Relaxation of Voronoi shells in hydrated molecular ionic liquids.

The relaxation of solvation shells is studied following a twofold strategy based on a direct analysis of simulated data as well as on a solution of a Markovian master equation. In both cases solvation shells are constructed by Voronoi decomposition or equivalent Delaunay tessellation. The theoretical framework is applied to two types of hydrated molecular ionic liquids, 1-butyl-3-methyl-imidazolium tetrafluoroborate and 1-ethyl-3-methyl-imidazolium trifluoromethylsulfonate, both mixed with water. Molecular dynamics simulations of both systems were performed at various mole fractions of water. A linear relationship between the mean residence time and the system's viscosity is found from the direct analysis independent of the system's type. The complex time behavior of shell relaxation can be modeled by a Kohlrausch-Williams-Watts function with an almost universal stretching parameter of 1/2 indicative of a square root time law. The probabilistic model enables an intuitive interpretation of essential motional parameters otherwise not accessible by direct analysis. Even more, incorporating the square root time law into the probabilistic model enables a quantitative prediction of shell relaxation from very short simulation studies. In particular, the viscosity of the respective systems can be predicted.

On the collective network of ionic liquid/water mixtures. III. Structural analysis of ionic liquids on the basis of Voronoi decomposition.

Three different mixtures of 1-butyl-3-methyl-imidazolium tetrafluoroborate with water have been studied by means of molecular dynamics simulations. Based on the classical Lopes-Padua force field trajectories of approximately 60 ns were computed. This is the third part of a series concerning the collective network of 1-butyl-3-methyl-imidazolium tetrafluoroborate/water mixtures. The first part [C. Schröder et al., J. Chem. Phys. 127, 234503 (2007)] dealt with the orientational structure and static dielectric constants. The second part [C. Schröder et al., J. Chem. Phys. 129, 184501 (2008)] was focused on the decomposition of the dielectric spectrum of these mixtures. In this work the focus lies on the characterization of the neighborhood of ionic liquids by means of the Voronoi decomposition. The Voronoi algorithm is a rational tool to uniquely decompose the space around a reference molecule without using any empirical parameters. Thus, neighborhood relations, direct and indirect ones, can be extracted and were used in combination with g-coefficients. These coefficients represent the generalization of the traditional radial distribution function in order to include the mutual positioning and orientation of anisotropic molecules. Furthermore, the Voronoi method provides, as a by-product, the mutual coordination numbers of molecular species.

Flow-mediated vasodilation of the femoral and brachial artery induced by exercise in healthy nonsmoking and smoking men.

OBJECTIVES: We sought to analyze diameter changes of conduit arteries in response to whole-body exercise and hypothesized that this response might be endothelium-dependent and, therefore, impaired in smokers. BACKGROUND: Hyperemia and coincident vasodilation are pivotal mechanisms for meeting the increased metabolic demands of active muscle tissue during physical exercise, but studies in humans are sparse. METHODS: We studied diameter and blood flow of the femoral and brachial arteries in response to a submaximal bicycle exercise test in 10 nonsmoking and 8 smoking healthy male subjects. During an exercise period of 40 min the investigated conduit arteries were periodically scanned in longitudinal sections by high-resolution ultrasound. In the same subjects flow-mediated dilation (FMD) of the brachial artery was recorded by inducing an ischemia through a forearm-occluding cuff. RESULTS: In response to exercise the diameter of the femoral artery significantly increased in both nonsmokers and smokers, with a diminished response in smokers (9.2 +/- 1.9% vs. 4.8 +/- 1.6%, p < 0.001). Flow-mediated dilation of the brachial artery induced by forearm occlusion was also reduced in smoking subjects, revealing a strong correlation between these different methods of FMD (exercise vs. forearm ischemia) (r = 0.88, p < 0.001). In contrast, blood flow increase of the femoral artery was similar in nonsmoking and smoking subjects (392 +/- 77% vs. 382 +/- 109%, p = NS). CONCLUSIONS: Conduit arteries react with a flow-mediated dilation in response to whole-body exercise. The impairment of this vasodilation observed in smokers was strongly related to a decrease of endothelium-dependent dilation induced by forearm ischemia, indicating that endothelial dysfunction represents the underlying mechanism.

Pronounced postprandial lipemia impairs endothelium-dependent dilation of the brachial artery in men.

OBJECTIVE: Pronounced postprandial lipemia has been established as a risk factor for cardiovascular disease, but reports regarding its effect on endothelial function have been controversial. In the present study the influence of a standardized fatty meal with its ensuing postprandial lipemia of highly varying magnitude on endothelium-dependent dilation (EDD) was investigated. METHODS: In 17 healthy, normolipidemic men EDD of the brachial artery was quantified in two series of three measurements each. In both series initial measurements were performed at 08:00 h after an overnight fast followed by measurements at 12:00 and 16:00 h, in the first series with continued fasting and in the second following the ingestion of a standardized fatty test meal 4 and 8 h postprandially. RESULTS: Measurements of EDD in the fasting state revealed the recently appreciated diurnal variation with higher values in noon and afternoon hours compared with morning values (2.5+/-1.6% at 08:00, 7.5+/-2.7% at 12:00, and 7.0+/-2.1% at 16:00 h, P<0.001 by analysis of variance). Postprandial EDD values measured at 12:00 h were, at the average, lower than fasting EDD values measured at 12:00 h and correlated inversely with the magnitude of postprandial triglyceridemia (r=-0.81, P<0.001). In multivariate analysis, higher postprandial lipemia was associated with impaired postprandial EDD (P<0.001) independent of fasting triglycerides, low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol, insulin, age and body mass index. CONCLUSION: We conclude that pronounced postprandial lipemia is associated with transient impairment of endothelial function. Our findings support the notion that impaired triglyceride metabolic capacity plays an important role in atherogenesis.

Plasma levels of cardiac troponin I after prolonged strenuous endurance exercise.

This study provides biochemical evidence that ultraendurance exercise may cause subclinical myocardial damage, even in well-trained cyclists. The cellular nature of this damage and its clinical relevance remain unknown at present.

Plasma levels of troponin T after electrical cardioversion of atrial fibrillation and flutter.

To establish possible myocardial damage by direct-current countershock, we measured plasma levels of troponin T after electrical cardioversion in 33 nonselected patients with atrial fibrillation or flutter. Unchanged normal levels of troponin T indicate that significant myocardial cell injury by shocks in the usual dosage is unlikely to occur.

Lack of evidence for the heterosexual transmission of hepatitis C.

The importance of sexual transmission in the epidemiology of hepatitis C virus (HCV) infection is still controversial. To assess the risk of heterosexual HCV transmission, we examined eighty patients with chronic HCV-associated liver disease and their spouses in a cross-sectional clinical and serological cohort study. Serum samples from index patients and their spouses were assayed for HCV antibodies and HCV RNA. In the couples positive for both, further HCV genotyping was done. A questionnaire addressing points such as additional risk factors for HCV infection, sexual behaviour or duration of partnership was completed by all couples. HCV antibodies were detected in four (5%) spouses, of whom three (4%) were also positive for HCV-RNA. HCV genotyping revealed concordance (genotype 1) in two couples, indicating a risk of interspousal HCV transmission of 2.5%. Spouses of patients with HCV viraemia and chronic liver disease have a low risk for acquiring HCV. Even long-term spouses seem not to be at increased risk. We therefore suggest that the risk of HCV transmission between monogamous sex partners does not depend on the duration of sexual exposure.

Impact of anisotropy on the structure and dynamics of ionic liquids: a computational study of 1-butyl-3-methyl-imidazolium trifluoroacetate.

The complex ionic network of 1-butyl-3-methyl-imidazolium trifluoroacetate was simulated by means of the molecular dynamics methods over a time period of 100 ns. The influence of the anisotropy of the shape and charge distribution of both the cations and the anions on the local (molecular) and global (collective) structure and dynamics is analyzed. The distance-dependent g coefficients of the orientational probability function g(r,Omega) were found to be an excellent way to interpret local structure. Thereby, the combination and interrelation of individual g coefficients elucidate the mutual orientation. Dynamics at the molecular level is characterized by the time correlation function of the center-of-mass corrected molecular dipole moment mucm. Upon uniting the set of molecular dipoles to a single collective rotational dipole moment, MD, dynamics on a global level is studied. Decomposing into subsets of cations and anions respective self terms as well as the prominent cross term can be extracted. This decomposition also enables a detailed peak assignment in dielectric spectra.

On the collective network of ionic liquid/water mixtures. I. Orientational structure.

In this work, the collective structure of aqueous solutions of ionic liquids was studied by means of molecular dynamics simulations. Various concentrations of 1-butyl-3-methyl-imidazolium tetrafluoroborate and TIP3P water were simulated at the very same size of the simulation box. For the analysis, the ternary system cation/anion/water was subdivided into binary networks. The local structure of each of these six networks is investigated by atom-atom radial distribution functions as well as by the so-called g coefficients, which reveal the mutual orientation of the network constituting partners. Furthermore, the collective structure of the whole samples was characterized by the contribution of each species to the static dielectric constant epsilon(omega=0) and to the Kirkwood G(K) factor. The combination of the analysis tools mentioned above provides knowledge about the cross-linking of the ionic species with the dipolar water. Thereby, the interplay between charge-charge and hydrogen bond networks is analyzed in detail.

Renal function and plasma volume following ultramarathon cycling.

In recreational cyclists marathon cycling influences renal function only on a minimal scale. Respective information on extreme ultramarathon cycling in better trained athletes is not available. The objective was to evaluate the renal and haematological effects of ultraendurance cycling in the world's best ultramarathon cyclists. Creatinine (CR), urea, haemoglobin (Hb), haematocrit (Hct) and plasma volume (PV) were investigated in 16 male ultramarathon cyclists during the 1st Race Across the Alps in 2001 (distance: 525 km; cumulative altitude difference: 12,600 m). All renal functional parameters were normal pre-exercise. During the race serum CR, urea and uric acid rose significantly by 33, 97 % and 18 % (p <0.001 respectively) and nearly normalised again on the following day. The decline in calculated CR clearance was 25 %. There was a negative correlation (r=- 0.575, p=0.02) between the rise in serum CR and the athlete's training kilometers. The serum urea/CR ratio rose above 40 in 12 athletes (75 %). Mean fractional sodium excretion and fractional uric acid excretion fell below 0.5 % (p <0.001) and 7 %, indicating reduced renal perfusion. The deflection of the renal functional parameters was temporary and nearly gone after 24 hours of recovery. Hct declined during the race from 0.44 to 0.42, and continued falling on the next day (0.42 --> 0.40; p <0.001). The corresponding rises in calculated PV were + 8 % and + 22 %. The study affirms that in world class cyclists the enormous strains of ultramarathon cycling influence renal function only on a minimal scale. The impact on the PV, however, is pronounced leading to marked haemodilution post-exercise. This very temporary "impairment of renal function" seems to be the physiological response to ultramarathon cycling and may be attenuated to some extent by preceding high-volume training.

The impact of prolonged strenuous endurance exercise on interleukin 18 and interleukin 18 binding protein in recreational cyclists.

Interleukin 18 (IL-18) is an important pro-inflammatory cytokine in the early phase of human immune response to microbial infections. The influence of strenuous exercise on the intrinsic balance of IL-18 and its endogenous antagonist IL-18 binding protein (IL-18 BP) is unknown, but could be of major relevance for the athlete's immune function empirically and epidemiologically proven to be altered after exhaustive exertion. To study the effect of strenuous marathon cycling on the interaction of IL-18 and IL-18 BP we investigated 37 male, healthy, and well-trained amateur cyclists participating in the Otztaler Radmarathon in Tyrol (distance: 230 km; cumulative altitude difference: 5500 m). IL-18 was measured by a commercially available ELISA-Kit and IL-18 BP by a novel IL-18 BP ELISA method. Free, unbound IL-18 was calculated according to a standard equation. The mean plasma level of IL-18 was 142.27 +/- 21.85 pg/ml pre-race, remained nearly unchanged (124.35 +/- 13.16 pg/ml; p = 1.0) immediately after competition (mean race time 9 h 38 min), but declined significantly 24 h afterward (62.92 +/- 6.80 pg/ml; p = 0.002). The plasma levels of IL-18 BP increased considerably immediately after and kept on rising for the following 24 h (pre-race: 1.51 +/- 0.20 ng/ml; immediately post-race: 3.84 +/- 0.26 ng/ml, p < 0.001; 24 h post-race: 4.33 +/- 0.42 ng/ml, p < 0.001). Therefore, the calculated free IL-18 was 122.06 +/- 16.79 pg/ml pre-race, declined to 82.86 +/- 8.59 (p = 0.05) immediately post-race and to 39.17 +/- 3.76 pg/ml 24 h post-race (p < 0.001). The respective percentages of this post-exercise reduction in free IL-18 plasma levels were 32 % and 68 %. The present study reveals an exercise-induced significant decline in free IL-18 accompanied by an immediate up-regulation of IL-18 BP and decreased IL-18 in marathon cyclists. This down-regulation of free IL-18 may (i) limit the magnitude and duration of a too excessive inflammatory response to the exercise-induced tissue damage and (ii) on the other hand contribute to the elevated susceptibility to infection in athletes undergoing exhaustive exercise.

Physical and physiological factors associated with success in professional alpine skiing.

Scientific data on the physiological profile of world class skiers are sparse. During the last decade the Austria Ski Team was the most successful in the world. It was the objective of this study to describe the physical and physiological characteristics of World Cup (WC) skiers. Twenty female and 28 male members of the Austrian WC Ski Team were examined pre- and post-seasonally from 1997 to 2000. Physical parameters such as age, height, body mass, body mass index, percent body fat and thigh circumference were recorded from each athlete. The physiological variables investigated consisted in the aerobic power and in the muscle strength of the lower limbs. Racing performance was defined by the WC ranking position. The athlete's aerobic performance capacity was assessed by maximal exercise testing on a bicycle ergometer, and the isokinetic muscle strength of the knee extensor and flexor muscles by the use of a computer-interfaced dynamometer. From 1997 to 2000 about half (48 %; n = 106) of all alpine WC racing events (n = 221) were won by the athletes investigated. The typical world class skier is in the mid-twenties (25.2 y [female]; 27.6 y [male]). The mean values for height were 1.66 m (female) vs. 1.81 m (male), for body mass 65.1 kg (female) vs. 87 kg (male) and for the percentage of body fat 24.5 % (female) vs. 15.8 % (male). The maximum power output was 4.3 +/- 0.4 (female ) and 4.7 +/- 0.4 W/kg (male), the corresponding values for VO(2)max were 55 +/- 3.5 (female) and 60 +/- 4.7 ml/kg/min (male). The maximal values for peak torque and work for knee extension amounted to 206 +/- 21 (female) and 334 +/- 43 Nm (male), and 2690 +/- 364 (female) and 4414 +/- 629 J (male), respectively. In both sexes there were neither significant laterality nor dysbalance. The hamstring/quadriceps ratios were between 0.57 - 0.60. Among all physical and physiological variables, only the aerobic power in males was found to be strongly correlated (r = 0.947; p = 0.001 for W (max); r = 0.964; p < 0.001 for VO(2)max) to racing performance. The study proves the practical experience that success in professional alpine skiing is not related to single physiological variables. Two main factors, however, are crucial, i. e. high levels of aerobic power and muscle strength.

Exercise intensity of cycle-touring events.

The aim of the study was to analyze the exercise intensity of recreational cyclists participating in a cycling-touring event. In 14 male healthy recreational cyclists heart rate (HR) monitoring was performed during the Otztal Radmarathon 1999 (distance: 230 km; altitude difference: 5500 m) in order to evaluate the HR response and to estimate the cardiopulmonary strains for the less-trained athlete confronted with such a marathon. Four different exercise intensities were defined as percentages of maximal HR (HR(max)) as follows: recovery HR (HR(re)) < 70 % of HR max; moderate aerobic HR (HR(ma)) = 70 - 80 %; intense aerobic HR (HR(ia)) = 80 - 90 %; and anaerobic HR (HR(an)) > 90 %. All athletes finished the competition successfully. The mean racing time was 10 h 14 min, the average speed 22.5 km/h. The mean HR(max) was 188 bpm, the average value of the measured HRs (HR(average)) was 145 bpm resulting in a mean HR(average)/HR(max) ratio of 0.77. Athletes spent 18.5 % (1 h 54 min) of total race time within HR(re), 28 % (2 h 52 min) within HR(ma), 39.5 % (4 h 02 min) within HR(ia), and 14 % (1 h 26 min) within HR(an). The vast majority of exercise was done under "aerobic conditions" (HR(re) + HR(ma) + HR(ia) = 86 % or 8 h 48 min) - confirming the knowledge that the aerobic energy supply is crucial for the performance of long-term exercise. The large amount of high exercise intensities (HR(ia) + HR(an) = 53.5 % or 5 h 30 min), however, features the intense cardiopulmonary strains evoked by such competitions. The HR response was related to the course profile with HRs significantly declining in all subjects to an extent of 10 % during the course of race. Our findings show that the exercise intensity borne by recreational cyclists during a cycle-touring event is high and very similar to that of professionals. With respect to the high cardiovascular strains a thorough medical screening is advisable for any participant of such an event combining both high volume and high intensity loads.

[The significance of infection pathways for hepatitis C virus associated chronic liver disease]. / Die Bedeutung der Infektionswege für die Hepatitis-C-Virus-assoziierte chronische Lebererkrankung.

The importance of hepatitis C virus (HCV) infection as a cause of chronic liver disease has become clear with the introduction of serologic detection methods. On the basis of epidemiologic evidence the parenteral way of infection has been considered to be the most important one. However, the epidemiologic data regarding the significant route of infection are still limited. To study the ways of HCV-infection and their possible influence on the course of the disease, 73 patients with chronic hepatitis C infection were examined. Setting was the out-patient department of Gastroenterology of our University Hospital. Patients history, completed by a questionnaire, laboratory findings and liver histology were analysed. The study indicated that in 50% of the patients transmission had occurred through parenteral infection, the other 50% had been infected through the non-parenteral (sporadic) way. The study revealed further that the way of infection has an influence on the progression of liver disease with the patients infected sporadically showing histologically more serious hepatic changes. In 50 patients HCV-infection was the only cause of their chronic liver disease, in 23 patients additional pathogenic factors were detected. These 23 patients showed a rapid progress of the disease. Therefore, HCV-infection cannot be considered any longer as a disease that is primarily transmitted parenterally. Due to the large number of sporadic infections, HCV-infection will continue to be of great epidemiologic importance even after the effective elimination of contaminated blood products.

Short-term effects of prolonged strenuous endurance exercise on the level of haematocrit in amateur cyclists.

Knowledge is sparse about the extent of potential dehydration due to prolonged strenuous cycling and its haematological acute effects on the haematocrit (Hct) in study populations credibly not taking any kind of doping. With increasing training load levels of Hct and haemoglobin (Hb) decrease in both amateurs and professionals as a long-term consequence due to expanded plasma volume (PV). On a short-term basis, however, counteracting dehydration potentially brought about by endurance exercise may cause a rise in Hct bringing competitive cyclists into conflict with the current condition regulations and Hct cut-off of 50 % set by the International Cycling Union (UCI) in its fight against erythropoietin (rhEPO) doping. On the other hand adequate and sufficient fluid substitution being substantial for a successful endurance performance should prevent any pronounced Hct rises. To study the haematological acute effects of prolonged strenuous cycling we measured Hct, Hb, red blood cell (RBC) count and plasma protein in a reliably 'clean' population of 38 well-trained male amateur cyclists before, immediately after and one day after an extraordinary ultramarathon. The pre-race levels of Hct, Hb and RBC count were placed in the lower range of normal distribution and well below the Hct cut-off limit of the UCI. Immediately post-exercise the mean levels of Hct, Hb, RBC count and protein remained unchanged. One day after race, however, all four parameters significantly dropped by 3 %, 6.7 %, 6.5 %, 9.9 % respectively (p < 0.001), indicating marked post-exercise PV expansion. The calculated percentage increase in PV was 11.9 %. No evidence for coexisting exercise-induced haemolysis was found. Our study shows that in "clean, rhEPO-free" amateur cyclists who involve in strenuous marathon cycling the haematological short-term effects of extraordinary marathon cycling consist in considerable PV expansion making Hct values fall on the following day. The findings - gained from amateurs though - suggest that despite all its disadvantages the UCI Hct cut-off represents an appropriate means to discourage from excessive rhEPO doping at least as long as the available direct methods for detecting this kind of misuse are not yet applied by the international sports federations.

Heart rate response to ultraendurance cycling.

The heart rate (HR) response to ultraendurance cycling is poorly understood. This case report describes the exercise intensity of ultraendurance cycling by means of HR monitoring in a well trained male amateur cyclist performing the Otztal Radmarathon twice en bloque in a circuit of two identical laps (distance 460 km; cumulative altitude difference 11,000 m). The overall intensity was moderate (HR(mean) = 130 beats/min; HR(mean)/HR(max) = 0.71) corresponding to an average individual workload of 47% of VO(2)MAX. Almost the whole race was performed under aerobic conditions (99.6%); high intensity work was negligible (0.4%). The average speed and the HR response also declined in the course of the two laps, average speed by 17.2% (23.8 to 19.7 km/h), HR(mean) by 10.1% (138 to 124 beats/min), and HR(mean)/HR(max) by 10.7% (0.75 to 0.67). This scale of HR decrease corresponds to comparable data gained in the field of triathlon and represents a specific cardiac feature of ultraendurance exercise in general.

Effect of ultramarathon cycling on the heart rate in elite cyclists.

OBJECTIVES: To analyse the heart rate (HR) response and estimate the ultraendurance threshold-the optimum maintainable exercise intensity of ultraendurance cycling-in ultraendurance elite cyclists competing in the Race across the Alps. METHODS: HR monitoring was performed in 10 male elite cyclists during the first Race across the Alps in 2001 (distance: 525 km; cumulative altitude difference: 12 600 m) to investigate the exercise intensity of a cycle ultramarathon and the cardiopulmonary strains involved. Four different exercise intensities were defined as percentages of maximal HR (HR(max)) as follows: recovery HR (HR(re)), <70% of HR(max); moderate aerobic HR (HR(ma)), 70-80%; intense aerobic HR (HR(ia)), 80-90%; and high intensity HR (HR(hi)), >90%. RESULTS: All athletes investigated finished the competition. The mean racing time was 27 hours and 25 minutes, and the average speed was 18.6 km/h. The mean HR(max) was 186 beats/min, and the average value of measured HRs (HR(average)) was 126 beats/min resulting in a mean HR(average)/HR(max) ratio of 0.68, which probably corresponds to the ultraendurance threshold. The athletes spent 53% (14 hours 32 minutes) of total race time within HR(re), 25% (6 hours 51 minutes) within HR(ma), 19% (5 hours 13 minutes) within HR(ia), and only 3% (49 minutes) within HR(hi), which shows the exercise intensity to be predominantly moderate (HR(re) + HR(ma) = 78% or 21 hours 23 minutes). The HR response was influenced by the course profile as well as the duration. In all subjects, exercise intensity declined significantly during the race, as indicated by a decrease in HR(average)/HR(max) of 23% from 0.86 at the start to 0.66 at the end. CONCLUSIONS: A substantial decrease (10% every 10 hours) in the HR response is a general cardiovascular feature of ultramarathon cycling, suggesting that the ultraendurance threshold lies at about 70% of HR(max) in elite ultramarathon cyclists.