Background: Multiple sclerosis has an extremely variable natural course. In most patients, disease starts with a relapsing-remitting (RR) phase, which proceeds to a secondary progressive (SP) form. The duration of the RR phase is hard to predict, and to date predictions on the rate of disease progression remain suboptimal. This limits the opportunity to tailor therapy on an individual patient's prognosis, in spite of the choice of several therapeutic options. Approaches to improve clinical decisions, such as collective intelligence of human groups and machine learning algorithms are widely investigated. Methods: Medical students and a machine learning algorithm predicted the course of disease on the basis of randomly chosen clinical records of patients that attended at the Multiple Sclerosis service of Sant'Andrea hospital in Rome. Results: A significant improvement of predictive ability was obtained when predictions were combined with a weight that depends on the consistence of human (or algorithm) forecasts on a given clinical record. Conclusions: In this work we present proof-of-principle that human-machine hybrid predictions yield better prognoses than machine learning algorithms or groups of humans alone. To strengthen this preliminary result, we propose a crowdsourcing initiative to collect prognoses by physicians on an expanded set of patients
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