Fat oxidation kinetics during exercise in obese individuals.

Introduction An impaired ability to oxidize fat may be a factor in the obesity's aetiology (3). Moreover, the exercise intensity (Fatmax) eliciting the maximal fat oxidation rate (MFO) was lower in obese (O) compared with lean (L) individuals (4). However, difference in fat oxidation rate (FOR) during exercise between O and L remains equivocal and little is known about FORs during high intensities (>60% ) in O compared with L. This study aimed to characterize fat oxidation kinetics over a large range of intensities in L and O. Methods 12 healthy L [body mass index (BMI): 22.8±0.4] and 16 healthy O men (BMI: 38.9±1.4) performed submaximal incremental test (Incr) to determine whole-body fat oxidation kinetics using indirect calorimetry. After a 15-min resting period (Rest) and 10-min warm-up at 20% of maximal power output (MPO, determined by a maximal incremental test), the power output was increased by 7.5% MPO every 6-min until respiratory exchange ratio reached 1.0. Venous lactate and glucose and plasma concentration of epinephrine (E), norepinephrine (NE), insulin and non-esterified fatty acid (NEFA) were assessed at each step. A mathematical model (SIN) (1), including three variables (dilatation, symmetry, translation), was used to characterize fat oxidation (normalized by fat-free mass) kinetics and to determine Fatmax and MFO. Results FOR at Rest and MFO were not significantly different between groups (p≥0.1). FORs were similar from 20-60% (p≥0.1) and significantly lower from 65-85% in O than in L (p≤0.04). Fatmax was significantly lower in O than in L (46.5±2.5 vs 56.7±1.9 % respectively; p=0.005). Fat oxidation kinetics was characterized by similar translation (p=0.2), significantly lower dilatation (p=0.001) and tended to a left-shift symmetry in O compared with L (p=0.09). Plasma E, insulin and NEFA were significantly higher in L compared to O (p≤0.04). There were no significant differences in glucose, lactate and plasma NE between groups (p≥0.2). Conclusion The study showed that O presented a lower Fatmax and a lower reliance on fat oxidation at high, but not at moderate, intensities. This may be linked to a: i) higher levels of insulin and lower E concentrations in O, which may induce blunted lipolysis; ii) higher percentage of type II and a lower percentage of type I fibres (5), and iii) decreased mitochondrial content (2), which may reduce FORs at high intensities and Fatmax. These findings may have implications for an appropriate exercise intensity prescription for optimize fat oxidation in O. References 1. Cheneviere et al. Med Sci Sports Exerc. 2009 2. Holloway et al. Am J Clin Nutr. 2009 3. Kelley et al. Am J Physiol. 1999 4. Perez-Martin et al. Diabetes Metab. 2001 5. Tanner et al. Am J Physiol Endocrinol Metab. 2002

Gender differences in whole body fat oxidation kinetics during exercise

Introduction Discrepancies appear in studies comparing fat oxidation between men and women during exercise (1). Therefore, this study aimed to quantitatively describe and compare whole body fat oxidation kinetics between genders during exercise using a sinusoidal model (SIN) (2). Methods Twelve men and 11 women matched for age, body mass index (23.4±0.6 kg.m-2 and 21.5±0.8 kg.m-2, respectively) and aerobic fitness [maximal oxygen uptake ( ) (58.5±1.6 mL.kg FFM-1.min-1 and 55.3±2.0 mL.kg FFM-1.min-1, respectively) and power output ( ) per kilogram of fat-free mass (FFM)] performed submaximal incremental tests (Incr) with 5-min stages and 7.5% increment on a cycle ergometer. Respiratory and HR values were averaged over the last 2 minutes of each stage. All female study participants were eumenorrheic, reported regular menstrual cycles (28.6 ± 0.8 days) and were not taking oral contraceptives (OC) or other forms of exogenous ovarian hormones. Women were studied in the early follicular phase (FP) of their menstrual cycle (between days 3 and 8, where day 1 is the first day of menses). Fat oxidation rates were determined using indirect calorimetry and plotted as a function of exercise intensity. The SIN model (2), which includes three independent variables (dilatation, symmetry, translation), was used to mathematically describe fat oxidation kinetics and to determine the intensity (Fatmax) eliciting the maximal fat oxidation (MFO). Results During Incr, women exhibited greater fat oxidation rates from 35 to 85% , MFO (6.6 ± 0.9 vs. 4.5 ± 0.3 mgkg FFM-1min-1) and Fatmax (58.1 ± 1.9 vs. 50.0 ± 2.7% ) (P<0.05) than men. While men and women showed similar global shapes of fat oxidation kinetics in terms of dilatation and symmetry (P>0.05), the fat oxidation curve tended to be shifted towards higher exercise intensities in women (rightward translation, P=0.08). Conclusion These results showed that women, eumenorrheic, not taking OC and tested in FP, have a greater reliance on fat oxidation than men during submaximal exercise, but they also indicate that this greater fat oxidation is shifted towards higher exercise intensities in women compared with men. References 1. Blaak E. Gender differences in fat metabolism. Curr Opin Clin Nutr Metab Care 4: 499-502, 2001. 2. Cheneviere X, Malatesta D, Peters EM, and Borrani F. A mathematical model to describe fat oxidation kinetics during graded exercise. Med Sci Sports Exerc 41: 1615-1625, 2009.

Reproducibility of Fatmax and Fat Oxidation Rates during Exercise in Recreationally Trained Males.

Aerobic exercise training performed at the intensity eliciting maximal fat oxidation (Fatmax) has been shown to improve the metabolic profile of obese patients. However, limited information is available on the reproducibility of Fatmax and related physiological measures. The aim of this study was to assess the intra-individual variability of: a) Fatmax measurements determined using three different data analysis approaches and b) fat and carbohydrate oxidation rates at rest and at each stage of an individualized graded test. Fifteen healthy males [body mass index 23.1±0.6 kg/m2, maximal oxygen consumption ([Formula: see text]) 52.0±2.0 ml/kg/min] completed a maximal test and two identical submaximal incremental tests on ergocycle (30-min rest followed by 5-min stages with increments of 7.5% of the maximal power output). Fat and carbohydrate oxidation rates were determined using indirect calorimetry. Fatmax was determined with three approaches: the sine model (SIN), measured values (MV) and 3rd polynomial curve (P3). Intra-individual coefficients of variation (CVs) and limits of agreement were calculated. CV for Fatmax determined with SIN was 16.4% and tended to be lower than with P3 and MV (18.6% and 20.8%, respectively). Limits of agreement for Fatmax were -2±27% of [Formula: see text] with SIN, -4±32 with P3 and -4±28 with MV. CVs of oxygen uptake, carbon dioxide production and respiratory exchange rate were <10% at rest and <5% during exercise. Conversely, CVs of fat oxidation rates (20% at rest and 24-49% during exercise) and carbohydrate oxidation rates (33.5% at rest, 8.5-12.9% during exercise) were higher. The intra-individual variability of Fatmax and fat oxidation rates was high (CV>15%), regardless of the data analysis approach employed. Further research on the determinants of the variability of Fatmax and fat oxidation rates is required.

Incorporation and washout of n-3 PUFA after high dose intravenous and oral supplementation in healthy volunteers.

BACKGROUND & AIMS: Although the physiological effects of n-3 polyunsaturated fatty acids (n-3PUFA) are generally thought to require several weeks of exposure to allow their incorporation into plasma membranes, intravenous (IV) n-3PUFA attenuate the cardiovascular and neuroendocrine response to stress within 3 h. Whether oral n-3 PUFA exert similar early effects remains unknown. OBJECTIVE: To assess whether acute IV or short term oral n-3PUFA administration reproduces the metabolic effects of long term oral supplements during exercise, and how it relates to their incorporation into platelets and red blood cells (RBC) membranes. DESIGN: Prospective single center open label study in 8 healthy subjects receiving a 3-h infusion of 0.6 g/kg body weight n-3PUFA emulsion, followed one week later by an oral administration of 0.6 g/kg over 3 consecutive days. Maximal power output (cycling exercise), maximal heart rate (HR), blood lactate at exhaustion, and platelet function were measured at baseline and after IV or 3-day oral supplementation; platelet and RBC membrane composition were assessed until 15 days after n-3PUFA administration. RESULTS: Both IV and oral n-3PUFA significantly decreased maximal HR (-6% and -5%), maximal power output (-10%) and peak blood lactate (-47% and -52%) Platelet function tests were unchanged. The EPA and DHA membrane contents of RBC and platelets increased significantly, but only to 1.7-1.9% of fatty acid content. CONCLUSION: The cardiovascular and metabolic effects of n-3 PUFA during exercise occur already within 1-3 days of exposure, and may be unrelated to changes in membranes composition. Effects occur within hours of administration and are unrelated to lipid membrane composition. Trial registered at clinicaltrials.gov as NCT00516178.

Effect of a small dose of alcohol on the endurance performance of trained cyclists.

AIM: The aim of this study was to investigate the effect of an acute small ethanol (EtOH) dose (0.5 ml EtOH/kg fat-free mass, combined with carbohydrate) in a drink on endurance performance of trained cyclists. METHODS: Thirteen well-trained male cyclists took part in this study. A 60-min cycling endurance performance test (time trial) was performed in a calorimetric chamber after drinking an EtOH (30 +/- 1.8 ml) or a non-EtOH control (C) drink. RESULTS: Overall, EtOH induced a significant decrease in the average cycling power output (PO) (EtOH: 233 +/- 23 W versus C: 243 +/- 24 W, P < 0.01). The time course of mechanical PO showed an early decrease during the EtOH trial as compared to C (P < 0.01). Due to the lower PO, oxygen consumption, carbon dioxide production and glucose oxidation were significantly lower (P < 0.05) as compared to C. Relative to PO, heart rate response and ratings of perceived exertion (RPE) were increased by EtOH as compared to C (P < 0.05). In contrast, EtOH did not influence gross work efficiency, glycaemia and blood lactate concentration. CONCLUSIONS: These results show that the acute low dose of EtOH decreased endurance performance. An increase of cardio-vascular strain and psychobiological mechanisms may explain this decrease of endurance performance.

The effect of mountain bike suspensions on vibrations and off-road uphill performance.

AIM: This study evaluates the effect of front suspension (FS) and dual suspension (DS) mountain-bike on performance and vibrations during off-road uphill riding. METHODS: Thirteen male cyclists (27+/-5 years, 70+/-6 kg, VO(2max)59+/-6 mL.kg(-1).min(-1), mean+/-SD) performed, in a random sequence, at their lactate threshold, an off-road uphill course (1.69 km, 212 m elevation gain) with both type of bicycles. Variable measured: a) VO(2) consumption (K4b2 analyzer, Cosmed), b) power output (SRM) c) gain in altitude and d) 3-D accelerations under the saddle and at the wheel (Physilog, EPFL, Switzerland). Power spectral analy- sis (Fourier) was performed from the vertical acceleration data. RESULTS: Respectively for the FS and DS mountain bike: speed amounted to 7.5+/-0.7 km.h(-1) and 7.4+/-0.8 km.h(-1), (NS), energy expenditure 1.39+/-0.16 kW and 1.38+/-0.18, (NS), gross efficiency 0.161+/-0.013 and 0.159+/-0.013, (NS), peak frequency of vibration under the saddle 4.78+/-2.85 Hz and 2.27+/-0.2 Hz (P<0.01) and median-frequency of vertical displacements of the saddle 9.41+/-1.47 Hz and 5.78+/-2.27 Hz (P<0.01). CONCLUSION: Vibrations at the saddle level of the DS bike are of low frequencies whereas those of the FS bike are mostly of high frequencies. In the DS bike, the torque produced by the cyclist at the pedal level may generate low frequency vibrations. We conclude that the DS bike absorbs more high frequency vibrations, is more comfortable and performs as well as the FS bicycle.

Field Evaluation of Compaction Monitoring Technology: Phase I, 2004

This Phase I report describes a preliminary evaluation of a new compaction monitoring system developed by Caterpillar, Inc. (CAT), for use as a quality control and quality assurance (QC/QA) tool during earthwork construction operations. The CAT compaction monitoring system consists of an instrumented roller with sensors to monitor machine power output in response to changes in soil machine interaction and is fitted with a global positioning system (GPS) to monitor roller location in real time. Three pilot tests were conducted using CAT’s compaction monitoring technology. Two of the sites were located in Peoria, Illinois, at the Caterpillar facilities. The third project was an actual earthwork grading project in West Des Moines, Iowa. Typical construction operations for all tests included the following steps: (1) aerate/till existing soil; (2) moisture condition soil with water truck (if too dry); (3) remix; (4) blade to level surface; and (5) compact soil using the CAT CP-533E roller instrumented with the compaction monitoring sensors and display screen. Test strips varied in loose lift thickness, water content, and length. The results of the study show that it is possible to evaluate soil compaction with relatively good accuracy using machine energy as an indicator, with the advantage of 100% coverage with results in real time. Additional field trials are necessary, however, to expand the range of correlations to other soil types, different roller configurations, roller speeds, lift thicknesses, and water contents. Further, with increased use of this technology, new QC/QA guidelines will need to be developed with a framework in statistical analysis. Results from Phase I revealed that the CAT compaction monitoring method has a high level of promise for use as a QC/QA tool but that additional testing is necessary in order to prove its validity under a wide range of field conditions. The Phase II work plan involves establishing a Technical Advisor Committee, developing a better understanding of the algorithms used, performing further testing in a controlled environment, testing on project sites in the Midwest, and developing QC/QA procedures.

Effects of 2 different prior endurance exercises on whole-body fat oxidation kinetics: light vs. heavy exercise.

This study aimed to compare the effects of 2 different prior endurance exercises on subsequent whole-body fat oxidation kinetics. Fifteen men performed 2 identical submaximal incremental tests (Incr2) on a cycle ergometer after (i) a ∼40-min submaximal incremental test (Incr1) followed by a 90-min continuous exercise performed at 50% of maximal aerobic power-output and a 1-h rest period (Heavy); and (ii) Incr1 followed by a 2.5-h rest period (Light). Fat oxidation was measured using indirect calorimetry and plotted as a function of exercise intensity during Incr1 and Incr2. A sinusoidal equation, including 3 independent variables (dilatation, symmetry and translation), was used to characterize the fat oxidation kinetics and to determine the intensity (Fat(max)) that elicited the maximal fat oxidation (MFO) during Incr. After the Heavy and Light trials, Fat(max), MFO, and fat oxidation rates were significantly greater during Incr2 than Incr1 (p < 0.001). However, Δ (i.e., Incr2-Incr1) Fat(max), MFO, and fat oxidation rates were greater in the Heavy compared with the Light trial (p < 0.05). The fat oxidation kinetics during Incr2(Heavy) showed a greater dilatation and rightward asymmetry than Incr1(Heavy), whereas only a greater dilatation was observed in Incr2(Light) (p < 0.05). This study showed that although to a lesser extent in the Light trial, both prior exercise sessions led to an increase in Fat(max), MFO, and absolute fat oxidation rates during Incr2, inducing significant changes in the shape of the fat oxidation kinetics.

Kestomagneettitahtikoneen lämpömallinnus

Sähkökoneenterminen suunnittelu on yhtä tärkeätä kuin koneen sähköisten piirien ja magneettipiirin mitoitus, koska koneen lämpenemä määrää koneesta saatavan tehon. Pääosasähkökoneista suunnitellaan edelleen ns. perimätiedon avulla, jossa tukeudutaanvalmiiksi koeteltuihin ratkaisuihin ja kokemusperäiseen tietoon tiettyjen rakenteiden toimivuudesta. Perinteisin menetelmin uusia konerakenteita suunniteltaessa ei pystytä saamaan luotettavaa tietoa uusien ratkaisuiden toimivuudesta. Etenkin hitaasti pyörivien ja suuren vääntötiheyden omaavien kestomagneettitahtikoneiden jäähdytyksen mitoitus on ongelmallista. Siten tarve kehittää analyyttisiä työkaluja lämpenemän mallinnukseen on perusteltua. Tässä työssäperehdytään suuren tehotiheyden omaavien kestomagneettikoneiden urakoon ja virrantiheyden valintaan termisen mitoituksen kannalta. Työn tavoitteena on laatia yksinkertainen analyyttinen työkalu urakoon ja virrantiheyden valintaan. Työkaluavoidaan hyödyntää jo koneensuunnittelun alkuvaiheessa.

Sprint performance under heat stress: A review.

Training and competition in major track-and-field events, and for many team or racquet sports, often require the completion of maximal sprints in hot (>30 °C) ambient conditions. Enhanced short-term (<30 s) power output or single-sprint performance, resulting from transient heat exposure (muscle temperature rise), can be attributed to improved muscle contractility. Under heat stress, elevations in skin/core temperatures are associated with increased cardiovascular and metabolic loads in addition to decreasing voluntary muscle activation; there is also compelling evidence to suggest that large performance decrements occur when repeated-sprint exercise (consisting of brief recovery periods between sprints, usually <60 s) is performed in hot compared with cool conditions. Conversely, poorer intermittent-sprint performance (recovery periods long enough to allow near complete recovery, usually 60-300 s) in hotter conditions is solely observed when exercise induces marked hyperthermia (core temperature >39 °C). Here we also discuss strategies (heat acclimatization, precooling, hydration strategies) employed by "sprint" athletes to mitigate the negative influence of higher environmental temperatures.

Improvements in Air Intake on Frame 6 Gas Turbines

Työssä tarkastellaan kahta kaasuturbiinin imuilman sisäänottojärjestelmän kehitysmenetelmää, imuilman jäähdytystä ja sähköstaattista suodatusta. Imuilman jäähdytysmenetelmien tarkastelussa käytettiin kahta kaasuturbiinin tehonlisäystekniikoiden laskentatyökalua. Arviointi kohdistettiin Glanford Brigg Generating Station -voimalaitoksen kaasuturbiinityyppiin ja paikallisiin englantilaisiin ilmasto-olosuhteisiin. Tarkastelussa olivat kostutusjäähdytys ja overspray. Tuloksia vertailtiin keskenään ja näiden perusteella arvioitiin menetelmien vaikutuksia tehoon, hyötysuhteeseen sekä veden kulutukseen. Sähköstaattisen suodattimen prototyyppi oli rakennettu Briggin voimalaitokselle. Järjestelmää kehitetään kaupalliseksi tuotteeksi ja tätä varten kerättiin tekninen dokumentaatio kokonaisuudeksi, jota voitiin hyödyntää tuotteistusprosessissa. Imuilman jäähdyttämisellä voidaan saavuttaa merkittävä tehonlisäys ilmasto-olosuhteista riippuen. Menetelmällä voidaan myös tasata lämpötilan vuorokausi-vaihtelusta aiheutuvia tehoeroja. Sähköstaattisen suodattimen prototyyppi saavutti kehitysvaiheelle asetetut tavoitteet. Sähköstaattinen suodatus tarjoaa useita etuja perinteiseen mekaaniseen suodatukseen verrattuna.

Sähköä ja lämpöä tuottavien maakaasukäyttöisten pienvoimalaitosten kannattavuus Turengissa

Diplomityössä tutkitaan sähkön ja lämmön yhteistuotannon kannattavuutta Turengin nykyisen lämmöntuotannon yhteydessä. Tavoitteena on löytää taloudellisesti kilpailukykyiset tuotantovaihtoehdot Turengin energiahuollon kehittämisessä. Ensimmäisenä tarkasteltarkastellaan voimalaitoksen nykyiseen tuotantolaitteistoon kuuluvan vastapainehöyryturbiinin käyttöönoton mahdollisuuksia. Tämän jälkeen suoritetaan kannattavuuslaskelmat neljälle vaihtoehtoiselle investointitapaukselle. Voimalaitosinvestoinnit kohdistuvat kaasumoottori- ja kaasuturbiinivoimalaitoksiin, joilla tuotetaan sähköä, kaukolämpöä ja eräissä tapauksissa myös prosessihöyryä. Voimalaitosten nettosähkötehot ovat neljästä yhdeksään megawattia. Voimalaitosyksiköiden energiantuotanto määritetään Turengin lämpökuormien perusteella. Tuotannon määrityksessä apuna käytetään WinTEHO –ohjelmistoa, johon luodaan tarvittavat energiatiedostot. Kannattavuuslaskelmat suoritetaan vertaamalla investointivaihtoehtojen aiheuttamia vuotuisia kassavirtoja nykyisen tuotannon mukaisiin kassavirtoihin. Kassavirtalaskelmasta saadaan kullekin vaihtoehdolle nettonykyarvo, sisäinen korko ja takaisinmaksuaika. Tarkastelun tuloksena saatiin, että voimalaitosvaihtoehdoista kannattavin on investointi yhteen kaasumoottoriin, jolla tuotetaan sähkön lisäksi vain kaukolämpöä. Alhaisilla sähkön hinnoilla kaasuturbiinivaihtoehdot ovat suunnilleen yhtä kannattavia. Investointien nykyarvo valitulla korkokannalla on positiivinen, kun sähkön markkinahinnan keskiarvo tuotantokaudella ylittää likimain tason 130 mk/MWh. Nykyisillä markkinahinnoilla investoinnit eivät ole kannattavia. Investoiminen uuteen kaasumoottoriin tai -turbiiniin osoittautui kannattavammaksi kuin sähkön tuotannon aloittaminen laitoksen nykyisellä höyryturbiinilla. Merkittävin syy tähän oli höyryturbiinituotannon korkeat henkilöstökustannukset. Tehty selvitys tukee vallitsevaa käsitystä, että nykytekniikalla sähkön ja lämmön yhteistuotanto on taloudellisesti kilpailukykyistä myös pienessä kokoluokassa.

Effect of aerobic exercise on skeletal muscle mitochondrial content and function in older adults

Regular aerobic exercise training, which is touted as a way to ameliorate metabolic diseases, increases aerobic capacity. Aerobic capacity usually declines with advanced age. The decline in aerobic capacity is typically associated by a decrease in the quality of skeletal muscle. At the molecular level, this decreased quality comes in part from perturbations in skeletal muscle mitochondria. Of particular is a decrease in the total amount of mitochondria that occupy the skeletal muscle volume. What is not well established is if this decrease in mitochondrial content is due to inactive lifestyle or the process of aging. Herein, the work of the thesis shows a clear connection between mitochondrial content and aerobic capacity. This indicates that active individuals with higher VChmax levels also contain higher volumes of mitochondria inside their muscle as opposed to sedentary counterparts who have lower levels of mitochondrial content. Upon taking these previously sedentary individuals and entering them into an aerobic exercise intervention, they are able to recover their mitochondrial content as well as function to similar levels of lifelong athletes of the same age. Furthermore, the results of this thesis show that mitochondrial content and function also correlate with exercise efficiency. If one is more efficient, he/she is able to expend less energy for a similar power output. Furthermore, individuals who increase in efficiency also increase in the ability to oxidize and utilize fat during pro-longed exercise. This increased reliance on fat after the intervention is associated with an increased amount of mitochondria, particularly in the intermyofibrillar region of skeletal muscle. Therefore, elderly adults who were once sedentary were able to recover mitochondrial content and function and are able to reap other health benefits from regular aerobic exercise training. Aging per se does not seem to be the culprit that will lead to metabolic diseases but rather it seems to be a lack of physical activity. -- Un entraînement sportif d'endurance, connu pour réduire le risque de développer des maladies métaboliques, augmente notre capacité aérobie. La capacité aérobie diminue généralement avec l'âge. Ce déclin est typiquement associé d'une diminution de la qualité du muscle squelettique. Au niveau moléculaire, cette diminution est due à des perturbations dans les mitochondries du muscle squelettique,, ce qui conduit à une diminution de la quantité totale des mitochondries présentes dans le muscle squelettique. Il n'a pas encore été établi si cette diminution de la teneur mitochondriale est due à un mode de vie sédentaire ou au processus du vieillissement. Ce travail de thèse montre un lien clair entre le contenu mitochondrial et la capacité aérobie. Il indique que des personnes âgées actives, avec des niveaux de V02max plus élevés, possèdent également un volume plus élevé de mitochondries dans leurs muscles en comparaison à leurs homologues sédentaires. En prenant des individus sédentaires et leur faisant pratiquer une activité physique aérobie, il est possible d'accroître leur contenu de même que leur fonction mitochondriale à des niveaux similaires à ceux d'athlètes du même âge ayant pratiqué une activité physique tout au long de leur vie. De plus, les résultats de ce travail démontrent que le contenu et la fonction mitochondriale sont en corrélation avec l'efficiscience lors d'exercice physique. En agumentant l'effiscience, les personnes sont alors capables de dépenser moins d'énergie pour une puissance d'exercice similaire. Donc, un volume mitochondrial accru dans le muscle squelettique, associé à une fonction mitochondriale améliorée, est associté à une augmentation de l'effiscience. En outre, les personnes qui augmentent leur effiscience, augmentent aussi leur capacité à oxyder les graisses durant l'exercice prolongé. Une augmentation du recours au graisses après l'intervention est associée à une quantité accrue de mitochondries, en particulier dans la région inter-myofibrillaire du muscle squelettique. Par conséquent, les personnes âgées autrefois sédentaires sont en mesure de récupérer leur contenu et leur fonction mitochondriale ainsi que d'autres avantages pour la santé grâce à un entraînement aérobie régulier. Le vieillissement en soi ne semble donc pas être le coupable conduisant aux maladies métaboliques qui semblent plutôt être lié à un manque d'activité physique.

Kaksiakselisen välijäähdytyksellä, välipoltolla ja rekuperaattorilla varustetun mikrokaasuturbiinin osakuormahyötysuhteen säilyvyyden optimointi

Työssä pyrittiin etsimään differentiaalievoluutioalgoritmilla kaksiakseliselle, välijäähdytyksellä, välipoltolla ja rekuperaattorilla varustetulle mikrokaasuturbiinille sellaiset kompressorien painesuhteet ja rekuperaattorin rekuperaatioaste, että saavutettaisiin mandollisimman hyvä osakuormahyötysuhteen säilyvyys. Osakuormatehon säätömenetelmäksi oli valittu pyörimisnopeussäädön ja turbiinien sisääntulolämpötilan alentamisen yhdistelmä, jossa generaattorilla varustetun akselin pyörimisnopeus sekä molempien turbiinien sisääntulolämpötilat olivat toisistaan riippumatta vapaasti säädettävissä. Työssä löydettiin optimaalinen säätömenetelmien yhdistelmä, jolla saavutetaan parempi osakuormahyötysuhteen säilyvyys, kuin millään käytetyistä menetelmistä yksinään. Lisäksi havaittiin, ettei optimaalinen säätömenetelmä merkittävästi riipu koneikolle valituista suunnittelupisteen parametreista. Osakuormahyötysuhteen säilyvyyden kannalta optimaalinen koneikko ei merkittävästi poikennut suunnittelupisteen hyötysuhteen kannalta optimaalisesta.

Sustainable Waste-to-Energy Production: Performance Evaluation of Distributed Generation fuelled by Landfill Gas

The environmental impact of landfill is a growing concern in waste management practices. Thus, assessing the effectiveness of the solutions implemented to alter the issue is of importance. The objectives of the study were to provide an insight of landfill advantages, and to consolidate landfill gas importance among others alternative fuels. Finally, a case study examining the performances of energy production from a land disposal at Ylivieska was carried out to ascertain the viability of waste to energy project. Both qualitative and quantitative methods were applied. The study was conducted in two parts; the first was the review of literatures focused on landfill gas developments. Specific considerations were the conception of mechanism governing the variability of gas production and the investigation of mathematical models often used in landfill gas modeling. Furthermore, the analysis of two main distributed generation technologies used to generate energy from landfill was carried out. The review of literature revealed a high influence of waste segregation and high level of moisture content for waste stabilization process. It was found that the enhancement in accuracy for forecasting gas rate generation can be done with both mathematical modeling and field test measurements. The result of the case study mainly indicated the close dependence of the power output with the landfill gas quality and the fuel inlet pressure.