The Big Vitamin D Mistake

Papadimitriou, Dimitrios T. The Korean Society for Preventive Medicine 2017 Journal of Preventive Medicine and Public Health Vol.50 No.4

Since 2006, type 1 diabetes in Finland has plateaued and then decreased after the authorities' decision to fortify dietary milk products with cholecalciferol. The role of vitamin D in innate and adaptive immunity is critical. A statistical error in the estimation of the recommended dietary allowance (RDA) for vitamin D was recently discovered; in a correct analysis of the data used by the Institute of Medicine, it was found that 8895 IU/d was needed for 97.5% of individuals to achieve values ${\geq}50nmol/L$. Another study confirmed that 6201 IU/d was needed to achieve 75 nmol/L and 9122 IU/d was needed to reach 100 nmol/L. The largest meta-analysis ever conducted of studies published between 1966 and 2013 showed that 25-hydroxyvitamin D levels <75 nmol/L may be too low for safety and associated with higher all-cause mortality, demolishing the previously presumed U-shape curve of mortality associated with vitamin D levels. Since all-disease mortality is reduced to 1.0 with serum vitamin D levels ${\geq}100nmol/L$, we call public health authorities to consider designating as the RDA at least three-fourths of the levels proposed by the Endocrine Society Expert Committee as safe upper tolerable daily intake doses. This could lead to a recommendation of 1000 IU for children <1 year on enriched formula and 1500 IU for breastfed children older than 6 months, 3000 IU for children >1 year of age, and around 8000 IU for young adults and thereafter. Actions are urgently needed to protect the global population from vitamin D deficiency.

Bayesian estimation of tension in bridge hangers using modal frequency measurements

Papadimitriou, Costas,Giakoumi, Konstantina,Argyris, Costas,Spyrou, Leonidas A.,Panetsos, Panagiotis Techno-Press 2016 Structural monitoring and maintenance Vol.3 No.4

The tension of an arch bridge hanger is estimated using a number of experimentally identified modal frequencies. The hanger is connected through metallic plates to the bridge deck and arch. Two different categories of model classes are considered to simulate the vibrations of the hanger: an analytical model based on the Euler-Bernoulli beam theory, and a high-fidelity finite element (FE) model. A Bayesian parameter estimation and model selection method is used to discriminate between models, select the best model, and estimate the hanger tension and its uncertainty. It is demonstrated that the end plate connections and boundary conditions of the hanger due to the flexibility of the deck/arch significantly affect the estimate of the axial load and its uncertainty. A fixed-end high fidelity FE model of the hanger underestimates the hanger tension by more than 20 compared to a baseline FE model with flexible supports. Simplified beam models can give fairly accurate results, close to the ones obtained from the high fidelity FE model with flexible support conditions, provided that the concept of equivalent length is introduced and/or end rotational springs are included to simulate the flexibility of the hanger ends. The effect of the number of experimentally identified modal frequencies on the estimates of the hanger tension and its uncertainty is investigated.

Theories, Strategies and Elements of Gamified MOOCs: A Systematic Literature Review

Alexandros Papadimitriou 한국경영정보학회 2024 Asia Pacific Journal of Information Systems Vol.34 No.1

A few years before, MOOCs appeared and developed at a rapid pace. Various MOOC methods, theories, strategies, elements, and techniques were used to improve distance education. In their development, their weaknesses like dropout, low participation, low completion rate, low engagement, and others have emerged that are addressed by recent studies including that of gamified and adaptive gamified MOOCs. This article presents the most important theories, strategies, and elements used in gamification and their usefulness and contribution to MOOCs, with the ultimate goal of proving rich information to researchers, application designers, and practitioners of gamified and adaptive gamified MOOCs.

Effect of resistance exercise training on Crohn’s disease patients

( Konstantinos Papadimitriou ) 대한장연구학회 2021 Intestinal Research Vol.19 No.3

Crohn’s disease (CD) is observed with increased levels of cytokines which cause inflammation in many parts of the digestive tract. Aerobic exercise contributes to the reduction of the intestine’s inflammation and increases the quality of life. Another type of exercise that shows research interest about its effects on CD symptoms is the resistance exercise (RE). The aim of the study was to review the influence of RE on CD patients. The study’s literature was collected from PubMed and Scholar databases. According to the results, the main phase of a RE training program must have a gradual increase of intensity (60%-80%) and resting periods of 15-30 seconds after each exercise, and 2-3 minutes between exercises. Also, CD patients who were in remission improved the muscle strength and quality of life via their participation in RE training program. However, the secretion of interleukin-6 in both CD and RE contributes in various physiological mechanisms setting a contradictory role in the effectiveness of RE at the disease’s inflammatory situation. So, the use of RE training in CD patients needs more research for safer participation. (Intest Res 2021;19:275-281)

Seismic and vibration tests for assessing the effectiveness of GFRP for retrofitting masonry structures

Costas Papadimitriou,Paul Michelis,Grigoris K. Karaiskos,Dimitra-Christina Papadioti,Clemente Fuggini 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.9 No.3

Full-scale shake table seismic experiments and low-amplitude vibration tests on a masonry building are carried out to assess its seismic performance as well as study the effectiveness of a new multifunctional textile material for retrofitting masonry structures against earthquakes. The un-reinforced and the retrofitted with glass fiber reinforced polymer (GFRP) strips masonry building was subjected to a series of earthquake excitations of increasing magnitude in order to progressively induce various small, moderate and severe levels of damage to the masonry walls. The performance of the original and retrofitted building states is evaluated. Changes in the dynamic characteristics (lowest four modal frequencies and damping ratios) of the building are used to assess and quantify the damage states of the masonry walls. For this, the dynamic modal characteristics of the structure states after each earthquake event were estimated by performing low-amplitude impulse hammer and sine-sweep forced vibration tests. Comparisons between the modal results calculated using traditional accelerometers and those using Fiber Bragg Grating (FBG) sensors embedded in the reinforcing textile were carried on to investigate the reliability and accuracy of FBG sensors in tracking the dynamic behaviour of the building. The retrofitting actions restored the stiffness characteristics of the reinforced masonry structure to the levels of the original undamaged un-reinforced structure. The results show that despite a similar dynamic behavior identified, corresponding to reduction of the modal frequencies, the unreinforced masonry building was severely damaged, while the reinforced masonry building was able to withstand, without visual damage, the induced strong seismic excitations. The applied GFRP reinforcement architecture for one storey buildings was experimentally proven reliable for the most severe earthquake accelerations. It was easily placed in a short time and it is a cost effective solution (covering only 20% of the external wall surfaces) when compared to the cost for full wall coverage by GFRPs.

GUIDELINES FOR BIOLOGICAL TREATMENT OF VEGETABLE OIL EXTRACTION WASTEWATERS

( E . K . Papadimitriou,I . E . Alexiou,T . Y . Chew,I . Chatijipavlidis,F . Flouri,C . Balis,E . I . Stentiford ) 한국물환경학회 1997 제6차 국제수질보전학회 아시아 태평양지역 학술회의 Vol.1 No.-

The Big Vitamin D Mistake

Dimitrios T. Papadimitriou 대한예방의학회 2017 Journal of Preventive Medicine and Public Health Vol.50 No.4

Since 2006, type 1 diabetes in Finland has plateaued and then decreased after the authorities’ decision to fortify dietary milk products with cholecalciferol. The role of vitamin D in innate and adaptive immunity is critical. A statistical error in the estimation of the recommended dietary allowance (RDA) for vitamin D was recently discovered; in a correct analysis of the data used by the Institute of Medicine, it was found that 8895 IU/d was needed for 97.5% of individuals to achieve values ≥50 nmol/L. Another study confirmed that 6201 IU/d was needed to achieve 75 nmol/L and 9122 IU/d was needed to reach 100 nmol/L. The largest meta-analysis ever conducted of studies published between 1966 and 2013 showed that 25-hydroxyvitamin D levels <75 nmol/L may be too low for safety and associated with higher all-cause mortality, demolishing the previously presumed U-shape curve of mortality associated with vitamin D levels. Since all-disease mortality is reduced to 1.0 with serum vitamin D levels ≥100 nmol/L, we call public health authorities to consider designating as the RDA at least three-fourths of the levels proposed by the Endocrine Society Expert Committee as safe upper tolerable daily intake doses. This could lead to a recommendation of 1000 IU for children <1 year on enriched formula and 1500 IU for breastfed children older than 6 months, 3000 IU for children >1 year of age, and around 8000 IU for young adults and thereafter. Actions are urgently needed to protect the global population from vitamin D deficiency.

Supersymmetry anomalies in N = 1 $$ \mathcal{N}=1 $$ conformal supergravity

Springer-Verlag 2019 Journal of high energy physics Vol.2019 No.4

Seismic and vibration tests for assessing the effectiveness of GFRP for retrofitting masonry structures

Michelis, Paul,Papadimitriou, Costas,Karaiskos, Grigoris K.,Papadioti, Dimitra-Christina,Fuggini, Clemente Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.9 No.3

Full-scale shake table seismic experiments and low-amplitude vibration tests on a masonry building are carried out to assess its seismic performance as well as study the effectiveness of a new multifunctional textile material for retrofitting masonry structures against earthquakes. The un-reinforced and the retrofitted with glass fiber reinforced polymer (GFRP) strips masonry building was subjected to a series of earthquake excitations of increasing magnitude in order to progressively induce various small, moderate and severe levels of damage to the masonry walls. The performance of the original and retrofitted building states is evaluated. Changes in the dynamic characteristics (lowest four modal frequencies and damping ratios) of the building are used to assess and quantify the damage states of the masonry walls. For this, the dynamic modal characteristics of the structure states after each earthquake event were estimated by performing low-amplitude impulse hammer and sine-sweep forced vibration tests. Comparisons between the modal results calculated using traditional accelerometers and those using Fiber Bragg Grating (FBG) sensors embedded in the reinforcing textile were carried on to investigate the reliability and accuracy of FBG sensors in tracking the dynamic behaviour of the building. The retrofitting actions restored the stiffness characteristics of the reinforced masonry structure to the levels of the original undamaged un-reinforced structure. The results show that despite a similar dynamic behavior identified, corresponding to reduction of the modal frequencies, the un-reinforced masonry building was severely damaged, while the reinforced masonry building was able to withstand, without visual damage, the induced strong seismic excitations. The applied GFRP reinforcement architecture for one storey buildings was experimentally proven reliable for the most severe earthquake accelerations. It was easily placed in a short time and it is a cost effective solution (covering only 20% of the external wall surfaces) when compared to the cost for full wall coverage by GFRPs.

A Novel Approach to Forecasting the Bulk Freight Market

Vangelis TSIOUMAS,Stratos PAPADIMITRIOU,Yiannis SMIRLIS,Shaher Zahran ZAHRAN 한국해운물류학회 2017 The Asian journal of shipping and Logistics Vol.33 No.1

The fast-paced and ever changing freight market compels maritime executives to use sound forecasting tools. This paper aims to enhance the forecasting accuracy of the Baltic Dry Index (BDI) by means of developing a multivariate Vector Autoregressive model with exogenous variables (VARX). The proposed model incorporates the Chinese steel production, the dry bulk fleet development and a new composite indicator, the Dry Bulk Economic Climate Index (DBECI). The predictive power of this approach is evaluated against a univariate ARIMA framework, which serves as a benchmark model. The selection of explanatory variables and the model specification are validated using a series of pertinent tests. The results demonstrate that the VARX model outperforms the ARIMA approach, suggesting that the selected independent variables can substantially improve the accuracy of BDI forecasts. The present study is of interest to maritime practitioners, as it provides useful insights into the direction of the freight market and allows them to make informed decisions.