Ecology and biogeography of Pinus Richardson, D.M. (ed.) (Institute for Plant Conservation, Botany Department, University of Cape Town, Rondebosch 7700 (South Africa))
1998
Book
Women in the Ancient Near East offers a lucid account of the daily life of women in Mesopotamia from the third millennium BCE until the beginning of the Hellenistic period. The book systematically ...presents the lives of women emerging from the available cuneiform material and discusses modern scholarly opinion. Stol’s book is the first full-scale treatment of the history of women in the Ancient Near East.
Zygomycetes are unique among filamentous fungi in their great ability to infect a broader, more heterogeneous population of human hosts than other opportunistic moulds. Various members of the ...Zygomycetes have been implicated in zygomycosis, although those belonging to the family Mucoraceae are isolated more frequently than those of any other family. The environmental microbiology literature provides limited insights into how common zygomycetes are in the environment, and provides a few clues about which ecological niches these fungi are found in. Mucorales are thermotolerant moulds that are supposedly ubiquitous in nature and widely found on organic substrates, including bread, decaying fruits, vegetable matter, crop debris, soil between growing seasons, compost piles, and animal excreta. The scientific and medical literature does not support this generalization. Sporangiospores released by mucorales range from 3 to 11 μm in diameter, are easily aerosolized, and are readily dispersed throughout the environment. This is the major mode of transmission. However, there are very few data concerning the levels of zygomycete sporangiospores in outdoor and indoor air, especially in geographical areas where zygomycosis is particularly prevalent. Airborne fungal spores are almost ubiquitous and can be found on all human surfaces in contact with air, especially on the upper and lower airway mucosa. Inhalation of sporangiospores must be a daily occurrence. Surprisingly, members of the Mucorales are very rarely found in nasal mucus, suggesting that spores in the mucus of airway mucosa are cleared by mucociliary transport or that there is a low level of airborne contamination. Zygomycetes are found occasionally in water-damaged buildings, as demonstrated by air-sampling, and analysis of settled dust by quantitative PCR. Moreover, inhalation of sporangiospores in dust has been linked to outbreaks of rhinocerebral or pulmonary zygomycosis due to excavation, construction, or contaminated air-conditioning filters. Whereas most zygomycete infections are community-acquired, nosocomial acquisition due to percutaneous routes of exposure is very important. Sporadic cases, and pseudo-outbreaks, have been linked to contaminated bandages and adhesive dressings, needles, and tongue depressors used to construct splints for intravenous and arterial cannulation sites in preterm infants. Insect bites or stings have been implicated in disease transmission in cases of cutaneous and subcutaneous zygomycosis, e.g. diseases caused by the Entomophthorales. Traumatic implantation of spores in dirt or in contaminated water, e.g. as occurred during the Asian tsunami, has led to infection in multiple patients.
Abstract
The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we ...investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M
* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M
* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M
* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the M
SMBH–M
* relation with redshift, particularly for galaxies with M
* ≤ 1010 M⊙. M
SMBH/M
* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.
Mutualisms structure ecosystems and mediate their functioning. They also enhance invasions of many alien species. Invasions disrupt native mutualisms, often leading to population declines, reduced ...biodiversity, and altered ecosystem functioning. Focusing on three main types of mutualisms (pollination, seed dispersal, and plant-microbial symbioses) and drawing on examples from different ecosystems and from species- and community-level studies, we review the key mechanisms whereby such positive interactions mediate invasions and are in turn influenced by invasions. High interaction generalization is "the norm" in most systems, allowing alien species to infiltrate recipient communities. We identify traits that influence invasiveness (e.g., selfing capacity in plants, animal behavioral traits) or invasibility (e.g., partner choice in mycorrhizas/rhizobia) through mutualistic interactions. Mutualistic disruptions due to invasions are pervasive, and subsequent cascading effects are also widespread. Ecological networks provide a useful framework for predicting tipping points for community collapse in response to invasions and other synergistic drivers of global change.
Accurate cosmology from upcoming weak lensing surveys relies on knowledge of the total matter power spectrum at per cent level at scales k < 10 h Mpc^−1, for which modelling the impact of baryonic ...physics is crucial. We compare measurements of the total matter power spectrum from the Horizon cosmological hydrodynamical simulations: a dark-matter-only run, one with full baryonic physics, and another lacking active galactic nucleus (AGN) feedback. Baryons cause a suppression of power at k ≃ 10 h Mpc^−1 of |${\lt}15{{\ \rm per\ cent}}$| at |$z$| = 0, and an enhancement of a factor of a few at smaller scales due to the more efficient cooling and star formation. The results are sensitive to the presence of the highest mass haloes in the simulation and the distribution of dark matter is also impacted up to a few per cent. The redshift evolution of the effect is non-monotonic throughout |$z$| = 0−5 due to an interplay between AGN feedback and gas pressure, and the growth of structure. We investigate the effectiveness of an analytic ‘baryonic correction model’ in describing our results. We require a different redshift evolution and propose an alternative fitting function with four free parameters that reproduces our results within |$5{{\ \rm per\ cent}}$|. Compared to other simulations, we find the impact of baryonic processes on the total matter power spectrum to be smaller at |$z$| = 0. Correspondingly, our results suggest that AGN feedback is not strong enough in the simulation. Total matter power spectra from the Horizon simulations are made publicly available at https://www.horizon-simulation.org/catalogues.html.
Hemp fibre reinforced unsaturated polyester composites (HFRUPE) were subjected to water immersion tests in order to study the effects of water absorption on the mechanical properties. HFRUPE ...composites specimens containing 0, 0.10, 0.15, 0.21 and 0.26 fibre volume fraction were prepared. Water absorption tests were conducted by immersing specimens in a de-ionised water bath at 25
°C and 100
°C for different time durations. The tensile and flexural properties of water immersed specimens subjected to both aging conditions were evaluated and compared alongside dry composite specimens. The percentage of moisture uptake increased as the fibre volume fraction increased due to the high cellulose content. The tensile and flexural properties of HFRUPE specimens were found to decrease with increase in percentage moisture uptake. Moisture induced degradation of composite samples was significant at elevated temperature. The water absorption pattern of these composites at room temperature was found to follow Fickian behaviour, whereas at elevated temperatures it exhibited non-Fickian.
Aim Woody plants were not widely considered to be important invasive alien species until fairly recently. Thousands of species of trees and shrubs have, however, been moved around the world. Many ...species have spread from planting sites, and some are now among the most widespread and damaging of invasive organisms. This article presents a global list of invasive alien trees and shrubs. It discusses taxonomic biases, geographical patterns, modes of dispersal, reasons for introductions and key issues regarding invasions of non-native woody plants around the world. Location Global. Methods An exhaustive survey was made of regional and national databases and the literature. Correspondence with botanists and ecologists and our own observations in many parts of the world expanded the list. Presence of invasive species was determined for each of 15 broad geographical regions. The main reasons for introduction and dissemination were determined for each species. Results The list comprises 622 species (357 trees, 265 shrubs in 29 plant orders, 78 families, 286 genera). Regions with the largest number of woody invasive alien species are: Australia (183); southern Africa (170); North America (163); Pacific Islands (147); and New Zealand (107). Species introduced for horticulture dominated the list (62% of species: 196 trees and 187 shrubs). The next most important reasons for introduction and dissemination were forestry (13%), food (10%) and agroforestry (7%). Three hundred and twenty-three species (52%) are currently known to be invasive in only one region, and another 126 (20%) occur in only two regions. Only 38 species (6%) are very widespread (invasive in six or more regions). Over 40% of invasive tree species and over 60% of invasive shrub species are bird dispersed. Main conclusions Only between 0.5% and 0.7% of the world's tree and shrub species are currently invasive outside their natural range, but woody plant invasions are rapidly increasing in importance around the world. The objectively compiled list of invasive species presented here provides a snapshot of the current dimensions of the phenomenon and will be useful for screening new introductions for invasive potential.
The literature on biological invasions is biased in favour of invasive species – those that spread and often reach high abundance following introduction by humans. It is, however, also important to ...understand previous stages in the introduction'naturalization invasion continuum (‘the continuum’), especially the factors that mediate naturalization. The emphasis on invasiveness is partly because most invasions are only recognized once species occupy large adventive ranges or start to spread. Also, many studies lump all alien species, and fail to separate introduced, naturalized and invasive populations and species. These biases impede our ability to elucidate the full suite of drivers of invasion and to predict invasion dynamics, because different factors mediate progression along different sections of the continuum. A better understanding of the determinants of naturalization is important because all naturalized species are potential invaders. Processes leading to naturalization act differently in different regions and global biogeographical patterns of plant invasions result from the interaction of population-biological, macroecological and human-induced factors. We explore what is known about how determinants of naturalization in plants interact at various scales, and how their importance varies along the continuum. Research that is explicitly linked to particular stages of the continuum can generate new information that is appropriate for improving the management of biological invasions if, for example, potentially invasive species are identified before they exert an impact.
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