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Model I (model + i)
Selected AbstractsThe fundamental and realized niche of the Monterey Pine aphid, Essigella californica (Essig) (Hemiptera: Aphididae): implications for managing softwood plantations in AustraliaDIVERSITY AND DISTRIBUTIONS, Issue 4 2004Trudi N. Wharton ABSTRACT Essigella californica is a pine aphid native to western North America. In Australia, E. californica is considered an invasive pest that has the potential to cause severe economic loss to the Australian forestry industry. Two CLIMEX models were developed to predict the Australian and global distribution of E. californica under current climate conditions based upon the aphid's known North American distribution. The first model (model I) was fitted using the reasonably contiguous set of location records in North America that constituted the known range of E. californica, and excluded consideration of a single (reliable) location record of the aphid in southern Florida. The second model (model II) was fitted using all known records in North America. Model I indicated that the aphid would be climatically restricted to the temperate, Mediterranean and subtropical climatic regions of Australia. In northern Australia it would be limited by hot, wet conditions, while in more central areas of Australia it is limited by hot, dry conditions. Model II is more consistent with the current Australian distribution of E. californica. The contrast in geographical range and climatic conditions encompassed between the two models appears to represent the difference between the realized niche (model I) and fundamental niche (model II) of E. californica. The difference may represent the strength of biotic factors such as host limitation, competition and parasitism in limiting geographical spread in the native range. This paper provides a risk map for E. californica colonization in Australia and globally. E. californica is likely to remain a feature of the Australian pine plantations, and any feasibility studies into establishing coniferous plantations in lower rainfall areas should consider the likely impact of E. californica. [source] Mathematical Frameworks for Modeling Listeria Cross-contamination in Food-JOURNAL OF FOOD SCIENCE, Issue 6 2004D.W. Schaffner ABSTRACT: The possibility of modeling the cross-contamination of Listeria species, total Listeria monocytogenes, or specific L. monocytogenes strains using a quantitative mathematical model using Monte Carlo simulation techniques is proposed. This article illustrates this approach using 2 different models: one that tracks L. monocytogenes number and prevalence for 4 different strains (Model I) and one that tracks only prevalence for a single strain (Model II). These models have been developed to provide a starting framework for predictive modelers and scientists studying L. monocytogenes to begin research together with the ultimate goal of understanding and controlling L. monocytogenes in food-processing plants. [source] The fundamental and realized niche of the Monterey Pine aphid, Essigella californica (Essig) (Hemiptera: Aphididae): implications for managing softwood plantations in AustraliaDIVERSITY AND DISTRIBUTIONS, Issue 4 2004Trudi N. Wharton ABSTRACT Essigella californica is a pine aphid native to western North America. In Australia, E. californica is considered an invasive pest that has the potential to cause severe economic loss to the Australian forestry industry. Two CLIMEX models were developed to predict the Australian and global distribution of E. californica under current climate conditions based upon the aphid's known North American distribution. The first model (model I) was fitted using the reasonably contiguous set of location records in North America that constituted the known range of E. californica, and excluded consideration of a single (reliable) location record of the aphid in southern Florida. The second model (model II) was fitted using all known records in North America. Model I indicated that the aphid would be climatically restricted to the temperate, Mediterranean and subtropical climatic regions of Australia. In northern Australia it would be limited by hot, wet conditions, while in more central areas of Australia it is limited by hot, dry conditions. Model II is more consistent with the current Australian distribution of E. californica. The contrast in geographical range and climatic conditions encompassed between the two models appears to represent the difference between the realized niche (model I) and fundamental niche (model II) of E. californica. The difference may represent the strength of biotic factors such as host limitation, competition and parasitism in limiting geographical spread in the native range. This paper provides a risk map for E. californica colonization in Australia and globally. E. californica is likely to remain a feature of the Australian pine plantations, and any feasibility studies into establishing coniferous plantations in lower rainfall areas should consider the likely impact of E. californica. [source] RELATIONSHIPS BETWEEN PRIMARY PLANT CELL WALL ARCHITECTURE AND MECHANICAL PROPERTIES FOR ONION BULB SCALE EPIDERMAL CELLSJOURNAL OF TEXTURE STUDIES, Issue 6 2004DAVID G. HEPWORTH ABSTRACT This article investigates onion epidermal tissue (Allium cepa) using a combination of mechanical testing, microscopy and modeling and relates tissue mechanical properties to the known structure of the cell walls. Onion epidermal tissue has a simple, regular structure of elongated cells, which have been used to enable the contributions to mechanical properties of cell walls and of higher order structures to be separated and analyzed. Two models of wall behavior were used to explore how Poisson's ratio of cell walls parallel to the plane of the epidermal surface may vary with applied strain. In the first model, cellulose microfibrils can be reorientated in an unrestricted way with the result that the cell wall volume decreases. In the second model the volume of the cell wall remains constant, which controls the reorientation of microfibrils, hence the Poisson's ratio. Measurements made from uniaxially stretched cells show that the data most closely fits model I, therefore, it is concluded that the bulk of the matrix has little influence on the observed mechanical properties (at a test rate of 1 mm/min), allowing cellulose microfibrils to reorient through the matrix in an unrestricted way during uniaxial tests. In its mechanical attributes the primary cell wall resembles more a knitted cloth than a semisolid composite material. When biaxial stretching is applied to tissue, so that there is no re-orientation of microfibrils, the cell wall material is still able to reach surprisingly large elastic strains of up to 12.5% and no plastic deformation was recorded. Current theory suggests that cellulose microfibrils can stretch elastically by a maximum of 7%, therefore further work is required to identify mechanisms that could account for the extra elastic strain. [source] Ly, leaks and reionizationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008Longlong Feng ABSTRACT Ly, absorption spectra of QSOs at redshifts z, 6 show complete Gunn,Peterson absorption troughs (dark gaps) separated by tiny leaks. The dark gaps are from the intergalactic medium (IGM) where the density of neutral hydrogen are high enough to produce almost saturated absorptions, however, where the transmitted leaks come from is still unclear so far. We demonstrate that leaking can originate from the lowest density voids in the IGM as well as the ionized apatches around ionizing sources using semi-analytical simulations. If leaks are produced in lowest density voids, the IGM must already be highly ionized, and the ionizing background should be almost uniform; in contrast, if leaks come from ionized patches, the neutral fraction of IGM should be still high, and the ionizing background is significantly inhomogeneous. Therefore, the origin of leaking is crucial to determining the epoch of inhomogeneous-to-uniform transition of the ionizing photon background. We show that the origin could be studied with the statistical features of leaks. Actually, Ly, leaks can be well defined and described by the equivalent width W and the full width of half-area WH, both of which are less contaminated by instrumental resolution and noise. It is found that the distributions of W and WH of Ly, leaks are sensitive to the modelling of the ionizing background. We consider four representative models: uniform ionizing background (model 0), the photoionization rate of neutral hydrogen ,H i and the density of IGM are either linearly correlated (model I), or anticorrelated (model II), and ,H i is correlated with high-density peaks containing ionizing sources (model III). Although all of these models can match to the mean of the observed effective optical depth of the IGM at z, 6, the distributions of W and WH are very different from each other. Consequently, the leak statistics provides an effective tool to probe the evolutionary history of reionization at z, 5,6.5. Similar statistics will also be applicable to the reionization of He ii at z, 3 [source] Velvet Revolution: An Actor-based ModelPEACE & CHANGE, Issue 2 2006Patrick Van Inwegen Using a process-oriented theoretical model I explain why some revolutions are violent while others are velvet. Velvet revolutions (those with little or no violence) occur because of a peculiar interaction between dissidents and the state. A dynamic model illustrates how dissidents, the state, and the mass public interact in revolution, emphasizing each group's decisions and the impact this has on the other groups. Successful velvet revolutions occur when (1) dissidents committed to nonviolence are (2) sufficiently organized to successfully provoke the state into (3) ineffectively repressing dissidents or inadequately implementing reform. I utilize the 1986 Philippines revolution to test this model and hypothesis. [source] Mixtures of correlated bosons and fermions: Dynamical mean-field theory for normal and condensed phasesANNALEN DER PHYSIK, Issue 9 2009K. Byczuk Abstract We derive a dynamical mean-field theory for mixtures of interacting bosons and fermions on a lattice (BF-DMFT). The BF-DMFT is a comprehensive, thermodynamically consistent framework for the theoretical investigation of Bose-Fermi mixtures and is applicable for arbitrary values of the coupling parameters and temperatures. It becomes exact in the limit of high spatial dimensions d or coordination number Z of the lattice. In particular, the BF-DMFT treats normal and condensed bosons on equal footing and thus includes the effects caused by their dynamic coupling. Using the BF-DMFT we investigate two different interaction models of correlated lattice bosons and fermions, one where all particles are spinless (model I) and one where fermions carry a spin one-half (model II). In model I the local, repulsive interaction between bosons and fermions can give rise to an attractive effective interaction between the bosons. In model II it can also lead to an attraction between the fermions. [source] | |||||||||||||