Pareto optimality in multilayer network growth

We model the formation of multi-layer transportation networks as a multi-objective optimization process, where service providers compete for passengers, and the creation of routes is determined by a multi-objective cost function encoding a trade-off between efficiency and competition. The resulting model reproduces well real-world systems as diverse as airplane, train and bus networks, thus suggesting that such systems are indeed compatible with the proposed local optimization mechanisms. In the specific case of airline transportation systems, we show that the networks of routes operated by each company are placed very close to the theoretical Pareto front in the efficiency-competition plane, and that most of the largest carriers of a continent belong to the corresponding Pareto front. Our results shed light on the fundamental role played by multi-objective optimization principles in shaping the structure of large-scale multilayer transportation systems, and provide novel insights to service providers on the strategies for the smart selection of novel routes

Importance of the logistics performance index in international trade

This is an author's accepted manuscript of an article published in: “Applied Economics"; Volume 46, Issue 24, 2014; copyright Taylor & Francis; available online at: http://dx.doi.org/10.1080/00036846.2014.916394Logistics and transport increasingly play a pivotal role in international trade relations. The Logistics Performance Index (LPI) analyses differences between countries in terms of customs procedures, logistics costs and the quality of the infrastructure for overland and maritime transport. The aim of this article is to analyse the impact that each of these components has on trade in emerging economies using a gravity model. Furthermore, the study also attempts to detect possible advances in logistics in developing countries, which are grouped into five regions (Africa, South America, Far East, Middle East and Eastern Europe) by comparing the first LPI data published in 2007 with the most recent data, released in 2012. The results obtained reveal that improvements in any of the components of the LPI can lead to significant growth in a country’s trade flows. Specifically, LPI components are becoming increasingly important for international trade in many countries in Africa, South America and Eastern Europe.Martí Selva, ML.; Puertas Medina, RM.; García, L. (2014). Importance of the logistics performance index in international trade. Applied Economics. 46(24):2982-2992. doi:10.1080/00036846.2014.916394S298229924624Anderson, J. E., & van Wincoop, E. (2003). Gravity with Gravitas: A Solution to the Border Puzzle. American Economic Review, 93(1), 170-192. doi:10.1257/000282803321455214Bergstrand, J. H. (1985). The Gravity Equation in International Trade: Some Microeconomic Foundations and Empirical Evidence. The Review of Economics and Statistics, 67(3), 474. doi:10.2307/1925976Bergstrand, J. H. (1989). The Generalized Gravity Equation, Monopolistic Competition, and the Factor-Proportions Theory in International Trade. The Review of Economics and Statistics, 71(1), 143. doi:10.2307/1928061De Souza, R., Goh, M., Gupta, S.et al.(2007) An investigation into the measures affecting the integration of ASEAN’s priority sectors: phase 2: the case of logistics.REPSF ProjectNo. 06/001d Regional Economic Policy Support Facility, Association of Southeast Asian Nations, Manila.Heckman, J. J. (1979). Sample Selection Bias as a Specification Error. Econometrica, 47(1), 153. doi:10.2307/1912352Hoekman, B., & Nicita, A. (2010). Assessing the Doha Round: Market access, transactions costs and aid for trade facilitation. The Journal of International Trade & Economic Development, 19(1), 65-79. doi:10.1080/09638190903327476Iwanow, T., & Kirkpatrick, C. (2009). Trade Facilitation and Manufactured Exports: Is Africa Different? World Development, 37(6), 1039-1050. doi:10.1016/j.worlddev.2008.09.014Marti, L., Puertas, R., & García, L. (2012). Relevance of trade facilitation in emerging countries’ exports. The Journal of International Trade & Economic Development, 23(2), 202-222. doi:10.1080/09638199.2012.698639Martínez-Zarzoso, I., & Suárez-Burguet, C. (2000). The determinants of trade performance: influence of R&D on export flows. Applied Economics, 32(15), 1939-1946. doi:10.1080/00036840050155869Mustra, M. A. (2011) Logistic Performance Index, connecting to compete 2010, inUNESCAP Regional Forum and Chief Executives Meeting, The World Bank, Cairo

A universal model for mobility and migration patterns

Introduced in its contemporary form by George Kingsley Zipf in 1946, but with roots that go back to the work of Gaspard Monge in the 18th century, the gravity law is the prevailing framework to predict population movement, cargo shipping volume, inter-city phone calls, as well as bilateral trade flows between nations. Despite its widespread use, it relies on adjustable parameters that vary from region to region and suffers from known analytic inconsistencies. Here we introduce a stochastic process capturing local mobility decisions that helps us analytically derive commuting and mobility fluxes that require as input only information on the population distribution. The resulting radiation model predicts mobility patterns in good agreement with mobility and transport patterns observed in a wide range of phenomena, from long-term migration patterns to communication volume between different regions. Given its parameter-free nature, the model can be applied in areas where we lack previous mobility measurements, significantly improving the predictive accuracy of most of phenomena affected by mobility and transport processes.Comment: Main text and supplementary informatio

Enhanced user performance in an image gallery application with a mobile autostereoscopic touch display

In this study, we explored how stereoscopic depth affects performance and user experience in a mobile device with an autostereoscopic touch display. Participants conducted a visual search task with an image gallery application on three layouts with different depth ranges. The task completion times were recorded, and the participants were asked to rate their experiences. The results revealed that the image search times were facilitated by a mild depth effect and that too great a depth slowed search times and decreased user-experience ratings. © 2014 Elsevier B.V. All rights reserved

Revisiting left atrial volumetry by magnetic resonance imaging : the role of atrial shape and 3D angle between left ventricular and left atrial axis

Background Accurate measurement of left atrial (LA) volumes is needed in cardiac diagnostics and the follow up of heart and valvular diseases. Geometrical assumptions with 2D methods for LA volume estimation contribute to volume misestimation. In this study, we test agreement of 3D and 2D methods of LA volume detection and explore contribution of 3D LA axis orientation and LA shape in introducing error in 2D methods by cardiovascular magnetic resonance imaging. Methods 30 patients with prior first-ever ischemic stroke and no known heart disease, and 30 healthy controls were enrolled (age 18-49) in a substudy of a prospective case-control study. All study subjects underwent cardiac magnetic resonance imaging and were pooled for this methodological study. LA volumes were calculated by biplane area-length method from both conventional long axis (LAV(AL-LV)) and LA long axis-oriented images (LAV(AL-LA)) and were compared to 3D segmented LA volume (LAV(SAX)) to assess accuracy of volume detection. 3D orientation of LA long axis to left ventricular (LV) long axis and to four-chamber plane were determined, and LA 3D sphericity indices were calculated to assess sources of error in LA volume calculation. Shapiro-Wilk test, Bland-Altman analysis, intraclass and Pearson correlation, and Spearman's rho were used for statistical analysis. Results Biases were - 9.9 mL (- 12.5 to - 7.2) for LAV(AL-LV) and 13.4 (10.0-16.9) for LAV(AL-LA) [mean difference to LAV(SAX) (95% confidence interval)]. End-diastolic LA long axis 3D deviation angle to LV long axis was 28.3 +/- 6.2 degrees [mean +/- SD] and LA long axis 3D rotation angle to four-chamber plane 20.5 +/- 18.0 degrees. 3D orientation of LA axis or 3D sphericity were not correlated to error in LA volume calculation. Conclusions Calculated LA volume accuracy did not improve by using LA long axis-oriented images for volume calculation in comparison to conventional method. We present novel data on LA axis orientation and a novel metric of LA sphericity and conclude that these measures cannot be utilized to assess error in LA volume calculation.Peer reviewe

Validity of the Polar V800 heart rate monitor to measure RR intervals at rest

Purpose To assess the validity of RR intervals and short-term heart rate variability (HRV) data obtained from the Polar V800 heart rate monitor, in comparison to an electrocardiograph (ECG). Method Twenty participants completed an active orthostatic test using the V800 and ECG. An improved method for the identification and correction of RR intervals was employed prior to HRV analysis. Agreement of the data was assessed using intra-class correlation coefficients (ICC), Bland–Altman limits of agreement (LoA), and effect size (ES). Results A small number of errors were detected between ECG and Polar RR signal, with a combined error rate of 0.086 %. The RR intervals from ECG to V800 were significantly different, but with small ES for both supine corrected and standing corrected data (ES 0.999 for both supine and standing corrected intervals. When analysed with the same HRV software no significant differences were observed in any HRV parameters, for either supine or standing; the data displayed small bias and tight LoA, strong ICC (>0.99) and small ES (≤0.029). Conclusions The V800 improves over previous Polar models, with narrower LoA, stronger ICC and smaller ES for both the RR intervals and HRV parameters. The findings support the validity of the Polar V800 and its ability to produce RR interval recordings consistent with an ECG. In addition, HRV parameters derived from these recordings are also highly comparable

Breast cancer in neurofibromatosis type 1: overrepresentation of unfavourable prognostic factors

AbstractBACKGROUND: An increased breast cancer incidence and poor survival have been reported for women with neurofibromatosis 1 (NF1). To explain the poor survival, we aimed to link the histopathology and clinical characteristics of NF1-associated breast cancers.METHODS: The Finnish Cancer Registry and the Finnish NF Registry were cross-referenced to identify the NF1 patients with breast cancer. Archival NF1 breast cancer specimens were retrieved for histopathological typing and compared with matched controls.RESULTS: A total of 32 breast cancers were diagnosed in 1404 NF1 patients during the follow-up. Women with NF1 had an estimated lifetime risk of 18.0% for breast cancer, and this is nearly two-fold compared with that of the general Finnish female population (9.74%). The 26 successfully retrieved archival NF1 breast tumours were more often associated with unfavourable prognostic factors, such as oestrogen and progesterone receptor negativity and HER2 amplification. However, survival was worse in the NF1 group (P=0.053) even when compared with the control group matched for age, diagnosis year, gender and oestrogen receptor status. Scrutiny of The Cancer Genome Atlas data set showed that NF1 mutations and deletions were associated with similar characteristics in the breast cancers of the general population.CONCLUSIONS: These results emphasise the role of the NF1 gene in the pathogenesis of breast cancer and a need for active follow-up for breast cancer in women with NF1.</p

Elevated serum squalene and cholesterol synthesis markers in pregnant obese women with gestational diabetes mellitus

Peer reviewe