234 research outputs found
Worldwide spreading of economic crisis
We model the spreading of a crisis by constructing a global economic network
and applying the Susceptible-Infected-Recovered (SIR) epidemic model with a
variable probability of infection. The probability of infection depends on the
strength of economic relations between the pair of countries, and the strength
of the target country. It is expected that a crisis which originates in a large
country, such as the USA, has the potential to spread globally, like the recent
crisis. Surprisingly we show that also countries with much lower GDP, such as
Belgium, are able to initiate a global crisis. Using the {\it k}-shell
decomposition method to quantify the spreading power (of a node), we obtain a
measure of ``centrality'' as a spreader of each country in the economic
network. We thus rank the different countries according to the shell they
belong to, and find the 12 most central countries. These countries are the most
likely to spread a crisis globally. Of these 12 only six are large economies,
while the other six are medium/small ones, a result that could not have been
otherwise anticipated. Furthermore, we use our model to predict the crisis
spreading potential of countries belonging to different shells according to the
crisis magnitude.Comment: 13 pages, 4 figures and Supplementary Materia
A k-shell decomposition method for weighted networks
We present a generalized method for calculating the k-shell structure of
weighted networks. The method takes into account both the weight and the degree
of a network, in such a way that in the absence of weights we resume the shell
structure obtained by the classic k-shell decomposition. In the presence of
weights, we show that the method is able to partition the network in a more
refined way, without the need of any arbitrary threshold on the weight values.
Furthermore, by simulating spreading processes using the
susceptible-infectious-recovered model in four different weighted real-world
networks, we show that the weighted k-shell decomposition method ranks the
nodes more accurately, by placing nodes with higher spreading potential into
shells closer to the core. In addition, we demonstrate our new method on a real
economic network and show that the core calculated using the weighted k-shell
method is more meaningful from an economic perspective when compared with the
unweighted one.Comment: 17 pages, 6 figure
The Role of Nano-Technology in Sustainable Construction: A Case Study of Using Nano Granite Waste Particles in Cement Mortar
Better understanding of the properties of cement-based materials, one of the most widely used building materials, at the nano-scale is crucial to improve its functionality in the built environment. This paper presents areas of using nano-materials in improving the characteristics of cement-based materials as well as introducing a new role of nano-technology together with waste management in enhancing the concept of sustainable construction. A case study on the use of nano-granite waste particles as a replacement of cement and fine aggregate in mortar production is presented. The research concluded that replacing 5% cement and 10% sand with nano-granite waste in the mortar mix increased the compressive strength of the green mortar by 41% compared to that of the control mix (CM). SEM images reinforced this result as the green mortar mix showed maximum density and minimum micro cracks and number of pores. A comparative study between the green mortar and traditional mortar was carried out using sustainability indicators to examine the environmental, social and economic implications. The environmental and social attributes showed a saving of 10% in the field of resource consumption, whereas savings in energy consumption and CO2 emissions reached 5%. The economic field showed saving of 6.5% indicating promising results in enhancing the sustainable construction industry
The Swiss Board Directors Network in 2009
We study the networks formed by the directors of the most important Swiss
boards and the boards themselves for the year 2009. The networks are obtained
by projection from the original bipartite graph. We highlight a number of
important statistical features of those networks such as degree distribution,
weight distribution, and several centrality measures as well as their
interrelationships. While similar statistics were already known for other board
systems, and are comparable here, we have extended the study with a careful
investigation of director and board centrality, a k-core analysis, and a
simulation of the speed of information propagation and its relationships with
the topological aspects of the network such as clustering and link weight and
betweenness. The overall picture that emerges is one in which the topological
structure of the Swiss board and director networks has evolved in such a way
that special actors and links between actors play a fundamental role in the
flow of information among distant parts of the network. This is shown in
particular by the centrality measures and by the simulation of a simple
epidemic process on the directors network.Comment: Submitted to The European Physical Journal
How big is too big? Critical Shocks for Systemic Failure Cascades
External or internal shocks may lead to the collapse of a system consisting
of many agents. If the shock hits only one agent initially and causes it to
fail, this can induce a cascade of failures among neighoring agents. Several
critical constellations determine whether this cascade remains finite or
reaches the size of the system, i.e. leads to systemic risk. We investigate the
critical parameters for such cascades in a simple model, where agents are
characterized by an individual threshold \theta_i determining their capacity to
handle a load \alpha\theta_i with 1-\alpha being their safety margin. If agents
fail, they redistribute their load equally to K neighboring agents in a regular
network. For three different threshold distributions P(\theta), we derive
analytical results for the size of the cascade, X(t), which is regarded as a
measure of systemic risk, and the time when it stops. We focus on two different
regimes, (i) EEE, an external extreme event where the size of the shock is of
the order of the total capacity of the network, and (ii) RIE, a random internal
event where the size of the shock is of the order of the capacity of an agent.
We find that even for large extreme events that exceed the capacity of the
network finite cascades are still possible, if a power-law threshold
distribution is assumed. On the other hand, even small random fluctuations may
lead to full cascades if critical conditions are met. Most importantly, we
demonstrate that the size of the "big" shock is not the problem, as the
systemic risk only varies slightly for changes of 10 to 50 percent of the
external shock. Systemic risk depends much more on ingredients such as the
network topology, the safety margin and the threshold distribution, which gives
hints on how to reduce systemic risk.Comment: 23 pages, 7 Figure
The association of fat and other macronutrients with breast cancer: a case-control study from Greece.
The Greek diet is characterized by a high total fat but low saturated fat intake. In a hospital-based case-control study of female breast cancer conducted in Athens (1989-91), 820 patients with confirmed cancer of the breast were compared with 795 orthopaedic patient controls and 753 hospital visitor controls, matched to the cases by age and interviewer. Diet was ascertained through a semiquantitative food frequency questionnaire; macronutrient intakes were estimated from the nutrient content of a selected typical portion size for each specified food item, summed for all items. Logistic regression was used to analyse the data, controlling for demographic and reproductive risk factors for breast cancer as well as for total energy intake and mutual confounding influences among nutrients. There was no significant or suggestive association of total protein, total fat, categories of fat or total carbohydrates with breast cancer risk. Thus, the mutually adjusted relative risk per quintile and (in parenthesis) 95% confidence interval were: for protein, 1.06 (0.94-1.20); saturated fat, 0.99 (0.89-1.11); monounsaturated fat, 0.97 (0.88-1.07), polyunsaturated fat, 1.05 (0.97-1.13); and total carbohydrates, 1.03 (0.94-1.12). In alternative analytical approaches only total protein appeared to be positively associated to the occurrence of breast cancer with some consistency, but the results were far from statistically significant. These findings do not support a role for fat or other energy-generating nutrients in the aetiology of breast cancer
CD24 expression does not affect dopamine neuronal survival in a mouse model of Parkinson's disease
Parkinson's disease (PD) is a progressive neurodegenerative condition that is characterised by the loss of specific populations of neurons in the brain. The mechanisms underlying this selective cell death are unknown but by using laser capture microdissection, the glycoprotein, CD24 has been identified as a potential marker of the populations of cells that are affected in PD. Using in situ hybridization and immunohistochemistry on sections of mouse brain, we confirmed that CD24 is robustly expressed by many of these subsets of cells. To determine if CD24 may have a functional role in PD, we modelled the dopamine cell loss of PD in Cd24 mutant mice using striatal delivery of the neurotoxin 6-OHDA. We found that Cd24 mutant mice have an anatomically normal dopamine system and that this glycoprotein does not modulate the lesion effects of 6-OHDA delivered into the striatum. We then undertook in situ hybridization studies on sections of human brain and found-as in the mouse brain-that CD24 is expressed by many of the subsets of the cells that are vulnerable in PD, but not those of the midbrain dopamine system. Finally, we sought to determine if CD24 is required for the neuroprotective effect of Glial cell-derived neurotrophic factor (GDNF) on the dopaminergic nigrostriatal pathway. Our results indicate that in the absence of CD24, there is a reduction in the protective effects of GDNF on the dopaminergic fibres in the striatum, but no difference in the survival of the cell bodies in the midbrain. While we found no obvious role for CD24 in the normal development and maintenance of the dopaminergic nigrostriatal system in mice, it may have a role in mediating the neuroprotective aspects of GDNF in this system.SRWS was funded by a Parkinson's UK Innovation grant (https://www.parkinsons.org.uk/); Cure Parkinsons's trust grant (https://www.cureparkinsons.org.uk/); and DDPDGENES (FP7-HEALTH #278871; http://cordis.europa.eu/project/rcn/101801_en.html). SH was also funded by DDPDGENES. TC & SG received no specific funding for this work (summer interns). JPS was funded by the Klinikum Mannheim gGmbH. RAB was funded by the NIHR Biomedical Research Centre and also receives funding from the UKRMP PSP hub
Problems of training international students to pass the final test exam during distance learning in medical universities
Abstract. The article shows problems of training the graduates-citizens of foreign countries to licensing integrated exam «Krok 2. Medicine», such as academic dishonesty of students, particularly, during online classes and remote diagnostic-training testing. Thus, remote diagnostic-training testing requires improvement of the methodology with the involvement of new information and communication technologies. The written diagnostic-training testing allowed to select students of high-risk group of not passing the licensing integrated exam «Krok 2. Medicine» and should be modified as a change in content on each testing
Characterization of a prenatally assessed de novo supernumerary minute ring chromosome 20 in a phenotypically normal male
<p>Abstract</p> <p>Background</p> <p>The heterogeneous group of small supernumerary marker chromosomes (sSMCs) presents serious counseling problems, especially if they are present de novo and diagnosed prenatally. The incidence has been estimated at 1 in 1000 prenatal samples. We present a case of mosaic sSMC diagnosed prenatally after amniocentesis. The sSMC was characterized by various molecular cytogenetic techniques and determined to be a r(20) chromosome. After genetic counseling, the parents decided to continue the pregnancy, and a boy with minor phenotypic variants was born after 39 weeks of pregnancy. The case is compared with four other cases of prenatally detected r(20) mosaicism.</p> <p>Results</p> <p>Here we describe a 3 months old male child with normal pre- and postnatal development and with a de novo ring supernumerary marker chromosome in amniocytes cultures. Using new fluorescence in situ hybridization (FISH) techniques, three distinguishable sSMCs (cryptic mosaicism), all derived from chromosome 20, were observed, including ring and minute chromosomes. This heterogeneity was impossible to detect by the conventional G-banding technique or conventional FISH technique that were used before the application of new FISH techniques (subcentromere-specific multicolor-FISH [subcenM-FISH]) and a probe, specific for the 20p12.2 band. The sSMC present in 25% of the cells was present as r(20)(::p12.2~12.3->q11.1::)<abbrgrp><abbr bid="B5">5</abbr></abbrgrp>/r(20;20)(::p12.1->q11.1::q11.1 >p12.1::)<abbrgrp><abbr bid="B2">2</abbr></abbrgrp>/min(20;20)(:p12.1->q11.1::q11.1->p12.1:)<abbrgrp><abbr bid="B1">1</abbr></abbrgrp>. The final karyotype was 47,XY,+r(20)[25%]/46,XY[75%].</p> <p>Conclusion</p> <p>We emphasize the importance of application of molecular cytogenetics in a prenatally diagnostic laboratory and description of more cases to enable a better genetic counseling and risk evaluation.</p
Credit Default Swaps Drawup Networks: Too Tied To Be Stable?
We analyse time series of CDS spreads for a set of major US and European
institutions on a pe- riod overlapping the recent financial crisis. We extend
the existing methodology of {\epsilon}-drawdowns to the one of joint
{\epsilon}-drawups, in order to estimate the conditional probabilities of
abrupt co-movements among spreads. We correct for randomness and for finite
size effects and we find significant prob- ability of joint drawups for certain
pairs of CDS. We also find significant probability of trend rein- forcement,
i.e. drawups in a given CDS followed by drawups in the same CDS. Finally, we
take the matrix of probability of joint drawups as an estimate of the network
of financial dependencies among institutions. We then carry out a network
analysis that provides insights into the role of systemically important
financial institutions.Comment: 15 pages, 5 figures, Supplementary informatio
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