1,338 research outputs found
Crop Rotations and Dynamic Analysis of Southeastern Peanut Farms
Agricultural policy objectives provide green payment incentives for farmers to initiate practices with environmental benefits. Velvet beans planted as a cover crop offer an alternative for southeastern peanut farmers to control nematodes without chemicals, while increasing soil fertility. Commodity programs provide government payments that are essential to rural economies of the southeast.Environmental Economics and Policy,
Influence of geologic parent material and climate on distribution of shortleaf pine in Missouri
This bulletin is a report on Department of Forestry Research Project 260, 'Soil and Species'--P. [2].Digitized 2007 AES.Includes bibliographical references (pages 27-28)
Influence of light and nutrition on color and growth of redcedar seedlings
Digitized 2007 AES.Includes bibliographical references (page 15)
Counterintuitive Effects of Large-Scale Predator Removal on a Midlatitude Rodent Community
Historically, small mammals have been focal organisms for studying predator–prey dynamics, principally because of interest in explaining the drivers of the cyclical dynamics exhibited by northern vole, lemming, and hare populations. However, many small-mammal species occur at relatively low and fairly stable densities at temperate latitudes, and our understanding of how complex predator assemblages influence the abundance and dynamics of these species is surprisingly limited. In an intact grassland ecosystem in western Montana, USA, we examined the abundance and dynamics of Columbian ground squirrels (Spermophilus columbianus), deer mice (Peromyscus maniculatus), and montane voles (Microtus montanus) on 1-ha plots where we excluded mammalian and avian predators and ungulates, excluded ungulates alone, or allowed predators and ungulates full access. Our goal was to determine whether the relatively low population abundance and moderate population fluctuations of these rodents were due to population suppression by predators. Our predator-exclusion treatment was divided into two phases: a phase where we excluded all predators except weasels (Mustela spp.; 2002–2005), and a phase where all predators including weasels were excluded (2006–2009). Across the entire duration of the experiment, predator and/or ungulate exclusion had no effect on the abundance or overall dynamics of ground squirrels and deer mice. Ground squirrel survival (the only species abundant enough to accurately estimate survival) was also unaffected by our experimental treatments. Prior to weasel exclusion, predators also had no impacts on montane vole abundance or dynamics. However, after weasel exclusion, vole populations reached greater population peaks, and there was greater recruitment of young animals on predator-exclusion plots compared to plots open to predators during peak years. These results suggest that the impacts of predators cannot be generalized across all rodents in an assemblage. Furthermore, they suggest that specialist predators can play an important role in suppressing vole abundance even in lower-latitude vole populations that occur at relatively low densities
Isolation of a Collagenase cDNA Clone and Measurement of Changing Collagenase mRNA Levels during Induction in Rabbit Synovial Fibroblasts.
To facilitate our studies on the mechanisms controlling collagenase production at a molecular level in rabbit synovial fibroblasts, we have constructed a cDNA library using mRNAs isolated from cells induced with crystals of monosodium urate monohydrate. We have screened this library with cDNA probes made from induced and control mRNA populations. From among 30 clones that hybridized preferentially to the induced-cell probe, 4 contained collagenase sequences. The largest, a clone of 650 base pairs, was identified by its ability to hybrid select a mRNA that could be translated in a cell-free system into a product that was precipitable with monospecific antibody to collagenase. Using this clone to probe blots of RNA from induced cells, we detected the appearance of a collagenase mRNA of 2.7 kilobases within 5 hr of addition of urate. The level of collagenase mRNA continued to increase for 35-40 hr, when it was 60 to 90 times more abundant in induced cells than in control cells. The increase in mRNA levels correlated with an increase in immunoreactive collagenase protein that was detectable in culture medium by 10 hr
Redox Signaling in Colonial Hydroids: Many Pathways for Peroxide
Studies of mitochondrial redox signaling predict that
the colonial hydroids Eirene viridula and Podocoryna
carnea should respond to manipulations of reactive oxygen
species (ROS). Both species encrust surfaces with feeding
polyps connected by networks of stolons; P. carnea is more
‘sheet-like’ with closely spaced polyps and short stolons,
while E. viridula is more ‘runner-like’ with widely spaced
polyps and long stolons. Treatment with the chemical antioxidant
vitamin C diminishes ROS in mitochondrion-rich
epitheliomuscular cells (EMCs) and produces phenotypic
effects (sheet-like growth) similar to uncouplers of
oxidative phosphorylation. In peripheral stolon tips,
treatment with vitamin C triggers a dramatic increase of
ROS that is followed by tissue death and stolon regression.
The enzymatic anti-oxidant catalase is probably not taken
up by the colony but, rather, converts hydrogen peroxide
in the medium to water and oxygen. Exogenous catalase
does not affect ROS in mitochondrion-rich EMCs, but
does increase the amounts of ROS emitted from
peripheral stolons, resulting in rapid, runner-like growth.
Treatment with exogenous hydrogen peroxide increases
ROS levels in stolon tips and results in somewhat faster
colony growth. Finally, untreated colonies of E. viridula
exhibit higher levels of ROS in stolon tips than untreated
colonies of P. carnea. ROS may participate in a number of
putative signaling pathways: (1) high levels of ROS may
trigger cell and tissue death in peripheral stolon tips; (2)
more moderate levels of ROS in stolon tips may trigger
outward growth, inhibit branching and, possibly, mediate
the redox signaling of mitochondrion-rich EMCs; and (3)
ROS may have an extra-colony function, perhaps in
suppressing the growth of bacteria
An Untriggered Search for Optical Bursts
We present an untriggered search for optical bursts with the ROTSE-I
telephoto array. Observations were taken which monitor an effective 256 square
degree field continuously over 125 hours to m_{ROTSE}=15.7. The uniquely large
field, moderate limiting magnitude and fast cadence of 10 minutes permits
transient searches in a new region of sensitivity. Our search reveals no
candidate events. To quantify this result, we simulate potential optical bursts
with peak magnitude, m_{p}, at t=10 s, which fade as f=(\frac{t}{t_{0}})
^{\alpha_{t}}, where \alpha_t < 0. Simple estimates based on observational
evidence indicate that a search of this sensitivity begins to probe the
possible region occupied by GRB orphan afterglows. Our observing protocol and
image sensitivity result in a broad region of high detection efficiency for
light curves to the bright and slowly varying side of a boundary running from
[\alpha_{t},m_{p}]=[-2.0,6.0] to [-0.3,13.2]. Within this region, the
integrated rate of brief optical bursts is less than 1.1\times 10^{-8} {\rm
s}^{-1} {\rm deg}^{-2}. At 22 times the observed GRB rate from BATSE,
this suggests a limit on \frac{\theta_{opt}}{\theta_{\gamma}}\lesssim 5 where
\theta_{opt} and \theta_{\gamma} are the optical and gamma-ray collimation
angles, respectively. Several effects might explain the absence of optical
bursts, and a search of the kind described here but more sensitive by about 4
magnitudes should offer a more definitive probe.Comment: 8 pages, 6 figures, 1 tabl
Quantum Error Correction via Convex Optimization
We show that the problem of designing a quantum information error correcting
procedure can be cast as a bi-convex optimization problem, iterating between
encoding and recovery, each being a semidefinite program. For a given encoding
operator the problem is convex in the recovery operator. For a given method of
recovery, the problem is convex in the encoding scheme. This allows us to
derive new codes that are locally optimal. We present examples of such codes
that can handle errors which are too strong for codes derived by analogy to
classical error correction techniques.Comment: 16 page
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