Differential effects of food availability on minimum and maximum rates of metabolism

Metabolic rates reflect the energetic cost of living but exhibit remarkable variation among conspecifics, partly as a result of the constraints imposed by environmental conditions. Metabolic rates are sensitive to changes in temperature and oxygen availability, but effects of food availability, particularly on maximum metabolic rates, are not well understood. Here, we show in brown trout (Salmo trutta) that maximum metabolic rates are immutable but minimum metabolic rates increase as a positive function of food availability. As a result, aerobic scope (i.e. the capacity to elevate metabolism above baseline requirements) declines as food availability increases. These differential changes in metabolic rates likely have important consequences for how organisms partition available metabolic power to different functions under the constraints imposed by food availability

Transport Coefficients of the Yukawa One Component Plasma

We present equilibrium molecular-dynamics computations of the thermal conductivity and the two viscosities of the Yukawa one-component plasma. The simulations were performed within periodic boundary conditions and Ewald sums were implemented for the potentials, the forces, and for all the currents which enter the Kubo formulas. For large values of the screening parameter, our estimates of the shear viscosity and the thermal conductivity are in good agreement with the predictions of the Chapman-Enskog theory.Comment: 11 pages, 2 figure

Pattern of Reaction Diffusion Front in Laminar Flows

Autocatalytic reaction between reacted and unreacted species may propagate as solitary waves, namely at a constant front velocity and with a stationary concentration profile, resulting from a balance between molecular diffusion and chemical reaction. The effect of advective flow on the autocatalytic reaction between iodate and arsenous acid in cylindrical tubes and Hele-Shaw cells is analyzed experimentally and numerically using lattice BGK simulations. We do observe the existence of solitary waves with concentration profiles exhibiting a cusp and we delineate the eikonal and mixing regimes recently predicted.Comment: 4 pages, 3 figures. This paper report on experiments and simulations in different geometries which test the theory of Boyd Edwards on flow advection of chemical reaction front which just appears in PRL (PRL Vol 89,104501, sept2002

The RCR and ATP/O indices can give contradictory messages about mitochondrial efficiency.

Mitochondrial efficiency is typically taken to represent an animal's capacity to convert its resources into ATP. However, the term mitochondrial efficiency, as currently used in the literature, can be calculated as either the respiratory control ratio, RCR (ratio of mitochondrial respiration supporting ATP synthesis to that required to offset the proton leak) or as the amount of ATP generated per unit of oxygen consumed, ATP/O ratio. The question of how flexibility in mitochondrial energy properties (i.e. in rates of respiration to support ATP synthesis and offset proton leak, and in the rate of ATP synthesis) affects these indices of mitochondrial efficiency has tended to be overlooked. Furthermore, little is known of whether the RCR and ATP/O ratio vary in parallel, either among individuals or in response to environmental conditions. Using data from brown trout Salmo trutta we show that experimental conditions affect mitochondrial efficiency, but the apparent direction of change depends on the index chosen: a reduction in food availability was associated with an increased RCR (i.e. increased efficiency) but a decreased ATP/O ratio (decreased efficiency) in liver mitochondria. Moreover, there was a negative correlation across individuals held in identical conditions between their RCR and their ATP/O ratio. These results show that the choice of index of mitochondrial efficiency can produce different, even opposing, conclusions about the capacity of the mitochondria to produce ATP. Neither ratio is necessarily a complete measure of efficiency of ATP production in the living animal (RCR because it contains no assessment of ATP production, and ATP/O because it contains no assessment of respiration to offset the proton leak). Consequently, we suggest that a measure of mitochondrial efficiency obtained nearer to conditions where respiration simultaneously offsets the proton leak and produce ATP would be sensitive to changes in both proton leakage and ATP production, and is thus likely to be more representative of the state of the mitochondria in vivo

Differences in mitochondrial efficiency explain individual variation in growth performance

The physiological causes of intraspecific differences in fitness components such as growth rate are currently a source of debate. It has been suggested that differences in energy metabolism may drive variation in growth, but it remains unclear whether covariation between growth rates and energy metabolism is: (i) a result of certain individuals acquiring and consequently allocating more resources to growth, and/or is (ii) determined by variation in the efficiency with which those resources are transformed into growth. Studies of individually housed animals under standardized nutritional conditions can help shed light on this debate. Here we quantify individual variation in metabolic efficiency in terms of the amount of adenosine triphosphate (ATP) generated per molecule of oxygen consumed by liver and muscle mitochondria and examine its effects, both on the rate of protein synthesis within these tissues and on the rate of whole-body growth of individually fed juvenile brown trout (Salmo trutta) receiving either a high or low food ration. As expected, fish on the high ration on average gained more in body mass and protein content than those maintained on the low ration. Yet, growth performance varied more than 10-fold among individuals on the same ration, resulting in some fish on low rations growing faster than others on the high ration. This variation in growth for a given ration was related to individual differences in mitochondrial properties: a high whole-body growth performance was associated with high mitochondrial efficiency of ATP production in the liver. Our results show for the first time, to our knowledge, that among-individual variation in the efficiency with which substrates are converted into ATP can help explain marked variation in growth performance, independent of food intake. This study highlights the existence of inter-individual differences in mitochondrial efficiency and its potential importance in explaining intraspecific variation in whole-animal performance

Differences in mitochondrial efficiency explain individual variation in growth performance

The physiological causes of intraspecific differences in fitness components such as growth rate are currently a source of debate. It has been suggested that differences in energy metabolism may drive variation in growth, but it remains unclear whether covariation between growth rates and energy metabolism is: (i) a result of certain individuals acquiring and consequently allocating more resources to growth, and/or is (ii) determined by variation in the efficiency with which those resources are transformed into growth. Studies of individually housed animals under standardized nutritional conditions can help shed light on this debate. Here we quantify individual variation in metabolic efficiency in terms of the amount of adenosine triphosphate (ATP) generated per molecule of oxygen consumed by liver and muscle mitochondria and examine its effects, both on the rate of protein synthesis within these tissues and on the rate of whole-body growth of individually fed juvenile brown trout (Salmo trutta) receiving either a high or low food ration. As expected, fish on the high ration on average gained more in body mass and protein content than those maintained on the low ration. Yet, growth performance varied more than 10-fold among individuals on the same ration, resulting in some fish on low rations growing faster than others on the high ration. This variation in growth for a given ration was related to individual differences in mitochondrial properties: a high whole-body growth performance was associated with high mitochondrial efficiency of ATP production in the liver. Our results show for the first time, to our knowledge, that among-individual variation in the efficiency with which substrates are converted into ATP can help explain marked variation in growth performance, independent of food intake. This study highlights the existence of inter-individual differences in mitochondrial efficiency and its potential importance in explaining intraspecific variation in whole-animal performance

Individuals with higher metabolic rates have lower levels of reactive oxygen species in vivo

There is increasing interest in the effect of energy metabolism on oxidative stress, but much ambiguity over the relationship between the rate of oxygen consumption and the generation of reactive oxygen species (ROS). Production of ROS (such as hydrogen peroxide, H2O2) in the mitochondria is primarily inferred indirectly from measurements in vitro, which may not reflect actual ROS production in living animals. Here, we measured in vivo H2O2 content using the recently developed MitoB probe that becomes concentrated in the mitochondria of living organisms, where it is converted by H2O2 into an alternative form termed MitoP; the ratio of MitoP/MitoB indicates the level of mitochondrial H2O2 in vivo. Using the brown trout Salmo trutta, we tested whether this measurement of in vivo H2O2 content over a 24 h-period was related to interindividual variation in standard metabolic rate (SMR). We showed that the H2O2 content varied up to 26-fold among fish of the same age and under identical environmental conditions and nutritional states. Interindividual variation in H2O2 content was unrelated to mitochondrial density but was significantly associated with SMR: fish with a higher mass-independent SMR had a lower level of H2O2. The mechanism underlying this observed relationship between SMR and in vivo H2O2 content requires further investigation, but may implicate mitochondrial uncoupling which can simultaneously increase SMR but reduce ROS production. To our knowledge, this is the first study in living organisms to show that individuals with higher oxygen consumption rates can actually have lower levels of H2O2

Wave Number of Maximal Growth in Viscous Magnetic Fluids of Arbitrary Depth

An analytical method within the frame of linear stability theory is presented for the normal field instability in magnetic fluids. It allows to calculate the maximal growth rate and the corresponding wave number for any combination of thickness and viscosity of the fluid. Applying this method to magnetic fluids of finite depth, these results are quantitatively compared to the wave number of the transient pattern observed experimentally after a jump--like increase of the field. The wave number grows linearly with increasing induction where the theoretical and the experimental data agree well. Thereby a long-standing controversy about the behaviour of the wave number above the critical magnetic field is tackled.Comment: 19 pages, 15 figures, RevTex; revised version with a new figure and references added. submitted to Phys Rev

Статистическая оценка деятельности коллективных средств размещения и их вклада в экономику субъектов Российской Федерации

The purpose of the study. Tourism is a priority area of economic development. Short-term accommodation of tourists plays an important role in the tourism industry. The indicator of the number of persons placed in collective accommodation facilities is used to determine the tourist flow in the context of the regions of the Russian Federation. The approach we have used in this study aims to analyze the activity of collective accommodation facilities and assess their contributionto the economy of the Russian Federation regions based on current statistical information. The research was carried out at the expense of budgetary funds on the state assignment to the Financial University under the Government of the Russian Federation. The study focuses on:analysis of the activity of collective accommodation facilities on the territory of Russia,testing the hypothesis that the differences in the main indicators, characterizing the activity of collective accommodation facilities are due to the influence of the territorial factor,evaluate the efficiency of functioning of collective accommodation facilities and their profitability, and highlight the regions of Russia with low, medium and high levels of profitability of tourist accommodation facilities,assess the contribution of the activity of collective accommodation facilities for tourists to the economy of the regions of Russia. Materials and methods. In the paper, the authors considered definitions, classification, a system of indicators that form a methodological basis for statistical observation of the activity of collective accommodation facilities and their presentation in accordance with the current international and national statistical standards. We applied the grouping method, structural and dynamic data analysis. The hypothesis of the normal distribution of the data was tested on the basis of the Shapiro-Wilk Test. The hypothesis that the differences in indicators characterizing tourist activity are due to the influence of the regional factor was tested using the nonparametric Kruskal-Wallis Test. To assess the contribution of the activity of collective accommodation facilities to the economy of the Russian region, the authors calculated an integral index assessing the resources and results of tourism activities in the region. The analysis was carried out according to 5 indicators characterizing tourist activity in 82 regions of the Russian Federation in 2019.Results. The study found that the territorial factor has a statistically significant effect on the number of seats for receiving tourists, the number of accommodated persons, the number of overnight stays. At the same time, the differences in the distribution of the collective accommodation facilities over the territory of Russia are caused not by the belonging of the region of Russia to a certain federal district, but by other factors. The study also made it possible to come to the conclusion that, in terms of the profitability of collective accommodation facilities, the regions of Russia are extremely heterogeneous. The authors identified groups of Russian regions with profitability of collective accommodation facilities below average, above average and high. The integral index, based on the resources and results of tourist activity, made it possible to determine the regions of Russia, in which the results of tourist activities are ahead, correspond or lag behind the available resources for the implementation of tourist activities. Conclusion. The results obtained will make it possible to correlate the resources of each Russian region for the implementation of tourist activities with its results. An increase in the number of accommodations, an increase in their level of comfort, accessibility, and convenient location will give an impetus to the development of the tourism sector in Russia; arouse interest in tourist trips both among citizens of the country and among foreign guests. The regional aspect of the location of accommodation facilities is extremely important, since it is not only the basic position of the tourist infrastructure, but also has a direct impact on the contribution of tourist activity to the economy of the region of Russia. Therefore, the issue of the influence of accommodation facilities on the region’s economy requires further study.Цель исследования. Приоритетным направлением развития экономики России является туризм. Краткосрочное размещение туристов занимает важное место в индустрии туризма. Показатель численности лиц, размещенных в коллективных средствах размещения, применяется для определения туристского потока в разрезе субъектов Российской Федерации. В рамках реализации исследований, выполненных за счет бюджетных средств по государственному заданию Финансовому университету при Правительстве РФ, авторы предприняли попытку проанализировать деятельность коллективных средств размещения и оценить их вклад в экономику субъектов Российской Федерации на основе актуальной статистической информации. В соответствии с целью исследования были поставлены следующие задачи:Провести анализ деятельности коллективных средств размещения на территории России.Проверить гипотезу о том, что различия в основных показателях, характеризующих деятельность коллективных средств размещения, обусловлены влиянием территориального фактора.Оценить эффективность функционирования коллективных средств размещения и их доходность, и выделить субъекты России с низким, средним и высоким уровнем доходности средств размещения туристов.Произвести оценку вклада деятельности коллективных средств размещения туристов в экономику субъекта России. Материалы и методы. В работе авторы рассмотрели определения, классификацию, систему показателей, образующие методологическую основу для статистического наблюдения деятельности коллективных средств размещения и их представления в соответствии с действующими международными и национальными стандартами статистического учета. Применили метод группировки, структурный и динамический анализ данных. Проверка гипотезы о нормальности распределения данных осуществлялась на основе критерия Шапиро-Уилка (Shapiro-Wilk Test). Проверка гипотезы о том, что различия в показателях, характеризующих туристскую деятельность, обусловлены влиянием регионального фактора, производилась с применением непараметрического теста Краскела-Уолиса (Kruskal-Wallis Test). Для оценки вклада деятельности коллективных средств размещения в экономику субъекта России авторы рассчитали интегральный индекс, оценивающий ресурсы и результаты туристской деятельности в регионе. Анализ проведен по 5 показателям, характеризующим туристскую деятельность по 82 субъектам Российской Федерации за 2019 год. Результаты. В ходе исследования установлено, что территориальный фактор оказывает статистически значимое влияние на количество мест для приема туристов, число размещенных лиц, количество ночевок. При этом различия в распределении самих коллективных средств размещения по территории России обусловлены не принадлежностью субъекта России к определенному федеральному округу, а прочими факторами. Исследование, также, позволило прийти к выводу, что по показателю доходности коллективных средств размещения субъекты России крайне неоднородны. Авторы выделили группы субъектов России с доходностью коллективных средств размещения ниже среднего, выше среднего и высокой. Интегральный индекс, основанный на ресурсах и результатах туристской детальности, позволил определить субъекты России, в которых результаты туристской деятельности опережают, соответствуют или отстают от располагаемых ресурсов для осуществления туристской деятельности.Заключение. Результаты, полученные в ходе исследования, позволят соотнести ресурсы каждого субъекта России для осуществления туристской деятельности с ее результатами. Увеличение числа мест размещения, повышение их уровня комфорта, доступность, удобное расположение придаст импульс развитию сферы туризма в России, вызовет интерес к туристским поездкам как у граждан страны, так и у иностранных гостей. Региональный аспект расположения средств размещения имеет чрезвычайно важное значение, так как не только является базовой позицией туристской инфраструктуры, но и оказывает прямое воздействие на вклад туристской деятельности в экономику субъектов России. Поэтому вопрос влияния средств размещения на экономику региона требует дальнейшего изучения