1,901 research outputs found
WETLANDS, WILDLIFE, AND WATER QUALITY: TARGETING AND TRADE OFFS
Cost-effective targeting of conservation activities has only recently been addressed by economists. Most work to date has focused on finding the best locations to set aside land for the protection of biodiversity. An economic approach to the problem, where biodiversity reserve networks are delineated to maximize the number of species protected subject to a budget constraint, has been shown to be much more cost-effective than the standard approach, where reserve networks are delineated subject to an area constraint, ignoring differences in costs across sites. This paper is among the first to use spatially explicit models of production functions for ecosystem services in an optimization framework for prioritizing sites for wetlands restoration. Tradeoffs between two classes of environmental benefits from wetlands restoration, habitat, and water quality were assessed in the Central Valley of California. Habitat benefits were estimated by a count regression model that relates breeding mallard abundances to the configuration of land use types in the study area, and water quality benefits were estimated by a spatially distributed model of nonpoint source pollution and nutrient attenuation in wetlands. Two decision scenarios were analyzed. In the first scenario the optimal configuration of restoration activity was determined for a small watershed, and in the second scenario sites were selected from those offered for enrollment in an easement program throughout the valley. The results reveal the potential for gains in effectiveness from spatial targeting, and they suggest that there will be substantial tradeoffs between environmental benefits. Maximizing habitat quality in the small watershed yielded a 34% increase in mallard abundance and a 3% decrease in nitrogen loads to the river. In contrast, maximizing water quality resulted in a 25% decrease in nitrogen loads and a 2% increase in mallard abundance. Qualitatively similar results were obtained when sites were selected from a set of offered sites throughout the valley, but the tradeoffs were not as severe. The results also suggest that at traditional funding levels the Wetlands Reserve Program in California could reduce nitrogen loads to rivers by approximately 29,000 kg and increase total mallard abundance in the breeding season by approximately 150 individuals throughout the Central Valley in a given year.Resource /Energy Economics and Policy,
Extension of a three-dimensional viscous wing flow analysis user's manual: VISTA 3-D code
Three-dimensional unsteady viscous effects can significantly influence the performance of fixed and rotary wing aircraft. These effects are important in both flows about helicopter rotors in forward flight and flows about three-dimensional (swept and tapered) supercritical wings. A computational procedure for calculating such flow field was developed. The procedure is based upon an alternating direction technique employing the Linearized Block Implicit method for solving three-dimensional viscous flow problems. In order to demonstrate the viability of this method, two- and three-dimensional problems are computed. These include the flow over a two-dimensional NACA 0012 airfoil under steady and oscillating conditions, and the steady, skewed, three-dimensional flow on a flat plate. Although actual three-dimensional flows over wings were not obtained, the ground work was laid for considering such flows. In this report a description of the computer code is given
Multiple-channel generalization of Lellouch-Luscher formula
We generalize the Lellouch-Luscher formula, relating weak matrix elements in
finite and infinite volumes, to the case of multiple strongly-coupled decay
channels into two scalar particles. This is a necessary first step on the way
to a lattice QCD calculation of weak decay rates for processes such as D -> pi
pi and D -> KK. We also present a field theoretic derivation of the
generalization of Luscher's finite volume quantization condition to multiple
two-particle channels. We give fully explicit results for the case of two
channels, including a form of the generalized Lellouch-Luscher formula
expressed in terms of derivatives of the energies of finite volume states with
respect to the box size. Our results hold for arbitrary total momentum and for
degenerate or non-degenerate particles.Comment: 16 pages, 2 figures. v3: Added references, clarified relation to and
corrected comments about previous work, and minor stylistic improvements. v4:
Minor clarifications added, typos fixed, references updated---matches
published versio
Extension of a three-dimensional viscous wing flow analysis
Three-dimensional unsteady viscous effects can significantly influence the performance of fixed and rotary wing aircraft. These effects are important in both flows about helicopter rotors in forward flight and flows about 3-D (swept and tapered) supercritical wings. A computational procedure for calculating such flow field is developed, and therefore would be of great value in the design process as well as in understanding the corresponding flow phenomena. The procedure is based upon an alternating direction technique employing the Linearized Block Implicit method for solving 3-D viscous flow problems. In order to demonstrate the viability of this method, 2-D and 3-D problems are computed. These include the flow over a 2-D NACA 0012 airfoil under steady and oscillating conditions, and the steady, skewed, 3-D flow on a flat plate. Although actual 3-D flows over wings were not obtained, the ground work was laid for considering such flows. The description of the computational procedure and results are given
Problems with the Quenched Approximation in the Chiral Limit
In the quenched approximation, loops of the light singlet meson (the )
give rise to a type of chiral logarithm absent in full QCD. These logarithms
are singular in the chiral limit throwing doubt upon the utility of the
quenched approximation. In previous work, I summed a class of diagrams, leading
to non-analytic power dependencies such as \cond\propto
m_q^{-\delta/(1+\delta)}. I suggested, however, that these peculiar results
could be redefined away. Here I give an alternative derivation of the results,
based on the renormalization group, and argue that they cannot be redefined
away. I discuss the evidence (or lack thereof) for such effects in numerical
data.Comment: (talk given at Lattice '92), 4 pages latex, 3 postscript figures,
uses espcr2.sty and psfig.tex (all included) UW/PT-92-2
Relativistically invariant quantum information
We show that quantum information can be encoded into entangled states of
multiple indistinguishable particles in such a way that any inertial observer
can prepare, manipulate, or measure the encoded state independent of their
Lorentz reference frame. Such relativistically invariant quantum information is
free of the difficulties associated with encoding into spin or other degrees of
freedom in a relativistic context.Comment: 5 pages, published versio
Loose Constitutivity and Armchair Philosophy
Standard philosophical methodology which proceeds by appeal to intuitions accessible "from the armchair" has come under criticism on the basis of empirical work indicating unanticipated variability of such intuitions. Loose constitutivity---the idea that intuitions are partly, but not strictly, constitutive of the concepts that appear in them---offers an interesting line of response to this empirical challenge. On a loose constitutivist view, it is unlikely that our intuitions are incorrect across the board, since they partly fix the facts in question. But we argue that this ratification of intuitions is at best rough and generic, and can only do the required methodological work if it operates in conjunction with some sort of further criteria of theory selection. We consider two that we find in the literature: naturalness (Brian Weatherson, borrowing from Lewis) and charity (Henry Jackman, borrowing from Davidson). At the end of the day, neither provides the armchair philosopher complete shelter from extra-armchair inquiry
Probabilistic Fluorescence-Based Synapse Detection
Brain function results from communication between neurons connected by
complex synaptic networks. Synapses are themselves highly complex and diverse
signaling machines, containing protein products of hundreds of different genes,
some in hundreds of copies, arranged in precise lattice at each individual
synapse. Synapses are fundamental not only to synaptic network function but
also to network development, adaptation, and memory. In addition, abnormalities
of synapse numbers or molecular components are implicated in most mental and
neurological disorders. Despite their obvious importance, mammalian synapse
populations have so far resisted detailed quantitative study. In human brains
and most animal nervous systems, synapses are very small and very densely
packed: there are approximately 1 billion synapses per cubic millimeter of
human cortex. This volumetric density poses very substantial challenges to
proteometric analysis at the critical level of the individual synapse. The
present work describes new probabilistic image analysis methods for
single-synapse analysis of synapse populations in both animal and human brains.Comment: Current awaiting peer revie
A Strategy for a Vanishing Cosmological Constant in the Presence of Scale Invariance Breaking
Recent work has shown that complex quantum field theory emerges as a
statistical mechanical approximation to an underlying noncommutative operator
dynamics based on a total trace action. In this dynamics, scale invariance of
the trace action becomes the statement , with the operator stress energy tensor, and with the trace over the
underlying Hilbert space. We show that this condition implies the vanishing of
the cosmological constant and vacuum energy in the emergent quantum field
theory. However, since the scale invariance condition does not require the
operator to vanish, the spontaneous breakdown of scale
invariance is still permitted.Comment: Second award in the Gravity Research Foundation Essay Competition for
1997; to appear in General Relativity and Gravitation. Plain Tex, no figure
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