The energy budget of man at high altitudes

Observations (mid-July) were made, at high altitudes (3,080 m to 4,267 m, White Mountains, California), of the radiative physical and physiological parameters of importance to man. The data was used to show how man was actually coupled to the climatological events and processes going on at the physical-horizontal interface. Such observations were then used to test theoreticalempirical models predicting such interactions between man and the environment. High correlations were found between hypothesis and observations during the investigational period. Subsequently, an all-year simulation was conducted which attempted to predict the annual march of net radiation on the human and its causal components for high elevations in arid regions.

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Zusammenfassung In der Höhe von 3.080 bis 4.267 m (White Mountain, California) wurden Mitte Juli Strahlungsmessungen vorgenommen. Die Messungen sollten die enge Kopplung der menschlichen Funktionen mit den klimatischen Bedingungen aufzeigen. Die Beobachtungen wurden weiter zur Prüfung theoretischempirischer Modelle zur Voraussage von Mensch-Umwelt Beziehungen verwendet. Während der Untersuchungsperiode wurden signifikante Korrelationen zwischen Hypothese und Beobachtung gefunden. Deshalb wurde die Beziehung simuliert für alle Monate berechnet, um den Jahresgang der Strahlungsbilanz auf den Menschen und ihre Komponenten für grosse Erhöhungen in ariden Gebieten vorauszusagen.

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Resume A la mi-juillet, on a effectuê des mesures du rayonnement entre 3.080 et 4.267 m d'altitude dans les White Montain de Californie. Ces mesures avaient pour but d'établir une relation étroite entre les fonctions humaines et les conditions climatiques ambiantes. Ces observations ont en outre été utilisées pour vérifier des modèles théoriques et empiriques, modèles permettant un pronostic des réactions de l'homme selon le milieu. On a obtenu de hautes corrélations entres les hypothèses émises et les observations faites durant la période d'investigations. Par conséquent, on a calculé pour chaque mois la relation trouvée afin de prévoir les réactions humaines à haute altitude et en climat aride sur la base de l'évolution annuelle de la radiation nette.

     

An energy budget for Porites porites (Scleractinia), growing in a stressed environment

An energy budget was determined for the coral Porites porites living in a stressed environment for comparison of the energy inputs and expenditure with those of the same species living in an adjacent clear water fore reef environment. The stressed site was characterised by higher sedimentation and lower irradiances than at the fore reef site. Zooplankton ingestion was found to be an insignificant component of the energy intake: the coral is fully autotrophic under stress conditions. The integrated 24 h rate of photosynthetic energy production on a clear sunny day was 20% higher for stressed corals compared to fore reef corals. This was largely the result of photoadaptation which resulted in increased values for and decreased values for I_k in the hyperbolic tangent function equation for the photosynthesis versus irradiance curve. The energy investment in growth of animal tissue was lower in stressed corals. The percentage translocation of photosynthase to the animal tissue remained at about 78%, but the respiration rate of the animal tissue was reduced by 3 fold. These data combined with the high rate of photosynthetic production predict a net daily energy surplus of 67% in stressed corals compared with the 45% surplus in unstressed corals. Scope for growth is reduced under stress conditions.     

The quantitative genetics of sustained energy budget in a wild mouse

We explored how morphological and physiological traits associated with energy expenditure over long periods of cold exposure would be integrated in a potential response to natural selection in a wild mammal, Phyllotis danwini. In particular, we studied sustained energy expenditure (SusMR), the rate of expenditure fueled by concurrent energy intake, basal metabolic rate (BMR), and sustained metabolic scope (SusMS = SusMR/BMR), a measure of the reserve for sustained work. We included the masses of different central processing organs as an underlying factor that could have a mechanistic link with whole animal traits. Only the liver had heritability statistically different from zero (0.73). Physiological and morphological traits had high levels of specific environmental variance (average 70%) and postnatal common environmental variance (average 30%) which could explain the low heritabilities estimates. Our results, (1) are in accordance with previous studies in mammals that report low heritabilities for metabolic traits (SusMR, BMR, SusMS), (2) but not completely with previous ones that report high heritabilities for morphological traits (masses of central organs), and (3) provide important evidence of the relevance of postnatal common environmental variance to sustained energy expenditure.     

Comfort of man in the city. An energy balance model of man — environment coupling

The powerful energy-balance systems approach was applied to the quantification of man-environment relations in an urban area. Nine special purpose energy-balance models of man-environment relations are summarized. Physiologic comfort is defined. Research resulted in the development of a general purpose man model for predicting the elements which can be used to derive the comfort of man in any environment as well as the magnitudes and directions of the various energy exchanges. The model has been applied to the special case of summertime thermal comfort of individuals in various parts of a large city (Sacramento, California) and has revealed quantitative information on the unique microclimates within a city.     

How to budget metabolic energy: torpor in a small Neotropical mammal

Neotropical nectar-feeding bats (Glossophaginae) are highly specialized in the exploitation of floral nectar and have one of the highest mass-specific metabolic rates among mammals. Nevertheless, they are distributed throughout the tropics and subtropics over a wide elevational range, and thus encounter many extreme and energetically challenging environmental conditions. Depressing their otherwise high metabolic rate, e.g., in situations of food restriction, might be an important adaptive physiological strategy in these dietary specialists. We investigated the thermoregulatory behavior of captive 10-g nectar feeding bats (Glossophaga soricina; Chiroptera, Phyllostomidae) under variable ambient temperatures (T _a) and feeding regimes and predicted that bats would use torpor as an energy-conserving behavior under energetic constraints. All tested animals entered torpor in response to energetic restrictions and the depth of torpor was dependent on the body condition of the animals and hence on their degree of physiological constraints. Periods of torpor with body temperatures (T _b) below 34°C were precisely adjusted to the photoperiod. The median length of diurnal torpor was 11.43 h. The lowest T _b measured was 21°C at a T _a of 19°C. Estimated energy savings due to torpor were considerable, with reductions in metabolic rate to as low as 5% of the metabolic rate of normothermic bats at the same T _a. However, contrary to temperate zone bats that also employ diurnal torpor, G. soricina regulated their T _b to the highest possible levels given the present energetic supplies. To summarize, G. soricina is a precise thermoregulator, which strategically employs thermoregulatory behavior in order to decrease its energy expenditure when under energetic restrictions. This adaptation may play a crucial role in the distribution and the assembly of communities of nectar-feeding bats and may point to a general capacity for torpor in tropical bats.     

The Chitty effect: a consequence of dynamic energy allocation in a fluctuating environment

An important biological feature of cyclic populations of voles and lemmings is phase-related changes in average body mass, with adults in high-density phases being 20-30% heavier than those in low-density phases of a cycle. This observation, called the "Chitty effect," is considered to be a ubiquitous feature of cyclic populations. It has been argued that understanding the Chitty effect is fundamental to unraveling the enigma of population cycles. However, there exists no agreement among biologists regarding the causes of the Chitty effect. Here, I propose a simple hypothesis to explain the Chitty effect, based on phase-related, dynamic allocation of energy between reproductive and somatic effort. The essence of the hypothesis is that: (1) reproduction is suppressed in animals born or raised in the later part of the increase phase by environmental factors, including social influences; (2) suppression of reproduction limits the amount of energy that is diverted for reproductive effort, and forces a disproportionately greater amount of surplus power (the energy left after the energetic costs of standard and active metabolism are met) to be allocated for somatic effort; (3) the surplus energy, above and beyond what is required for routine biological activities, will allow continuous growth and deposition of additional body mass, which causes an increase in body mass; and (4) animals grow to a larger size as a population enters the peak density phase, causing an increase in the average body mass. The Chitty effect is predicted to be most pronounced at the late increase or peak phase of a population cycle. Possible causes of reproductive suppression include direct or indirect influences of the environmental factors. The Chitty effect may be a consequence, not a cause, of population cycles in small mammals.     

The soil fauna of a beech forest on limestone: trophic structure and energy budget

Summary The soil fauna of a mull beech forest on lime-stone in southern Lower Saxony (West Germany) was sampled quantitatively. Biomass estimates, trophic characteristics, and measurement and calculation of the energetic parameters of the constituent animal populations were used to construct an energy budget of the total heterotrophic subsystem of the forest. Mean annual zoomass amounted to about 15 g d wt m^–2; earthworms (about 10 g d wt m^–2) and other groups of the macrofauna were dominant. Protozoa constituted about 1.5 g d wt m^–2. Relative distribution of zoomass among the trophic categories was 50% macrosaprophages, 30% microsaprophages, 12% microphytophages, and 4% zoophages. Total annual consumption rate of the saprophagous and microphytophagous soil fauna (6328 and 4096 kJ m^–2 yr^–1, respectively) was of the same order of magnitude as annual litter fall (canopy leaves 6124 kJ m^–2 yr^–1, flowers and fruits 944 kJ m^–2 yr^–1, herbs 1839 kJ m^–2 yr^–1, fine woody material 870 kJ m^–2 yr^–1, tree roots 3404 kJ m^–2 yr^–1, without coarse woody litter). Primary decomposers (macrosaprophages) were the key group for litter comminution and translocation onto and into the soil, thus contributing to the high decomposition rate (k=0.8) for leaf litter. Consumption rates of the other trophic groups were (values as kJ m^–2 yr^–1): bacteriophages 2954, micromycophages 416, zoophages 153. Grazing pressure of macrophytophages (including rhizophages) was low. Faeces input from the canopy layer was not significant. Grazing pressure on soil microflora almost equalled microbial biomass; hence, a large fraction of microbial production is channelled into the animal component. Predator pressure on soil animals is high, as a comparison between consumption rates by zoophages and production by potential prey — mainly microsaprophages, microphytophages and zoophages — demonstrated. Soil animals contributed only about 11% to heterotrophic respiration. However, there is evidence that animals are important driving variables for matter and energy transfer: key processes are the transformation of dead organic material and grazing on the microflora. It is hypothesized that the soil macrosaprophages are donor-limited.     

Stylized facts in microalgal growth: interpretation in a dynamic energy budget context

A dynamic energy budget (DEB) model for microalgae is proposed. This model deviates from the standard DEB model as it needs more reserves to cope with the variation of assimilation pathways, requiring a different approach to growth based on the synthesizing unit (SU) theory for multiple substrates. It is shown that the model is able to accurately predict experimental data in constant and light-varying conditions with most of the parameter values taken directly from the literature. Also, model simulations are shown to be consistent with stylized facts (SFs) concerning NC ratio. These SFs are reinterpreted and the general conclusion is that all forcing variables (dilution rate, temperature and irradiance) impose changes in the nitrogen or carbon limitation status of the population, and consequently on reserve densities. Model predictions are also evaluated in comparison with SFs on chlorophyll concentration. It is proposed that an extra structure, more dependent on the nitrogen reserve, is required to accurately model chlorophyll dynamics. Finally, SFs concerning extracellular polymeric substances (EPSs) production by benthic diatoms are collected and interpreted and a formulation based on product synthesis and rejection flux is proposed for the EPSs production rate.     

The energy budget of two sympatric Daphnia species in Lake Constance: productivity and energy residence times

Summary Two Daphnia species, D. hyalina and D. galeata, are living in Lake Constance. Both populations show logistic growth, with the phase of exponential increase in May and the phase of steady state during the summer. In spring, food is not limited and both daphnids reveal an exploitative strategy: females mature early, primiparae are small, egg weights are small, but clutch sizes are large. From June on, when food limiting conditions prevail, D. hyalina starts to migrate vertically with a diurnal rhythm whereas D. galeata keeps on living in the epilimnion over the whole season. The differing thermal environments of the populations lead to short generation times (age of first reproduction) of 11 days for D. galeata in mid-summer, and to 47 days (July) for D. hyalina. The annual production (P) of D. hyalina and D. galeata were 18 and 24 g DW/m², respectively. The average standing stocks (B) were 1.6 and 0.9 g DW/m². This corresponds to turnover rates of 11 x and 27 x per season (200 days), and to turnover times of 18 days and 7.5 days, respectively. From 1980 to 1982 the cumulative annual primary production (PPR) varied between 260 and 330 g C/m². The common productivity (P) of the functional component Daphnia (=sum of both Daphnia species) followed the PPR, but the Daphnia stading stock was constant at 2.5 g DW/m². The increase of secondary production (P) was a consequence of a shift in abundance between the two Daphnia species: at low PPR, D. hyalina was 4 x more abundant, but at high PPR, the two species were equally abundant. Such internal regulatory mechanism within a system component is in accordance with the hypothesis of Cheslak and Lamarra (1981): increase of energy residence time (B/R) with declining nutrients and increasing strength of competitive interrelationships within a given functional component of an ecosystem.This research was supported by the Deutsche Forschungsgemeinschaft within Sonderforschungsbereich Stoffhaushalt des Bodensees (SFB 248)     

The relative influence of urban climates on outdoor human energy budgets and skin temperature II. Man in an urban environment

Four typical urban neighborhoods or street canyon settings (including street parks) were simulated. These urban morphologies were exposed to typical summer and winter climatic scenarios for latitudes 10, 34, and 50N. The changes induced in the components of the human energy budget were examined. Resultant skin temperatures were compared with non-urban, unobstructed environments.     

动物长期能量收支理论及研究进展

阐述了持续代谢率和持续代谢范围的概念,并介绍有关制约因子的４种假说：食物可利用性假说、外周制约假说、中心制约假说以及同形态椹制约假说。此外,还就持续代谢率的进化原因、实验验证的方法和结论,以及与最小维持消耗（ＢＭＲ）的关系和机制进行了分析。持续代谢率对动物生活具有影响,具有生态学意义。最后,分析了本领域未来的４个发展方向。     

防御性攻击行为对黑线仓鼠能量收支的影响

攻击行为是增强个体生存能力和提高繁殖成功机会的最有效竞争方式之一。为理解攻击行为对小型哺乳动物能量学收支策略的影响,以具有独居且好斗习性的黑线仓鼠为研究对象,基于居留者-入侵者（resident-intruder）争斗方式将入侵鼠放入居留鼠笼中（10min / d）,21d后测定能量摄入、基础代谢率（BMR）,分析BMR和内脏器官重量的相关性。结果显示,攻击行为使居留组BMR增加了26.2%,使摄入能和消化能显著增加。居留组体重、胴体重,以及某些代谢活性器官（肝脏、肺脏、肾脏、胃、小肠和盲肠）重量显著增加,且这些器官重量与BMR显著正相关。结果表明,增加能量摄入和BMR是黑线仓鼠应对攻击行为的主要能量学收支策略;在种内个体之间强烈的攻击行为可能是该鼠维持较高水平BMR的原因之一。     

The urban environment and mental disorders: Epigenetic links

For the first time in human history, more than half of the world''s population lives in urban areas and this is projected to increase to two-thirds by 2030. This increased urbanity of the world''s population has substantial public health implications. Nearly a century of research has shown higher risk of mental disorder among persons living in urban versus rural areas. Epidemiologic research has documented that associations between particular features of the urban environment, such as concentrated disadvantage, residential segregation and social norms, contribute to the risk of mental illness. We propose that changes in DNA methylation may be one potential mechanism through which features of the urban environment contribute to psychopathology. Recent advances in animal models and human correlation studies suggest DNA methylation as a promising mechanism that can explain how the environment “gets under the skin.” Aberrant DNA methylation signatures characterize mental disorders in community settings. Emerging evidence of associations between exposure to features of the environment and methylation patterns may lead toward the identification of mechanisms that explain the link between urban environments and mental disorders. Importantly, evidence that epigenetic changes are reversible offers new opportunities for ameliorating the impact of adverse urban environments on human health.Key words: urban environment, mental disorders, DNA methylation, epigenetics, posttraumatic stress disorder, depressionThe 20th century has been characterized by the world-wide movement of populations from rural to urban areas. For the first time in human history, more than half of the world''s population lives in urban areas and this is projected to increase to two-thirds by 2030. The movement of populations to urban environments is probably the most important demographic shift in the past century. In particular, the increased urbanity of the world''s population has substantial public health implications. A body of research has long shown that there are different burdens of disease and disability in urban vs. non-urban areas and more recent work has linked specific features of the urban environment to particular health indicators (for reviews of the literature about urban health see refs. ¹ and ²).Some of the more promising work in this area concerns research that has shown relations between urbanity and mental disorders. There is more than a century of work that has shown higher risk of most mental disorders among persons living in urban versus rural areas.^3–8 Early research proposed several factors that may explain this association including selective migration and social disorganization.³ For example, it has been proposed that persons within disadvantaged areas may have a more difficult time building and sustaining supportive social relationships, therefore increasing susceptibility to mental illness. Subsequent work has shown associations between particular features of the urban environment and risk of mental illness. Living in poorer urban neighborhoods is associated with greater risk of new episodes of depression compared to living in richer neighborhoods, even when accounting for individual income or exposure to stressful or adverse circumstances.^6,9,10 Living in neighborhoods characterized by residential racial segregation is associated with a greater risk of depression and anxiety, compared to living in less segregated neighborhoods.¹¹ Other evidence suggests that neighborhood collective efficacy and norms are associated with the risk of substance use disorders12 and suicide attempts,¹³ again when taking into account individual experiences.Coincident with the growing number of studies that have demonstrated links between features of the urban environment and mental health, there has been an increase in work that has sought to understand the mechanisms underlying these epidemiologic observations. In particular, there is an emerging interest in identifying biologic explanations that may clarify the link between features of the urban environment and individual mental health. Existing research has documented a role for changes in immune function,¹⁴ gene-environment interactions¹⁵ and psychological mechanisms,¹⁶ among others, that may explain the links between the urban environment and mental health. This paper adds to this growing field and proposes that changes in DNA methylation may be one potential mechanism through which features of the urban environment contribute to psychopathology.     

The airborne metagenome in an indoor urban environment

The indoor atmosphere is an ecological unit that impacts on public health. To investigate the composition of organisms in this space, we applied culture-independent approaches to microbes harvested from the air of two densely populated urban buildings, from which we analyzed 80 megabases genomic DNA sequence and 6000 16S rDNA clones. The air microbiota is primarily bacteria, including potential opportunistic pathogens commonly isolated from human-inhabited environments such as hospitals, but none of the data contain matches to virulent pathogens or bioterror agents. Comparison of air samples with each other and nearby environments suggested that the indoor air microbes are not random transients from surrounding outdoor environments, but rather originate from indoor niches. Sequence annotation by gene function revealed specific adaptive capabilities enriched in the air environment, including genes potentially involved in resistance to desiccation and oxidative damage. This baseline index of air microbiota will be valuable for improving designs of surveillance for natural or man-made release of virulent pathogens.     

北京地区热力景观格局及典型城市景观的热环境效应

城市热环境是城市生态环境中的一个重要指标,将景观生态学理论融入到热环境研究中,尝试探讨北京地区热力景观格局及城市公园、道路景观的热环境效应。地表温度反演是分析热力景观格局及典型城市景观热环境效应的前提,论文以北京地区为例,首先利用两景ASTER影像数据采用TES算法定量反演地表温度。通过半变异函数分析地表温度空间异质性,确定最大采样尺度,然后在景观统计软件Fragstats中,计算不同粒度下的景观格局指数,分析热力景观格局及其尺度效应。通过景观斑块特征分析和缓冲区分析,探讨公园景观斑块、道路景观廊道特征的热环境效应。总体上公园景观对应的平均温度随着公园面积、边界长度的增加而减小,随着公园周长面积比增大而增大;随着距离公园渐远,地表温度升高,且升温趋势变缓。随着道路密度增加,道路平均温度显著升高,标准差显著降低,道路密度等级与道路平均温度的相关系数达到0.8021;随着距离道路中心线距离增加,缓冲区内的平均温度略有下降,但变化微弱。因此,应充分重视公园景观在缓解城市热环境方面的作用,合理布局城市道路。