543 research outputs found
The Economics of Terrestrial Invasive Species: A Review of the Literature
This paper reviews the literature on the economics of invasive species management as it applies to invasive species in general and terrestrial invasive species in particular. The paper summarizes a number of recent studies that assign values to the economic impact of terrestrial invasive species on a national scale. This is followed by a review of the economic literature on control and prevention of a biological invasion and the literature on international trade and trade policy with invasive species. The paper then reviews selected studies on terrestrial invasive plants, animals, and microbes, respectively.terrestrial invasive species, prevention, control, international trade, bioeconomic, Resource /Energy Economics and Policy,
THE ECONOMICS OF CONTROLLING A BIOLOGICAL INVASION
The paper develops a simple economic model of a biological invasion. The natural growth of the invasion is non-convex and the immediate cost of controlling the invasion depends on the level of current control as well as the current size of the invasion. Greater control raises control costs today while reducing damages - now and in the future. In addition, by decreasing the size of the invasion, increased control today raises the marginal cost of control in the future. As a consequence, the optimal path of an invasion is not necessarily monotonic. When the marginal control cost declines sharply with the size of invasion, it may be optimal to allow an invasion to grow naturally before it is controlled. We characterize conditions under which it is optimal to eradicate an invasive species (immediately and eventually) and conditions under which it is optimal to manage an invasion without complete eradication.Resource /Energy Economics and Policy,
On Prevention and Control of an Uncertain Biological Invasion
This paper examines how optimal prevention and control policies depend on the economic and biological characteristics of a randomly introduced biological invasion where the objective is to minimize the expected social costs from prevention, control, and invasion damages. The results characterize how optimal prevention and control policies vary with the initial invasion size, the invasion growth rate, and the probability distribution of introductions. The paper also examines the conditions under which the optimal policy relies solely on either prevention or control, the conditions under which it is optimal to completely prevent new introductions, and the conditions under which eradication of established invasions is optimal.Resource /Energy Economics and Policy,
Theory of Stochastic Optimal Economic Growth
This paper is a survey of the theory of stochastic optimal economic growth.International Development,
A Comparative Life Cycle Assessment between a Metered Dose Inhaler and Electric Nebulizer
Life cycle assessment (LCA) evaluates the environmental impact of a product based on the materials and processes used to manufacture the item as well as the itemās use and disposal. The objective of this LCA was to evaluate and compare the environmental impact of a metered dose inhaler, specifically the ProventilĀ® HFA inhaler (Merk & Co., Inc., Kenilworth, NJ, USA), and an electric nebulizer, specifically the DeVilbiss Pulmo-AideĀ® nebulizer (DeVilbiss, Port Washington, NY, USA). GaBi LCA software was used to model the global warming potential (GWP) of each product by using substantiated data and well-justified assumptions for the components, manufacturing, assembly, and use of both devices. The functional unit used to model each device was one dose of the active drug, albuterol sulfate. The inhalerās GWP, 0.0972 kg CO2-eq, was greater than the nebulizerās even when uncertain parameters were varied Ā±100x. During the use phase ofa the inhaler, which accounted for approximately 96% of the inhalerās total GWP, HFA 134a is used as a propellant to deliver the drug. The total GWP for the electric nebulizer was 0.0294 kg CO2-eq assuming that the mouthpiece was cleaned in a dishwasher, while it was 0.0477 kg CO2-eq when the nebulizer mouthpiece was hand washed between uses. The GWP breakeven scenario between dishwashing and hand washing occurred when the mouthpiece accounted for 10% of the dishwasher load
Rat models of spinal cord injury: from pathology to potential therapies
A long-standing goal of spinal cord injury research is to develop effective spinal cord repair strategies for the clinic. Rat models of spinal cord injury provide an important mammalian model in which to evaluate treatment strategies and to understand the pathological basis of spinal cord injuries. These models have facilitated the development of robust tests for assessing the recovery of locomotor and sensory functions. Rat models have also allowed us to understand how neuronal circuitry changes following spinal cord injury and how recovery could be promoted by enhancing spontaneous regenerative mechanisms and by counteracting intrinsic inhibitory factors. Rat studies have also revealed possible routes to rescuing circuitry and cells in the acute stage of injury. Spatiotemporal and functional studies in these models highlight the therapeutic potential of manipulating inflammation, scarring and myelination. In addition, potential replacement therapies for spinal cord injury, including grafts and bridges, stem primarily from rat studies. Here, we discuss advantages and disadvantages of rat experimental spinal cord injury models and summarize knowledge gained from these models. We also discuss how an emerging understanding of different forms of injury, their pathology and degree of recovery has inspired numerous treatment strategies, some of which have led to clinical trials
Expression of Nerve Growth Factor, Brain-Derived Neurotrophic Factor and Neurotrophin-3 mRNAs in Human Cortical Xenografts
Trophic factors play an important role in the
development of neurons and glia. In order to
study the involvement of neurotrophins in
human cortical development, human fetal
parietal cortical tissue, obtained after early
elective abortions, was transplanted to cortical
cavities in immunosuppressed rats. Using in situ
hybridization it was demonstrated that nerve
growth factor, brain-derived neurotrophic factor
and neurotrophin-3 mRNAs are expressed in
developing human cortical xenografts. We conclude
that neurotrophins may play a role in
human cortical development and rat-derived
astroglial cells could be involved in establishing
reciprocal āpermissive sitesā
Fibrin Glue Used as an Adhesive Agent in CNS Tissues
One of the limitations of many bridging
experiments in neural transplantation is that the
CNS tissues cannot be sutured. Fibrin glue is a
two-component system derived from whole
blood which, when mixed, reproduces the final
stage of blood coagulation and solidifies. Many
experimental studies of humans and animals
show that fibrin glue repair of peripheral nerves
is almost equivalent to microsurgical sutures. In
this study, we attempted to extend its use to
CNS tissues and transplants. Two techniques
were tried: (1) Bilateral parietal knife cuts were
performed by stereotaxic technique in six rats.
Fibrin glue was applied in the right-side cortical
lesion. Immunohistochemistry using antisera to
tyrosine hydroxylase (TH), glial fibrillary acidic
protein (GFAP), laminin and neurofilament
(NF) was essentially similar between the control
and treatment groups. The immunoreactivity of
each marker revealed no significant differences
between the two groups on days 1, 7 and 30.
There was no difference in terms of gliosis or
microvascular proliferation. (2) Embryonic day
16 fetal locus coeruleus was grafted together
with E16 cortex to the anterior chamber of sympathectomized
eyes. In the six eyes of the glue
treatment group, the parietal cortical piece and
the locus coeruleus piece were joined together
before grafting by immersing them in the
solution of fibrin glue. In the eight eyes of the
control group, pieces of parietal cortex and locus
coeruleus were introduced individually and approximated
by gently pressing the cornea. The
sizes of double grafts showed no significant
difference between groups during six weeks
postgrafting. The immunohistochemical pictures
using antisera against TH, GFAP and laminin
were similar in both groups. Catecholaminergic
fibers from the grafted locus coeruleus were
found bridging over into the parietal cortical
piece in both the control and treatment groups.
There was no significant difference in TH-positive
nerve fiber density between tissue glue joined
and control double intraocular grafts. In
conclusion, fibrin glue can be used as an adhesive
agent in CNS tissues without hampering
the outgrowth of neurites or causing adverse
tissue reactions in fetal or adult nervous tissues
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