119 research outputs found
The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan
The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys
The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan
The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys
Rapid fixation of non-native alleles revealed by genome-wide SNP analysis of hybrid tiger salamanders
<p>Abstract</p> <p>Background</p> <p>Hybrid zones represent valuable opportunities to observe evolution in systems that are unusually dynamic and where the potential for the origin of novelty and rapid adaptation co-occur with the potential for dysfunction. Recently initiated hybrid zones are particularly exciting evolutionary experiments because ongoing natural selection on novel genetic combinations can be studied in ecological time. Moreover, when hybrid zones involve native and introduced species, complex genetic patterns present important challenges for conservation policy. To assess variation of admixture dynamics, we scored a large panel of markers in five wild hybrid populations formed when Barred Tiger Salamanders were introduced into the range of California Tiger Salamanders.</p> <p>Results</p> <p>At three of 64 markers, introduced alleles have largely displaced native alleles within the hybrid populations. Another marker (<it>GNAT1</it>) showed consistent heterozygote deficits in the wild, and this marker was associated with embryonic mortality in laboratory F2's. Other deviations from equilibrium expectations were idiosyncratic among breeding ponds, consistent with highly stochastic demographic effects.</p> <p>Conclusion</p> <p>While most markers retain native and introduced alleles in expected proportions, strong selection appears to be eliminating native alleles at a smaller set of loci. Such rapid fixation of alleles is detectable only in recently formed hybrid zones, though it might be representative of dynamics that frequently occur in nature. These results underscore the variable and mosaic nature of hybrid genomes and illustrate the potency of recombination and selection in promoting variable, and often unpredictable genetic outcomes. Introgression of a few, strongly selected introduced alleles should not necessarily affect the conservation status of California Tiger Salamanders, but suggests that genetically pure populations of this endangered species will be difficult to maintain.</p
High-Mass X-ray Binaries and the Spiral Structure of the Host Galaxy
We investigate the manifestation of the spiral structure in the distribution
of high-mass X-ray binaries (HMXBs) over the host galaxy. We construct the
simple kinematic model. It shows that the HMXBs should be displaced relative to
the spiral structure observed in such traditional star formation rate
indicators as the Halpha and FIR emissions because of their finite lifetimes.
Using Chandra observations of M51, we have studied the distribution of X-ray
sources relative to the spiral arms of this galaxy observed in Halpha. Based on
K-band data and background source number counts, we have separated the
contributions from high-mass and low-mass X-ray binaries and active galactic
nuclei. In agreement with model predictions, the distribution of HMXBs is wider
than that of bright HII regions concentrated in the region of ongoing star
formation. However, the statistical significance of this result is low, as is
the significance of the concentration of the total population of X-ray sources
to the spiral arms. We also predict the distribution of HMXBs in our Galaxy in
Galactic longitude. The distribution depends on the mean HMXB age and can
differ significantly from the distributions of such young objects as
ultracompact HII regions.Comment: 18 pages, 6 figures; Astronomy Letters, Vol. 33, No. 5, 2007, pp.
299-30
In Vivo Mapping of Vascular Inflammation Using Multimodal Imaging
Plaque vulnerability to rupture has emerged as a critical correlate to risk of adverse coronary events but there is as yet no clinical method to assess plaque stability in vivo. In the search to identify biomarkers of vulnerable plaques an association has been found between macrophages and plaque stability--the density and pattern of macrophage localization in lesions is indicative of probability to rupture. In very unstable plaques, macrophages are found in high densities and concentrated in the plaque shoulders. Therefore, the ability to map macrophages in plaques could allow noninvasive assessment of plaque stability. We use a multimodality imaging approach to noninvasively map the distribution of macrophages in vivo. The use of multiple modalities allows us to combine the complementary strengths of each modality to better visualize features of interest. Our combined use of Positron Emission Tomography and Magnetic Resonance Imaging (PET/MRI) allows high sensitivity PET screening to identify putative lesions in a whole body view, and high resolution MRI for detailed mapping of biomarker expression in the lesions.Macromolecular and nanoparticle contrast agents targeted to macrophages were developed and tested in three different mouse and rat models of atherosclerosis in which inflamed vascular plaques form spontaneously and/or are induced by injury. For multimodal detection, the probes were designed to contain gadolinium (T1 MRI) or iron oxide (T2 MRI), and Cu-64 (PET). PET imaging was utilized to identify regions of macrophage accumulation; these regions were further probed by MRI to visualize macrophage distribution at high resolution. In both PET and MR images the probes enhanced contrast at sites of vascular inflammation, but not in normal vessel walls. MRI was able to identify discrete sites of inflammation that were blurred together at the low resolution of PET. Macrophage content in the lesions was confirmed by histology.The multimodal imaging approach allowed high-sensitivity and high-resolution mapping of biomarker distribution and may lead to a clinical method to predict plaque probability to rupture
Submillimeter Follow-up of WISE-Selected Hyperluminous Galaxies
We have used the Caltech Submillimeter Observatory (CSO) to follow-up a
sample of WISE-selected, hyperluminous galaxies, so called W1W2-dropout
galaxies. This is a rare (~ 1000 all-sky) population of galaxies at high
redshift (peaks at z=2-3), that are faint or undetected by WISE at 3.4 and 4.6
um, yet are clearly detected at 12 and 22 um. The optical spectra of most of
these galaxies show significant AGN activity. We observed 14 high-redshift (z >
1.7) W1W2-dropout galaxies with SHARC-II at 350 to 850 um, with 9 detections;
and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer
follow-up of 25 targets at 3.6 and 4.5 um, as well as optical spectra of 12
targets are also presented in the paper. Combining WISE data with observations
from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral
energy distributions (SEDs). These SEDs have a consistent shape, showing
significantly higher mid-IR to submm ratios than other galaxy templates,
suggesting a hotter dust temperature. We estimate their dust temperatures to be
60-120 K using a single-temperature model. Their infrared luminosities are well
over 10^{13} Lsun. These SEDs are not well fitted with existing galaxy
templates, suggesting they are a new population with very high luminosity and
hot dust. They are likely among the most luminous galaxies in the Universe. We
argue that they are extreme cases of luminous, hot dust-obscured galaxies
(DOGs), possibly representing a short evolutionary phase during galaxy merging
and evolution. A better understanding of their long-wavelength properties needs
ALMA as well as Herschel data.Comment: Will be Published on Sep 1, 2012 by Ap
The ACS Nearby Galaxy Survey Treasury
The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to
establish a legacy of uniform multi-color photometry of resolved stars for a
volume-limited sample of nearby galaxies (D<4 Mpc). The survey volume
encompasses 69 galaxies in diverse environments, including close pairs, small &
large groups, filaments, and truly isolated regions. The galaxies include a
nearly complete range of morphological types spanning a factor of ~10^4 in
luminosity and star formation rate. The survey data consists of images taken
with ACS on HST, supplemented with archival data and new WFPC2 imaging taken
after the failure of ACS. Survey images include wide field tilings covering the
full radial extent of each galaxy, and single deep pointings in uncrowded
regions of the most massive galaxies in the volume. The new wide field imaging
in ANGST reaches median 50% completenesses of m_F475W=28.0 mag, m_F606W=27.3
mag, and m_F814W=27.3 mag, several magnitudes below the tip of the red giant
branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the
structure in the red clump. The resulting photometric catalogs are publicly
accessible and contain over 34 million photometric measurements of >14 million
stars. In this paper we present the details of the sample selection, imaging,
data reduction, and the resulting photometric catalogs, along with an analysis
of the photometric uncertainties (systematic and random), for both the ACS and
WFPC2 imaging. We also present uniformly derived relative distances measured
from the apparent magnitude of the TRGB.Comment: 54 pages, including 24 pages of figures and 16 pages of tables.
Project website and data available at http://www.nearbygalaxies.org/ . Data
is also available through MAST. Scheduled to appear in the Astrophysical
Journal Supplements. (Replaced to fix several figures that were damaged
during compression
Downregulation of NR3A-Containing NMDARs Is Required for Synapse Maturation and Memory Consolidation
NR3A is the only NMDA receptor (NMDAR) subunit that down-regulates sharply prior to the onset of sensitive periods for plasticity, yet the functional importance of this transient expression remains largely unknown. To investigate the possibility that removal/replacement of juvenile NR3A-containing NMDARs is involved in experience-driven synapse maturation, we used a reversible transgenic system that allowed persistent NR3A expression in the postnatal forebrain. We found that removal of NR3A is required to develop strong NMDAR currents, full expression of long-term synaptic plasticity, a mature synaptic organization characterized by more synapses and larger postsynaptic densities, and the ability to form long-term memories. Deficits associated with prolonged NR3A were reversible, as late-onset suppression of transgene expression rescued both the synaptic and memory impairments. Our results suggest that NR3A behaves as a molecular brake to prevent the premature strengthening and stabilization of excitatory synapses, and that NR3A removal might thereby initiate critical stages of synapse maturation during early postnatal neural development
Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial
Background
Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy
Machine learning algorithms performed no better than regression models for prognostication in traumatic brain injury
Objective: We aimed to explore the added value of common machine learning (ML) algorithms for prediction of outcome for moderate and severe traumatic brain injury. Study Design and Setting: We performed logistic regression (LR), lasso regression, and ridge regression with key baseline predictors in the IMPACT-II database (15 studies, n = 11,022). ML algorithms included support vector machines, random forests, gradient boosting machines, and artificial neural networks and were trained using the same predictors. To assess generalizability of predictions, we performed internal, internal-external, and external validation on the recent CENTER-TBI study (patients with Glasgow Coma Scale <13, n = 1,554). Both calibration (calibration slope/intercept) and discrimination (area under the curve) was quantified. Results: In the IMPACT-II database, 3,332/11,022 (30%) died and 5,233(48%) had unfavorable outcome (Glasgow Outcome Scale less than 4). In the CENTER-TBI study, 348/1,554(29%) died and 651(54%) had unfavorable outcome. Discrimination and calibration varied widely between the studies and less so between the studied algorithms. The mean area under the curve was 0.82 for mortality and 0.77 for unfavorable outcomes in the CENTER-TBI study. Conclusion: ML algorithms may not outperform traditional regression approaches in a low-dimensional setting for outcome prediction after moderate or severe traumatic brain injury. Similar to regression-based prediction models, ML algorithms should be rigorously validated to ensure applicability to new populations
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