Ecological networks are complex systems forming hierarchical structures in which energy and matter is transferred between the network’s compartments. Predicting energy flows in food webs usually involves complex parameter-rich models. In this thesis, the application of the principle of maximum entropy (MaxEnt) to obtain least biased probability distributions based on prior knowledge is proposed as an alternative to predict the most likely energy flows in food webs from the network topology alone. This approach not only simplifies the characterisation of food web flow patterns based on little empirical knowledge but can also be used to investigate the role of bottom-up and top-down controlling forces in ecosystems resulting from the emergent phenomena based on the complex interactions on the level of species and individuals. The integrative measure of “flow extent”, incorporating both bottom- up and top-down controlling forces on ecosystems, is proposed as a principle behind ecosystem evolution and evaluated against empirical data on food web structure. It could be demonstrated that the method of predicting energy flow with the help of MaxEnt is very flexible, applicable to many different setting and types of questions in ecology, and therefore providing a powerful tool for modelling the energy transfer in ecosystems. Further research has to show in how far the most likely flow patterns are realised in real-word ecosystems. The concept of flow extent maximisation as a selection principle during ecosystem evolution can enhance the understanding of emergent phenomena in complex ecosystems and maybe help to draw a link between thermodynamics and ecology.

The purpose of this thesis is to extend understanding of the muscle metabolic responses of children and adolescents during exercise using the non-invasive technique of 31P-magnetic resonance spectroscopy (31P-MRS). The first experimental paper examined the reliability of measuring parameters of muscle metabolism in 11-12 year old children over three exhaustive incremental tests using a single-legged quadriceps ergometer. Exercise performance (peak power: ~ 10% coefficient of variation [CV]) and metabolic variables (muscle phosphate and pH intracellular thresholds [IT]: ~ 10% CV, and pH: ~ 1% CV at exhaustion) demonstrated good reliability, whereas the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) at exhaustion had poor reproducibility (~ 50% CV). The second paper examined the influence of age and sex on the muscle metabolic responses during incremental exercise in 9-12 year old children and young adults. The Pi/PCr and pH responses before and at the ITs were independent of age and sex, although during exercise above the ITs, the anaerobic energy contribution (increase in Pi/PCr, fall in pH) was higher in adults than children and in females compared with males, indicating an intensity dependence on age- and sex-related differences in muscle energetics. The third paper examined the relationship between the dynamics of muscle PCr, a putative controller of muscle respiration, and pulmonary oxygen uptake (pVO2) in 9-10 year old children during moderate intensity quadriceps and cycling exercise respectively. No differences were found between the PCr and phase II VO2 time constants at the onset (PCr 23 s [SD 5] vs. pVO2 23 s [SD 4]; P=1.000) or offset (PCr 28 s [SD 5] vs. pVO2 29 s [SD 5]; P=1.000) of exercise, suggesting an age-related slowing of the phosphate linked controller(s) of mitochondrial oxidative phosphorylation may underlie the faster pVO2 kinetics found in children compared to adults. The final experimental chapter tested this hypothesis, but no age or sex related differences were found in the PCr kinetic time constant at the onset (boys: 21 s [SD 4]; girls: 24 s [SD 5]; men: 26 s [SD 9]; women: 24 s [SD 7], P>0.200) or offset (boys: 26 s [SD 5]; girls: 29 s [SD 7]; men: 23 s [SD 9]; women: 29 s [SD 7], P>0.070) of exercise. In conclusion, this thesis has demonstrated that muscle metabolic parameters determined by 31P-MRS are suitable for the study of developmental exercise metabolism. During exercise below the metabolic ITs, the phosphate-linked regulation of muscle respiration is comparable between children and adults, although during exercise above the ITs children are characterised by a lower ‘anaerobic’ energy turnover than adults, indicating an age-related modulation of metabolic control during high intensity exercise.

Rates and energy equivalents of consumption (C), egestion+ excretion (FU) , assimilation (A), respiration (R) and production (P) were measured in two groups of Sceloporus olivaceus: 1) a laboratory group acclimated at four seasonally encountered temperatures (15, 20, 25 and 30°C) ; and 2) four acclimatization groups collected at different seasons when ambient temperatures corresponded to 15, 20, 25 and 30°C.

The relationships among energetics, environment and associated climatic changes is beginning to be a subject of a complex interest of not just science but also politics and law. The reason for this is the fact that we are now at a breaking point of the development of mankind and our future steps will significantly influence its path. To obtain the energy man cannot live without, we frequently use fossil fuels, producing greenhouse gases that are warming our planet. This situation needs to change. We either find a sustainable solution or we will cause a catastrophe. The energetics must not be the cause, it has to be the solution as well. One of possible solutions for this problem is the law. It is not a stand-alone solution but it is a fundamental one nonetheless. To come up with an effective solution, a large-scale cooperation is necessary in politics, science, economics and in society as well - and there is not much time to come up with it. Keywords: energetics, environment, climate change

A atmosfera é um complexo sistema termodinâmico na qual a geração, conversão e dissipação de energia desempenham um papel fundamental no desenvolvimento e manutenção dos diversos sistemas de movimento de escala sinótica e na circulação geral. Neste trabalho, o ciclo de energia de Lorenz em área limitada foi aplicado para três casos de ciclogêneses, onde cada um desses se formou em uma das três principais regiões ciclogenéticas da costa leste da América do Sul. Além disso, foram analisadas as condições sinóticas, bem como a evolução da estrutura tridimensional de cada sistema desde o período prévio à formação até o seu decaimento. As análises mostraram que o ciclone que se formou na costa sul/sudeste do Brasil originou-se a partir de uma baixa desprendida nos níveis médios em uma região de fraca baroclinia. As conversões de energia mostraram que o sistema extraía energia cinética do escoamento zonal médio indicando, assim, que a instabilidade barotrópica foi dominante na sua formação. O sistema que se desenvolveu região da foz do Rio da Prata apresentou características de uma ciclogenêse do tipo bomba, com rápida intensificação. Além disso, devido à esse rápido crescimento foi observado a seclusão das frentes quente e fria. O ciclo de energia mostrou uma natureza baroclínica com forte contribuição de geração de energia potencial disponível pela liberação de calor latente da convecção. Já o sistema da região da costa sul da Argentina apresentou um desenvolvimento baroclínico clássico (com conversão de energia potencial disponível para energia cinética da perturbação) de uma ciclogenêse extratropical, desde a amplificação da onda até oclusão final das frentes associadas. Com base nessas análises observa-se que as ciclogêneses que se formam na América do Sul podem apresentar características variadas, tanto de desenvolvimento como de estrutura, que não são muitas vezes relacionadas à ciclogenêse clássica. / The atmosphere is a complex thermodynamic system in which energy generation, conversion and dissipation play a key role in the development and maintenance of the synoptic scale movement systems. In this paper, the Lorenz energy cycle in a limited area was applied for three cases of cyclogenesis, where each one of them formed in an important cyclogenetic region in the east of South America. Furthermore, the synoptic conditions were analyzed, as well as the evolution of the tridimensional structure, from its early formation until its decay. The analysis showed that the cyclone, which formed on Brazil south/southeastern coast, originated through a cut off low in the mid levels on a weak baroclinic region. The energy conversions indicated the system extracted kinetic energy from the basic flow, showing that the barotropic instability was dominant in its development. The system that occurred in the Rio da Prata mouth had features of a bomb-type cyclogenesis with fast intensification. Moreover, due to this event, the fronts seclusion were observed. The baroclinic nature with a strong contribution from the available potential energy generation term, through the latent heat release of the convection, can be observed by the conversion terms. Meanwhile, the system of the Argentina south coast presented a classical baroclinic development (which has the conversion from eddy available potential energy to eddy kinetic energy) of an extratropical cyclogenesis, from the wave amplification until the final occlusion of the associated frontal system. Based in this analysis, it is worthy to note that both the development and structure of the cyclogenesis that occur in the South American eastern coast can present varied features, which are often not related to classical cyclogenesis.

The purpose of this study was two-fold: (1) to compare different home dehydrators and determine if the operation and design of the home dehydrators affected the color, cost, nutrient content, acceptability or flavor of the resulting products and (2) to determine the effect of physical parameters on product color, nutrient content, acceptability and flavor. The physical parameters that were measured during the dehydration process were temperature, relative humidity, and mass flow rate of air. Two products, Daucus carota var sativa (carrot) and juice of Lycopersicon sp. (tomato), were dried in each of six dehydrators (treatments). A sensory panel was used to determine the color, acceptability and flavor differences in dehydrated carrots and tomato juice form the different treatments. Carotene and ascorbic acid content were determined in the carrots and tomato juice, respectively. The total cost of dehydration was calculated by summing the fresh produce cost, energy costs, equipment and cost of labor. The design and operation of the five dehydrators designated for home use had significantly different effects on the cost, color, flavor, and acceptability of both carrots and tomato juice. Ascorbic acid content in dehydrated tomato juice production from the six dehydrators differed significantly, but, the carotene content of dehydrated carrots did not differ statistically between treatments.

In the Everest valley of Nepal, because of the rugged mountain terrain, the ‘roads' are nothing more than dirt mountain footpaths. Most of the material is conveyed over long distances by professional porters who carry impressive burdens in a wicker basket supported by a strap looped over their head. We measured the body weight and loads carried by the Himalayan porters passing along the busy footpath to Namche Bazaar, the main market place of the Everest region. On average, the porters were carrying loads equivalent to 90% of their body weight on the last day of a 7-9 day trip covering a horizontal distance of ~100 km with >8000 m of total ascents and >6300 m of total descents. Interestingly, these porters adopt a specific rhythm of walking: they generally walk slowly and make very frequent rest stops using a T-stick or stone-platforms built along the trail to support the load during the pause. It has been shown that African women could carry head-supported loads more economically than Western subjects because they have developed a mechanical energy-saving strategy. Similarly, Nepalese porters could also have developed a mechanism to carry economically their very heavy loads. To test this hypothesis, we measured the energy consumption and the mechanical work done during level walking under different loading and speed conditions in the Nepali porters and in Western subjects. We compared these results to those of the African women. Nepalese porters carry loads at a lower cost than either the control subjects or the African women. For example, for a load equivalent to 60% of body weight, western Caucasian subjects increases their metabolic rate by 60%, the African women by 40% and the Nepalese porters by only 30%. Contrary to the African women who are taking advantage of the load to reduce the work performed, Nepalese porters do not modify their gait while carrying a load. Consequently, the mechanical work performed is not reduced as compared to control subjects walking at same speed-load combinations. Yet the Nepalese porters are the most economical load-carriers measured to date, particularly while carrying heavy loads at walking speeds slower than 1.4 m/s, but the exact mechanisms by which they save energy are still unknown. G. J. Bastien et al. Eur J Appl Physiol 94, 76 (2005); G. J. Bastien et al. Science 308, 1755 (2005); G. J. Bastien et al. J Exp Biol submitted.

Environmental conditions on wintering or spring-staging areas may influence subsequent reproductive performance in migratory birds. These cross-seasonal effects may result from habitat loss and degradation (e.g., via contamination) which in turn reduce reproductive success, particularly in waterfowl that use stored nutrients for reproduction. North American lesser scaup (<i>Aythya affinis</i>) and white-winger scoter (<i>Melanitta fusca</i>) numbers have declined over the past 20 years, particularly in the boreal forest, and remain well below conservation goals, whereas ring-necked duck (<i>A. collaris</i>) numbers have increased. Environmental changes on scaup and scoter wintering and staging areas have raised concern about possible cross-seasonal effects on birds arriving on breeding grounds. The spring condition hypothesis (SCH) purports that many female scaup fail to acquire sufficient nutrients in late winter and spring, causing a decrease in breeding propensity and productivity. The contaminant hypothesis proposes that increased exposure to contaminants (particularly selenium [Se]) on wintering and staging areas has decreased scaup productivity. Accordingly, I compared body condition and studied Se concentrations in scaup, scoters and ringnecks to test the condition and contaminant hypotheses. <p>Scaup had similar body condition to ringnecks, and had similar body mass compared to scaup collected near Yellowknife, NT, in 1968-70. There was no relationship between scaup and ringneck nutrient levels and claw tip carbon, nitrogen or hydrogen isotope values, suggesting that arrival body condition likely was not related to location or diet several months prior. Instead, scaup and ringnecks nutrient levels may be more affected by feeding or habitat conditions on or near the breeding grounds. Scaup had slightly higher liver Se concentrations than ringnecks, but levels in both species were below recognized harmful threshold concentrations; I found no relationship between Se and breeding propensity, or between Se and somatic lipid or protein stores. Scoters had much higher Se concentrations, yet contrary to predictions, there were positive relationships between Se and both lipid stores and breeding status. Follicle [Se] in scaup was below threshold concentrations; despite high liver Se in scoters, egg and follicle levels also were well below threshold concentrations. Using both body composition analysis and stable-isotope analysis I determined that scoters derive egg protein from their breeding ground diet, which likely prevents Se deposition from somatic protein to eggs, and egg lipids are apparently derived from somatic tissues. In all three species, liver Se concentrations were significantly correlated with claw tip ä15N. As the claw tip likely represents assimilated diet from 2-5 months prior to sampling, this correlation suggests that Se in these boreal breeding species is carried over from wintering and staging areas. <p>Overall, results did not support either the spring condition or contaminant hypotheses. Scaup and scoters are late-nesting species, with highest pair densities occurring at the northern extent of their range. Maximum ring-neck pair densities occur at more southern latitudes. Ring-necks also nest earlier and appear to be more flexible in timing of nest initiation. Therefore, it is possible that due to climate change, early spring conditions alter the optimal timing of nest initiation to the detriment of late-nesting species such as scaup and scoters, and favour earlier nesters like ringnecks. Further research into this mismatch hypothesis is warranted.

A growing interest in the strengths of several interactions that play important structural roles in biochemical systems has been building over the past couple decades. The binding energies and entropies of formation of the clusters of several protonated amino acids and nucleic acid bases with methanol have been measured using High Pressure Mass Spectrometry. The results generally show that binding energy decreases when the proton affinity difference between the alcohol and amino acid is increased. The structures and energies of various alcohol stabilized conformers of these protonated biomolecules were computed using ab initio calculations at the MP2(Full)/6‐311++g(2d,2p) level of theory. The enthalpies of formation of the lowest energy conformers of the proton‐bound clusters between the alcohols and amino acids or peptides match very closely with the experimental values, indicating that protonation and subsequent methanol attachment occurs primarily at the terminal amine functionality. The methanol stabilized protonated nucleic acid bases have energies that match closely with a more entropically favourable conformation of the cluster, hence yielding less negative enthalpy changes experimentally. The effect of alcohol size on binding energy was also monitored through measurements of enthalpies and entropies of formation for the clusters of protonated diglycine with several alcohols. The binding energy between protonated diglycine and benzene was also measured, yielding a measurable cation‐π interaction of over 20 kcal mol‐1, a comparable value to typical strong hydrogen bonds.

A growing interest in the strengths of several interactions that play important structural roles in biochemical systems has been building over the past couple decades. The binding energies and entropies of formation of the clusters of several protonated amino acids and nucleic acid bases with methanol have been measured using High Pressure Mass Spectrometry. The results generally show that binding energy decreases when the proton affinity difference between the alcohol and amino acid is increased. The structures and energies of various alcohol stabilized conformers of these protonated biomolecules were computed using ab initio calculations at the MP2(Full)/6‐311++g(2d,2p) level of theory. The enthalpies of formation of the lowest energy conformers of the proton‐bound clusters between the alcohols and amino acids or peptides match very closely with the experimental values, indicating that protonation and subsequent methanol attachment occurs primarily at the terminal amine functionality. The methanol stabilized protonated nucleic acid bases have energies that match closely with a more entropically favourable conformation of the cluster, hence yielding less negative enthalpy changes experimentally. The effect of alcohol size on binding energy was also monitored through measurements of enthalpies and entropies of formation for the clusters of protonated diglycine with several alcohols. The binding energy between protonated diglycine and benzene was also measured, yielding a measurable cation‐π interaction of over 20 kcal mol‐1, a comparable value to typical strong hydrogen bonds.