1,140 research outputs found
Very high resolution Earth Observation features for testing the direct and indirect effects of landscape structure on local habitat quality
No full texttModelling the empirical relationships between habitat quality and species distribution patterns is the firststep to understanding human impacts on biodiversity. It is important to build on this understanding todevelop a broader conceptual appreciation of the influence of surrounding landscape structure on localhabitat quality, across multiple spatial scales. Traditional models which report that ‘habitat amount’in the landscape is sufficient to explain patterns of biodiversity, irrespective of habitat configurationor spatial variation in habitat quality at edges, implicitly treat each unit of habitat as interchange-able and ignore the high degree of interdependence between spatial components of land-use change.Here, we test the contrasting hypothesis, that local habitat units are not interchangeable in their habitatattributes, but are instead dependent on variation in surrounding habitat structure at both patch- andlandscape levels. As the statistical approaches needed to implement such hierarchical causal models areobservation-intensive, we utilise very high resolution (VHR) Earth Observation (EO) images to rapidlygenerate fine-grained measures of habitat patch internal heterogeneities over large spatial extents. Weuse linear mixed-effects models to test whether these remotely-sensed proxies for habitat quality wereinfluenced by surrounding patch or landscape structure. The results demonstrate the significant influenceof surrounding patch and landscape context on local habitat quality. They further indicate that such aninfluence can be direct, when a landscape variable alone influences the habitat structure variable, and/orindirect when the landscape and patch attributes have a conjoined effect on the response variable. Weconclude that a substantial degree of interaction among spatial configuration effects is likely to be thenorm in determining the ecological consequences of habitat fragmentation, thus corroborating the notion of the spatial context dependence of habitat qualit
Resilience of New Zealand indigenous forest fragments to impacts of livestock and pest mammals
No full textA number of factors have combined to diminish ecosystem integrity in New Zealand indigenous lowland forest fragments surrounded by intensively grazed pasture. Livestock grazing, mammalian pests, adventive weeds and altered nutrient input regimes are important drivers compounding the changes in fragment structure and function due to historical deforestation and fragmentation. We used qualitative systems modelling and empirical data from Beilschmiedia tawa dominated lowland forest fragments in the Waikato Region to explore the relevance of two common resilience paradigms – engineering resilience and ecological resilience – for addressing the conservation management of forest fragments into the future. Grazing by livestock and foraging/predation by introduced mammalian pests both have direct detrimental impacts on key structural and functional attributes of forest fragments. Release from these perturbations through fencing and pest control leads to partial or full recovery of some key indicators (i.e. increased indigenous plant regeneration and cover, increased invertebrate populations and litter mass, decreased soil fertility and increased nesting success) relative to levels seen in larger forest systems over a range of timescales. These changes indicate that forest fragments do show resilience consistent with adopting an engineering resilience paradigm for conservation management, in the landscape context studied. The relevance of the ecological resilience paradigm in these ecosystems is obscured by limited data. We characterise forest fragment dynamics in terms of changes in indigenous species occupancy and functional dominance, and present a conceptual model for the management of forest fragment ecosystems
Generalized TASE-RK methods for stiff problems
No full textA family of Time-Accurate and Stable Explicit (TASE) methods for the numerical integration of Initial Value Problems in stiff Ordinary Differential Equations (ODEs) y'(t) = f (t, y) was recently introduced in [1]. The main idea was to make local extrapolation of a stabilized Euler method. More recently, in [3] a similar approach by considering the stabilization of arbitrary explicit Runge-Kutta methods (TASE-RK) was analyzed. In this case the explicit Runge-Kutta method integrates a transformed ODE obtained by multiplying the vector field f (t, y) by a certain operator which approximates the identity mapping up to a given order p. The main inconvenience of both approaches is that to reach order p the solution of p2 linear systems plus the evaluation of p derivatives are required per integration step.In order to substantially reduce the computational costs of the former approaches in the linear system solution, but maintaining the good accuracy and stability properties, a new family of TASE-RK methods which allow to introduce a few more free parameters are considered. The formulation of the methods was conceived to be implemented not only in sequential mode but it admits parallelism in a straightforward way. Furthermore, since these methods are linearly implicit, connections to the class of W-methods [19] are properly established. The order conditions for the new class of methods are widely studied by using the rooted tree theory. For p = 3, 4, new methods with p sequential stages and order p are derived and compared on semidiscrete 1D and 2D Partial Differential Equations (PDEs) to those in [1,3] and other standard Rosenbrock and W-methods in the literature.(c) 2023 The Author(s). Published by Elsevier B.V. on behalf of IMACS. This is an open access article under the CC BY-NC-ND license (http:// creativecommons .org /licenses /by-nc -nd /4 .0/)
The morphological effects of sediment diversions the Lower Mississippi River
No full textThe wetlands in the Mississippi delta (USA) are drastically subsiding and eroding. Many projects and researches are ongoing to determine how this “drowning effect” of the delta can be stopped. One of the solutions that could be feasible is implementing sediment diversions in the levees of the Lower Mississippi River in order to divert sediment into the delta. This thesis addresses the morphological effects of river diversions on the Lower Mississippi River. The main objective is to analyze and optimize trade-offs between delta building and river navigability. For this purpose a 2DH numerical model with Delf3D has been created; the model simulates the hydro- and morphodynamic behavior. The river reach which has been studied is the final 110 km of the river from Point a la Hache at River Kilometer 78 (RK 78) down to the mouth of the river (RK -30), below Head of Passes. The hydrodynamic model has been calibrated and verified with flow and stage data from daily observations on the river. With the available sediment data a calibration has been carried out of the morphological behavior in the river. The model has been used to simulate several scenarios to get insight in the problems in the delta. From analysis of the model results the river bed in the study area can be divided into three categories. Upstream of RK 4 the bed is subject to erosion, around RK 4 the bed is practically in equilibrium and downstream of RK 4 the bed is subject to sedimentation. The reach downstream of RK 4 is the dredging reach; after analyzing the long-term simulation of 20 years it is not expected that the dredging quantities will decrease in the future. Closing off West Bay diversion has a positive effect on the dredging quantities. The best diversion site for this study area is found in the inner bend of the river upstream of Empire (RK 47) at RK 53. This site is most efficient and diverts the largest quantities of sand through the diversion.Hydraulic EngineeringCivil Engineering and Geoscience
The Dunston Manuscript
No full textVariously titled 80 Slides and a Memory, Fit for a King and others this is the definitive performed version as an invited reading in 2001 to the Urban Design Group. It describes in blank verse the early stages of the Gateshead Garden Festival illustrated with slide
Associating Gender with Neighbourhood Deprivation in Lagos State, Nigeria
No full textAJOL has removed this paper from the website after it was found to be published in another academic publication. AJOL has requestd that both journal editorial boards investigate this matter further with the author
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Transcriptions of Albanian Violin Music for Viola: History, Musical Style and Teaching Tools for the Intermediate to Advanced Player
No full textABSTRACTTranscriptions of Albanian Violin Music for Viola: History, Musical Style and Teaching Tools for the Intermediate to Advanced Player byBesnik YzeiriThe aim of the present study was fourfold: to add valuable new pieces to the viola repertoire; to do so specifically highlighting Albanian classical music; to develop a methodology for making transcriptions for that instrument; and to demonstrate the usefulness of such works specifically to guide intermediate and advanced viola performance students toward higher technical levels. The author accomplished these goals by carefully choosing appropriate pieces, exploring and comparing the transcribing methodologies of William Primrose, Watson Forbes, and Lionel Tertis, and synthesizing a framework for accomplishing the best transcription method for the task. The author then applied this framework specifically to Albanian composer Pjetër Gaci’s Concertino and Concerto for Violin and Piano, transcribing them for viola and piano, and finally using these transcriptions as case studies as teaching tools for intermediate to advanced viola students
Rankine models for time-dependent gravity spreading of terrestrial source flows over subplanar slopes
No full textGeological mass flows extruding from a point source include mud, lava, and salt issued from subsurface reservoirs and ice from surface feeders. The delivery of the material may occur via a salt stock, a volcanic pipe (for magma and mud flows), or a valley glacier (for ice). All these source flows are commonly skewed by a superposed far-field velocity vector imposed by the topographic slope and thus develop plumes having a wide range of shapes. The morphological evolution of the perimeter of the plumes (in plan view) can be simulated by varying the key parameters in a simple analytical flow description on the basis of Rankine equations. Our model systematically varies the strength of the point source relative to the downslope far-field velocity of its expelled mass. The flow lines are critically controlled by the relative speed of the two rates, which can be concisely expressed by the dimensionless Rankine number (Rk, introduced in this study). For steady flows, plume widths can be expressed as a function of Rk. The viscosity of the rock, mud, or lava mass involved in the gravity flow affects Rk and thus the appearance of the plumes. For unsteady source strength, Rk becomes time dependent and the plume width varies over time. The model flow shapes suggest that the plume shapes of natural gravity flows of terrestrial surface materials (mud, lava, salt, and ice) commonly express fast initial flux of the source, followed by an exponential decline of the source strength. Flows having initially higher Rk but otherwise equal life cycles create broader plumes. Peaks in the source flux due to magmatic pulsing during the eruption cycle can explain the formation of pillow lavas. Rather than instantaneously reaching full strength before declining, some natural source flows start by swelling slowly, leading to the creation of unique plume shapes like a flying saucerGeoscience & EngineeringCivil Engineering and Geoscience
RWP-RK Domain 3 (OsRKD3) induces somatic embryogenesis in black rice
No full textBackground: Plants have the unique capability to form embryos from both gametes and somatic cells, with the latter process known as somatic embryogenesis. Somatic embryogenesis (SE) can be induced by exposing plant tissues to exogenous growth regulators or by the ectopic activation of embryogenic transcription factors. Recent studies have revealed that a discrete group of RWP-RK DOMAIN-CONTAINING PROTEIN (RKD) transcription factors act as key regulators of germ cell differentiation and embryo development in land plants. The ectopic overexpression of reproductive RKDs is associated with increased cellular proliferation and the formation of somatic embryo-like structures that bypass the need for exogenous growth regulators. However, the precise molecular mechanisms implicated in the induction of somatic embryogenesis by RKD transcription factors remains unknown. Results: In silico analyses have identified a rice RWP-RK transcription factor, named Oryza sativa RKD3 (OsRKD3), which is closely related to Arabidopsis thaliana RKD4 (AtRKD4) and Marchantia polymorpha RKD (MpRKD) proteins. Our study demonstrates that the ectopic overexpression of OsRKD3, which is expressed preferentially in reproductive tissues, can trigger the formation of somatic embryos in an Indonesian black rice landrace (Cempo Ireng) that is normally resistant to somatic embryogenesis. By analyzing the transcriptome of induced tissue, we identified 5,991 genes that exhibit differential expression in response to OsRKD3 induction. Among these genes, 50 were up-regulated while the other half were down-regulated. Notably, approximately 37.5 of the up-regulated genes contained a sequence motif in their promoter region, which was also observed in RKD targets from Arabidopsis. Furthermore, OsRKD3 was shown to mediate the transcriptional activation of a discrete gene network, which includes several transcription factors such as APETALA 2-like (AP2-like)/ETHYLENE RESPONSE FACTOR (ERF), MYB and CONSTANS-like (COL), and chromatin remodeling factors associated with hormone signal transduction, stress responses and post-embryonic pathways. Conclusions: Our data show that OsRKD3 modulates an extensive gene network and its activation is associated with the initiation of a somatic embryonic program that facilitates genetic transformation in black rice. These findings hold substantial promise for improving crop productivity and advancing agricultural practices in black rice. © 2023, The Author(s)
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