302 research outputs found
\u3cem\u3eEscherichia coli\u3c/em\u3e Pathotypes Occupy Distinct Niches in the Mouse Intestine
Since the first step of the infection process is colonization of the host, it is important to understand how Escherichia coli pathogens successfully colonize the intestine. We previously showed that enterohemorrhagic O157:H7 strain E. coli EDL933 colonizes a niche in the streptomycin-treated mouse intestine that is distinct from that of human commensal strains, which explains how E. coli EDL933 overcomes colonization resistance imparted by some, but not all, commensal E. coli strains. Here we sought to determine if other E. coli pathogens use a similar strategy. We found that uropathogenic E. coli CFT073 and enteropathogenic E. coli E2348/69 occupy intestinal niches that are distinct from that of E. coli EDL933. In contrast, two enterohemorrhagic strains, E. coli EDL933 and E. coli Sakai, occupy the same niche, suggesting that strategies to prevent colonization by a given pathotype should be effective against other strains of the same pathotype. However, we found that a combination of commensal E. coli strains that can prevent colonization by E. coli EDL933 did not prevent colonization by E. coli CFT073 or E. coli E2348/69. Our results indicate that development of probiotics to target multiple E. coli pathotypes will be problematic, as the factors that govern niche occupation and hence stable colonization vary significantly among strains
Consistent Nest Site Selection by Turtles Across Habitats With Varying Levels of Human Disturbance
Human disturbance impacts the breeding behavior of many species, and it is particularly important to understand how these human-caused changes affect vulnerable taxa, such as turtles. Habitat alteration can change the amount and quality of suitable nesting habitat, while human presence during nesting may influence nesting behavior. Consequently, both habitat alteration and human presence can influence the microhabitat that females choose for nesting. In the summer of 2019, we located emydid turtle nests in east-central Alabama, USA, in areas with varying levels of human disturbance (high, intermediate, low). We aimed to determine whether turtles selected nest sites based on a range of microhabitat variables comparing maternally selected natural nests to randomly chosen artificial nests. We also compared nest site choice across areas with different levels of human disturbance. Natural nests had less variance in canopy openness and average daily mean and minimum temperature than artificial nests, but microhabitat variables were similar across differing levels of disturbance. Additionally, we experimentally quantified nest predation across a natural to human-disturbed gradient. Nest predation rates were higher in areas with low and intermediate levels of disturbance than in areas with high human disturbance. Overall, these results show that turtles are not adjusting their choices of nest microhabitat when faced with anthropogenic change, suggesting that preserving certain natural microhabitat features will be critical for populations in human-disturbed areas
Magellan/M2FS and MMT/Hectochelle Spectroscopy of Dwarf Galaxies and Faint Star Clusters within the Galactic Halo
We present spectroscopic data for 16369 stellar targets within and/or toward
38 dwarf spheroidal galaxies and faint star clusters within the Milky Way halo
environment. All spectra come from observations with the multi-object,
fiber-fed echelle spectrographs M2FS at the Magellan/Clay telescope or
Hectochelle at the MMT, reaching a typical limiting magnitude G < 21. Data
products include processed spectra from all observations and catalogs listing
estimates -- derived from template model fitting -- of line-of-sight velocity
(median uncertainty 1.1 km/s) effective temperature (234 K), (base10 logarithm
of) surface gravity (0.52 dex in cgs units), [Fe/H] (0.38 dex) and [Mg/Fe]
(0.24 dex) abundance ratios. The sample contains multi-epoch measurements for
3720 sources, with up to 15 epochs per source, enabling studies of intrinsic
spectroscopic variability. The sample contains 6078 likely red giant stars
(based on surface gravity), and 4494 likely members (based on line-of-sight
velocity and Gaia-measured proper motion) of the target systems. The number of
member stars per individual target system ranges from a few, for the faintest
systems, to ~ 850 for the most luminous. For most systems, our new samples
extend over wider fields than have previously been observed; of the likely
members in our samples, 823 lie beyond twice the projected halflight radius of
their host system, and 42 lie beyond 5 Rhalf.Comment: Published September 2023 in The Astrophysical Journal Supplement
Series, processed spectra and catalogs publicly available at the Zenodo
database doi:10.5281/zenodo.783792
Spectroscopic Confirmation of the Sixth Globular Cluster in the Fornax Dwarf Spheroidal Galaxy
The Fornax dwarf spheroidal galaxy has an anomalous number of globular
clusters, five, for its stellar mass. There is a longstanding debate about a
potential sixth globular cluster (Fornax~6) that has recently been
`rediscovered' in DECam imaging. We present new Magellan/M2FS spectroscopy of
the Fornax~6 cluster and Fornax dSph. Combined with literature data we identify
members of the Fornax~6 cluster that this overdensity is indeed a
star cluster and associated with the Fornax dSph. The cluster is significantly
more metal-rich (mean metallicity of ) than
the other five Fornax globular clusters () and more
metal-rich than the bulk of Fornax. We measure a velocity dispersion of
corresponding to anomalously high
mass-to-light of 15M/L258 at 90\% confidence when calculated assuming
equilibrium. Two stars inflate this dispersion and may be either Fornax field
stars or as yet unresolved binary stars. Alternatively the Fornax~6 cluster may
be undergoing tidal disruption. Based on its metal-rich nature, the Fornax 6
cluster is likely younger than the other Fornax clusters, with an estimated age
of Gyr when compared to stellar isochrones. The chemodynamics and star
formation history of Fornax shows imprints of major events such as infall into
the Milky Way, multiple pericenter passages, star formation bursts, and/or
potential mergers or interactions. Any of these events may have triggered the
formation of the Fornax~6 cluster.Comment: 17 pages, 9 figures. Accepted to ApJ. Data catalogs included.
Comments welcom
Obesity, but not hypohydration, mediates changes in mental task load during passive heating in females
Background The independent effects of hypohydration and hyperthermia on cognition and mood is unclear since the two stresses often confound each other. Further, it is unknown if obese individuals have the same impairments during hyperthermia and hypohydration that is often observed in non-obese individuals. Methods The current study was designed to assess the independent and combined effects of mild hypohydration and hyperthermia on cognition, mood, and mental task load in obese and non-obese females. Twenty-one healthy females participated in two passive heating trials, wherein they were either euhydrated or hypohydrated prior to and throughout passive heating. Cognition (ImPACT), mental task load (NASA-TLX), and mood (Brunel Mood Scale; BRUMS) were measured before and after a 1.0 °C increase in core temperature (TC). Results After a 1.0 °C TC elevation, hypohydration resulted in greater (p 0.05). Hyperthermia, regardless of hydration status, impaired (∼5 A.U) measures of memory-based cognition (verbal and visual memory), and increased mental task load, while worsening mood (p 0.05). Conclusion These data indicate that hyperthermia independently impairs memory-based aspects of cognitive performance, mental task load, and leads to a negative mood state. Mild hypohydration did not exacerbate the effects of hyperthermia. However, obese individuals had increased mental task load during hyperthermia
Better Pumps: Reliable Handpump Infrastructure
Approximately 90 million people in Africa lack access to safe drinking water, despite having water infrastructure installed in their community. The India Mark II and the Afridev handpumps are among the most widely used handpumps in the world. Sadly, studies show that approximately 30% of these handpumps are non-operational due to failures of the bearings, seals, head flange, and other common components. The Better Pumps team of the Collaboratory provides engineering support for partners who are working to improve handpump sustainability. We partnered with Tony Beers and AlignedWorks to validate a bearing test methodology for the India Mark II handpump. By modifying the loading conditions in our handpump test machine, we were able to replicate failures observed by AlignedWorks in a field trial of their bearing design. We partnered with Matt Schwiebert and Living Water International to test new seal designs for the India Mark II and Afridev handpumps and to measure head flange deflections in the India Mark II handpump. Seal performance data collected by the team was used to validate a new design in advance of field trials by Living Water International. Head flange deflection data was collected for partner benchmarking of their computational analysis. Test methodologies and results are reported.https://mosaic.messiah.edu/engr2021/1000/thumbnail.jp
Stellar kinematics of dwarf galaxies from multi-epoch spectroscopy: application to Triangulum II
We present new MMT/Hectochelle spectroscopic measurements for 257 stars
observed along the line of sight to the ultra-faint dwarf galaxy Triangulum II.
Combining with results from previous Keck/DEIMOS spectroscopy, we obtain a
sample that includes 16 likely members of Triangulum II, with up to 10
independent redshift measurements per star. To this multi-epoch kinematic data
set we apply methodology that we develop in order to infer binary orbital
parameters from sparsely sampled radial velocity curves with as few as two
epochs. For a previously-identified (spatially unresolved) binary system in
Tri~II, we infer an orbital solution with period , semi-major axis , and a systemic velocity that we then use in the analysis of Tri~II's
internal kinematics. Despite this improvement in the modeling of binary star
systems, the current data remain insufficient to resolve the velocity
dispersion of Triangulum II. We instead find a 95% confidence upper limit of
The Kinematics, Metallicities, and Orbits of Six Recently Discovered Galactic Star Clusters with Magellan/M2FS Spectroscopy
We present Magellan/M2FS spectroscopy of four recently discovered Milky Way
star clusters (Gran 3, Gran 4, Garro 01, LP 866) and two newly discovered open
clusters (Gaia 9, Gaia 10) at low Galactic latitudes. We measure line-of-sight
velocities and stellar parameters ([Fe/H], , , [Mg/Fe])
from high resolution spectroscopy centered on the Mg triplet and identify 20-80
members per star cluster. We determine the kinematics and chemical properties
of each cluster and measure the systemic proper motion and orbital properties
by utilizing Gaia astrometry. We find Gran 3 to be an old, metal-poor (mean
metallicity of [Fe/H]=-1.84) globular cluster located in the Galactic bulge on
a retrograde orbit. Gran 4 is an old, metal-poor ([Fe/H]}=-1.84) globular
cluster with a halo-like orbit that happens to be passing through the Galactic
plane. The orbital properties of Gran 4 are consistent with the proposed
LMS-1/Wukong and/or Helmi streams merger events. Garro 01 is an old, metal-rich
([Fe/H]=-0.30) globular cluster on a near circular orbit in the outer disk.
Gaia 9 and Gaia 10 are among the most distant known open clusters at
and most metal-poor with [Fe/H]~-0.50,-0.46 for Gaia
9 and Gaia 10, respectively. LP 866 is a nearby, metal-rich open cluster
([Fe/H]). The discovery and confirmation of multiple star clusters in
the Galactic plane shows the power of {\it Gaia} astrometry and the star
cluster census remains incomplete.Comment: 19 pages, 15 figures, submitted to MNRAS, associated data products
available at https://doi.org/10.5281/zenodo.780912
Potential for Supernova Neutrino Detection in MiniBooNE
The MiniBooNE detector at Fermilab is designed to search for oscillation appearance at and to make a
decisive test of the LSND signal. The main detector (inside a veto shield) is a
spherical volume containing 0.680 ktons of mineral oil. This inner volume,
viewed by 1280 phototubes, is primarily a \v{C}erenkov medium, as the
scintillation yield is low. The entire detector is under a 3 m earth
overburden. Though the detector is not optimized for low-energy (tens of MeV)
events, and the cosmic-ray muon rate is high (10 kHz), we show that MiniBooNE
can function as a useful supernova neutrino detector. Simple trigger-level cuts
can greatly reduce the backgrounds due to cosmic-ray muons. For a canonical
Galactic supernova at 10 kpc, about 190 supernova
events would be detected. By adding MiniBooNE to the international network of
supernova detectors, the possibility of a supernova being missed would be
reduced. Additionally, the paths of the supernova neutrinos through Earth will
be different for MiniBooNE and other detectors, thus allowing tests of
matter-affected mixing effects on the neutrino signal.Comment: Added references, version to appear in PR
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