Energy Networks, Natural Monopolies and Tariff Regulation

Energy networks, such as the networks for the transportation of electricity and gas, are natural monopolies, which implies that competition among these networks is not possible. In order to protect network users against monopoly prices and to give the network operators the incentive to operate efficiently, many countries have implemented tariff regulation. After discussing the economic consequences of natural monopolies and the need for regulation, this chapter briefly compares the various types of tariff regulation, discussing the incentive power, the ability to make a profit, and the reward on the costs of capital. The chapter concludes by discussing how tariff regulation may enable network operators to finance the necessary investments to connect new renewable energy production facilities

Effects of 21 days of bed rest and whey protein supplementation on plantar flexor muscle fatigue resistance during repeated shortening contractions.

PURPOSE:Space flight and bed rest (BR) lead to a rapid decline in exercise capacity. Whey protein plus potassium bicarbonate diet-supplementation (NUTR) could attenuate this effect by improving oxidative metabolism. We evaluated the impact of 21-day BR and NUTR on fatigue resistance of plantar flexor muscles (PF) during repeated shortening contractions, and whether any change was related to altered energy metabolism and muscle oxygenation. METHODS:Ten healthy men received a standardized isocaloric diet with (n = 5) or without (n = 5) NUTR. Eight bouts of 24 concentric plantar flexions (30 s each bout) with 20 s rest between bouts were employed. PF muscle size was assessed by means of peripheral quantitative computed tomography. PF muscle volume was assessed with magnetic resonance imaging. PF muscle force, contraction velocity, power and surface electromyogram signals were recorded during each contraction, as well as energy metabolism (31P nuclear magnetic resonance spectroscopy) and oxygenation (near-infrared spectroscopy). Cardiopulmonary parameters were measured during an incremental cycle exercise test. RESULTS:BR caused 10-15% loss of PF volume that was partly recovered 3 days after re-ambulation, as a consequence of fluid redistribution. Unexpectedly, PF fatigue resistance was not affected by BR or NUTR. BR induced a shift in muscle metabolism toward glycolysis and some signs of impaired muscle oxygen extraction. NUTR did not attenuate the BR-induced-shift in energy metabolism. CONCLUSIONS:Twenty-one days' BR did not impair PF fatigue resistance, but the shift to glycolytic metabolism and indications of impaired oxygen extraction may be early signs of developing reduced muscle fatigue resistance

The Importance of Impact Loading and the Stretch Shortening Cycle for Spaceflight Countermeasures

Pronounced muscle and bone losses indicate that the musculoskeletal system suffers substantially from prolonged microgravity. A likely reason for these detrimental adaptations in the lower extremity is the lack of impact loading and the difficulty to apply large loading forces on the human body in microgravity. The human body is well adapted to ambulating in Earth’s gravitational field. A key principle herein is the periodic conversion of kinetic to elastic energy and vice versa. Predominantly tendons and to a lesser extent muscles, bones and other tissues contribute to this storage and release of energy, which is most efficient when organized in the stretch-shortening cycle (SSC). During SSC, muscles, especially those encompassing the ankle, knee, and hip joints, are activated in a specific manner, thereby enabling the production of high muscle forces and elastic energy storage. In consequence, the high forces acting throughout the body deform the viscoelastic biological structures sensed by mechanoreceptors and feedback in order to regulate the resilience of these structures and keep strains and strain rates in an uncritical range. Recent results from our lab indicate, notably, that SSC can engender a magnitude of tissue strains that cannot be achieved by other types of exercise. The present review provides an overview of the physiology and mechanics of the natural SSC as well as the possibility to mimic it by the application of whole-body vibration. We then report the evidence from bed rest studies on effectiveness and efficiency of plyometric and resistive vibration exercise as a countermeasure. Finally, implications and applications of both training modalities for human spaceflight operations and terrestrial spin-offs are discussed

The relationship between exercise-induced muscle fatigue, arterial blood flow and muscle perfusion after 56 days of muscle unloading

In the light of the dynamic nature of habitual plantar flexor activity, we utilized an incremental isokinetic exercise test (IIET) to assess the work-related power deficit (WoRPD) as a measure for exercise-induced muscle fatigue before and after prolonged calf muscle unloading and in relation to arterial blood flow and muscle perfusion. Eleven male subjects (31 ± 6 years) wore the HEPHAISTOS unloading orthosis unilaterally for 56 days. It allows habitual ambulation while greatly reducing plantar flexor activity and torque production. Endpoint measurements encompassed arterial blood flow, measured in the femoral artery using Doppler ultrasound, oxygenation of the soleus muscle assessed by near-infrared spectroscopy, lactate concentrations determined in capillary blood and muscle activity using soleus muscle surface electromyography. Furthermore, soleus muscle biopsies were taken to investigate morphological muscle changes. After the intervention, maximal isokinetic torque was reduced by 23·4 ± 8·2% (P<0·001) and soleus fibre size was reduced by 8·5 ± 13% (P = 0·016). However, WoRPD remained unaffected as indicated by an unchanged loss of relative plantar flexor power between pre- and postexperiments (P = 0·88). Blood flow, tissue oxygenation, lactate concentrations and EMG median frequency kinematics during the exercise test were comparable before and after the intervention, whereas the increase of RMS in response to IIET was less following the intervention (P = 0·03). In conclusion, following submaximal isokinetic muscle work exercise-induced muscle fatigue is unaffected after prolonged local muscle unloading. The observation that arterial blood flow was maintained may underlie the unchanged fatigability

Effects of Individualized Centrifugation Training on Orthostatic Tolerance in Men and Women

Aims Exposure to artificial gravity (AG) at different G loads and durations on human centrifuges has been shown to improve orthostatic tolerance in men. However, the effects on women and of an individual-specific AG training protocol on tolerance are not known. Methods We examined the effects of 90 minutes of AG vs. 90 minutes of supine rest on the orthostatic tolerance limit (OTL), using head up tilt and lower body negative pressure until presyncope of 7 men and 5 women. Subjects were placed in the centrifuge nacelle while instrumented and after one-hour they underwent either: 1) AG exposure (90 minutes) in supine position [protocol 1, artificial gravity exposure], or 2) lay supine on the centrifuge for 90 minutes in supine position without AG exposure [protocol 2, control]. The AG training protocol was individualized, by first determining each subject’s maximum tolerable G load, and then exposing them to 45 minutes of ramp training at sub-presyncopal levels. Results Both sexes had improved OTL (14 minutes vs 11 minutes, p &lt; 0.0019) following AG exposure. When cardiovascular (CV) variables at presyncope in the control test were compared with the CV variables at the same tilt-test time (isotime) during post-centrifuge, higher blood pressure, stroke volume and cardiac output and similar heart rates and peripheral resistance were found post-centrifuge. Conclusions These data suggest a better-maintained central circulating blood volume post-centrifugation across gender and provide an integrated insight into mechanisms of blood pressure regulation and the possible implementation of in-flight AG countermeasure profiles during spaceflights

VaPER-Studie: Strikte Einhaltung der -6°-Kopftieflage in Bettruhe - Eine Verbesserung des Bettruhe-Modells?

Einleitung: Im Herbst 2017 wurde eine Bettruhestudie mit dem Titel “Medium-term Bed Rest Study - VIIP and Psychological :envihab Research Study (VaPER)” als gemeinsames Projekt der NASA und des DLR in Köln durchgeführt. Hauptziel dieser Studie war es unter Simulation von physiologischen Effekten der Schwerelosigkeit, in dem Fall 30-tägiger Bettruhe in -6°-Kopftieflage, Einflüsse auf Anatomie und Physiologie des Gehirns sowie des Auges zu untersuchen. Seit 2011 bekannt wurde, dass bei einzelnen Astronauten nach ihrer Rückkehr aus mehrmonatiger Mission auf der ISS Augenveränderungen festgestellt worden sind (1), das sogenannte SANS, das Spaceflight Associated Neuroocular Syndrome (früher VIIP-Syndrom), steht die Erforschung dieser Augenveränderung verstärkt im Fokus, so auch bei der VaPER-Studie. Die Raumfahrt-Medizin bedient sich zur Erforschung der Auswirkungen von Schwerlosigkeit auf den menschlichen Körper auf der Erde seit Jahrzehnten eines Modells für Mikrogravitations-Simulation, der Bettruhe in -6° Kopftieflage (Head-Down-Tilt=HDT). Die strenge Einhaltung dieser Form der Bettruhe führt zu vergleichbaren physiologischen Auswirkungen im menschlichen Körper wie sie in realer Schwerelosigkeit beobachtet werden. Bei der VaPER-Studie wurde dieses Modell der Bettruhe nun mit erhöhtem CO2-Gehalt (0,5%) in der Raumluft kombiniert. Auf der ISS, der Internationalen Weltraumstation, herrschen generell hohe Kohlendioxid-Konzentrationen vor, diese können bis zu 0,7% betragen (zum Vergleich: die CO2- Konzentration in der Erdatmosphäre liegt bei 0,04%). Fragestellung: Erhöhte CO2-Konzentrationen (Hyperkapnie) in Mikrogravitation verstärken die zerebrale Durchblutung, die das intrakraniale Blutvolumen (2, 3) und den intrakraniellen Druck (4) erhöhen können. Wenn nun erhöhte CO2-Konzentrationen, wie auf der ISS üblich, zusätzlichen Einfluss auf die durch Schwerlosigkeit bedingte kraniale Flüssigkeitsverschiebung haben, könnte dadurch der intrakraniale Druck und damit das Risiko der Entstehung des SANS ggf. weiter erhöht werden. Im Gegensatz zu echter Schwerelosigkeit wirkt in HDT-Bettruhe nach wie vor der Gravitationsvektor, was zu abweichenden physiologischen Effekten führen kann. Bei Studien in Kopftieflage konnten bisher keine zerebralen oder ophthalmologischen Befunde wie bei von SANS betroffenen Astronauten beobachtet werden. Möglicherweise reicht aber `-6° HDT´ als Modell allein nicht aus, um diese Effekte auch am Boden zu erzeugen. Dies kann auch dadurch bedingt sein, dass Bettruhestudien-Probanden bisher generell Kissen verwendet haben, die eine Flüssigkeitsverschiebung in den Kopf möglicherweise abgeschwächt haben können. Steilere HDT-Neigungswinkel zur Erzeugung der Erhöhung des intrakranialen Blutvolumens sind bei Langzeit-Bettruhestudien nicht umsetzbar. Folglich sollte in der VaPER-Studie herausgefunden werden, ob das Bettruhemodell für SANS-bezogene Forschung verbessert werden kann, indem die CO2-Konzentration in der Atmosphäre erhöht und gleichzeitig die Bettruheposition in -6° HDT streng eingehalten wird. Methodik: Während der VaPER-Studie war den Probanden so erstmals keine Kissennutzung erlaubt, mit Ausnahme eines sehr dünnen Kissens beim Liegen auf der Seite. Die Probanden wurden während der gesamten Bettruhe durchgehend 24 Stunden kameraüberwacht und lückenlos auf strenge Einhaltung kontrolliert. Für die erfolgreiche Durchführung von Bettruhestudien ist die Adhärenz der Probanden äußerst wichtig. Voraussetzung hierfür ist u.a. ein sorgfältiges und umfassendes Screening der Studien-Bewerber vor Studieneinschluss, auch in Bezug auf psychologische Aspekte. Zum anderen ist neben der umfangreichen medizinischen Betreuung und der hohen wissenschaftlichen Expertise der beteiligtenExperimentatoren die Qualität der operationellen Umsetzung für die Durchführung von Langzeitbettruhestudien von großer Bedeutung. So ist in der hochmodern und vielseitig ausgestatteten Großforschungsanlage :envihab des Instituts für Luft- und Raumfahrtmedizin des DLR auch eine gute soziale Atmosphäre während der stationären Phase der Bettruhestudien für deren Erfolg essentiell, was die sehr niedrige Abbruchrate der Studienteilnehmer seit Jahren beweist und die durch die DLR Mitarbeiter in besonderem Maße umgesetzt wird. Schlussfolgerungen: Während der gesamten Studie zeigten alle Probanden eine sehr hohe Adhärenz und hielten die strikte -6° Kopftieflage ohne Einschränkungen ein. Die strikte -6° Kopftieflage verbunden mit der Erhöhung der CO2-Konzentration in der Raumluft auf 0,5% führte somit zu einer Verbesserung des Modells zur Erforschung der Effekte von Schwerelosigkeit. Zukünftige Studien müssen zeigen, ob allein strenge -6°- HDT-Bettruhe, Hyperkapnie oder beides in Kombination SANS-ähnliche Effekte hervorrufen, wie sie auch vereinzelt bei der VaPER-Studie beobachtet wurden

The :envihab - Linking biomedical research and technological innovation for Astronaut health

The DLR Institute of Aerospace Medicine has longtime experience in supporting human spaceflights. Ever since contributing to the Spacelab Program, the Institute has supported the psychological and medical astronaut selection, training, and mission operations. The program is flanked by state-of-the-art ground based biological, medical, and psychological research. The :envihab, derived from the words environment and habitat, is a unique medical research facility operated by the DLR Institute of Aerospace Medicine. Within its eight modules, :envihab houses multi-purpose laboratories and specialized equipment for life science research. Furthermore, :envihab features a high-end research ward accommodating study participants in bedrest studies and sleep investigations among others. The module comprises 12 individual rooms and can be conditioned using normobaric hypoxia or hypercapnia. :envihab offers a fully equipped human short-arm centrifuge equipped with a robotic-controlled ultrasonography device for examinations of cardiovascular parameters during exposure to centrifugation. The 3 Tesla PET-MRI allows for sophisticated structural, functional, and molecular imaging. The Biology Lab consists of four microbiology laboratory rooms, one of them is an ISO class 8 clean room. A large hypobaric chamber is suitable for hypobaric hypoxia, normobaric hypoxia, and hypercapnia studies. Finally, advanced cardiovascular, musculoskeletal, metabolic, ophthalmological, and psychological testing as well as highly controlled dietary support make :envihab a worldwide unique human research facility. Meanwhile, several mechanism-oriented sleep studies as well as bed rest studies up to 60 days have been successfully completed. The Institute supports postflight activities of ESA astronauts – the so-called “Direct Return”. Astronauts, crew surgeon and operational staff can be accommodated. The Crew Quarters are access-controlled for infection control and astronaut privacy. All medical post-flight examinations required according to the Medical Standards for Crewmembers can be performed at the adjacent DLR Flight Medicine Clinic. Pre- and post-flight examinations and measurements can be performed at the same site with the same equipment and the same staff, thus, limiting variability. Similarly, post-flight experiments are conducted by DLR scientists within :envihab. In November 2014, Alexander Gerst was the first astronaut to directly return to Cologne, followed by Andreas Mogensen (Sept. 2015), Timothy Peake (June 2016) and Thomas Pesquet (June 2017). We expect ISS commander Alexander Gerst as the next astronaut hosted at :envihab in 2018

Effects of long-term immobilisation on endomysium of the soleus muscle in humans

Muscle fibres atrophy during conditions of disuse. Whilst animal data suggest an increase in endomysium content with disuse, that information is not available for humans. We hypothesised that endomysium content increases during immobilisation. To test this hypothesis, biopsy samples of the soleus muscle obtained from 21 volunteers who underwent 60 days of bed rest were analysed using immunofluorescence-labelled laminin γ-1 to delineate individual muscle fibres as well as the endomysium space. The endomysium-to-fibre-area ratio (EFAr, as a percentage) was assessed as a measure related to stiffness, and the endomysium-tofibre-number ratio (EFNr) was calculated to determine whether any increase in EFAr was absolute, or could be attributed to muscle fibre shrinkage. As expected, we found muscle fibre atrophy (P = 0.0031) that amounted to shrinkage by 16.6% (SD 28.2%) on day 55 of bed rest. ENAr increased on day 55 of bed rest (P < 0.001). However, when analysing EFNr, no effect of bed rest was found (P = 0.62). These results demonstrate that an increase in EFAr is likely to be a direct effect of muscle fibre atrophy. Based on the assumption that the total number of muscle fibres remains unchanged during 55 days of bed rest, this implies that the absolute amount of connective tissue in the soleus muscle remained unchanged. The increased relative endomysium content, however, could be functionally related to an increase in muscle stiffness