3,194 research outputs found
Testing of Great Bay Oysters for Two Protozoan Pathogens
Two protozoan pathogens, Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo) are known to be present in Great Bay oysters. With funds provided by the New Hampshire Estuaries Project (NHEP), the Marine Fisheries Division of New Hampshire Fish and Game Department, (NHF&G) continues to assess the presence and intensity of both disease conditions in oysters from the major beds, some open for harvest, within the Great Bay estuarine system. Histological examination of Great Bay oysters has also revealed other endoparasites
Testing of Great Bay Oysters for Two Protozoan Pathogens
Two protozoan pathogens, Haplosporidium nelsoni (MSX) and Perkinsus marinus(Dermo) are known to be present in Great Bay oysters. With funds provided by the New Hampshire Estuaries Project (NHEP), the Marine Fisheries Division of New Hampshire Fish and Game Department, (NHF&G) continues to assess the presence and intensity of both disease conditions in oysters from the major beds, some open for harvest, within the Great Bay estuarine system. Histological examination of Great Bay oysters has also revealed other endoparasites
Testing of Great Bay Oysters for Two Protazoan Pathogens
Two protozoan pathogens, Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo) are known to be present in Great Bay oysters. With funds provided by the New Hampshire Estuaries Project (NHEP), the Marine Fisheries Division of New Hampshire Fish and Game Department, (NHF&G) continues to assess the presence and intensity of both disease conditions in oysters from the major beds, some open for harvest, within the Great Bay estuarine system. Histological examination of Great Bay oysters has also revealed other endoparasites
Centrality dependence of hyperon global polarization in Au+Au collisions at RHIC
We present the centrality dependence of Lambda and Anti-Lambda hyperon global
polarization in Au+Au collisions at sqrt{s_NN}=62 GeV and 200 GeV measured with
the STAR detector at RHIC. Within the precision of the measurement, we observe
no centrality dependence of Lambda and Anti-Lambda hyperon global polarization
and within our acceptance it is consistent with zero. Different sources of
systematic uncertainties (feed down effects, spin precession) are discussed and
estimated. The obtained upper limit, |P_{Lambda,Anti-Lambda}| < 0.02, is
compared to theoretical predictions discussed recently in literatures.Comment: Talk given at QM 2006, The 19th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, November 14-20, 2006,
Shanghai, China; 4 pages, 2 figure
Measurements of Transverse Spin Effects with the Forward Pion Detector of STAR
Measurements by the STAR collaboration of neutral pion production at large
Feynman x (x_F) in the first polarized proton collisions at GeV
were reported previously. Cross sections measured at , 3.8 and 4.0
are found to be consistent with next-to-leading order perturbative QCD
calculations. The analyzing power is consistent with zero at negative x_F and
at positive x_F up to ~0.3, then grows more positive with increasing x_F. This
behavior can be described by phenomenological models including the Sivers
effect, the Collins effect or higher twist contributions in the initial and
final states. Forward calorimetry at STAR has been extended, and there are
plans for further expansion. An integrated luminosity of 6.8 pb^ with
average beam polarization of 60% from online polarimetry measurements was
sampled with the upgraded FPD in the 2006 RHIC run. This data sample will allow
for a detailed map of the \pi^0 analyzing power over kinematic variables
bounded by 0.3 < x_F < 0.6 and 1.2 < p_T < 5.0 GeV/c at GeV. The
expanded FPD has observed multi-photon final states expected to have "jet-like"
characteristics. The transverse spin dependence of jet-like events can
discriminate between the Collins and Sivers effects and lead to further
progress in understanding the origin of single spin asymmetries in forward
particle production. Data were also obtained at GeV for x_F ->
1 to test predictions based on phenomenological fits to earlier STAR results.
Recent results, the status of the analysis of 2006 run data and near-term plans
will be discussed.Comment: 4 pages, 3 figures, to be published in the proceedings of the 17th
International Spin Physics Symposium (SPIN2006), October 2-7, 2006, Kyoto,
Japa
A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
Recent observations have shown that a growing number of the most massive
Galactic globular clusters contain multiple populations of stars with different
[Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been
recognized as a member of this "iron-complex" cluster class, and we provide
here a chemical and kinematic analysis of > 300 red giant branch (RGB) and
asymptotic giant branch (AGB) member stars using high resolution spectra
obtained with the Magellan-M2FS and VLT-FLAMES instruments. Multiple lines of
evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that
ranges from about [Fe/H] = -2 to -1 dex, and may include at least three
populations with different [Fe/H] values. The three populations identified here
contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars,
but a Mg-Al anti-correlation may only be present in stars with [Fe/H] > -1.65.
The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process
must have dominated the heavy element enrichment at higher metallicities. A
small group of stars with low [alpha/Fe] is identified and may have been
accreted from a former surrounding field star population. The cluster's large
abundance variations are coupled with a complex, extended, and multimodal blue
horizontal branch (HB). The HB morphology and chemical abundances suggest that
NGC 6273 may have an origin that is similar to omega Cen and M 54.Comment: Accepted for Publication in The Astrophysical Journal; 50 pages; 18
figures; 8 tables; higher resolution figures are available upon request or in
the published journal articl
Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569
Photometric and spectroscopic analyses have shown that the Galactic bulge
cluster Terzan 5 hosts several populations with different metallicities and
ages that manifest as a double red horizontal branch (HB). A recent
investigation of the massive bulge cluster NGC 6569 revealed a similar, though
less extended, HB luminosity split, but little is known about the cluster's
detailed chemical composition. Therefore, we have used high-resolution spectra
from the Magellan-M2FS and VLT-FLAMES spectrographs to investigate the chemical
compositions and radial velocity distributions of red giant branch and HB stars
in NGC 6569. We found the cluster to have a mean heliocentric radial velocity
of -48.8 km/s (sigma = 5.3 km/s; 148 stars) and a mean [Fe/H] =-0.87 dex (19
stars), but the cluster's 0.05 dex [Fe/H] dispersion precludes a significant
metallicity spread. NGC 6569 exhibits light- and heavy-element distributions
that are common among old bulge/inner Galaxy globular clusters, including clear
(anti)correlations between [O/Fe], [Na/Fe], and [Al/Fe]. The light-element data
suggest that NGC 6569 may be composed of at least two distinct populations, and
the cluster's low mean [La/Eu] = -0.11 dex indicates significant pollution with
r-process material. We confirm that both HBs contain cluster members, but
metallicity and light-element variations are largely ruled out as sources for
the luminosity difference. However, He mass fraction differences as small as
delta Y ~ 0.02 cannot be ruled out and may be sufficient to reproduce the
double HB.Comment: 72 pages, 14 figures, 8 tables; published in The Astronomical
Journal; electronic versions of all tables are available in the published
versio
The visual binary AG Tri in Pictoris Association: can a debris disc cause very different rotation periods of its components?
We measure the photometric rotation periods of the components of multiple
systems in young stellar associations to investigate the causes of the observed
rotation period dispersion. We present the case of the wide binary AG Tri in
the 23-Myr young beta Pictoris Association consisting of K4 + M1 dwarfs. Our
multi-band, multi-season photometric monitoring allowed us to measure the
rotation periods of both components P_A = 12.4d and P_B = 4.66d, to detect a
prominent magnetic activity in the photosphere, likely responsible for the
measured radial velocity variations, and for the first time, a flare event on
the M1 component AG Tri B. We investigate either the possibility that the
faster rotating component may have suffered an enhanced primordial disc
dispersal, starting its PMS spin-up earlier than the slower rotating component,
or the possibility that the formation of a debris disc may have prevented AG
Tri A from gaining part of the angular momentum from the accreting disc.Comment: 28 pages, 7 figures, accepted for publication in Astrophysics and
Space Science 2015, (ASTR-D-15-00445R2
Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield
Tree root pruning is a potential tool for managing below-ground competition when trees and crops are grown together in agroforestry systems. This study investigates its effects on growth and root distribution of Alnus acuminata (HB & K), Casuarina equisetifolia (L), Grevillea robusta (A. Cunn. ex R. Br), Maesopsis eminii (Engl.), and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was re-opened and roots re-cut at 50 and 62 months after planting. Effects on tree growth and root distribution were assessed over a 3 year period, and crop yield after the third root pruning at 62 months is reported here. Overall, root pruning had only a slight effect on tree growth: height growth was unaffected and diameter growth was reduced by only 4 %. A substantial amount of root re-growth was observed by 11 months after pruning. Tree species varied in the number and distribution of their roots, and Casuarina and Markhamia had considerably more roots per unit of trunk volume than the other tree species, especially in the surface soil layers. Casuarina and Maesopsis were the most competitive tree species with crops and Grevillea and Markhamia the least. Crop yield data provides strong evidence of the redistribution of root activity following root pruning, so that competition increased on the unpruned side of tree rows. Thus, one-sided root pruning will only be of use to farmers in a few circumstances.
Key words: Alnus acuminata, Casuarina equisetifolia, Grevillea robusta, Maesopsis eminii, Markhamia lutea, root distribution, root functio
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