231 research outputs found
MP 2012-02
Final report to BP.The Prudhoe Bay oil fields, Alaska were discovered in 1968,
and commercial production commenced in 1977 with the
completion of the Trans-Alaska Pipeline. Oil production has
been declining since 1989, although additional exploratory
drilling continues. Support facilities for oil production are
built on permafrost soils that surface-thaw in summer to form
extensive wetlands composed of moist meadows, sedge marshes,
moist sedge-dwarf shrub tundra, grass marshes, small ponds
and lakes (Walker and Acevedo 1987). To prevent thawing and
subsidence of subsurface, ice-rich soils, gravel pads, 2m (6 ft) or
more thickness have been built to support drilling sites as well as
roads, airstrips and building pads (Kidd et al. 2006). As well sites
are decommissioned, the gravel is wholly or partially removed
resulting in the need for site rehabilitation and/or restoration to
support wetland plants and, in some instances, enhance wildlife
habitat (McKendrick 1991, Jorgenson and Joyce 1994, Kidd et
al. 2004, 2006). Since the 1970s, methods to revegetate arctic wetlands have
included a variety of planting techniques, seed treatments,
seeding with native and non-native species (mostly grasses),
and fertilizer applications (Chapin and Chapin 1980; Bishop
and Chapin 1989, Jorgenson 1988, Kidd and Rossow 1998,
Kidd et al. 2004, 2006, Maslen and Kershaw 1989, McKendrick
1987, 1991, 2000, McKendrick et al. 1980, McKendrick and
Mitchell 1978, Mitchell et al. 1974). Treatments also have
included sprigging and plug transplantation (Kidd et al. 2004,
2006), surface manipulation (Streever et al. 2003), as well as
natural re-colonization (Ebersole 1987, Schwarzenbach 1996).
These methods have been partially successful. The gravelly soils
often are dry, nutrient-poor, and have a higher pH and lower
organic matter content than surrounding soils, so natural recolonization
does not occur readily (Bishop and Chapin 1989,
Jorgenson and Joyce 1994). Methods such as sprigging and plug
transplanting are slow, labor intensive and expensive compared
to direct seeding. Fertilization, especially with phosphorus, is
recommended for long-term survival of plants grown on gravelly
sandy soils (BP Exploration and McKendrick 2004).
Two common species in the arctic coastal wetlands are water
sedge, Carex aquatilis Wahlenb. and cotton sedge, Eriophorum
angustifolium Honck. Carex aquatilis in particular forms large
populations that spread vegetatively by rhizomes and often
dominate these wetland environments (Shaver and Billings
1975). Despite their abundance, these species have not been
considered for revegetation because of poor seed germination
and inadequate information on seed development and viability
(Dr. William Streever, BP Alaska, pers. comm.). Both Carex and
Eriophorum in arctic environments produce abundant seeds, but
seed viability and germination often is low and highly variable
among years and locations (Archibold 1984, Billings and
Mooney 1968, Ebersole 1989, Gartner et al. 1983).
Germination recommendations for both species vary by
location and have included an array of pretreatments such as light, alternating temperatures, cold stratification, scarification,
and high and low temperature dry storage (Amen 1966, Billings
and Mooney 1960, Bliss 1958, Hunt and Moore 2003, Johnson
et al. 1965, Phillips 1954 and Steinfeld 2001). The purpose
of this project was to explore methods of seed germination of
Carex aquatilis and Eriophorum angustifolium, to learn the
conditions for germination and dormancy control mechanisms,
and identify seed treatments that might enhance germination
for eventual use in direct-seeding or plug production for arctic
wetland revegetation
Is the economic crisis over (and out)?
This note analyzes the recent global recession: its causes, the predictability of the timing of its start and of its end, and the implications for macro policy. These follow from the general-equilibrium macro model of Abadir and Talmain (2002) and its implications for a new type of macroeconometrics. The note also proposes some banking regulations, and presents prospects for the future.recession, recovery, causes and symptoms, turning points, prediction, macro policy
Recommended from our members
The envenomation of general physiology throughout the last century.
Toxins are the poisonous products of organisms. Toxins serve vital defensive and offensive functions for those that harbor them: stinging scorpions, pesticidal plants, sanguinary snakes, fearless frogs, sliming snails, noxious newts, and smarting spiders. For physiologists, toxins are integral chemical tools that hijack life's fundamental processes with remarkable molecular specificity. Our understanding of electrophysiological phenomena has been transformed time and time again with the help of some terrifying toxins. For this reason, studies of toxin mechanism are an important and enduring facet of The Journal of General Physiology (JGP). This Milestone in Physiology reflects on toxins studied in JGP over its first 100 years, what they have taught us, and what they have yet to reveal
A Proposal for Constraining Initial Vacuum by CMB
We propose a theoretical framework that can possibly constrain the initial
vacuum by Cosmic Microwave Background (CMB) observations. With a generic vacuum
without any particular choice a priori, thereby keeping both the Bogolyubov
coefficients in the analysis, we compute observable parameters from two- and
three-point correlation functions. We are thus left with constraining four
model parameters from the two complex Bogolyubov coefficients. We also
demonstrate a method of finding out the constraint relations between the
Bogolyubov coefficients using the theoretical normalization condition and
observational data of power spectrum and bispectrum from CMB. Finally, we
discuss the possible pros and cons of the analysis.Comment: revised version. 22 pages, 5 figure
An Intermediate State of the {gamma}-Aminobutyric Acid Transporter GAT1 Revealed by Simultaneous Voltage Clamp and Fluorescence
The rat {gamma}-aminobutyric acid transporter GAT1 expressed in Xenopus oocytes was labeled at Cys74, and at one or more other sites, by tetramethylrhodamine-5-maleimide, without significantly altering GAT1 function. Voltage-jump relaxation analysis showed that fluorescence increased slightly and monotonically with hyperpolarization; the fluorescence at -140 mV was ~0.8% greater than at +60 mV. The time course of the fluorescence relaxations was mostly described by a single exponential with voltage-dependent but history-independent time constants ranging from ~20 ms at +60 mV to ~150 ms at -140 mV. The fluorescence did not saturate at the most negative potentials tested, and the midpoint of the fluorescenceāvoltage relation was at least 50 mV more negative than the midpoint of the chargeāvoltage relation previously identified with Na+ binding to GAT1. The presence of {gamma}-aminobutyric acid did not noticeably affect the fluorescence waveforms. The fluorescence signal depended on Na+ concentration with a Hill coefficient approaching 2. Increasing Cl- concentration modestly increased and accelerated the fluorescence relaxations for hyperpolarizing jumps. The fluorescence change was blocked by the GAT1 inhibitor, NO-711. For the W68L mutant of GAT1, the fluorescence relaxations occurred only during jumps to high positive potentials, in agreement with previous suggestions that this mutant is trapped in one conformational state except at these potentials. These observations suggest that the fluorescence signals monitor a novel state of GAT1, intermediate between the E*out and Eout states of Hilgemann, D.W., and C.-C. Lu (1999. J. Gen. Physiol. 114:459ā476). Therefore, the study provides verification that conformational changes occur during GAT1 function
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