Energy cost and running mechanics during a treadmill run to voluntary exhaustion in humans

The aim of the present study was to examine the physiological and mechanical factors which may be concerned in the increase in energy cost during running in a fatigued state. A group of 15 trained triathletes ran on a treadmill at velocities corresponding to their personal records over 3000m [mean 4.53 (SD 0.28) m · s⁻¹] until they felt exhausted. The energy cost of running (C _R) was quantified from the net O₂ uptake and the elevation of blood lactate concentration. Gas exchange was measured over 1 min firstly during the 3rd–4th min and secondly during the last minute of the run. Blood samples were collected before and after the completion of the run. Mechanical changes of the centre of mass were quantified using a kinematic arm. A significant mean increase [6.9 (SD 3.5)%, P < 0.001] in C _R from a mean of 4.4 (SD 0.4) J · kg⁻¹ · m⁻¹ to a mean of 4.7 (SD 0.4) J · kg⁻¹ · m⁻¹ was observed. The increase in the O₂ demand of the respiratory muscles estimated from the increase in ventilation accounted for a considerable proportion [mean 25.2 (SD 10.4)%] of the increase in C_R. A mean increase [17.0 (SD 26.0)%, P < 0.05] in the mechanical cost (C _M) from a mean of 2.36 (SD 0.23) J · kg⁻¹ · m⁻¹ to a mean of 2.74 (SD 0.55) J · kg⁻¹ · m⁻¹ was also noted. A significant correlation was found between C _R and C _M in the non-fatigued state (r = 0.68, P < 0.01), but not in the fatigued state (r = 0.25, NS). Furthermore, no correlations were found between the changes (from non-fatigued to fatigued state) in C _R and the changes in C _M suggesting that the increase in C _R is not solely dependent on the external work done per unit of distance. Since step frequency decreased slightly in the fatigued state, the internal work would have tended to decrease slightly which would not be compatible with an increase in C _R. A stepwise regressions showed that the changes in C _R were linked (r = 0.77, P < 0.01) to the changes in the variability of step frequency and in the variability of potential cost suggesting that a large proportion of the increase in C _R was due to an increase in the step variability. The underlying mechanisms of the relationship between C _R and step variability remains unclear. Accepted: 15 September 1997     

Statistical entropy analysis to evaluate resource efficiency: Phosphorus use in Austria

In a resource efficient economy, entropy generation must be kept low and high-entropy wastes should be transformed into low-entropy recycled products, thus saving natural resources. Based on this idea, statistical entropy analysis (SEA) was put forward as a method to evaluate material flow systems with respect to their ability to concentrate or dilute a substance throughout its life cycle using a single metric, relative statistical entropy (RSE). Whereas its application has so far been restricted to highly aggregated material flow systems or to assessments at plant or process level, in the present study the SEA method was adapted to assess the efficiency of resource use in material flow systems which consist of numerous resource flows and include multiple recycling loops. Phosphorus (P) use in Austria served as a case study to illustrate SEA-based resource efficiency assessment for different scenarios and over time. The evaluation enabled exploiting the outcomes of existing P flow studies in a straightforward way and produced additional insights related to the characteristics of resource use within the system. Changes in P management over time had a significant effect on the resource efficiency of P use. The RSE increased by 40% due to P use in Austria in the year 2000 compared to an increase of 30% in 2010. The generally favorable trend of statistical entropy (lower dissipation) in 2010 could be attributed mainly to lower dissipative emissions, more efficient bio-industry, and increasing P removal rates in waste water treatment, which overcompensated the negative impact of the ban of recycling of meat and bone meal (in 2001) on P use efficiency. Further, the SEA-based assessment applied to a scenario of optimized P management reflected the positive effects of measures to reduce emissions, enhance recycling, and reduce consumption of P on resource efficiency (50% lower RSE increase in the target system compared to the original state). In synthesis, this study shows that the SEA method is able to integrate various dimensions of resource use into a single indicator, which can serve as a basis to assess and improve the resource efficiency of macro-scale material flow systems.     

Iron deficiency leads to repression of a non-canonical methionine salvage pathway in Schizosaccharomyces pombe

The methionine salvage pathway (MSP) regenerates methionine from 5′-methylthioadenosine (MTA). Aerobic MSP consists of six enzymatic steps. The mug14⁺ and adi1⁺ genes that are involved in the third and fifth steps of the pathway are repressed when Schizosaccharomyces pombe undergoes a transition from high- to low-iron conditions. Results consistently show that methionine auxotrophic cells (met6Δ) require iron for growth in the presence of MTA as the sole source of methionine. Inactivation of the iron-using protein Adi1 leads to defects in the utilization of MTA. In the case of the third step of the pathway, co-expression of two distinct proteins, Mta3 and Mde1, is required. These proteins are interdependent to rescue MTA-dependent growth deficit of met6Δ cells. Coimmunoprecipitation experiments showed that Mta3 is a binding partner of Mde1. Meiotic met6Δ cells co-expressing mta3⁺ and mde1⁺ or mta3⁺ and mug14⁺ produce comparable levels of spores in the presence of MTA, revealing that Mde1 and Mug14 share a common function when co-expressed with Mta3 in sporulating cells. In sum, our findings unveil several novel features of MSP, especially with respect to its regulation by iron and the discovery of a non-canonical third enzymatic step in the fission yeast.     

Absentee herd owners and part-time pastoralists: The political economy of resource use in northern Kenya

The prevalence of absentee herd ownership in Africa's pastoral areas is increasing. Its presence has important implications both for local resource management systems and for research programs that address pastoral ecology and related topics. This paper examines patterns of absentee herd ownership in the Baringo District of northern Kenya. This region has been the source of much debate regarding herder mismanagement of range lands. Three categories of absentee herd owners are discussed in the paper: (1) ranchers, (2) livestock traders, and (3) townsmen. It is suggested that the blame for some of the apparent resource mismanagement in the region may lie more with actors in these categories than with the pastoralists themselves. Data collected during an 18-month period in 1980–1981 on pastoral ecology, grazing patterns, and tenure institutions are presented in support of the argument. The paper concludes with a comparative analysis of contemporary resource management strategies in pastoral Africa, emphasizing that: (1) the Baringo case is not an isolated anomaly, and (2) a new orientation toward pastoral studies is warranted.     

Extreme water efficiency of Cape gannet Morus capensis chicks as an adaptation to water scarcity and heat stress in the breeding colony

Cape gannet Morus capensis chicks depend entirely on fish prey and metabolic water for water requirements during development. Water loss through evaporative cooling due to heat stress is substantial. We measured water flux and field metabolic rates (FMR) of Cape gannet chicks and adults to determine if gannets developed water saving strategies. The water economy index (WEI, g kJ^?1) decreased with chick age according to the model WEI = 0.676 – 0.272 × log₁₀(t), indicating that water efficiency increased with age. At fledging, the WEI of chicks was at the level expected of adult desert birds. Desert birds maintain a low WEI by also having a low FMR, whereas Cape gannet chicks have FMR comparable to other seabird species’ nestling requirements. We propose that maintaining low WEI is adaptive for Cape gannets because (1) chicks need to balance water loss through evaporative cooling, (2) fledglings need to overcome a period of up to a week when they cannot ingest any water and (3) adults spend extended periods in the breeding colony during which water can become a limiting factor. Understanding the physiological mechanism of maintaining low WEI will become increasingly important with future rising temperatures.     

北京浅山区香山特色小镇规划设计探索

香山小镇位于北京浅山区军庄镇,面对旅游、经济发展的压力和脆弱生态环境保育的课题,本案设计突出生态优先、绿色经济和文化共赢的可持续发展策略,把浅山区视为一个生命系统,从区域层面建立有指导性的生态保护导则,提升区域水资源管理、林相修复和栖息地复建的长远效益,推动有机果园和绿色旅游的发展;在设计过程中高度结合现状,设计结合自然,设计结合策划,修复基于保护。景观设计同步整合生态保护和策划、建设的要求,积极发掘民间工艺并创造性地应用于景观设计,发动当地居民的主动参与,塑造有温度、有记忆、有传承、亲切宜人的浅山特色生态小镇。     

The business perspective in ecological restoration: issues and challenges

Much of the practice of restoration is conducted by businesses—contractors, consultants, designers, engineers. Restoration businesses interact with a variety of stakeholders to complete projects on time and on budget, and to achieve ecological and business objectives. Our research explores the business perspective in restoration; it is based on data collected from businesses (contractors, consultants, design engineers), agencies, and nongovernmental organizations involved in a Superfund cleanup project in Montana, one of the largest river restoration efforts ever. Our findings highlight several areas restoration businesses must navigate. First, restoration businesses must juggle potentially competing goals, maintaining ecological integrity while achieving profitability objectives. Second, these businesses must manage the risk that arises from variability in the natural environment as well as individuals' risk tolerances. Third, they must navigate the disconnect between “science” and “practice,” including how to best monitor restoration projects. Fourth, they must make decisions about new techniques and innovations. Fifth, on‐the‐ground implementation must acknowledge that personnels' motives and expertise might conflict with original plans. We discuss these findings in relation to relevant scholarly research, offering implications for theory and practice. For example, the business of ecological restoration requires learning over time to be profitable while achieving the desired ecological and social outcomes; restoration businesses leverage monitoring in pursuit of adaptive management and engage “frontline personnel” as important voices in the restoration process. Understanding the business of restoration adds an important perspective in the complex dynamics of social‐ecological systems.     

Enhancing biological nitrogen fixation: An appraisal of current and alternative technologies for N input into plants

Biological nitrogen fixation (BNF) involves a highly specialized and intricately evolved interactions between soil microorganisms and higher plants for harnessing the atmospheric elemental nitrogen (N). This process has been researched for almost a century for efficient N input into plants. The basic mechanism and biochemical steps involved in BNF have been unraveled. It has become abundantly clear that the host plant (legumes) dominates in regulating the BNF process. Environmental factors as well influence this process. Perturbation or any manipulation of the interactions between the bacteria and the legumes seems to offset the critical balance, usually to the detriment of N fixation efficiency. Not much success has been obtained in either enhancing BNF in legumes or transferring important BNF traits to non-nitrogen fixing organisms. An appraisal is given for the lack of success in making the BNF process a popular and efficient agronomic practice. Alternative physiological approaches are presented for improving mobilization, redistribution and utilization of stored N reserves within the host plant.     

Skeletal economy in certain herbivorous beetles as an adaptation to a poor dietary supply of nitrogen

ABSTRACT.

• 1 Flying Coleoptera were sampled with light traps from the tree canopy of lowland alluvial rain forest in Brunei, Borneo.
• 2 Adult chrysomelid beetles were found to carry significantly less skeleton relative to their overall mass than those of any family other than herbivorous scarabaeids (subfamily: Rutelinae). Xylophagous lucanids and cerambycids and dung-feeding scarabaeids (subfamilies: Aphodiinae and Scarabaeinae) carried as large a proportion of skeleton by mass as predatory carabids and cicindelids.
• 3 Skeletal production requires the commitment of assimilated nitrogen to chitin and proteins. Adequate nitrogen is more readily available to predators, carrion or dung-feeders, and xylophages (given enough time) than to leaf-chewing chrysomelids, which are also environmentally exposed to predatory attack. Female chrysomelids were found to carry a larger number of mature eggs/insect than those of any other family. A larger proportion of their mass was represented by eggs than skeleton, as reproductive compensation for reduced skeletal protection.
• 4 It was estimated that a chrysomelid beetle required approximately 43% of the nitrogen incorporated by a predatory carabid of the same mass, whereas xylophagous cerambycids and lucanids would need between 84% and 98% of that in the predator.