Vegetation-soil relations in a highly sodic landscape, Yelarbon, southern Queensland

Soil and vegetation data were collected from a sodic-scald near Yelarbon in southern Queensland. The surface of the landscape includes relatively light textured pedestals of the A-horizon with slightly alkaline pH and slopes leading down to scalded basement representing the surface of the strongly alkaline B-horizon. The strongest gradient within the floristic patterns was associated with wetland vegetation in drainage lines, but a secondary and orthogonal gradient was related to soil pH, which was probably a function of lower alkalinity on the more stable and weathered A-horizons. There were few significant differences between soil or vegetation characteristics from plot data comparing parts of the landscape with differing historical grazing regimes. Sites included stock routes heavily grazed between the 1920s and 1970s, and subsequently almost ungrazed; and grazed paddocks that have had moderate use throughout this period. There is clear evidence that the area is naturally active in terms of erosion and deposition during flooding regardless of grazing

ESR study of development of RFM/Un murine myeloid leukaemia.

The blood, spleen and liver of RFM/Un mice were examined by means of electron spin resonance (ESR) throughout the course of myeloid leukaemia induced by i.v. injection of leukaemic spleen cells. Marked changes in the concentration of iron transferrin and caeruloplasmin were observed in the blood 1 day after injection. As the disease progressed, changes occurred in the concentrations of the ascorbyl radical and of paramagnetic metal complexes in both spleen and liver. These changes are compared with those induced in RF/J mice injected with normal and leukaemic spleen cells from RFM/Un mice

First Record of a Ross\u27 Gull for Nebraska

On 17 December, 1992, we observed a Ross\u27 Gull in second-winter plumage at Sutherland Reservoir, Lincoln County. We studied the bird in detail from 7:35-10.00 a.m. and again from 11:15 a.m.-1:00 p.m. CST as it fed with several Bonaparte\u27s Gulls at the outlet between the cooling pond and the reservoir. The Ross\u27 Gull remained at this location through 28 December and was seen by many birders from around the Midwest. During all of our observations, the small size, dark underwings, and wedge-shaped tail set this bird apart from the Bonaparte\u27s Gulls. At first, we overlooked the tail shape and tentatively identified the bird as a Little Gull. However, after studying the bird in greater detail, we noted the wedge-shaped tail and agreed that it was indeed a Ross\u27 Gull in second-winter plumage. We estimated that the Ross\u27 Gull was about 10% smaller than a Bonaparte\u27s Gull, and had proportionately longer wings, a smaller head, and larger eyes. It had a buoyant flight, and often hovered over the water as it fed on small fish. The undersides of the flight feathers were dark gray, similar to the appearance of the underwing of an adult Little Gull. The axillars and wing linings were white. The upperwing was mostly pale gray, with clear remnants of a dark carpal bar. The carpal bar was black, and appeared as a series of spots across the secondary coverts, with a larger black spot at the base of the primaries. There was also a very broad, white trailing edge to the flight feathers, especially along the inner primaries. The mantle was also pale gray, the same color as the upperwing. The head was white except for the hint of a black collar, which appeared as a darker spot behind each eye, connected by a faint, dark line across the back of the neck

Managed livestock grazing is compatible with the maintenance of plant diversity in semidesert grasslands.

Even when no baseline data are available, the impacts of 150 years of livestock grazing on natural grasslands can be assessed using a combined approach of grazing manipulation and regional-scale assessment of the flora. Here, we demonstrate the efficacy of this method across 18 sites in the semidesert Mitchell grasslands of northeastern Australia. Fifteen-year-old exclosures (ungrazed and macropod grazed) revealed that the dominant perennial grasses in the genus Astrebla do not respond negatively to grazing disturbance typical of commercial pastoralism. Neutral, positive, intermediate, and negative responses to grazing disturbance were recorded amongst plant species with no single life-form group associated with any response type. Only one exotic species, Cenchrus ciliaris, was recorded at low frequency. The strongest negative response was from a native annual grass, Chionachne hubbardiana, an example of a species that is highly sensitive to grazing disturbance. Herbarium records revealed only scant evidence that species with a negative response to grazing have declined through the period of commercial pastoralism. A regional analysis identified 14 from a total of 433 plant species in the regional flora that may be rare and potentially threatened by grazing disturbance. However, a targeted survey precluded grazing as a cause of decline for seven of these based on low palatability and positive responses to grazing and other disturbance. Our findings suggest that livestock grazing of semidesert grasslands with a short evolutionary history of ungulate grazing has altered plant composition, but has not caused declines in the dominant perennial grasses or in species richness as predicted by the preceding literature. The biggest impact of commercial pastoralism is the spread of woody leguminous trees that can transform grassland to thorny shrubland. The conservation of plant biodiversity is largely compatible with commercial pastoralism provided these woody weeds are controlled, but reserves strategically positioned within water remote areas are necessary to protect grazing-sensitive species. This study demonstrates that a combination of experimental studies and regional surveys can be used to understand anthropogenic impacts on natural ecosystems where reference habitat is not available

First Record of a Ross\u27 Gull for Nebraska

On 17 December, 1992, we observed a Ross\u27 Gull in second-winter plumage at Sutherland Reservoir, Lincoln County. We studied the bird in detail from 7:35-10.00 a.m. and again from 11:15 a.m.-1:00 p.m. CST as it fed with several Bonaparte\u27s Gulls at the outlet between the cooling pond and the reservoir. The Ross\u27 Gull remained at this location through 28 December and was seen by many birders from around the Midwest. During all of our observations, the small size, dark underwings, and wedge-shaped tail set this bird apart from the Bonaparte\u27s Gulls. At first, we overlooked the tail shape and tentatively identified the bird as a Little Gull. However, after studying the bird in greater detail, we noted the wedge-shaped tail and agreed that it was indeed a Ross\u27 Gull in second-winter plumage. We estimated that the Ross\u27 Gull was about 10% smaller than a Bonaparte\u27s Gull, and had proportionately longer wings, a smaller head, and larger eyes. It had a buoyant flight, and often hovered over the water as it fed on small fish. The undersides of the flight feathers were dark gray, similar to the appearance of the underwing of an adult Little Gull. The axillars and wing linings were white. The upperwing was mostly pale gray, with clear remnants of a dark carpal bar. The carpal bar was black, and appeared as a series of spots across the secondary coverts, with a larger black spot at the base of the primaries. There was also a very broad, white trailing edge to the flight feathers, especially along the inner primaries. The mantle was also pale gray, the same color as the upperwing. The head was white except for the hint of a black collar, which appeared as a darker spot behind each eye, connected by a faint, dark line across the back of the neck

Parasitic Jaeger at Lake McConaughy

On 5 October, 1997, we joined Joel G. Jorgensen and John Sullivan for a pelagic trip on Lake McConaughy. A similar trip in late September 1996 yielded a Sabine\u27s Gull, but we were really hoping to see a jaeger. From 7:00 to 8:30 a.m. we gradually worked our way from the dam towards the western end of the lake. Besides moderate numbers of Franklin\u27s and Ring-billed Gulls, there were few birds on the lake. At approximately 8:45 a.m. Dinsmore noticed that all of the gulls at the western end of the lake had suddenly taken flight. Less than a minute later, we simultaneously spotted a jaeger soaring directly overhead. The size, dark coloration, and prominent white flashes in the Wings identified the bird as a jaeger. The bird made a couple of attacks on Franklin Gulls and then flew east down the lake. We chased the jaeger for more than ten miles before losing it. We relocated the bird a short time later just above the dam. This time, the bird attacked a couple of Ring-billed Gulls before flying west up the lake. We again took chase, but lost the bird before reaching Lemoyne. The gull-like shape, generally brown coloration, and prominent white bases to the primaries identified the bird as a jaeger. The bird was smaller but longer-winged than a Ring-billed Gull and larger and slimmer than a Franklin\u27s Gull. The overall coloration was dark brown, except for some warmer rufous tones on the underparts. We saw no visible barring on the underparts. The bill was straight and slender, but the color pattern was not noted. The upperwing was dark brown except for white at the base of at least the outermost four primaries. The underwing was also dark except for a prominent white area on the undersides of the bases of the primaries. The rectrices were dark and the central feathers were slightly elongated with pointed tips. We all agreed on the identification as a juvenile Parasitic Jaeger. Careful size comparisons to Franklin and Ring-billed Gulls eliminated juvenile Pomarine Jaeger, which also generally shows more white color on both surfaces of the wing. Juvenile Long-tailed Jaeger was eliminated on the basis of the pattern of white on the wing and size and wing proportions. We further concluded the bird was an intermediate or dark morph individual based on the dark plumage and lack of a contrasting paler head or rump. This represents the second accepted record of a Parasitic Jaeger for Nebraska. The only other record is of a juvenile picked up alive in Sheridan County on 23 Aug 1968 which died the next day (specimen number UNSM ZM12309) (Gates, Doris. 1969. Parasitic Jaeger rather than Skua. Nebraska Bird Review 37:31.). There are also five records of Pomarine Jaegers and a single Long-tailed Jaeger record for Nebraska. Another 16 reports are of jaegers that were not identified to species

Programmer friendly and efficient distributed shared memory integrated into a distributed operating system

Distributed Shared Memory (DSM) provides programmers with a shared memory environment in systems where memory is not physically shared. Clusters of Workstations (COWs), an often untapped source of computing power, are characterised by a very low cost/performance ratio. The combination of Clusters of Workstations (COWs) with DSM provides an environment in which the programmer can use the well known approaches and methods of programming for physically shared memory systems and parallel processing can be carried out to make full use of the computing power and cost advantages of the COW. The aim of this research is to synthesise and develop a distributed shared memory system as an integral part of an operating system in order to provide application programmers with a convenient environment in which the development and execution of parallel applications can be done easily and efficiently, and which does this in a transparent manner. Furthermore, in order to satisfy our challenging design requirements we want to demonstrate that the operating system into which the DSM system is integrated should be a distributed operating system. In this thesis a study into the synthesis of a DSM system within a microkernel and client-server based distributed operating system which uses both strict and weak consistency models, with a write-invalidate and write-update based approach for consistency maintenance is reported. Furthermore a unique automatic initialisation system which allows the programmer to start the parallel execution of a group of processes with a single library call is reported. The number and location of these processes are determined by the operating system based on system load information. The DSM system proposed has a novel approach in that it provides programmers with a complete programming environment in which they are easily able to develop and run their code or indeed run existing shared memory code. A set of demanding DSM system design requirements are presented and the incentives for the placement of the DSM system with a distributed operating system and in particular in the memory management server have been reported. The new DSM system concentrated on an event-driven set of cooperating and distributed entities, and a detailed description of the events and reactions to these events that make up the operation of the DSM system is then presented. This is followed by a pseudocode form of the detailed design of the main modules and activities of the primitives used in the proposed DSM system. Quantitative results of performance tests and qualitative results showing the ease of programming and use of the RHODOS DSM system are reported. A study of five different application is given and the results of tests carried out on these applications together with a discussion of the results are given. A discussion of how RHODOS’ DSM allows programmers to write shared memory code in an easy to use and familiar environment and a comparative evaluation of RHODOS DSM with other DSM systems is presented. In particular, the ease of use and transparency of the DSM system have been demonstrated through the description of the ease with which a moderately inexperienced undergraduate programmer was able to convert, write and run applications for the testing of the DSM system. Furthermore, the description of the tests performed using physically shared memory shows that the latter is indistinguishable from distributed shared memory; this is further evidence that the DSM system is fully transparent. This study clearly demonstrates that the aim of the research has been achieved; it is possible to develop a programmer friendly and efficient DSM system fully integrated within a distributed operating system. It is clear from this research that client-server and microkernel based distributed operating system integrated DSM makes shared memory operations transparent and almost completely removes the involvement of the programmer beyond classical activities needed to deal with shared memory. The conclusion can be drawn that DSM, when implemented within a client-server and microkernel based distributed operating system, is one of the most encouraging approaches to parallel processing since it guarantees performance improvements with minimal programmer involvement

Evaluation of the Environmental Impact of Milk Quotas

The aim of this study is to examine the environmental impacts of the different systems for allocation and transfer of milk quota under the Common Agricultural Policy (CAP) in individual Member States of the European Union (EU). In particular, it seeks to identify the ways in which differences in the implementation of milk quota regimes can impact on various sectoral and farm management trends and the environmental implications of these