Was basking important in the evolution of mammalian endothermy?

The first mammals were small, nocturnal, and presumably had low metabolic rates and were therefore probably unable to maintain a constant high body temperature throughout cool nights. How these animals, without sufficient heat production for endogenous rewarming, were able to become warm and active again before the next activity period remains unresolved. However, we discovered that, similar to reptiles, the carnivorous marsupial mammal Pseudantechinus macdonnellensis (body mass 30.8LJ.0 g) uses the morning sun to rewarm from low (26.3dž.5°C) body temperatures during torpor. Our findings provide the first evidence of basking during rewarming from torpor in mammals and may provide an alternative explanation as to how ancestral mammals could have become nocturnal to avoid diurnal predators despite their small size and a low endogenous heat production.     

Nitrogen critical loads and management alternatives for N-impacted ecosystems in California

Empirical critical loads for N deposition effects and maps showing areas projected to be in exceedance of the critical load (CL) are given for seven major vegetation types in California. Thirty-five percent of the land area for these vegetation types (99,639 km²) is estimated to be in excess of the N CL. Low CL values (3–8 kg N ha^?1 yr^?1) were determined for mixed conifer forests, chaparral and oak woodlands due to highly N-sensitive biota (lichens) and N-poor or low biomass vegetation in the case of coastal sage scrub (CSS), annual grassland, and desert scrub vegetation. At these N deposition critical loads the latter three ecosystem types are at risk of major vegetation type change because N enrichment favors invasion by exotic annual grasses. Fifty-four and forty-four percent of the area for CSS and grasslands are in exceedance of the CL for invasive grasses, while 53 and 41% of the chaparral and oak woodland areas are in exceedance of the CL for impacts on epiphytic lichen communities. Approximately 30% of the desert (based on invasive grasses and increased fire risk) and mixed conifer forest (based on lichen community changes) areas are in exceedance of the CL. These ecosystems are generally located further from emissions sources than many grasslands or CSS areas. By comparison, only 3–15% of the forested and chaparral land areas are estimated to be in exceedance of the NO₃^? leaching CL. The CL for incipient N saturation in mixed conifer forest catchments was 17 kg N ha^?1 yr^?1. In 10% of the CL exceedance areas for all seven vegetation types combined, the CL is exceeded by at least 10 kg N ha^?1 yr^?1, and in 27% of the exceedance areas the CL is exceeded by at least 5 kg N ha^?1 yr^?1. Management strategies for mitigating the effects of excess N are based on reducing N emissions and reducing site N capital through approaches such as biomass removal and prescribed fire or control of invasive grasses by mowing, selective herbicides, weeding or domestic animal grazing. Ultimately, decreases in N deposition are needed for long-term ecosystem protection and sustainability, and this is the only strategy that will protect epiphytic lichen communities.     

Empirical and simulated critical loads for nitrogen deposition in California mixed conifer forests

Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO(3)(-) leaching in streamwater, and reduced fine root biomass in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community impacts of 3.1kg ha(-1) year(-1) is expected to protect all components of the forest ecosystem from the adverse effects of N deposition. Much of the western Sierra Nevada is above the lichen-based CL, showing significant changes in lichen indicator groups. The empirical N deposition threshold and that simulated by the DayCent model for enhanced NO(3)(-)leaching were 17kg N ha(-1) year(-1). DayCent estimated that elevated NO(3)(-) leaching in the San Bernardino Mountains began in the late 1950s. Critical values for litter C:N (34.1), ponderosa pine foliar N (1.1%), and N concentrations (1.0%) in the lichen Letharia vulpina ((L.) Hue) are indicative of CL exceedance.     

Vertebrate diet decreases winter torpor use in a desert marsupial

One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and, therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing torpor or whether differences in prey composition among individuals influence torpor characteristics. Here, we test the hypothesis that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara (Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates (mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass among individuals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal.     

Latency and quarantine vs. backward bifurcation

Two models are presented which can show a backward bifurcation. The possibilities are analyzed whether latency, quarantine, vaccine efficacy, and other parameters of the models can affect the appearance of a backward bifurcation. Explicit conditions on the parameters are given for the backward bifurcation to be present, to be reduced, or to disappear.     

清洁生产观点2:把清洁生产纳入可持续性战略

清洁生产已经作为一套手段、一个计划和一种思维方式而产生了影响.对这些影响可以从不同的层面进行评价.清洁生产虽然在过去十年取得了进步，但是仍需解决的清洁生产问题包括政府的政策、环境技术、废物减少、工作场所的安全、经济发展和社会消费.下一个十年需要取得进展的三个环境目标是去除毒性、非物质化和脱碳.另外还提出了清洁生产的一些更长期的目标.     

Characterization of industrial aqueous discharges by the TLC/Ames’ assay

The $\text{in situ}$ detection of mutagens by the TLC/Ames’ assay has been applied to aqueous discharges from a textile plant. The samples were fractionated in acid/neutral and basic fractions which subsequently were subject to the TLC/Ames’ test. The results demonstrate the presence of a number of both direct and indirect mutagens in the waste water. The chemical properties of these compounds are discussed in light of their chromatographic behaviour. The applicability of this method for characterizing mutagens in complex mixtures is demonstrated.     

Torpor in free-ranging antechinus: does it increase fitness?

Antechinus are small, insectivorous, heterothermic marsupial mammals that use torpor from late summer to early winter and reproduce once a year in late winter/early spring. Males die after mating, most females produce only a single litter, but some survive a second winter and produce another litter. As it is not known how these females manage to survive the second winter after the energetically demanding reproductive period and then reproduce a second time, we aimed to provide the first data on thermal biology of free-ranging antechinus by using temperature telemetry. Male Antechinus stuartii and Antechinus flavipes rarely entered torpor in autumn/early winter in the wild, expressing only shallow bouts of <2 h. Female A. stuartii used torpor extensively, employing bouts up to 16.7 h with body temperatures as low as 17.8 °C. Interestingly, although first and second year females used similar torpor patterns, torpor occurrence was almost twofold in second year (93 % of days) than first year females (49 %), and the proportion of the overall monitoring period animals spent torpid was 3.2-fold longer in the former with a corresponding shorter activity period. Our study suggests that intensive use of torpor is crucial for second year females for autumn and winter survival and production of a second litter. We provide the first evidence of an age-related pattern in daily torpor expression in free-ranging mammals and show that torpor use is a complex process that is affected not only by the current energy availability and thermal conditions but also by the reproductive history and age of individuals.     

Evidence of enhanced atmospheric ammoniacal nitrogen in Hells Canyon national recreation area: implications for natural and cultural resources

Agriculture releases copious fertilizing pollutants to air sheds and waterways of the northwestern United States. To evaluate threats to natural resources and historic rock paintings in remote Hells Canyon, Oregon and Idaho, deposition of ammonia (NH3), nitrogen oxides (NOx), sulfur dioxide (SO2), and hydrogen sulfide (H2S) at five stations along 60 km of the Snake River valley floor were passively sampled from July 2002 through June 2003, and ozone data and particulate chemistry were obtained from the Interagency Monitoring of Protected Visual Environments (IMPROVE) station at Hells Canyon. NH3 concentrations were high; biweekly averages peaked at 5-19 ppb in spring and summer and the nutrient-laden Snake River is a likely source. Fine particulate ammonium nitrate (NH4NO3) averaged 2.6 microg/m3 during the 20% of worst visibility days with winter drainage of air masses from the Snake River Basin and possibly long distance transport from southern California. Other pollutants were within background ranges. NH3 is corrosive to clay-based pictographs; nitrogen deposition can alter natural biotic communities and terrestrial ecosystem processes at levels reported here.