1,361,599 research outputs found
QCD symmetries in eta- and eta '-mesic nuclei
No full textWe discuss the role of QCD symmetries and confinement in understanding η- and η′-mesic nuclei. η and η′ bound states in nuclei are sensitive to the flavour-singlet component in the meson. The bigger the singlet component, the more attraction and the greater the binding. Recent results on the η′ mass in nuclei from the CBELSA/TAPS Collaboration are very similar to the prediction of the Quark Meson Coupling model. In the model, η–η′ mixing induces a factor of two enhancement of the η-nucleon scattering length aηN relative to the prediction with a pure octet η with real part about 0.8 fm.Steven D. Bass, Anthony W. Thoma
Some consequences of woody plant encroachment in a mesic South African savanna
No full textThis study investigates the diversity present in the patch mosaic of vegetation, and also investigates how woody plant encroachment is affecting ecosystem services in Hluhluwe Game Reserve, with a focus on biodiversity, carbon storage and recreation and tourism
Phylogeography of eastern grey kangaroos, Macropus giganteus, suggests a mesic refugium in eastern Australia
No full textPhylogeographic studies around the world have identified refugia where fauna were able to persist during unsuitable climatic periods, particularly during times of glaciation. In Australia the effects of Pleistocene climate oscillations on rainforest taxa have been well studied but less is known about the effects on mesic-habitat fauna, such as the eastern grey kangaroo (Macropus giganteus). The eastern grey kangaroo is a large mammal that is common and widespread throughout eastern Australia, preferring dry mesic habitat, rather than rainforest. As pollen evidence suggests that the central-eastern part of Australia (southeast Queensland and northern New South Wales) experienced cycles of expansion in mesic habitat with contraction in rainforests, and vice versa during glacial and interglacial periods, respectively, we hypothesise that the distribution of the eastern grey kangaroo was affected by these climate oscillations and may have contracted to mesic habitat refugia. From 375 mitochondrial DNA control region sequences from across the distribution of eastern grey kangaroos we obtained 108 unique haplotypes. Phylogenetic analysis identified two clades in Queensland, one of which is newly identified and restricted to a small coastal region in southern Queensland north of Brisbane, known as the Sunshine Coast. The relatively limited geographic range of this genetically isolated clade suggests the possibility of a mesic habitat refugium forming during rainforest expansion during wetter climate cycles. Other potential, although less likely, reasons for the genetic isolation of the highly distinct clade include geographic barriers, separate northward expansions, and strong local adaptation
Frequent burning promotes invasions of alien plants into a mesic African savanna
No full textFire is both inevitable and necessary for maintaining the structure and functioning of mesic savannas. Without disturbances such as fire and herbivory, tree cover can increase at the expense of grass cover and over time dominate mesic savannas. Consequently, repeated burning is widely used to suppress tree recruitment and control bush encroachment. However, the effect of regular burning on invasion by alien plant species is little understood. Here, vegetation data from a long-term fire experiment, which began in 1953 in a mesic Zimbabwean savanna, were used to test whether the frequency of burning promoted alien plant invasion. The fire treatments consisted of late season fires, lit at 1-, 2-, 3-, and 4-year intervals, and these regularly burnt plots were compared with unburnt plots. Results show that over half a century of frequent burning promoted the invasion by alien plants relative to areas where fire was excluded. More alien plant species became established in plots that had a higher frequency of burning. The proportion of alien species in the species assemblage was highest in the annually burnt plots followed by plots burnt biennially. Alien plant invasion was lowest in plots protected from fire but did not differ significantly between plots burnt triennially and quadrennially. Further, the abundance of five alien forbs increased significantly as the interval (in years) between fires became shorter. On average, the density of these alien forbs in annually burnt plots was at least ten times as high as the density of unburnt plots. Plant diversity was also altered by long-term burning. Total plant species richness was significantly lower in the unburnt plots compared to regularly burnt plots. These findings suggest that frequent burning of mesic savannas enhances invasion by alien plants, with short intervals between fires favouring alien forbs. Therefore, reducing the frequency of burning may be a key to minimising the risk of alien plant spread into mesic savannas, which is important because invasive plants pose a threat to native biodiversity and may alter savanna functioning
White pine restoration in a mesic forest: 3-year results
No full textPinus strobus (Eastern White Pine) was an important component of mesic and dry-mesic northern temperate forests prior to European settlement. We evaluated the efficacy of restoration on a degraded, mesic hardwood site with a low post-harvest residual basal area (11.5 m \u3c sup\u3e 2 ha \u3c sup\u3e -1 ). Three-year survival of planted pines was 57% (n = 299), with 40% mortality occurring the first year. Additional losses, however, were minimal: 2% and 1%) following years two and three, respectively. Survival was associated with presence of bare soil near the seedling (P \u3c 0.05). High initial mortality was likely attributable to drought. Our results suggest that White Pine establishment on more mesic hardwood sites may be possible given sufficient soil and canopy disturbance, but that high initial mortality may be expected under dry climatic conditions
The ratio of non-mesic to π<SUP>-</SUP>-mesic decay of light hyperfragments
No full textA new method of obtaining the charge spectrum of light hyperfragments from their residual range distribution is described. This method has been used to determine the ratio (Q-) of non-mesic to π--mesic decay of light hyperfragments. The values of Q- for hyperfragments of different charges are found to be in good agreement with theoretical calculations of Dalitz
Meson properties from mesic atoms and mesic nuclei
No full textMeson properties are believed to have close connection to the fundamental theory, QCD, and have been studied for a long time both theoretically and experimentally. In this report, we study the recent activities in this field and consider the η(958) mesic nuclei and the deeply bound pionic atoms. We summarize the possible formation of the η(958) mesic nuclei by the (p, d) reactions and report the new possibilities of the spectroscopic study of the pionic atoms using the (d,3He) reactions
Meson properties from mesic atoms and mesic nuclei
No full textMeson properties are believed to have close connection to the fundamental theory, QCD, and have been studied for a long time both theoretically and experimentally. In this report, we study the recent activities in this field and consider the η(958) mesic nuclei and the deeply bound pionic atoms. We summarize the possible formation of the η(958) mesic nuclei by the (p, d) reactions and report the new possibilities of the spectroscopic study of the pionic atoms using the (d,3He) reactions
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ETA-mesic nucleus: a new nuclear species
No full textThe strong-interaction dynamics of the eta N system can cause the eta meson to be captured into nuclear orbitals in nuclei with mass numbers greater than 10. A prediction for what should be the experimental signature of the formation of an eta-mesic nucleus is presented and a forthcoming experiment at Brookhaven is described briefly. The scientific significance of the eta-mesic nuclei is also discussed. 4 refs., 3 figs
Biocrusts: Overlooked hotspots of managed soils in mesic environments.
No full textBiological soil crusts, or “biocrusts”, are biogeochemical hotspots that can significantly influence ecosystem processes in arid environments. Although they can cover large areas, particularly in managed sites with frequent anthropogenic disturbance, their importance in mesic environments is not well understood. As in arid regions, biocrusts in mesic environments can significantly influence nutrient cycling, soil stabilization, and water balance; however, their persistence may differ. We call for interdisciplinary physical, biological, microbiological, chemical, and applied soil science research with a special focus on biocrusts of managed soils from mesic environments, to better understand their impact on overall ecosystem health and resilience, particularly with regard to climate change
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