947 research outputs found
TEMPORAL COST ANALYSIS OF A NEW DEVELOPMENT IN CONTROLLED ATMOSPHERE STORAGE: THE CASE OF VIDALIA ONIONS
Agribusiness,
Modelling the spread of Wolbachia in spatially heterogeneous environments
The endosymbiont Wolbachia infects a large number of insect species and is capable of rapid spread when introduced into a novel host population. The bacteria spread by manipulating their hosts' reproduction, and their dynamics are influenced by the demographic structure of the host population and patterns of contact between individuals. Reactionâdiffusion models of the spatial spread of Wolbachia provide a simple analytical description of their spatial dynamics but do not account for significant details of host population dynamics. We develop a metapopulation model describing the spatial dynamics of Wolbachia in an age-structured host insect population regulated by juvenile density-dependent competition. The model produces similar dynamics to the reactionâdiffusion model in the limiting case where the host's habitat quality is spatially homogeneous and Wolbachia has a small effect on host fitness. When habitat quality varies spatially, Wolbachia spread is usually much slower, and the conditions necessary for local invasion are strongly affected by immigration of insects from surrounding regions. Spread is most difficult when variation in habitat quality is spatially correlated. The results show that spatial variation in the density-dependent competition experienced by juvenile host insects can strongly affect the spread of Wolbachia infections, which is important to the use of Wolbachia to control insect vectors of human disease and other pests
Directly Measured Denitrification Reveals Oyster Aquaculture and Restored Oyster Reefs Remove Nitrogen at Comparable High Rates
Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster restoration and aquaculture are both hypothesized to mitigate excessive nitrogen (N) loads via benthic denitrification. The degree to which these management activities perform similar functions for removing N, however, has not been extensively examined in New England, a place where nutrient runoff is high and increasing oyster (Crassostrea virginica) restoration and aquaculture activity is taking place. Here, we use a novel in situ methodology to directly measure net N2 and O2 fluxes across the sediment-water interface in a shallow (~1 m) coastal pond in southern Rhode Island. We collected data seasonally during 2013 and 2014 at restored oyster reefs, oyster aquaculture, oyster cultch (shell), and bare sediment. Restored oyster reefs and aquaculture had the highest mean (±SE) denitrification rates, 581.9 (±164.2) and 346 (±168.6) ÎŒmol N2âN mâ2 hâ1, respectively, and are among the highest recorded for oyster-dominated environments. Denitrification rates at sites with oyster cultch were 60.9 (±44.3) ÎŒmol N2âN mâ2 hâ1, which is substantially less than the sites with active oysters but still more than 50% higher than denitrification rates measured in bare sediment (24.4 ± 10.1 ÎŒmol N2âN mâ2 hâ1). The increase in denitrification rates at treatments, however, varied by season and the greatest rates for restored reefs were in the fall. Overall, the greatest aggregate denitrification rates occurred in the fall. Sediment oxygen demand (SOD) followed similar patterns but with greater overall rates in the summer, and displayed a strong linear relationship with denitrification (R2 = 0.93). Our results demonstrate that habitats associated with live oysters have higher net denitrification rates and that oyster reef restoration and oyster aquaculture may provide similar benefits to the ecosystem in terms of N removal. However, gas fluxes may also be affected where three-dimensional structure is introduced via oyster shell cultch and this appears to be seasonally-dependent. These data will be important for managers as they incorporate oysters into nutrient reduction strategies and consider system-level trade-offs in services provided by oyster reef restoration and aquaculture activities
Directly Measured Denitrification Reveals Oyster Aquaculture and Restored Oyster Reefs Remove Nitrogen at Comparable High Rates
Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster restoration and aquaculture are both hypothesized to mitigate excessive nitrogen (N) loads via benthic denitrification. The degree to which these management activities perform similar functions for removing N, however, has not been extensively examined in New England, a place where nutrient runoff is high and increasing oyster (Crassostrea virginica) restoration and aquaculture activity is taking place. Here, we use a novel in situ methodology to directly measure net N2 and O2 fluxes across the sediment-water interface in a shallow (~1 m) coastal pond in southern Rhode Island. We collected data seasonally during 2013 and 2014 at restored oyster reefs, oyster aquaculture, oyster cultch (shell), and bare sediment. Restored oyster reefs and aquaculture had the highest mean (±SE) denitrification rates, 581.9 (±164.2) and 346 (±168.6) ÎŒmol N2âN mâ2 hâ1, respectively, and are among the highest recorded for oyster-dominated environments. Denitrification rates at sites with oyster cultch were 60.9 (±44.3) ÎŒmol N2âN mâ2 hâ1, which is substantially less than the sites with active oysters but still more than 50% higher than denitrification rates measured in bare sediment (24.4 ± 10.1 ÎŒmol N2âN mâ2 hâ1). The increase in denitrification rates at treatments, however, varied by season and the greatest rates for restored reefs were in the fall. Overall, the greatest aggregate denitrification rates occurred in the fall. Sediment oxygen demand (SOD) followed similar patterns but with greater overall rates in the summer, and displayed a strong linear relationship with denitrification (R2 = 0.93). Our results demonstrate that habitats associated with live oysters have higher net denitrification rates and that oyster reef restoration and oyster aquaculture may provide similar benefits to the ecosystem in terms of N removal. However, gas fluxes may also be affected where three-dimensional structure is introduced via oyster shell cultch and this appears to be seasonally-dependent. These data will be important for managers as they incorporate oysters into nutrient reduction strategies and consider system-level trade-offs in services provided by oyster reef restoration and aquaculture activities
The Effect of Locally Delivered ControlledĂą Release Doxycycline or Scaling and Root Planing on Periodontal Maintenance Patients Over 9 Months
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142157/1/jper0022.pd
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Detection of AÎČ plaque-associated astrogliosis in Alzheimerâs disease brain by spectroscopic imaging and immunohistochemistry
Recent work using micro-Fourier transform infrared (ÎŒFTIR) imaging has revealed that a lipid-rich layer
surrounds many plaques in post-mortem Alzheimerâs brain. However, the origin of this lipid layer is not
known, nor is its role in the pathogenesis of Alzheimerâs disease (AD). Here, we studied the biochemistry
of plaques in situ using a model of AD. We combined FTIR, Raman and immunofluorescence images,
showing that astrocyte processes co-localise with the lipid-ring surrounding many plaques. We used
ÎŒFTIR imaging to rapidly measure chemical signatures of plaques over large fields of view, and selected
plaques for higher resolution analysis with Raman. Raman maps showed similar lipid-rings and dense
protein cores as in FTIR images, but also revealed cell bodies. We confirmed the presence of plaques
using amylo-glo staining, and measured astrocytes using immunohistochemistry, revealing astrocyte colocalisation
with lipid-rings. This work is important because it correlates biochemically changes surrounding
the plaque with the biological process of astrogliosis
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at âs=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Two MultiĂą Center Studies Evaluating Locally Delivered Doxycycline Hyclate, Placebo Control, Oral Hygiene, and Scaling and Root Planing in the Treatment of Periodontitis
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142011/1/jper0490.pd
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+Ï+Ï- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bcâ(2S31)+ state reconstructed without the low-energy photon from the Bcâ(1S31)+âBc+Îł decay following Bcâ(2S31)+âBcâ(1S31)+Ï+Ï-. A second state is seen with a global (local) statistical significance of 2.2Ï (3.2Ï) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
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