1,298 research outputs found
Foreword
The land trust community and governments at all levels have become married to conservation easements as their land conservation tool of choice. The numbers speak for themselves: as of the date of this writing, there were reportedly 1,700 land trusts that have protected twelve million acres of land by use of conservation easements. The bulk of this growth both in conservation easements and the land trusts that deploy them has occurred since the 1980s when federal income tax incentives became more fully utilized by conservation easement donors. But the parties to this marriage have become complacent and inattentive in the face of a rapidly changing world resulting from global ecological catastrophes such as climate change and accelerated species extinction
The Invisible Forest: Conservation Easement Databases and the End of the Clandestine Conservation of Natural Lands
Olmsted talks about invisible forest refers to forest lands -- and, for that matter, any other land types -- protected by a perpetual conservation easement, the existence and location of which are concealed from the public, whether deliberately or because of the opaque nature of the easement process. Because easements, like other forms of deeds, must be recorded at the local land registry or recorder\u27s office, they can never be made undiscoverable. But, despite the efforts of some states and conservation organizations to compile conservation easement data for public consumption, there are few functional systems that comprehensively track and provide easy access to conservation easement data
A Minimal Model for Vorticity and Gradient Banding in Complex Fluids
A general phenomenological reaction-diffusion model for flow-induced phase
transitions in complex fluids is presented. The model consists of an equation
of motion for a nonconserved composition variable, coupled to a Newtonian
stress relations for the reactant and product species. Multivalued reaction
terms allow for different homogeneous phases to coexist with each other,
resulting in banded composition and shear rate profiles. The one-dimensional
equation of motion is evolved from a random initial state to its final
steady-state. We find that the system chooses banded states over homogeneous
states, depending on the shape of the stress constitutive curve and the
magnitude of the diffusion coefficient. Banding in the flow gradient direction
under shear rate control is observed for shear-thinning transitions, while
banding in the vorticity direction under stress control is observed for
shear-thickening transitions.Comment: 11 pages, submitted to Eur Phys J
Two-dimensional perturbations in a scalar model for shear banding
We present an analytical study of a toy model for shear banding, without
normal stresses, which uses a piecewise linear approximation to the flow curve
(shear stress as a function of shear rate). This model exhibits multiple
stationary states, one of which is linearly stable against general
two-dimensional perturbations. This is in contrast to analogous results for the
Johnson-Segalman model, which includes normal stresses, and which has been
reported to be linearly unstable for general two-dimensional perturbations.
This strongly suggests that the linear instabilities found in the
Johnson-Segalman can be attributed to normal stress effects.Comment: 16 pages, 10 figures, to appear in EPJE, available online first,
click DOI or http://www.springerlink.com/content/q1q0187385017628
Modelling diffusion in crystals under high internal stress gradients
Diffusion of vacancies and impurities in metals is important in many processes occurring in structural materials. This diffusion often takes place in the presence of spatially rapidly varying stresses. Diffusion under stress is frequently modelled by local approximations to the vacancy formation and diffusion activation enthalpies which are linear in the stress, in order to account for its dependence on the local stress state and its gradient. Here, more accurate local approximations to the vacancy formation and diffusion activation enthalpies, and the simulation methods needed to implement them, are introduced. The accuracy of both these approximations and the linear approximations are assessed via comparison to full atomistic studies for the problem of vacancies around a Lomer dislocation in Aluminium. Results show that the local and linear approximations for the vacancy formation enthalpy and diffusion activation enthalpy are accurate to within 0.05 eV outside a radius of about 13 Å (local) and 17 Å (linear) from the centre of the dislocation core or, more generally, for a strain gradient of roughly up to 6 × 10^6 m^-1 and 3 × 10^6 m^-1, respectively. These results provide a basis for the development of multiscale models of diffusion under highly non-uniform stress
Structural phase transformations in metallic grain boundaries
Structural transformations at interfaces are of profound fundamental interest
as complex examples of phase transitions in low-dimensional systems. Despite
decades of extensive research, no compelling evidence exists for structural
transformations in high-angle grain boundaries in elemental systems. Here we
show that the critical impediment to observations of such phase transformations
in atomistic modeling has been rooted in inadequate simulation methodology. The
proposed new methodology allows variations in atomic density inside the grain
boundary and reveals multiple grain boundary phases with different atomic
structures. Reversible first-order transformations between such phases are
observed by varying temperature or injecting point defects into the boundary
region. Due to the presence of multiple metastable phases, grain boundaries can
absorb significant amounts of point defects created inside the material by
processes such as irradiation. We propose a novel mechanism of radiation damage
healing in metals which may guide further improvements in radiation resistance
of metallic materials through grain boundary engineering.Comment: 25 pages, 11 figure
Budding and Domain Shape Transformations in Mixed Lipid Films and Bilayer Membranes
We study the stability and shapes of domains with spontaneous curvature in
fluid films and membranes, embedded in a surrounding membrane with zero
spontaneous curvature. These domains can result from the inclusion of an
impurity in a fluid membrane, or from phase separation within the membrane. We
show that for small but finite line and surface tensions and for finite
spontaneous curvatures, an equilibrium phase of protruding circular domains is
obtained at low impurity concentrations. At higher concentrations, we predict a
transition from circular domains, or "caplets", to stripes. In both cases, we
calculate the shapes of these domains within the Monge representation for the
membrane shape. With increasing line tension, we show numerically that there is
a budding transformation from stable protruding circular domains to spherical
buds. We calculate the full phase diagram, and demonstrate a two triple points,
of respectively bud-flat-caplet and flat-stripe-caplet coexistence.Comment: 14 pages, to appear in Phys Rev
The Butterfly Effect: Conservation Easements, Climate Change, and Invasive Species
This Article explains that one of the consequences of climate change will be migrations of species from their native habitats to newer habitats, typically to the north, with climates similar to those in which such species evolved. These in-migrating species will in many cases be invasive, forcing the native species to out-migrate or be driven to extinction, thereby causing biodiversity loss. As many of these disrupted ecosystems may be protected by perpetual conservation easements, the Article discusses the negative legal consequences of incursions by non-native species on these existing conservation easements. Accordingly, the Article suggests a number of changes that can be made to future conservation easements to help insure their protection of land in perpetuity and to better protect species and their habitats from the effects of climate-change-caused migrations
Longitudinal analysis of student performance between host and cooperating college learners in the dental hygiene program at Northcentral Technical College in Wausau, Wisconsin
Includes bibliographical references
Climate Surfing: A Conceptual Guide to Drafting Conservation Easements in the Age of Global Warming
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