Statistical properties of online auctions

We characterize the statistical properties of a large number of online auctions run on eBay. Both stationary and dynamic properties, like distributions of prices, number of bids etc., as well as relations between these quantities are studied. The analysis of the data reveals surprisingly simple distributions and relations, typically of power-law form. Based on these findings we introduce a simple method to identify suspicious auctions that could be influenced by a form of fraud known as shill bidding. Furthermore the influence of bidding strategies is discussed. The results indicate that the observed behavior is related to a mixture of agents using a variety of strategies.Comment: 9 pages, 4 figures, to be published in Int. J. Mod. Phys.

Applying a novel combination of techniques to develop a predictive model for diabetes complications

© 2015 Sangi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Among the many related issues of diabetes management, its complications constitute the main part of the heavy burden of this disease. The aim of this paper is to develop a risk advisor model to predict the chances of diabetes complications according to the changes in risk factors. As the starting point, an inclusive list of (k) diabetes complications and (n) their correlated predisposing factors are derived from the existing endocrinology text books. A type of data meta-analysis has been done to extract and combine the numeric value of the relationships between these two. The whole n (risk factors) - k (complications) model was broken down into k different (n-1) relationships and these (n-1) dependencies were broken into n (1-1) models. Applying regression analysis (seven patterns) and artificial neural networks (ANN), we created models to show the (1-1) correspondence between factors and complications. Then all 1-1 models related to an individual complication were integrated using the naïve Bayes theorem. Finally, a Bayesian belief network was developed to show the influence of all risk factors and complications on each other. We assessed the predictive power of the 1-1 models by R2, F-ratio and adjusted R2 equations; sensitivity, specificity and positive predictive value were calculated to evaluate the final model using real patient data. The results suggest that the best fitted regression models outperform the predictive ability of an ANN model, as well as six other regression patterns for all 1-1 models

The effect of urban shading and canyon geometry on outdoor thermal comfort in hot climates: A case study of Ahvaz, Iran

© 2020 Elsevier Ltd This study investigated the role of urban geometry and urban shading in improving the pedestrians’ thermal comfort in hot climate of Ahvaz, Iran. Six urban canyons are selected in Ahvaz. To determine the outdoor thermal comfort range, micrometeorological measurements and questionnaire survey were conducted in July 2018. ENVI-met is used to investigate the role of urban geometry and urban shadings. To evaluate the outdoor thermal comfort, physiologically equivalent temperature (PET) is calculated using RayMan. Using the results of the field studies, the outdoor thermal comfort range in Ahvaz is obtained within 19.6 °C to 30.9 °C PET. Simulation results show that the closer the canyon orientation is to the north-south direction, the lower the air temperature (Ta) and mean radiant temperature (MRT) are. Also, by reducing the canyon aspect ratio, PET increases as well. Urban shadings decreased MRT and PET up to 34 °C and 17.6 °C, respectively. In contrast, shadings did not affect the air temperature, significantly. PET reduction caused by shadings is more notable in east-west canyons, as well as in wider canyons. MRT and PET in all cases are highly correlated to SVF. The observations showed no strong correlation between Ta, relative humidity, and wind speed, with SVF in all canyons

Decreased Na + /K + -ATPase activity and altered susceptibility to peroxidation and lipid composition in the erythrocytes of metabolic syndrome patients with coronary artery disease

Background: The increased generation of reactive oxygen species that occurs in the case of a metabolic syndrome (MetS) may be responsible for the increased oxidative injury to erythrocyte membranes in coronary artery disease (CAD). Therefore, we studied the effects of MetS on both indexes of oxidative damage and biochemical properties of erythrocyte membranes in CAD patients. Methods: We analyzed the markers of oxidative stress, Na + /K + -ATPase activity, total cholesterol content of erythrocyte membranes (CEM), and fatty acid compositions of the erythrocyte membrane in 82 patients with stable CAD and 39 non-CAD subjects. Results: The CAD patients had higher levels of CEM, membrane lipid peroxidation, erythrocyte superoxide dismutase (SOD) activity, and Na + /K + -ATPase activity compared with non-CAD subjects. The Na + /K + -ATPase activity was correlated negatively with membrane lipid peroxidation, and positively with the CEM. In CAD patients with MetS compared with those without MetS, we found that the membrane lipid peroxidation and CEM were increased, whereas the n-3 fatty acids content, SOD activity, Na + /K + -ATPase activity were decreased. Conclusion: These findings suggest an impairment of erythrocyte membrane biochemical properties in stable CAD patients as a consequence of oxidative injury that may contribute to the development of CAD. In addition, MetS may be related to increased oxidative injury to erythrocyte membranes. © 2019 S. Karger AG, Basel

Institutional Ownership and Investment Efficiency: Evidence from Iran

Investment efficiency shows how well a company invests its assets. Although institutional shareholders play undeniable roles in companies, it is not clear whether they are able to monitor managers and make investment decisions or not. This study gives answers to stakeholders, ad-dresses concerns about the effect of the owners on investment efficiency, and aims to add to the literature on emerging markets by investigating the relationship in Iran, a different environment from developed ones. Based on monitoring power, the shareholders are divided into two types: active and passive ones. Investment problems are classified into two types: over- and un-der-investment problems. The sample consists of 101 firms listed on the Tehran Stock Exchange between 2010 and 2016. Some regression models are used. The results illustrated that institutional owners have a positive effect on investment efficiency and decrease both over- and un-der-investment problems and so, the efficient monitoring school is approved. Additionally, active ones are positively correlated with investment efficiency and decrease both investment ineffi-ciency problems. Institutional ownership is the cause of investment efficiency, not the reverse. Based on findings, in emerging markets like Iran’s market, investors are recommended to give notice to the level of active ownership in firms; ownership structure is a good sign of efficiency

Positive effect of low dose vitamin D supplementation on growth of fetal bones: A randomized prospective study

The effect of vitamin D supplementation on growth of fetal bones during pregnancy is unclear. The aim of this study was to assess the effect of low dose vitamin D supplementation during pregnancy on bony anthropometric aspects of the fetus. In this prospective randomized trial, 140 patients were divided into two equally matched groups according to age, 25(OH)D level, exercise, and dietary intake. Then 1000 IU per day vitamin D supplement was given to the intervention group while the control group received placebo. Then crown-rump length (CRL) and femur length (FL) during the first trimester and humerus and femur lengths as well as their proximal metaphyseal diameter (PMD), midshaft diameter (MSD) and distal metaphyseal diameter (DMD) in the second and third trimester were measured using ultrasonography technique. Finally, no significant difference was observed for CRL (p = 0.93). Although FL was not statistically significant in the first trimester (p = 0.54), its measurement in the intervention group and the control group in the second (28.87 ± 2.14 vs. 26.89 ± 2.08; p ≤0.001) and the third (65.31 ± 2.17 vs. 62.85 ± 1.94; p ≤0.001) trimesters was significantly different. Femoral PMD, MSD, and DMD measurement increased more in the intervention group in comparison with the control group with P values <0.05. HL measurement in the intervention group and the control group in the second (28.62 ± 1.94 vs. 27.23 ± 2.08; p ≤0.001) and the third (61.29 ± 2.84 vs. 59.85 ± 1.79; p ≤0.001) trimesters revealed significant differences. Humeral PMD, MSD, and DMD measurement increased in the intervention group in comparison with the control group with P values <0.001 for all. It is suggested to prescribe low dose vitamin D (1000 IU per day) from early pregnancy with possible increment in length and diameter of femur and humerus bones of the fetus

Human factors for dementia: Evidence based design

Designing care environments for people living with dementia is a complex challenge as the key stakeholder may have difficulty communicating their capabilities, limitations and preferences. This paper describes the use of evidence-based design personas in a multi-disciplinary team with architects and chartered human factors specialists. Four individual personas (Alison, Barry, Christine and David) and a couple persona (Chris and Sally) were used to bring the voices of the people living with different stages of dementia to the design process. Their changing/fluctuating symptoms were communicated in two formats (wheel and matrix) within an inclusive design process to adapt a Victorian semi-detached house. The demonstrator house presents evidence based design, adaptation and support solutions to support people living with dementia to age well at home