Effect of acute hypoxia on respiratory muscle fatigue in healthy humans

<p>Abstract</p> <p>Background</p> <p>Greater diaphragm fatigue has been reported after hypoxic versus normoxic exercise, but whether this is due to increased ventilation and therefore work of breathing or reduced blood oxygenation per se remains unclear. Hence, we assessed the effect of different blood oxygenation level on isolated hyperpnoea-induced inspiratory and expiratory muscle fatigue.</p> <p>Methods</p> <p>Twelve healthy males performed three 15-min isocapnic hyperpnoea tests (85% of maximum voluntary ventilation with controlled breathing pattern) in normoxic, hypoxic (SpO₂= 80%) and hyperoxic (FiO₂= 0.60) conditions, in a random order. Before, immediately after and 30 min after hyperpnoea, transdiaphragmatic pressure (P_di,tw) was measured during cervical magnetic stimulation to assess diaphragm contractility, and gastric pressure (P_ga,tw) was measured during thoracic magnetic stimulation to assess abdominal muscle contractility. Two-way analysis of variance (time x condition) was used to compare hyperpnoea-induced respiratory muscle fatigue between conditions.</p> <p>Results</p> <p>Hypoxia enhanced hyperpnoea-induced P_di,twand P_ga,twreductions both immediately after hyperpnoea (P_di,tw: normoxia -22 ± 7% vs hypoxia -34 ± 8% vs hyperoxia -21 ± 8%; P_ga,tw: normoxia -17 ± 7% vs hypoxia -26 ± 10% vs hyperoxia -16 ± 11%; all <it>P </it>< 0.05) and after 30 min of recovery (P_di,tw: normoxia -10 ± 7% vs hypoxia -16 ± 8% vs hyperoxia -8 ± 7%; P_ga,tw: normoxia -13 ± 6% vs hypoxia -21 ± 9% vs hyperoxia -12 ± 12%; all <it>P </it>< 0.05). No significant difference in P_di,twor P_ga,twreductions was observed between normoxic and hyperoxic conditions. Also, heart rate and blood lactate concentration during hyperpnoea were higher in hypoxia compared to normoxia and hyperoxia.</p> <p>Conclusions</p> <p>These results demonstrate that hypoxia exacerbates both diaphragm and abdominal muscle fatigability. These results emphasize the potential role of respiratory muscle fatigue in exercise performance limitation under conditions coupling increased work of breathing and reduced O₂transport as during exercise in altitude or in hypoxemic patients.</p

A common biological basis of obesity and nicotine addiction

J. Kaprio ja J. Tuomilehto työryhmien jäseniä (yht. 281).Peer reviewe

Wet compression model for entropy production minimization

Compression-resorption heat pumps (CRHP) utilizing wet compression are a very promising option to upgrade waste heat from industry. CRHPs have the potential to have higher coefficient of performance (COP) than the traditionally used vapour-compression heat pumps (VCHP). However, commercial solutions utilizing wet compression are not available yet. Also, wet compression is a feasible option only if the efficiency of the compressor is sufficiently high, 0.7 or higher, as identified by several authors. In this study, we develop and validate a model of a twin screw compressor that is suitable for wet compression. The model is adapted to calculate the entropy production generation in order to identify where the major irreversibilities are located in the compressor. The effects of clearance size, rotational speed, ammonia concentrations, compressor inlet vapor quality as well as under- and over compression are analysed. The results show that the clearance size and the rotational speed have the largest effects on the entropy production. Additionally, increased ammonia concentration and decreased vapor quality lead to decreased losses. The results indicate that it should be feasible to reach the targeted performance if the clearances size is limited to 50 μm, the rotational speed maintained above 10,000 rpm, the ammonia concentration kept in the range of 30–40 wt.%, and the inlet vapor quality in the range 0.5–0.7.Engineering Thermodynamic

Permanent Electrochemical Doping of Quantum Dots and Semiconductor Polymers

Arguably the most controllable way to control the charge density in various semiconductors, is by electrochemical doping. However, electrochemically injected charges usually disappear within minutes to hours, which is why this technique is not yet used to make semiconductor devices. In this manuscript, electrochemical doping of different semiconductor films (ZnO Quantum Dots (QDs), PbS QDs, and P3DT) is investigated in various high melting-point nitrile-based solvents. It is shown that by charging the semiconductors at elevated temperatures, then cooling down to room temperature where these solvents are frozen, the doping stability increases immensely. Measurements performed in cyanoacetamide show that ion transport is entirely halted at room temperature, and that the n-type conductivity is stable for days, and only drops marginally (≈10%) in several weeks. For p-doped P3DT films, the conductivity is even completely stable during the entire 76 days of the measurement. In an ambient atmosphere, the p-type doping is stable, while the n-type doping disappears in several hours, as electrons react with molecular oxygen. Finally, a pn-junction diode made of a PbS QD film is demonstrated. These results highlight the possibility of using solidified electrolytes for electrochemical doping and for obtaining semiconductor devices wherein the doping density is controlled electrochemically.ChemE/Opto-electronic Material

Paul Petroff and Irina Baronova (centre), and artists of the company in, in Le mariage d'Aurore, Covent Garden Russian Ballet, Australian tour, His Majesty's Theatre, Melbourne, ca. 1938 [picture] /

From: Le mariage d'Aurore (Aurora's wedding) / music by Peter Ilich Tchaikovsky.; Inscription: "2G/3".; Part of the collection: Hugh P. Hall collection of photographs, 1938-1940.; Performed Sept-Nov 1938 and Mar-Apr 1939.; Choreography after Marius Petipa ; scenery by Léon Bakst ; costumes by Alexandre Benois.; Also available in an electronic version via the internet at: http://nla.gov.au/nla.pic-vn. One of a collection of photographs taken by Hugh P. Hall of 28 ballet productions performed by the Covent Garden Russian Ballet (toured Australia 1938-1939) and the Original Ballet Russe (toured Australia 1939-1940). These are the second and third of the three Ballets Russes companies which toured Australasia between 1936 and 1940. The photographs were taken from the auditorium during a live performance in His Majesty's Theatre, Melbourne and mounted on cardboard for display purposes. For conservation and storage, the photographs have been demounted. The original arrangement of the photographs has been recorded, and details are available from the Pictures Branch of the National Library