94 results on '"Christou, Georgios"'
Search Results
2. Unraveling the role of resistin, retinol-binding protein 4 and adiponectin produced by epicardial adipose tissue in cardiac structure and function: evidence of a paracrine effect
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Christou, Georgios A., Andriopoulou, Christina E., Liakopoulou, Alexandra, Tsape, Eirini, Apostolakis, Efstratios, Tselepis, Alexandros D., Konstandi, Maria, Frühbeck, Gema, and Kiortsis, Dimitrios N.
- Published
- 2023
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- View/download PDF
3. Multi-span composite girders with composite dowels – Experimental investigations and design approach to account for the beneficial effect of shear force redistribution along the composite interface
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Christou, Georgios, Hegger, Josef, and Classen, Martin
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- 2023
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4. The effect of concrete fatigue on the cyclic behaviour of composite dowels - derivation of a design approach based on experimental findings
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Christou, Georgios, Schmidt, Christopher, Hegger, Josef, and Classen, Martin
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- 2022
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5. Effect of Body Weight on Glycaemic Indices in People with Type 1 Diabetes Using Continuous Glucose Monitoring.
- Author
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Christou, Maria A., Christou, Panagiota A., Katsarou, Daphne N., Georga, Eleni I., Kyriakopoulos, Christos, Markozannes, Georgios, Christou, Georgios A., Fotiadis, Dimitrios I., and Tigas, Stelios
- Subjects
CONTINUOUS glucose monitoring ,GLYCEMIC index ,BODY mass index ,BODY weight ,TYPE 1 diabetes - Abstract
Background/Objectives: Obesity and overweight have become increasingly prevalent in different populations of people with type 1 diabetes (PwT1D). This study aimed to assess the effect of body weight on glycaemic indices in PwT1D. Methods: Adult PwT1D using continuous glucose monitoring (CGM) and followed up at a regional academic diabetes centre were included. Body weight, body mass index (BMI), waist circumference, glycated haemoglobin (HbA1c), and standard CGM glycaemic indices were recorded. Glycaemic indices were compared according to BMI, and correlation and linear regression analysis were performed to estimate the association between measures of adiposity and glycaemic indices. Results: A total of 73 PwT1D were included (48% normal weight, 33% overweight, and 19% obese). HbA1c was 7.2% (5.6–10), glucose management indicator (GMI) 6.9% (5.7–8.9), coefficient of variation (CV) for glucose 39.5% ± 6.4, mean glucose 148 (101–235) mg/dL, TIR (time in range, glucose 70–180 mg/dL) 66% (25–94), TBR
70 (time below range, 54–69 mg/dL) 4% (0–16), TBR54 (<54 mg/dL) 1% (0–11), TAR180 (time above range, 181–250 mg/dL) 20% ± 7, and TAR250 (>250 mg/dL) 6% (0–40). Glycaemic indices and achievement (%) of optimal glycaemic targets were similar between normal weight, overweight, and obese patients. BMI was associated negatively with GMI, mean glucose, TAR180 , and TAR250 and positively with TIR; waist circumference was negatively associated with TAR250 . Conclusions: CGM-derived glycaemic indices were similar in overweight/obese and normal weight PwT1D. Body weight and BMI were positively associated with better glycaemic control. PwT1D should receive appropriate ongoing support to achieve optimal glycaemic targets whilst maintaining a healthy body weight. [ABSTRACT FROM AUTHOR]- Published
- 2024
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6. Pretreatment antimüllerian hormone levels and outcomes of ovarian stimulation with gonadotropins/intrauterine insemination cycles
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Vagios, Stylianos, Hsu, Jennifer Y., Sacha, Caitlin R., Dimitriadis, Irene, Christou, Georgios, James, Kaitlyn E., Bormann, Charles L., and Souter, Irene
- Published
- 2021
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7. Physiological Changes in QRS Fragmentation in Athletes and Nonathletes without Cardiac Disease.
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Christou, Georgios A., Christou, Maria A., Christou, Konstantinos A., Christodoulou, Dimitrios K., and Kiortsis, Dimitrios N.
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ENDURANCE athletes , *BODY surface area , *BODY mass index , *SUPINE position , *ATHLETES - Abstract
Background/Objectives: QRS fragmentation has not been linked with increased mortality in individuals without known cardiac disease. We aimed to investigate the physiological determinants of QRS fragmentation in individuals without cardiac disease. Methods: Study participants were 163 (54 athletes, 109 nonathletes) asymptomatic individuals with QRS fragmentation but without cardiac disease. QRS fragmentation was assessed in the supine position after deep inspiration or standing up and during exercise. The changes in QRS fragmentation were evaluated over a median follow-up period of 2.3 (0.8–4.9) years. Results: The most common lead with QRS fragmentation was III (63.0% in athletes, 61.5% in nonathletes), immediately followed by V1 (50.0%) and aVF (42.6%) in athletes and aVF (55.0%) in nonathletes. QRS fragmentation in V1 was more frequent in athletes compared to nonathletes (p < 0.001). Among athletes, the presence of QRS fragmentation in V1 could be independently predicted by increased RVOTproxi (right ventricular outflow tract proximal diameter indexed to body surface area) (p < 0.001). Among individuals with QRS fragmentation in V1, deep inspiration resulted in disappearance of QRS fragmentation more frequently in nonathletes compared to athletes (100% vs. 20%, p = 0.003). Deep inspiration resulted in disappearance of QRS fragmentation in aVF (p < 0.001). The presence of QRS fragmentation in II or aVF was associated with increased body mass index (BMI) (p = 0.003). Among athletes without QRS fragmentation in V1 at baseline, the appearance of QRS fragmentation in V1 at the end of follow-up was associated with greater training age (p = 0.034). Among individuals with QRS fragmentation in aVF at baseline, the disappearance of QRS fragmentation in aVF at the end of follow-up was associated with greater reduction in BMI (p = 0.008). Conclusions: The characteristic feature of QRS fragmentation in athletes was the presence of QRS fragmentation in V1, which was associated with RVOTproxi. The persistence of QRS fragmentation in V1 after deep inspiration could serve as a specific marker of exercise-training-related cardiac adaptation. The presence of QRS fragmentation in the leads of the frontal plane was influenced by BMI and respiration phase. [ABSTRACT FROM AUTHOR]
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- 2024
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8. Fatigue of clothoid shaped rib shear connectors
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Christou, Georgios, Hegger, Josef, and Classen, Martin
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- 2020
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9. The regulation of serum resistin levels in metabolically healthy and unhealthy obese individuals
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Christou, Konstantinos A., Christou, Georgios A., Karamoutsios, Achilleas, Vartholomatos, Georgios, Gartzonika, Konstantina, Tsatsoulis, Agathocles, and Tigas, Stelios
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- 2020
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10. HRI usability evaluation of interaction modes for a teleoperated agricultural robotic sprayer
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Adamides, George, Katsanos, Christos, Parmet, Yisrael, Christou, Georgios, Xenos, Michalis, Hadzilacos, Thanasis, and Edan, Yael
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- 2017
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11. Advanced demand data collection technologies for multi modal strategic modelling
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Kelen, Csaba, Vilarino, Pablo, and Christou, Georgios
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- 2017
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12. Pathophysiological mechanisms of noncardiac syncope in athletes
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Christou, Georgios A., Kouidi, Evangelia J., Anifanti, Maria A., Sotiriou, Panagiota G., Koutlianos, Nikolaos A., and Deligiannis, Asterios P.
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- 2016
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13. Serum fetuin-A levels are associated with serum triglycerides before and 6 months after bariatric surgery
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Verras, Christos G., Christou, Georgios A., Simos, Yannis V., Ayiomamitis, George D., Melidonis, Andreas J., and Kiortsis, Dimitrios N.
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- 2017
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14. The interplay between immersion and appeal in video games
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Christou, Georgios
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- 2014
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15. Can Noncardiac Syncope Occur during Exercise?
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Christou, Georgios A., Christou, Konstantinos A., Christou, Evangelos A., and Kiortsis, Dimitrios N.
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- 2017
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16. Effects of Hypoglycemia on Cardiovascular Function in Patients with Diabetes.
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Christou, Maria A., Christou, Panagiota A., Kyriakopoulos, Christos, Christou, Georgios A., and Tigas, Stelios
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HYPOGLYCEMIA ,PEOPLE with diabetes ,TYPE 1 diabetes ,TYPE 2 diabetes ,CARDIOVASCULAR diseases ,HYPERGLYCEMIA ,HEART ,ARRHYTHMIA ,MYOCARDIUM - Abstract
Hypoglycemia is common in patients with type 1 and type 2 diabetes (T1D, T2D), treated with insulin or sulfonylureas, and has multiple short- and long-term clinical implications. Whether acute or recurrent, hypoglycemia significantly affects the cardiovascular system with the potential to cause cardiovascular dysfunction. Several pathophysiological mechanisms have been proposed linking hypoglycemia to increased cardiovascular risk, including hemodynamic changes, myocardial ischemia, abnormal cardiac repolarization, cardiac arrhythmias, prothrombotic and proinflammatory effects, and induction of oxidative stress. Hypoglycemia-induced changes can promote the development of endothelial dysfunction, which is an early marker of atherosclerosis. Although data from clinical trials and real-world studies suggest an association between hypoglycemia and cardiovascular events in patients with diabetes, it remains uncertain whether this association is causal. New therapeutic agents for patients with T2D do not cause hypoglycemia and have cardioprotective benefits, whereas increasing the use of new technologies, such as continuous glucose monitoring devices and insulin pumps, has the potential to reduce hypoglycemia and its adverse cardiovascular outcomes in patients with T1D. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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17. The relationship between retinol-binding protein 4 and apolipoprotein B-containing lipoproteins is attenuated in patients with very high serum triglycerides: A pilot study
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Christou, Georgios A., Tellis, Constantinos C., Elisaf, Moses S., Tselepis, Alexandras D., and Kiortsis, Dimitrios N.
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- 2016
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18. The Associations of Dietary Vitamin K Intake and Circulating Vitamin 25(OH)D with Serum Lipoprotein Levels: The Vitamin Deficiency Matters.
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Varsamis, Nikolaos, Christou, Georgios A, Derdemezis, Christos, Tselepis, Alexandros, and Kiortsis, Dimitrios
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VITAMIN deficiency , *VITAMIN K , *VITAMIN K2 , *VITAMIN D deficiency , *VITAMINS , *BLOOD lipoproteins , *HIGH density lipoproteins , *HDL cholesterol - Abstract
A synergistic interplay between vitamins K and D appears to exist. We aimed to investigate for the first time whether the associations of dietary vitamin K intake and circulating 25(OH)D with serum lipoprotein levels are influenced by the existence of deficiency of either or both vitamins K and D. Sixty individuals [24 males, 36(18–79) years old] were examined. Vitamin deficiency of K1 and D were defined as vitamin K1 intake/body weight (BW)<1.00 μg/kg/day and circulating 25(OH)D<20 ng/ml, respectively. In individuals with vitamin K1 deficiency, the vitamin K1 intake/BW correlated positively with high density lipoprotein-cholesterol (HDL-C) (r=0.509, p=0.008) and negatively with serum triglycerides (TG) (r=–0.638, p=0.001), whereas circulating 25(OH)D correlated negatively with TG (r=–0.609, p=0.001). In individuals with vitamin D deficiency, the vitamin K1 intake/BW correlated positively with HDL-C (r=0.533, p=0.001) and negatively with TG (r=–0.421, p=0.009), while circulating 25(OH)D correlated negatively with TG (r=–0.458, p=0.004). The above-mentioned associations of vitamin K1 intake/BW and circulating 25(OH)D with serum lipoproteins were not detected in individuals without vitamin K1 deficiency or the ones without vitamin D deficiency. The vitamin K2 intake/BW correlated negatively with low density lipoprotein-cholesterol (LDL-C) (r=–0.404, p=0.001). In conclusion, the associations of vitamin K1 intake with TG and HDL-C and of circulating 25(OH)D with TG were more pronounced in individuals with deficiency of either or both vitamins K1 and D. Increased dietary vitamin K2 intake was associated with decreased LDL-C. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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19. DEVELOPMENT OF A CONSISTENT DESIGN CONCEPT FOR COMPOSITE DOWELS.
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Broschart, Yannick, Kurz, Wolfgang, Wolters, Kevin, Christou, Georgios, Feldmann, Markus, Hegger, Josef, and Claßen, Martin
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TECHNICAL specifications - Abstract
Composite dowels are an economically and technically reasonable alternative to the conventional shear connectors, the headed studs. However, their competitiveness is limited by the fact that they are only approved nationally and for a limited period of time, whereas headed studs are firmly anchored in European regulations. Numerous investigations, performed on a national and international level for decades, were necessary in order to enable an integration of composite dowels into the European standards. This paper summarizes the extensive investigations on the influence of cracked concrete, of tensile and combined shear‐tensile loads as well as of composite dowel positions close to the surface on the load‐bearing behaviour of composite dowels. Based on these and former investigations, a consistent design concept for composite dowels was developed, which will also be presented within this paper and shall form the basis for the introduction into European standardization. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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20. PROBABILISTIC DESIGN OF COMPOSITE GIRDERS CONSIDERING THE DEGRADATION OF THE SHEAR CONNECTION AND THE REDISTRIBUTION OF FORCES.
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Wolters, Kevin, Christou, Georgios, and Feldmann, Markus
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COMPOSITE construction ,GIRDERS ,FATIGUE limit ,MONTE Carlo method ,MATERIAL fatigue ,CRACK propagation (Fracture mechanics) - Abstract
Fatigue design of composite girders and in particular shear connectors according to Eurocode 4 is based on fatigue strength curves. Therefore, the lifetime of a girder can be limited by failure of a critical shear connector. The failure probability of a component is thus determined by the failure probability of one shear stud or composite dowel, although a composite girder is an internally highly statically indeterminate system with the possibility of redistributing forces in the shear connection. This paper outlines the positive effects on the lifetime of a girder by considering crack propagation and residual capacity of shear connectors with cracks as well as redistributing forces towards less stressed and damaged connectors. The failure probability of a girder is determined by a Monte Carlo simulation using a lamella model with incremental calculation of the degradation of the shear connection. The results show the economic potential of a future global safety concept for composite girders especially with composite dowels. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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21. A novel strategy for evaluating tilt test in athletes with syncope
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Christou, Georgios A, Kouidi, Evangelia J, Anifanti, Maria A, Sotiriou, Panagiota G, and Deligiannis, Asterios P
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- 2016
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22. Prolonged QT Interval in Athletes: Distinguishing between Pathology and Physiology.
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Christou, Georgios A., Vlahos, Antonios P., Christou, Konstantinos A., Mantzoukas, Stefanos, Drougias, Chronis A., and Christodoulou, Dimitrios K.
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MALE athletes , *LONG QT syndrome , *EXERCISE tests , *WOMEN athletes , *PHYSIOLOGY , *ATHLETES - Abstract
Background: The physiological QT prolongation in athletes is expected to widen the gray zone between physiology and pathology of QT, increasing the diagnostic challenges encountered in athletes with QT prolongation. Summary: According to international recommendations for electrocardiogram in athletes, further evaluation for long QT syndrome (LQTS) is indicated in male athletes with corrected QT (QTc) ≥470 ms and in female athletes with QTc ≥480 ms. Apart from QTc ≥500 ms, diagnostic challenges arise in borderline cases of QTc prolongation, where further clinical investigations are needed to be performed to clarify whether LQTS exists. Clinical diagnostic investigations, including exercise testing, are more readily available, convenient, and easily interpretable, as well as less costly than genetic testing for LQTS. The main findings on exercise testing that are suggestive of LQTS can be the paradoxical prolongation of QTc during exercise and QTc ≥480 ms at fourth min of recovery. Key Messages: Exercise testing appears to have an important role in the diagnostic evaluation of athletes with prolonged QT interval, when genetic testing is not available. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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23. A comparison between experienced and inexperienced video game players’ perceptions
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Christou, Georgios
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- 2013
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24. Impact of a 246 Km ultra-marathon running race on heart: Insights from advanced deformation analysis.
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Pagourelias, Efstathios D., Christou, Georgios A., Sotiriou, Panagiota G., Anifanti, Maria A., Koutlianos, Nikolaos A., Tsironi, Maria P., Christou, Konstantinos A., Vassilikos, Vasileios P., Deligiannis, Asterios P., and Kouidi, Evangelia J.
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ECHOCARDIOGRAPHY , *LEFT heart ventricle , *CARDIOVASCULAR system physiology , *LONG-distance running , *RIGHT heart ventricle , *PHYSICAL fitness , *EXERCISE physiology , *HEART ventricles , *HEART rate monitoring , *HEART atrium , *HEART physiology , *EXTREME sports - Abstract
Although previous studies suggest that prolonged intense exercise such as marathon running transitorily alters cardiac function, there is little information regarding ultramarathon races. Aim of this study was to investigate the acute impact of ultra-endurance exercise (UEE) on heart, applying advanced strain imaging. Echocardiographic assessment was performed the day before and at the finish line of "Spartathlon": A 246 Km ultra-marathon running race. 2D speckle-tracking echocardiography was performed in all four chambers, evaluating longitudinal strain (LS) for both ventricles and atria. Peak strain values and temporal parameters adjusted for heart rate were extracted from the derived curves. Out of 60 participants initially screened, 27 athletes (19 male, age 45 ± 7 years) finished the race in 33:34:27(28:50:38-35:07:07) hours. Absolute values of right (RV) and left ventricular (LV) LS (RVLS −22.9 ± 3.6 pre- to −21.2 ± 3.0% post-, p=0.04 and LVLS −20.9 ± 2.3 pre- to −18.8 ± 2.0 post-, p=0.009) slightly decreased post-race, whereas atrial strain did not change. RV and LV LS decrease was caused mainly by strain impairment of basal regions with apical preservation. Inter-chamber relationships assessed through RV/LV, LV/LA, RV/RA and RA/LA peak values' ratios remained unchanged from pre to post-race. Finally, UEE caused an extension of the systolic phase of cardiac cycle with concomitant diastole reduction (p<0.001 for all strain curves). Conclusively, ventricular LS strain as well as effective diastolic period slightly decreased, whereas atrial strain and inter-chamber relationships remained unchanged after running a 246-km-ultra-marathon race. These changes may be attributed to concomitant pre- and afterload alterations following UEE. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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25. High density lipoprotein is positively correlated with the changes in circulating total adiponectin and high molecular weight adiponectin during dietary and fenofibrate treatment
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Christou, Georgios A., Tellis, Constantinos C., Elisaf, Moses S., Tselepis, Alexandros D., and Kiortsis, Dimitrios N.
- Published
- 2012
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26. Eccentric punching tests on column bases ‐ Influence of column geometry.
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Ungermann, Jan, Schmidt, Philipp, Christou, Georgios, and Hegger, Josef
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COMPOSITE columns ,ECCENTRIC loads ,LOAD factor design ,COLUMNS ,SHEARING force ,STRESS concentration ,SHEAR strength - Abstract
Experimental investigations on centrically loaded column bases provide the basis for current punching shear design provisions. However, this symmetric loading condition represents an exception in daily engineering practice since usually load eccentricities occur leading to uneven shear stress distributions along the control perimeter. To account for this effect, design approaches define different factors to either increase the acting shear force or to decrease the punching shear resistance in design. New punching test results of 14 eccentrically loaded and four centrically loaded column bases now allow the evaluation of design approaches depending on different geometric boundary conditions. In this new test series, the load eccentricities were systematically graded to analyze their influence on the punching behavior. Strain measurements in the multiaxial compression zone of the concrete in the column‐footing connection reveal new insights on the punching failure of column bases. As a result, a correlation between tangential concrete strains and the reduction of punching shear strength can be recognized for increasing load eccentricities. The comparison of experimentally determined load increase factors with the design results according to Eurocode 2, Model Code 2010 and the stable version of the next generation of Eurocode 2 reveals optimization potential for deriving more advanced design provisions in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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27. The role of cardiac computed tomography in pre-participation screening of mature athletes.
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Christou, Georgios A., Deligiannis, Asterios P., and Kouidi, Evangelia J.
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ATHLETES - Abstract
The overwhelming majority of sports-related sudden cardiac deaths in mature athletes is attributed to coronary artery disease (CAD). Coronary plaques of mature athletes appear to be more calcified compared to sedentary individuals and thus may be more stable and less likely to be associated with an acute coronary event. Cardiac computed tomography (CT), including unenhanced CT for coronary artery calcium scoring (CACS) and contrast-enhanced coronary CT angiography, is characterized by very high negative predictive value to rule out CAD. Cardiac CT has been shown to have additional diagnostic value for detection of CAD in athletes over and above exercise electrocardiogram. Moreover, measurement of CACS possibly enables a more precise cardiovascular risk stratification of mature athletes. The main advantage of cardiac CT is its noninvasive nature. Although cardiac CT appears to increase the overall cost of cardiac examinations, this additional cost is much lower than the cost of unnecessary invasive coronary angiographies that would be performed in case of false positive results of exercise electrocardiograms. Radiation exposure may not be a major concern for the application of this modality to pre-participation screening of athletes, since recent technical advancements have resulted in low radiation dose of cardiac CT. Highlights Coronary computed tomography angiography can be used in pre-participation screening of mature athletes to increase the negative predictive value for excluding coronary artery disease. The identification of coronary artery calcium score = 0 in an athlete can improve risk stratification, since this athlete can be reasonably managed as an individual with low cardiovascular risk. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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28. Combined Shear-Tension Loading of Composite Dowels in Cracked Concrete—Experimental Investigations and Design.
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Christou, Georgios, Wolters, Kevin, Ungermann, Jan, Classen, Martin, and Hegger, Josef
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CONCRETE fatigue ,AIR ducts ,EXPERIMENTAL design ,CONCRETE ,SHEARING force ,GIRDERS ,COMPOSITE construction - Abstract
The importance of slim decks has led engineers to the exploration of high-strength materials and also of innovative shallow shear connectors, such as composite dowels in the case of composite constructions. Minimizing the overall slab depth often leads to composite girders being weakened by means of web openings that are necessary for installations such as ventilation ducts. Depending on the geometrical and loading conditions, some of the shear connectors are subjected to a combination of tensile and shear forces. However, the load-bearing behaviour of these connectors has only been rudimentarily investigated in the case of shear-tensile interaction. In addition, the load-bearing capacity of composite dowels under combined tensile and shear forces has not been investigated in cracked concrete. Earlier investigations under pure shear and pure tensile loading indicate a dependence of the connectors' load-bearing behaviour on the crack width, so that under combined loading, a similar influence is expected. In this paper, experimental investigations on composite dowels in transversely cracked concrete under systematically varied shear-tension loading combinations are presented. Hereby, predefined crack widths and patterns were considered using a special test rig. Finally, a design approach for concrete failure of composite dowels under shear-tension loading is proposed based on the test results. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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29. The Changes in Plasma Retinol-Binding Protein 4 Levels are Associated With Those of the Apolipoprotein B-Containing Lipoproteins During Dietary and Drug Treatment
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Christou, Georgios A., Tellis, Constantinos C., Elisaf, Moses S., Tselepis, Alexandros D., and Kiortsis, Dimitrios N.
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- 2012
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30. Arterial Function after a 246 km Ultra-marathon Running Race.
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Koutlianos, Nikolaos, Sotiriou, Panagiota, Christou, Georgios, Pagourelias, Efstathios, Anifanti, Maria, Christou, Konstantinos, Tsironi, Maria, Andriopoulos, Panagiotis, Kouidi, Evangelia, and Deligiannis, Asterios
- Subjects
CAROTID artery ,CARDIOVASCULAR system physiology ,CAROTID intima-media thickness ,CONFIDENCE intervals ,ULTRASONIC imaging ,LONG-distance running ,EXERCISE physiology ,T-test (Statistics) ,DESCRIPTIVE statistics ,DATA analysis software ,EXTREME sports - Abstract
There is little research about the effects of ultra-endurance exercise on arterial morphological and functional properties. The aim was to assess the acute changes of the carotid-femoral pulse wave velocity and carotid doppler-derived parameters following an ultra-marathon race as well as the intima-media thickness of the carotid artery in ultra-marathon runners. Twenty athletes were examined at baseline and within 10 mins after a 246 km running race. Measurements included carotid-femoral pulse wave velocity, peak-systolic and end-diastolic velocities of carotid artery blood flow, pulsatility and resistivity indices and blood biochemical parameters. The intima-media thickness of the right and left carotid artery was measured before the race. Arterial stiffness and carotid artery intima media thickness at rest remained within known normal limits. The ultra-marathon race significantly increased carotid-femoral pulse wave velocity by 22.6% and pulsatility index by 10.2%. There was a decrease in body weight by 3.35% and an increase of all biochemical markers of muscle damage after the race. Additionally, C-reactive protein was correlated with both pulsatility and resistivity indices post-race. This study shows that immediately after a 246 km ultra-marathon running race, acute increase of arterial stiffness and vascular resistance were evident. The carotid artery thickness of ultra-marathon runners was within normal range. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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31. Exploring the Anthropometric, Cardiorespiratory, and Haematological Determinants of Marathon Performance.
- Author
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Christou, Georgios A., Pagourelias, Efstathios D., Deligiannis, Asterios P., and Kouidi, Evangelia J.
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TREADMILL exercise tests ,EXERCISE tests ,LONG-distance running ,ENDURANCE athletes ,ECHOCARDIOGRAPHY ,BODY surface area - Abstract
Aim: We aimed to investigate the main anthropometric, cardiorespiratory and haematological factors that can determine marathon race performance in marathon runners. Methods: Forty-five marathon runners (36 males, age: 42 ± 10 years) were examined during the training period for a marathon race. Assessment of training characteristics, anthropometric measurements, including height, body weight (n = 45) and body fat percentage (BF%) (n = 33), echocardiographic study (n = 45), cardiopulmonary exercise testing using treadmill ergometer (n = 33) and blood test (n = 24) were performed. We evaluated the relationships of these measurements with the personal best marathon race time (MRT) within a time frame of one year before or after the evaluation of each athlete. Results: The training age regarding long-distance running was 9 ± 7 years. Training volume was 70 (50–175) km/week. MRT was 4:02:53 ± 00:50:20 h. The MRT was positively associated with BF% (r = 0.587, p = 0.001). Among echocardiographic parameters, MRT correlated negatively with right ventricular end-diastolic area (RVEDA) (r = −0.716, p < 0.001). RVEDA was the only independent echocardiographic predictor of MRT. With regard to respiratory parameters, MRT correlated negatively with maximum minute ventilation indexed to body surface area (VEmax/BSA) (r = −0.509, p = 0.003). Among parameters of blood test, MRT correlated negatively with haemoglobin concentration (r = −0.471, p = 0.027) and estimated haemoglobin mass (Hbmass) (r = −0.680, p = 0.002). After performing multivariate linear regression analysis with MRT as dependent variable and BF% (standardised β = 0.501, p = 0.021), RVEDA (standardised β = −0.633, p = 0.003), VEmax/BSA (standardised β = 0.266, p = 0.303) and Hbmass (standardised β = −0.308, p = 0.066) as independent variables, only BF% and RVEDA were significant independent predictors of MRT (adjusted R
2 = 0.796, p < 0.001 for the model). Conclusions: The main physiological determinants of better marathon performance appear to be low BF% and RV enlargement. Upregulation of both maximum minute ventilation during exercise and haemoglobin mass may have a weaker effect to enhance marathon performance. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT04738877. [ABSTRACT FROM AUTHOR]- Published
- 2021
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32. A critical review of the effects of vitamin K on glucose and lipid homeostasis: its potential role in the prevention and management of type 2 diabetes.
- Author
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Varsamis, Nikolaos A., Christou, Georgios A., and Kiortsis, Dimitrios N.
- Published
- 2021
- Full Text
- View/download PDF
33. Crack propagation and residual load‐bearing behavior of composite dowels – effects on the global behavior of composite girders under cyclic loading.
- Author
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Wolters, Kevin, Christou, Georgios, and Feldmann, Markus
- Subjects
CRACK propagation (Fracture mechanics) ,CYCLIC loads ,STEEL fracture ,GIRDERS ,COMPOSITE construction - Abstract
Fatigue of a composite girder according to Eurocode 4 is carried out on the decisive shear connector. It is not taken into account that the composite girder is an internally highly statically indeterminate system in which the failure of a dowel does not necessarily lead to the failure of the girder. This applies in particular to composite dowels which are characterised by a crack propagation phase with a high residual load‐bearing capacity of a damaged dowel. In own small part and girder tests as well as numerical studies, numerous positive load‐bearing effects could be identified in composite girders with composite dowels, which increase the lifetime of the girder. In case of an initial crack in a steel dowel, followed by crack propagation, the stiffness degradation of the damaged connector leads to a redistribution of forces. The lifetime of a girder is limited by the residual capacity of the composite joint or by a global failure with increasing partial connection. A global safety concept for composite girders taking into account the crack development and residual strength of the dowels as well as the redistribution of forces within the composite joint holds an enormous economic potential. This article shows how these effects can be taken into account. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
34. Concrete fatigue of composite constructions with rib shear connectors.
- Author
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Christou, Georgios, Hegger, Josef, and Classen, Martin
- Subjects
COMPOSITE construction ,BRIDGE design & construction ,CYCLIC loads ,GIRDERS ,CONCRETE fatigue - Abstract
Rib shear connectors are gaining increasingly attention in the field of composite constructions. Especially in bridge constructions, rib shear connectors offer many advantages compared to conventional composite shear connectors such as headed studs. In order to describe the load‐bearing behaviour of rib shear connectors under cyclic loading, the successively increasing slip resulting from the cyclic loading of the shear connectors must be taken into account. The latter leads to the growth of the relative displacements along the composite joint and thus, to the degradation of the previously rigid shear connection. This effect leads to rearrangements of internal forces between the composite partners through which the load bearing behaviour and load bearing capacity of the structure alter. In this article results of experimental investigations on two cyclic single Push‐Out‐Tests (sPOT) and one full‐scale girder test regarding the degradation of the composite interconnection are presented and analysed. The investigated shear connectors in the full‐scale girder test are subjected to a comparable load history to that of the connectors in the sPOT. The results give insight into the effects of the degradation of the shear connection, as previously seen in sPOT, on the overall load bearing behaviour of composite girders. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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- View/download PDF
35. Development of a new design approach for composite dowels positioned close to the concrete surface.
- Author
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Broschart, Yannick, Kurz, Wolfgang, Wolters, Kevin, Christou, Georgios, and Claßen, Martin
- Subjects
COMPOSITE construction ,BRIDGE design & construction ,CONCRETE slabs ,CONCRETE ,SHEAR (Mechanics) ,BUILDING design & construction - Abstract
Composite dowels as shear connectors between steel profiles and concrete sections have been investigated for decades. The long‐term aim is to implement a consistent design concept within Eurocode 4 ‐ covering both, the fields of bridge and building construction. Especially in building construction, where the concrete slabs are dimensioned increasingly slimmer in contrast to bridge construction, the composite dowels are positioned unavoidably close to free concrete surfaces. This causes additional failure modes, leading to the overall failure of the structure, which have not been entirely investigated yet. At University of Kaiserslautern more than 30 push‐out tests were performed within a joint research project in cooperation with RWTH Aachen University. These tests were focused on the resistance of composite dowels close to the concrete surface in dependence of varying influence parameters. Some results showed a significant reduction in shear strength and deformation capacity, mostly accompanied by the spalling of the concrete cover. Simultaneously, numerical simulations were calibrated and utilized to get a deeper understanding of the load transfer mechanisms and to interpolate between existing experimental results. On the basis of experimental measurements and numerical simulations a load transfer model was developed with a corresponding design approach to calculate the theoretical resistance. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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- View/download PDF
36. Not only the status of body weight and metabolic health matters for cardiovascular events, but also the temporal changes.
- Author
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Christou, Georgios A
- Published
- 2021
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- View/download PDF
37. Exploring the determinants of the cardiac changes after ultra-long duration exercise: The echocardiographic Spartathlon study.
- Author
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Christou, Georgios A, Pagourelias, Efstathios D, Anifanti, Maria A, Sotiriou, Panagiota G, Koutlianos, Nikolaos A, Tsironi, Maria P, Andriopoulos, Panagiotis I, Christou, Konstantinos A, Kouidi, Evangelia J, and Deligiannis, Asterios P
- Published
- 2020
- Full Text
- View/download PDF
38. The impact of demographic, anthropometric and athletic characteristics on left atrial size in athletes.
- Author
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Christou, Georgios A. and O'Driscoll, Jamie M.
- Published
- 2020
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- View/download PDF
39. High Tolerability of Pitavastatin Therapy: A Case Report of Comparison with other Statins.
- Author
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Christou, Georgios A., Mprikos, Spyridon G, Christou, Konstantinos A., Christou, Maria A., Christou, Evangelos A., Nikas, Dimitrios N., and Kiortsis, Dimitrios N.
- Subjects
- *
DRUG side effects , *MYALGIA , *MUSCLE diseases , *FOREARM - Abstract
Introduction: Myopathy is possibly the most clinically relevant statin-induced side effect. Case Presentation: We report a case of a 63-year-old healthy male with mixed dyslipidemia. He developed bilateral myalgia of the forearms with fluvastatin 40 mg/day, pravastatin 20 mg/day, and combination of atorvastatin 10 mg and ezetimibe 10 mg/day. The only hypolipidemic treatment that was tolerable was the combination of pitavastatin 1 mg and ezetimibe 10 mg/day. Discussion: Pitavastatin demonstrated less potential for the development of myalgia compared to the so far considered most tolerable statins (i.e., fluvastatin and pravastatin). All the tested statins were used at the lowest approved dose for clinical use. Conclusion: The combination of pitavastatin 1 mg and ezetimibe appears to be a promising treatment choice for individuals who are intolerant to statin therapy due to muscle complaints. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
40. Ermüdung von Verbunddübelleisten: Analyse und Modellentwicklung.
- Author
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Christou, Georgios, Ungermann, Jan, Wolters, Kevin, Hegger, Josef, and Claßen, Martin
- Subjects
- *
CYCLIC loads , *ENGINEERING models , *SERVICE life , *MATERIAL fatigue , *CONCRETE fatigue , *ENGINEERING mathematics , *STEEL fatigue - Abstract
Fatigue of rib shear connectors – Analysis and engineering model The use of composite dowel shear connectors is becoming increasingly important in both building and bridge constructions. In addition to the high load‐bearing capacity and stiffness of the composite dowels, their significantly better load‐bearing behaviour under cyclic loading compared to headed studs is one further important advantage. As a result, the use of these innovative shear connectors in bridge construction is particularly promising. However, the existing regulations for the fatigue design of composite dowels were chosen conservatively due to the low experimental data basis, so that the advantageous cyclic load‐bearing behaviour cannot yet be fully deployed. Within the scope of this article, the load bearing behaviour of composite dowels under cyclic loading is analysed in detail on the basis of experimental findings. Based on this, a model for estimating the service life of the composite dowels is developed. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
41. Ermüdung von Verbunddübelleisten – experimentelle Untersuchungen.
- Author
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Christou, Georgios, Ungermann, Jan, Wolters, Kevin, Hegger, Josef, and Claßen, Martin
- Subjects
- *
FATIGUE cracks , *CONCRETE fatigue , *BRIDGE design & construction , *STEEL fracture , *STEEL fatigue , *CYCLIC loads , *COMPOSITE construction - Abstract
Fatigue of composite dowels – experimental investigations Composite dowels are becoming increasingly important in the field of composite constructions. In bridge constructions in particular, compo‐site dowels offer many advantages over other shear connectors. The weld seam‐free design of composite dowels shows a significantly better load‐bearing behaviour than, for example, conventional headed studs, especially under cyclic loading. The cyclic load‐bearing behaviour is mainly influenced by the continuous change of the characteristics in the shear connection. The degradation of the connection between steel and concrete over the lifespan and the resulting slip in the previously rigid connection leads to rearrangements of internal forces between the composite partners which alter the load‐bearing behaviour of the structure. In addition, fatigue failure of the composite joint can occur either in the form of fatigue cracks in the steel tooth or in the form of concrete failure, in which the increasing damage of the concrete in front of the steel dowel can result both in significant slip development and cyclic pry‐out failure. This paper presents results of cyclic shear tests in which different influencing variables on the fatigue behaviour of composite dowel bars were investigated. Based on the results, a correlation between the load‐bearing behaviour of the composite dowels and various load and material parameters could be derived. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
42. The effect of follicular phase length on cycle outcomes and endometrial development in gonadotrophin ovarian stimulation/intrauterine insemination cycles.
- Author
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Bakkensen, Jennifer B., Christou, Georgios, Dimitriadis, Irene, James, Kaitlyn, and Souter, Irene
- Subjects
- *
INDUCED ovulation , *FROZEN human embryos , *MENSTRUAL cycle , *MULTIPLE pregnancy , *OVARIAN reserve , *MISCARRIAGE - Abstract
Does a shorter follicular phase length (FPL) affect cycle outcomes and endometrial development among women undergoing gonadotrophin ovarian stimulation/intrauterine insemination (OS/IUI)? Retrospective cohort study of 4773 OS/IUI cycles among 2054 patients. FPL was analysed first continuously, then dichotomously using an arbitrary cut-off at the 15th percentile (8 days) to divide cycles into shorter and longer FPL groups. Receiver operating characteristic (ROC) curves were constructed to further analyse the impact of FPL on all outcomes. Primary outcomes included clinical pregnancy, spontaneous abortion, multiple pregnancy and non-viable (ectopic/biochemical) pregnancy rates (CPR, SABR, MPR and NVPR, respectively). Secondary outcomes included endometrial thickness. All analyses controlled for age, day 3 FSH and body mass index. When analysing FPL continuously, CPR increased by 6.0% (adjusted odds ratio [aOR] 1.06, 95% CI 1.03–1.09, P < 0.001) with each additional follicular phase day. Similarly, in the dichotomous analysis, cycles with a longer FPL resulted in higher CPR with 45% higher odds of clinical pregnancy (aOR 1.45, 95% CI 1.07–1.97, P = 0.018). No effect of FPL was noted on NVPR, SABR or MPR. Endometrial thickness increased by 0.09 mm (95% CI 0.06–0.12, P < 0.001) with each additional FPL day and was increased in the longer compared with the shorter FPL group (adjusted mean difference 1.08 mm, 95% CI 0.81–1.34, P < 0.001). The data suggest that in gonadotrophin OS/IUI cycles, FPL might impact both chance of clinical pregnancy and endometrial thickness, independent of maternal age and ovarian reserve. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
43. Indirect clinical markers for the detection of anabolic steroid abuse beyond the conventional doping control in athletes.
- Author
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Christou, Georgios A., Christou, Maria A., Žiberna, Lovro, and Christou, Konstantinos A.
- Subjects
- *
PREVENTION of doping in sports , *ACNE , *ANABOLIC steroids , *ATHLETES , *BIOMARKERS , *DRUG use testing , *FOLLICLE-stimulating hormone , *GYNECOMASTIA , *HEMATOCRIT , *HYPERTENSION , *SERUM , *TESTICULAR diseases - Abstract
Growing analytical challenges have arisen for the detection of misuse of androgenic anabolic steroids (AAS) in athletes the last years. Therefore, consideration of additional indirect markers can substantially aid the efforts to detect AAS abuse in athletes. Moreover, this approach can also help physicians to suspect AAS abuse when treating athletes. Laboratory markers highly indicative of AAS abuse in athletes include the considerable downregulation of high density lipoprotein-cholesterol, elevation of haematocrit or serum γ-glutamyl transpeptidase levels and for males reduced serum levels of both luteinizing hormone and follicle-stimulating hormone. Moreover, physical signs suggestive of current AAS abuse are hypertension, apparent changes in behaviour making the athlete more irritable and aggressive and the sudden appearance of acne vulgaris in an adult athlete with no recent history of acne, while testicular atrophy and gynecomastia raise suspicion of current or past AAS abuse in male athletes. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
44. Influencing Parameters on the Load‐bearing Capacity of Composite Dowels positioned close to the free Surface of Concrete Slabs.
- Author
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Broschart, Yannick, Kurz, Wolfgang, Wolters, Kevin, Christou, Georgios, and Claßen, Martin
- Subjects
CONCRETE slabs ,FREE surfaces ,BRIDGE design & construction ,STEEL walls ,BUILDING design & construction ,FAILURE mode & effects analysis ,MICROSOFT Surface (Computer) - Abstract
Composite dowels as shear connectors between steel profiles and concrete sections have been investigated for decades. The long‐term aim is to develop consistent design approaches and implement them within Eurocode 4 covering both fields of bridge and building construction. Especially in building construction, where the concrete slabs are dimensioned increasingly slimmer in contrast to bridge construction, the composite dowels are positioned unavoidably close to free concrete surfaces (1). This causes further failure modes which have not been entirely investigated yet. At University of Kaiserslautern experimental push‐out tests were performed within a research project in cooperation with RWTH Aachen University focusing on the behaviour of these composite dowels in dependence of varying influence parameters, such as the dowel's distance to the edge, the concrete strength and the position of the reinforcement stirrups. Some results showed a significant reduction of the load‐bearing capacity and an affection of the deformability, mostly accompanied by the spalling of the concrete cover. Based on the tests, numerical simulations were calibrated and utilized to understand more about the load transfer mechanisms and to interpolate between existing experimental results. This paper will particularly show the influence of three parameters and present considerations on the load transfer model including further primary, secondary and tertiary failure mechanisms leading to the overall failure of the specimens. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
45. Fatigue of composite constructions with composite dowels.
- Author
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Christou, Georgios, Classen, Martin, Wolters, Kevin, and Broschart, Yannick
- Subjects
COMPOSITE structures ,STEEL fracture ,SHEARING force ,DYNAMIC loads ,COMPOSITE construction - Abstract
Composite dowels are being applied increasingly over the past years. Especially in the field of small and medium span bridges, composite dowels offer many advantages in comparison to other shear connectors. In contrast to headed studs, where initial steel cracks already occur after a few load cycles, composite dowels have a better resistance against dynamic loading and thus an increased lifetime. The bearing capacity of composite dowels is mainly characterized by the compression of the multiaxial stressed concrete in front of the composite dowel, where shear forces are transferred between steel and concrete. Here, the multiaxial compressive stress leads to increasing strains, that accumulate over the load cycles and lead to a cyclic growth of relative displacements in the composite connection. These relative displacements subsist of two strain‐components, the elastic and the plastic strains. The plastic strain remains constant in the connection, even after release of external loading. These permanent displacements are called inelastic slip. Due to this inelastic slip the characteristics of the static dowel curve might change significantly over the lifetime of the composite structure. The initially rigid connection between steel and concrete degrades over the lifetime and rearrangements of internal forces between the composite partners occur, which may impact the fatigue behaviour of the construction. The degradation of the composite connection can be considered by a cyclic dowel curve, which may be developed from the static dowel curve by introducing the inelastic slip. In this paper, results of cyclic shear tests are presented, in which the inelastic slip between steel and concrete and the relative slip of the steel dowel to the steel web are measured and compared. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
46. Semaglutide as a promising antiobesity drug.
- Author
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Christou, Georgios A., Katsiki, Niki, Blundell, John, Fruhbeck, Gema, and Kiortsis, Dimitrios N.
- Abstract
Summary: Semaglutide is a glucagon‐like peptide‐1 receptor agonist (GLP‐1 RA) with a long elimination half‐life, allowing subcutaneous (sc) administration once per week. Both the European Medicines Agency (EMA) and the Food and Drug Administration (FDA) recently approved once‐weekly sc semaglutide for the treatment of type 2 diabetes mellitus (T2DM). The weight loss efficacy of once‐weekly sc semaglutide appears to be superior compared with the other once‐weekly GLP‐1 RAs in patients with T2DM. Semaglutide was recently evaluated as an antiobesity drug in a phase II dose‐finding trial, which demonstrated superior weight loss efficacy of once daily sc semaglutide compared with both placebo and once daily 3.0 mg liraglutide in patients with obesity but without T2DM. The magnitude of semaglutide‐induced weight loss in this study exceeded the criteria of both the EMA and FDA for antiobesity drugs, and there were no safety concerns, indicating the eligibility of once daily sc semaglutide as a future antiobesity drug. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
47. Metabolically Healthy Obesity Is Characterized by a Proinflammatory Phenotype of Circulating Monocyte Subsets.
- Author
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Christou, Konstantinos A., Christou, Georgios A., Karamoutsios, Achilleas, Vartholomatos, Georgios, Gartzonika, Konstantina, Tsatsoulis, Agathocles, and Tigas, Stelios
- Abstract
Background: Obesity is associated with macrophage infiltration in adipose tissue that induces insulin resistance and contributes to the development of metabolic syndrome (MS). The aim of this study was to investigate whether circulating monocyte subsets (macrophage precursors) differ among obese subjects with MS [metabolically unhealthy obese (MUO)], obese subjects without MS [metabolically healthy obese (MHO)], and metabolically healthy lean (MHL) individuals. Methods: Fifty-eight obese (33 MUO, 25 MHO) and 25 MHL individuals participated in the study. Absolute blood counts of classical (Mon1A), intermediate (Mon2A), and nonclassical (Mon3A) monocyte subsets were measured by flow cytometry. Results: Increased proinflammatory monocyte counts (Mon2A, Mon3A) were observed in obese compared with MHL individuals (P = 0.001 and P = 0.017 respectively). Mon2A count in MHO was lower compared with that in MUO subjects (P = 0.036) but higher compared with MHL controls (P = 0.032). Mon2A was positively associated with serum triglyceride levels (r = 0.328, P = 0.023) and mean blood pressure (BP) (r = 0.457, P = 0.001) in obese subjects. Among MS components, only the presence of elevated BP (≥130/85 mmHg) was independently associated with increased Mon2A in obese subjects (P < 0.001). Conclusions: Absolute counts of proinflammatory monocytes were lower in metabolically healthy compared with MUO individuals, but higher compared with healthy lean controls. The presence of low-grade inflammation suggests that "metabolically healthy" obesity is not a benign condition. ClinicalTrials.gov identifier: NCT03241394. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Pathophysiology of Noncardiac Syncope in Athletes.
- Author
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Christou, Georgios A., Christou, Konstantinos A., and Kiortsis, Dimitrios N.
- Subjects
- *
ATHLETES , *VASODILATION , *BRADYCARDIA , *CEREBRAL circulation , *DEHYDRATION , *EXERCISE physiology , *FEVER , *HYPERVENTILATION , *ORTHOSTATIC hypotension , *MEDLINE , *ONLINE information services , *PHYSICAL fitness , *POSTURE , *REFLEXES , *SYNCOPE , *SYSTEMATIC reviews , *EVIDENCE-based medicine , *COOLDOWN , *PHYSICAL training & conditioning , *VASOCONSTRICTION , *STROKE volume (Cardiac output) , *HYPOCAPNIA - Abstract
The most frequent cause of syncope in young athletes is noncardiac etiology. The mechanism of noncardiac syncope (NCS) in young athletes is neurally-mediated (reflex). NCS in athletes usually occurs either as orthostasis-induced, due to a gravity-mediated reduced venous return to the heart, or in the context of exercise. Exercise-related NCS typically occurs after the cessation of an exercise bout, while syncope occurring during exercise is highly indicative of the existence of a cardiac disorder. Postexercise NCS appears to result from hypotension due to impaired postexercise vasoconstriction, as well as from hypocapnia. The mechanisms of postexercise hypotension can be divided into obligatory (which are always present and include sympathoinhibition, histaminergic vasodilation, and downregulation of cardiovagal baroreflex) and situational (which include dehydration, hyperthermia and gravitational stress). Regarding postexercise hypocapnia, both hyperventilation during recovery from exercise and orthostasis-induced hypocapnia when recovery occurs in an upright posture can produce postexercise cerebral vasoconstriction. Athletes have been shown to exhibit differential orthostatic responses compared with nonathletes, involving augmented stroke volume and increased peripheral vasodilation in the former, with possibly lower propensity to orthostatic intolerance. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
49. Design and development of a semi-autonomous agricultural vineyard sprayer: Human-robot interaction aspects.
- Author
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Adamides, George, Katsanos, Christos, Constantinou, Ioannis, Christou, Georgios, Xenos, Michalis, Hadzilacos, Thanasis, and Edan, Yael
- Subjects
VINEYARDS ,PESTICIDES ,SPRAYING ,HUMAN-robot interaction ,AGRICULTURAL robots ,USER interfaces - Abstract
This article presents the design aspects and development processes to transform a general-purpose mobile robotic platform into a semi-autonomous agricultural robot sprayer focusing on user interfaces for teleoperation. The hardware and the software modules that must be installed onto the system are described, with particular emphasis on human-robot interaction. Details of the technology are given focusing on the user interface aspects. Two laboratory experiments and two studies in the field to evaluate the usability of the user interface provide evidence for the increased usability of a prototype robotic system. Specifically, the study aimed to empirically evaluate the type of target selection input device mouse and digital pen outperformed Wiimote in terms of usability. A field experiment evaluated the effect of three design factors: (a) type of screen output, (b) number of views, (c) type of robot control input device. Results showed that participants were significantly more effective but less efficient when they had multiple views, than when they had a single view. PC keyboard was also found to significantly outperform PS3 gamepad in terms of interaction efficiency and perceived usability. Heuristic evaluations of different user interfaces were also performed using research-based HRI heuristics. Finally, a study on participants' overall user experience found that the system was evaluated positively on the User Experience Questionnaire scales. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
50. Urinary triclosan concentrations and diminished ovarian reserve among women undergoing treatment in a fertility clinic.
- Author
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Mínguez-Alarcón, Lidia, Christou, Georgios, Messerlian, Carmen, Williams, Paige L., Carignan, Courtney C., Souter, Irene, Ford, Jennifer B., Calafat, Antonia M., Hauser, Russ, and EARTH Study Team
- Subjects
- *
INFERTILITY treatment , *TRICLOSAN , *OVARIAN physiology , *PROGESTERONE , *HIGH performance liquid chromatography , *SPECIFIC gravity , *PHYSIOLOGY - Abstract
Objective: To investigate the association between urinary triclosan concentrations and antral follicle count (AFC), a well-accepted marker of ovarian reserve, among women from a fertility center.Design: Prospective cohort study.Setting: Hospital fertility center.Patient(s): A total of 109 women.Intervention(s): Urinary triclosan concentrations quantified by online solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry.Main Outcome Measure(s): AFC through transvaginal ultrasonography on the third day of an unstimulated menstrual cycle or on the third day of a progesterone withdrawal bleed.Result(s): The geometric mean of the specific gravity-adjusted urinary triclosan concentrations for the 225 samples provided by the 109 women was 13.0 μg/L (95% confidence interval [CI], 8.9, 19.1). Women had median (with interquartile range) AFC of 13 (8, 18). The specific gravity-adjusted urinary triclosan concentrations were inversely associated with AFC (-4%; 95% CI, -7%, -1%). Women with triclosan concentrations above the median had lower AFC compared with those whose triclosan concentrations were equal to or below the median, with an adjusted difference of -3.2 (95% CI, -3.9, -1.6) among those with a body mass index <25 kg/m2 and -1.8 (95% CI, -3.2, -0.3) among those who were <35 years old.Conclusion(s): Specific gravity-adjusted urinary triclosan concentrations were inversely associated with AFC in women seeking care at a fertility center. This association was modified by age and body mass index, with the younger and leaner women showing larger decreases in AFC. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
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