Oscillatory combustion in rockets Semiannual report, 1 Jun. - 30 Nov. 1968

Vaporization of droplets near critical poin

Oscillatory combustion in rockets Semiannual report, 1 Jun. - 31 Nov. 1969

Droplet vaporization in region of critical point in flowing stream and stagnant gas at high pressures, and varying temperature

History of Polar Bears as Summer Residents on the St. Matthew Islands, Bering Sea

Polar bears were found as summer residents on the St. Matthew Islands in the northern Bering Sea from the time of their discovery in the mid-18th century until the late 19th century, when the last bears were presumably shot by crews from Canadian and American sealers and a U.S. revenue cutter. Historical documents suggest that the killing of the last summer-resident polar bears on the St. Matthew Islands was an indirect consequence of the controversy between the United States and Great Britain over management of the fur seal harvest and the associated pelagic hunting of these seals. Although polar bears have continued to be present near the St. Matthew Islands in winter, when sea ice is present, a metapopulation of summer-resident bears has not reestablished on these islands. In 1972, the State of Alaska considered a proposal to reestablish a summer-resident polar bear population on the St. Matthew Islands, and since 2008, when the United States listed the polar bear as a threatened species, such reestablishment has been suggested as a conservation strategy. However, given the observed changes in local Bering Sea ice conditions in recent decades, the lack of detailed information on the population ecology and habitat dependencies of the historical St. Matthew bears, and the unavailability of an analogous extant metapopulation of polar bears for comparison, it is highly unlikely that reestablishment of summer-resident polar bears on the St. Matthew Islands could be realized.Des ours polaires résidaient l’été sur les îles St. Matthew, dans le nord de la. mer de Béring, du moment où ils ont été découverts vers le milieu du XVIIIe siècle jusque vers la fin du XIXe siècle, lorsque les derniers ours auraient été tués par les équipages de phoquiers canadiens et américains ainsi que par des pataches de la douane américaine. Des documents historiques laissent entendre que la mise à mort des derniers ours polaires d’été sur les îles St. Matthew était une conséquence indirecte de la controverse entre les États-Unis et la Grande-Bretagne au sujet des récoltes d’otaries à fourrure et de la chasse pélagique connexe de ces otaries. Bien que la présence des ours polaires se soit poursuivie dans les environs des îles St. Matthew l’hiver, lorsqu’il y a de la glace de mer, une métapopulation d’ours d’été ne s’est pas réimplantée sur ces îles. En 1972, l’État de l’Alaska a considéré une proposition en vue du rétablissement de la population d’ours polaires résidant sur les îles St. Matthew l’été, et depuis 2008, lorsque les États-Unis ont ajouté les ours polaires à la liste des espèces menacées, ce rétablissement a été suggéré en guise de stratégie de conservation. Cependant, compte tenu des changements observés dans le régime des glaces de la mer de Béring ces dernières décennies, de l’absence de renseignements détaillés sur l’écologie de la population et sur les dépendances à l’habitat des ours historiques de St. Matthew, de même que de l’absence d’une métapopulation analogue historique à des fins de comparaison, il est peu vraisemblable que le rétablissement des ours polaires en résidence d’été sur les îles St. Matthew puisse se concrétiser

Oscillatory combustion in rockets Third semiannual report, Jun. 1 - Nov. 30, 1965

Rocket engine oscillatory combustion studie

Landscape composition influences abundance patterns and habitat use of three ungulate species in fragmented secondary deciduous tropical forests, Mexico

AbstractSecondary forests are extensive in the tropics. Currently, these plant communities are the available habitats for wildlife and in the future they will possibly be some of the most wide-spread ecosystems world-wide. To understand the potential role of secondary forests for wildlife conservation, three ungulate species were studied: Mazama temama, Odocoileus virginianus and Pecari tajacu. We analyzed their relative abundance and habitat use at two spatial scales: (1) Local, where three different successional stages of tropical deciduous forest were compared, and (2) Landscape, where available habitats were compared in terms of landscape composition (proportion of forests, pastures and croplands within 113 ha). To determine the most important habitat-related environmental factors influencing the Sign Encounter Rate (SER) of the three ungulate species, 11 physical, anthropogenic and vegetation variables were simultaneously analyzed through model selection using Akaike’s Information Criterion. We found, that P. tajacu and O. virginianus mainly used early successional stages, while M. temama used all successional stages in similar proportions. The latter species, however, used early vegetation stages only when they were located in landscapes mainly covered by forest (97%). P. tajacu and O. virginianus also selected landscapes covered essentially by forests, although they required smaller percentages of forest (86%). All ungulate species avoided landscape fragments covered by pastures. For all three species, landscape composition and human activities were the variables that best explained SER. We concluded that landscape is the fundamental scale for ungulate management, and that secondary forests are potentially important landscape elements for ungulate conservation

Captive-born collared peccary (Pecari tajacu, Tayassuidae) fails to discriminate between predator and non-predator models

Captive animals may lose the ability to recognize their natural predators, making conservation programs more susceptible to failure if such animals are released into the wild. Collared peccaries are American tayassuids that are vulnerable to local extinction in certain areas, and conservation programs are being conducted. Captive-born peccaries are intended for release into the wild in Minas Gerais state, southeastern Brazil. In this study, we tested the ability of two groups of captive-born collared peccaries to recognize their predators and if they were habituated to humans. Recognition tests were performed using models of predators (canids and felids) and non-predators animals, as well as control objects, such as a plastic chair; a human was also presented to the peccaries, and tested as a separate stimulus. Anti-predator defensive responses such as fleeing and threatening displayswere not observed in response to predator models. Predator detection behaviors both from visual and olfactory cues were displayed, although they were not specifically targeted at predator models. These results indicate that collared peccaries were unable to recognize model predators. Habituation effects, particularly on anti-predator behaviors, were observed both with a 1-h model presentation and across testing days. Behavioral responses to humans did not differ from those to other models. Thus, if these animals were to be released into the wild, they should undergo anti-predator training sessions to enhance their chances of survival

ALASKA’S RAT SPILL RESPONSE PROGRAM

The introduction of rodents on an island as a new predator usually interferes with natural island biodiversity, particularly on islands without any native mammalian predators. Many Alaskan islands, and most islands in the Aleutian Island region of the Alaska Maritime National Wildlife Refuge (AMNWR), are free of mammalian predators and are vulnerable to invasion by rodents. Rat introduction to islands can put ground-nesting birds, such as seabirds and endemic landbirds, at risk of extirpation. The refuge is also concerned about additional introductions of house mice. As far as we know, the introduction, or “spilling,” of rats onto refuge islands from ships and cargo was accidental, but probably preventable. This paper is about preventing new rodent invasions, especially rats, on Alaskan islands from shipwrecks, and using our experience on AMNWR as a basis for recommendations about improvements in the future

The Birds of St. Matthew Island, Bering Sea

St. Matthew Island (608 249 N, 1728 429 W) and its small nearby satellites, Hall Island and Pinnacle Rock, are isolated in the north-central Bering Sea. This infrequently visited location occupies a geographic position with a deep Bering Land Bridge history and is in an area of interdigitation of the Old World, New World, and Beringian avifaunas. It is known for its three Beringian endemics, a bird (McKay’s Bunting, Plectrophenax hyperboreus), a small mammal, and a plant. This level of endemism is striking for a high-latitude island. The only previous summary of the avifauna of St. Matthew Island (Hanna 1917) included 37 species. Our report considers more than 125 species and synthesizes data on presence and absence, abundance, and phenology. Because visits have been infrequent and concentrated during summer, our understanding of migration in this region remains poor, but the area is clearly affected by both the Old and New world migration systems. There is sufficient evidence to show that some profound changes among the island’s breeding birds have occurred during the past century. In particular, the breeding range of Glaucous-winged Gulls (Larus glaucescens) has been extended north to include St. Matthew, a change that is correlated with a northward shift in the extent of sea ice (Maslanik et al. 1996). King and Common eiders (Somateria spectabilis and S. mollissima) also have shown substantial changes in summer abundance. Other changes in the summer avifauna (e.g., among shorebirds) may reflect the dynamics of edge-of-range phenomena. Because of its central position in a region undergoing profound climate change and its demonstrated track record in showing avifaunal shifts, St. Matthew Island may represent an important bellwether for monitoring the biological effects of further climate change in the northern Bering Sea