The main topic of this thesis is analysis of an unidentified Galactic TeV gamma-ray source, MGRO J1908+06, discovered by Milagro instrument in 2007. We analyzed 54 hours of observational data from the Very Energetic Radiation Imaging Telescope Array System (VERITAS), a ground-based gamma-ray observatory in southern Arizona comprised of an array of four Cherenkov Telescopes that reconstructs the energy and direction of astrophysical gamma-rays by imaging Cherenkov light emitted by energetic particles in air showers produced by the primary gamma-rays. MGRO J1908+06 is located between a supernova remnant SNR G40.5-0.5 and a young, energetic pulsar PSR J1907+0602. We studied the energy dependent morphology of the TeV emission from the source and measured the source extent and spectrum. The source extends well past the boundary of the SNR and is not correlated with strong radio continuum or molecular line emission which likely excludes an origin for the emission as solely due to the SNR. While emission in the 0.5-1.25 TeV band was centered around the pulsar, higher energy emission was observed near the supernova remnant. This morphology is opposite that observed in other pulsar wind nebulae. We proposed two models for the high energy emission located well away from the pulsar but close to the SNR: (1) shock acceleration at the shock front created by an interaction between the pulsar wind and the dense gas at the edge of the SNR or (2) molecular clouds around the SNR provides seed photons with energies higher than those from Cosmic Microwave Backgrounds for inverse Compton scattering. The former model can be tested by looking for molecular emission lines that trace shocks and by measuring the pulsar velocity. In addition, we investigated the gamma-ray emission from the nova explosion of V407 Cygni that occurred in March 2010. The Fermi-LAT observed this event in the energy range of E >100 MeV. The origins of the gamma-ray emission that the Fermi-LAT team proposed are either protons (hadronic model) or electrons (leptonic model), both of which were accelerated at the nova shock via the Fermi acceleration mechanism. We did not consider their leptonic model because no TeV gamma-ray emission is predicted. Their hadronic model can generate TeV gamma-rays with the modeled parameters. We found no evidence for TeV emission. We showed that with the flux upper limit calculated using the VERITAS data imposes constraints on the extension of the proton spectrum at high energies.

This thesis reports on research that examines the early stage invasion process of Asparagus asparagoides (L.) W. Wight (bridal creeper), primarily a bird-dispersed weed, in a remnant vegetation patch. The study site is on Phillip Island, approximately 100 kilometres south east of Melbourne, Victoria. Asparagus asparagoides invasion of the remnant vegetation reserve is a relatively recent phenomenon. Landscape elements that affect bird dispersal and vegetation types that affect seedling establishment may be important factors that limit or enhance the spread of A. asparagoides. A systematic sampling strategy was adopted and data collected for a variety of landscape and vegetative variables including cover and abundance of A. asparagoides and the data were presented in a Geographic Information System (GIS). Preliminary results show that the distribution of A. asparagoides within a remnant vegetation patch is not random. It appears to have entered the reserve from two boundaries, spreading toward the centre, which to date remains sparsely colonised despite the capacity of this weed to spread rapidly over long distances by birds. A number of other outcomes are noted. Asparagus asparagoides establishment is prevented in pasture where sheep and cattle graze, and paddocks subjected to tillage practices. The exclusion of grazing in fenced off vegetation in pastures demonstrates rapid weed establishment and colonisation several hundred metres from main infestation. Field observation and visual inspection of temporal progress of invasion (using above ground weed density with tuber appearance to infer age) appear to suggest that invasion into remnant is associated with the track network. This age/density assumption is strengthened when spatial distribution is examined using a data set where low-density values for A. asparagoides are removed and compared with a data set using all A. asparagoides density values. The mapping of A. asparagoides in fenced off farm remnants suggests that velocity of spread at 191m/yr is a considerable underestimate. Subsequent analysis shows that the spatial distribution of A. asparagoides is not completely spatially random while intensity surface analysis highlights regions of low and high intensity located near track network. Mapping a density surface within GIS provided confirmatory evidence for the establishment of satellite clusters along the track network. The change in the intensity surface observed using the two data sets (lowdensity values and all density values) is also consistent with an expanding invasion occurring between two time periods. Spatial point pattern analysis using K-function statistics shows that xxii the clustering observed using GIS appears to be occurring at two scales or distances (130m- 160m and 195m-205m). The association between tracks and the invasion process observed in the initial stages of the study is examined. There is a change in density as a function of distance from a track where the density of A. asparagoides appears to reduce the further away from the track a site is and this relationship holds regardless of track width. The final stages of the study look at the development of a predictive model. Visual exploration of the data through mapping in a GIS and field observation made during data collection provide the starting point for the development of logistic models to estimate the probability of A. asparagoides presence. Finally the best overall logistic model is applied to a second independent site to determine the general applicability of the model. A number of variables that impact on the presence of A. asparagoides, particularly during the initial stages of the invasion process, are identified. While all the identified variables and the overall model are statistically significant, the model is found to correctly predict presence/absence in only 67% of cases overall. The model however could be expected to correctly predict the presence of A. asparagoides in 74% of cases and has a false positive rate of 40%. The model is applied at a second independent site and found to have an overall percent correct rate of 80% and correctly predicted A. asparagoides presence in 94% of cases. The variables identified as influential in the early stage of invasion are relatively easy to acquire by simple field survey that does not require specialist skills. When considering the model as a tool for the management of remnant vegetation communities, high false positive rates may lead to limited resources being spent on searching sites where there is no weed. However, a high false negative rate would have a larger impact on the management of the weed since the undetected infestations would form sources for new propagules. The model performs well from this point of view in that it provided low false negative rates at both sites. The value of the predictive model is its ability to provide managers with information regarding specific areas to target for weed eradication and management can use the model to assess the effectiveness of any control measures by going back to obtain new cover density data, then using the model to examine the changes over time. The model also provides a starting point for the development of a generic model of A. asparagoides invasion at sites outside of Phillip Island and could also provide the starting point for developing models that could be used for other bird-dispersed fleshy-fruited weed species.

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Clearance of Eucalyptus woodlands has resulted in soil deterioration and lost agricultural production, due to wind erosion, salinity and soil acidity. Despite increasing efforts to reverse these trends through Landcare and other revegetation and agroforestry programs, there is a lack of experimentally-based information about the effects of trees on native pasture performance. The study was carried out in a temperate environment (Southern Tablelands, New South Wales). The altitude at the study sites ranged from 740 to 880m and the aspect at the experimental plots varied from SE to SW. The nearest site was 16 km from Canberra Airport and all sites were situated within similar rainfall isohyets as Canberra Airport. Thus climatic conditions were expected to be similar. Climate records at Canberra Airport indicate that January is the hottest month with mean maximum temperature of 27.7 �C and July is the coldest month with a maximum of 11.1 �C. Rainfall in the area ranges from 37.5 to 66.0 mm monthly average in June and October respectively. The main tree species in the study area were Eucalyptus pauciflora, E. melliodora and E. mannifera. Furthermore, Poa labillardieri, P. sieberiana, Themeda australis, Danthonia penicillata and Microlaena stipoides were the most abundant pasture species on the experimental plots. Species of clover (Trifolium spp.) were also abundant among the herbs. This study used pasture assessment techniques to quantify the effects of remnant patches of Eucalyptus open woodlands on the composition, quality and biomass production of herbaceous understorey vegetation. Microclimate and soil nutrients were also compared under trees and in the open. In addition, consumption by vertebrate grazers under Eucalyptus trees and in the open was compared. Tree density and basal area were compared with herbage standing crop. Remnant patches of Eucalyptus open woodlands modify the microclimate by reducing wind reaching the understorey vegetation. However no significant effects on ambient air temperature and relative humidity were recorded. The effect of trees on soil moisture was contingent to differences between the four sites and soil depth. Despite a 13% higher soil organic matter in the top 15 cm of soil under trees, soil total nitrogen and total phosphorus did not differ from that in the open. Surface soil pH values were lower (by 0.2 units) under the trees. No significant effect of trees on pasture species richness was found. However the classification of quadrats on the basis of species presence showed a distinction between species composition under trees and in the open at one of the four sites. vi The contribution of pasture species to total dry weight on plots under trees and in the open did depend on the particular species involved and was also contingent to differences between sites. However at the sites where Vulpia bromoides and Poa sieberiana were abundant, the two species dominated the biomass under trees. Whereas Microlaena stipoides var. stipoides dominated the biomass under trees at two sites and in the open at only one of the four sites. Pasture total N content differed between sites. Two of the sites had significantly higher (5.9% and 19.7%) N content under trees. On the contrary, pastures at one site contained 18.7% higher N content in the open. The total P content was 18% higher in pastures under trees. Overall, the pasture standing crop under trees was 15% less than in the open during August to May. Vertebrate grazers consumed about the same amount of pasture under the trees and in the open at the four experimental sites.

This study is concerned with programs to conserve remnant stands of native vegetation in the agricultural regions of South Australia and concentrates on the development of explicit evaluation procedures which reflect stated conservation objectives. As botanical data are available for stands of native vegetation in most of the agricultural regions, stands in a particular region are able to be compared rather than assessed in isolation. Based on a review of conservation evaluation schemes in Australia and overseas, a hierarchical evaluation procedure using multiple criteria to compare stands was applied to stands of vegetation in the Mount Lofty Ranges. The conservation objective, of preserving samples of all plant communities in a region, led to the analysis of existing botanical data from two surveys of the Mount Lofty Ranges, to provide the basis for an inventory of regional plant communities. These surveys included 52 remnant stands of native vegetation and employed a point-centred quarter plotless sampling technique to summarise the vegetation. Numerical classificatory analysis of the raw sampling point data produced a more comprehensive floristic summary than the results from the plotless sampling. These floristic groups were correlated with physical environmental variables to produce an inventory of 45 regional vegetation types, as the first stage in the conservation evaluation of stands. Evaluation criteria of size, species richness and species rarity were quantified and used to select examples of each vegetation type on the basis of overall satisfaction of the criteria. In addition, the smallest suite of stands, in which all the vegetation types were represented, was determined, and was shown to be 24 stands. All of these were included in the 37 stands chosen using the three criteria. A third evaluation stage used stand parameters such as plant community richness to give a priority ranking of the 37 stands. A polythetic divisive classification of the vegetation types was developed to provide a means of evaluating communities in stands of native vegetation yet to be sampled in the region, and of comparing the vegetation types with communities in existing reservesr Examination of species-sampling area relationships led to recommended plot sizes for such future vegetation surveys in the Mount Lofty Ranges. The ease of collecting floristic data and the extensive time involved in quantitative measurements suggest that all perennial plant species be recorded and only estimations be made of vegetation quantity and structure for each sampling plot. This study demonstrates the usefulness of numerical classification techniques for conservation evaluation, and of continuous variables to quantify criteria of conservation value; and the application of those criteria in an explicit, hierarchical conservation evaluation procedure.

The main results of this work are the contribution to find the following results: <br />• The most general GRB is made by an early emission (P-GRB or Proper-GRB), with a time-scale not larger than 1 or 2 seconds and an afterglow, whose light curve is characterized by an increasing phase followed by a peak and a decreasing phase. This peak has been identified with the long GRBs prompt emission. In this scenario short GRBs are not but P-GRB, while long GRBs present both a peak and a decreasing late time emission, which is the observed afterglow.<br />• A possible GRB/SuperNova connection is based on the process of induced gravitational collapse of a companion star of the black hole originating the GRB. <br />• A thermal distribution in the comoving frame of the expanding system is assumed for X and γ bands of the spectrum. This assumption leads to a natural bending of the late time light curves making not necessary the hypothesis of a beamed emission within a collimated jet from the inner engine, which has been introduced in literature essentially to reduce the energy requirements.

Although semi-natural grasslands in Europe are declining there is often a time delay in the local extinction of grassland species due to development of remnant populations, i.e., populations with an extended persistence despite a negative growth rate. The objectives of this study were to examine the occurrence of remnant populations after abandonment of semi-natural grasslands and to examine functional traits of plants associated with the development of remnant populations. We surveyed six managed semi-natural grasslands and 20 former semi-natural grasslands where management ceased 60-100 years ago, and assessed species response to abandonment, assuming a space-for-time substitution. The response of species was related to nine traits representing life cycle, clonality, leaf traits, seed dispersal and seed mass. Of the 67 species for which data allowed analysis, 44 species declined after grassland abandonment but still occurred at the sites, probably as remnant populations. Five traits were associated with the response to abandonment. The declining but still occurring species were characterized by high plant height, a perennial life form, possession of a perennial bud bank, high clonal ability, and lack of dispersal attributes promoting long-distance dispersal. Traits allowing plants to maintain populations by utilizing only a part of their life cycle, such as clonal propagation, are most important for the capacity to develop remnant populations and delay local extinction. A considerable fraction of the species inhabiting semi-natural grasslands maintain what is most likely remnant populations after more than 60 years of spontaneous succession from managed semi-natural grasslands to forest. / <p>authorCount :3</p>

The Old Testament verbal expression of ‘the exile of Judah’ during the Babylonian exile has led to the perception that the land of Judah was emptied of all Judeans. This biblical expression is not necessarily contradictory to historical facts, but theologically and quality-orientated in nature. The exile of the elite from Jerusalem to Babylon, the execution of some of them and the flight of others to Egypt and other neighbouring states disrupted Jerusalem and rendered the city dysfunctional in every national sphere. The royal and religious services, which were based in Jerusalem, the capital city, were discontinued. The emptiness of Judah was signalled by the emptiness as regards the royal and religious authority wrought on Jerusalem by Babylon. Without their royalty, cult, trade, military and judiciary, Judah was indeed emptied and exiled. However, not all Judeans were exiled, for a remnant remained. There is almost no significant record of revelations by God in Judah during the exile, especially after compatriots that opted to flee to Egypt had forcefully taken Jeremiah with them. In addition to its land being emptied during the exile, Judah lost some of its land. The Judean identity in Judah disintegrated due to the influx of foreigners into the land and their subsequent influence on the remaining Judeans. Those that remained in Judah were unable to establish an exclusive Judean community and identity effectively; in any case, not before the Babylonian exiles returned early in the time of the Persian Empire. The paucity of information about the lifestyle in Judah during the exile attests to the veracity and rectitude of the theological concepts of the exile of Judah from 605 to 539 BCE. / Thesis (PhD (Old Testament))--North-West University, Potchefstroom Campus, 2013.

The Old Testament verbal expression of ‘the exile of Judah’ during the Babylonian exile has led to the perception that the land of Judah was emptied of all Judeans. This biblical expression is not necessarily contradictory to historical facts, but theologically and quality-orientated in nature. The exile of the elite from Jerusalem to Babylon, the execution of some of them and the flight of others to Egypt and other neighbouring states disrupted Jerusalem and rendered the city dysfunctional in every national sphere. The royal and religious services, which were based in Jerusalem, the capital city, were discontinued. The emptiness of Judah was signalled by the emptiness as regards the royal and religious authority wrought on Jerusalem by Babylon. Without their royalty, cult, trade, military and judiciary, Judah was indeed emptied and exiled. However, not all Judeans were exiled, for a remnant remained. There is almost no significant record of revelations by God in Judah during the exile, especially after compatriots that opted to flee to Egypt had forcefully taken Jeremiah with them. In addition to its land being emptied during the exile, Judah lost some of its land. The Judean identity in Judah disintegrated due to the influx of foreigners into the land and their subsequent influence on the remaining Judeans. Those that remained in Judah were unable to establish an exclusive Judean community and identity effectively; in any case, not before the Babylonian exiles returned early in the time of the Persian Empire. The paucity of information about the lifestyle in Judah during the exile attests to the veracity and rectitude of the theological concepts of the exile of Judah from 605 to 539 BCE. / Thesis (PhD (Old Testament))--North-West University, Potchefstroom Campus, 2013.

Pulsar wind nebulae (PWNe), nebulae harbouring a rotation-powered neutron star that was born in a supernova, provide opportunities to study highly relativistic pulsar winds and their interaction with the surrounding medium. Particularly interesting are PWNe that do not show any sign of the expected surrounding SNR shell and were thought to be born in subenergetic explosions or with unusual progenitors. The detection of a shell around one such PWN suggested that shells are indeed produced but may be faint due to unseen shocked ejecta, a low density environment, and/or a young age that has not yet allowed the shell to brighten and become visible. Here, by using observational X-ray data from modern telescopes with excellent spatial and energy resolution (Chandra and XMM-Newton), we target PWNe that do not have prominent SNR shells, and are known to be in varied environments, to further explore the characteristics of this growing, but poorly explored, class of PWNe. By combining imaging and spectroscopic results, we study the morphology of the PWNe, search for thermal emission from shock-heated material, investigate the energetics of the nebulae, and search for candidates for the neutron stars powering the nebulae. We find that while the faint shell surrounding G21.5–0.9 can be explained as a young PWN evolving in a low density medium, CTB 87 (G74.9+1.2) appears to be in an advanced stage of evolution, and G63.7+1.1 appears to be both in an advanced stage of evolution and in a dense environment. By performing spatially resolved spectroscopy, we have shown how the spectral characteristics vary across the PWNe, and note that more data will place better constraints on possible thermal emission in these remnants. The imaging portion of these studies has revealed intriguing large-scale morphologies for CTB 87 and G63.7+1.1, as well as a torus-jet structure in CTB 87 and neutron star candidates in both CTB 87 and G63.7+1.1. We conclude that both CTB 87 and G63.7+1.1 are likely interacting with the supernova remnant reverse shock, and CTB 87 may be additionally influenced by the motion of its neutron star.