1,157 research outputs found
Genetic and molecular characterization of Roc-Cullin interactions in Drosophila melanogaster E3 ubiquitin ligases
Cullin-dependent E3 ubiquitin ligases (CDL) are key regulators of protein destruction that participate in a wide range of cell biological processes. The Roc subunit of CDL contains an evolutionarily conserved RING domain that recruits ubiquitin charged E2 and is essential for ubiquitylation. Drosophila melanogaster contains three highly related Roc proteins: Roc1a, Roc1b, and Roc2. We previously reported that mutation of Roc1a and Roc1b causes lethality and male sterility, respectively. Here we show that these disparate phenotypes are partially due to the ability of the Rocs to bind specific Cullins. Roc1a binds Cul1-4, Roc1b binds Cul3, and Roc2 binds Cul5. Through domain swapping experiments, we demonstrate that specific Cullin binding is strongly influenced by the Roc NH2-terminal domain, which forms an inter-molecular β-sheet with the Cullin. Substitution of the Roc1a RING domain with that of Roc1b results in a protein with similar Cullin binding properties to Roc1a but that cannot complement Roc1a mutant lethality, indicating that the identity of the RING domain is an important determinant of CDL function as well. We also identified null mutations of Roc2 and Cul5 and show that they cause no overt developmental phenotype, consistent with our observation that Roc2 and Cul5 proteins are exclusive binding partners
Observations of X-rays and Thermal Dust Emission from the Supernova Remnant Kes 75
We present Spitzer Space Telescope and Chandra X-ray Observatory observations
of the composite Galactic supernova remnant Kes 75 (G29.7-0.3). We use the
detected flux at 24 microns and hot gas parameters from fitting spectra from
new, deep X-ray observations to constrain models of dust emission, obtaining a
dust-to-gas mass ratio M_dust/M_gas ~0.001. We find that a two-component
thermal model, nominally representing shocked swept-up interstellar or
circumstellar material and reverse-shocked ejecta, adequately fits the X-ray
spectrum, albeit with somewhat high implied densities for both components. We
surmise that this model implies a Wolf-Rayet progenitor for the remnant. We
also present infrared flux upper limits for the central pulsar wind nebula.Comment: 7 pages, 2 tables, 4 figures, uses emulateapj. Accepted for
publication in Ap
The Role of Diffusive Shock Acceleration on Nonequilibrium Ionization in Supernova Remnant Shocks II: Emitted Spectra
We present a grid of nonequilibrium ionization models for the X-ray spectra
from supernova remnants undergoing efficient diffusive shock acceleration. The
calculation follows the hydrodynamics of the blast wave as well as the
time-dependent ionization of the plasma behind the shock. The ionization state
is passed to a plasma emissivity code to compute the thermal X-ray emission,
which is combined with the emission from nonthermal synchrotron emission to
produce a self-consistent model for the thermal and nonthermal emission from
cosmic-ray dominated shocks. We show how plasma diagnostics such as the
G'-ratio of He-like ions, defined as the ratio of the sum of the
intercombination, forbidden, and satellite lines to the resonance line, can
vary with acceleration efficiency, and discuss how the thermal X-ray emission,
when the time-dependent ionization is not calculated self-consistently with the
hydrodynamics, can differ from the thermal X-ray emission from models which do
account for the hydrodynamics. Finally we compare the thermal X-ray emission
from models which show moderate acceleration (~ 35%) to the thermal X-ray
emission from test-particle models.Comment: 17 pages, 12 figures. accepted for publication in the Astrophysical
Journa
The Impact of Muscular Strength on Cardiovascular Disease Risk Factors
The purpose of this study was to determine the associations between isokinetic leg muscular strength and cardiovascular disease (CVD) risk factor characterizations in Americans aged 50 and older. Using a publicly available dataset from the National Health and Nutrition Examination Survey (NHANES), a secondary analysis was conducted on participants (males ≥50 yrs; females ≥55 yrs; N=10,858) pooled from 1999 to 2002. CVD risk factors were determined using the American College of Sports Medicine (ACSM) cutoff values. CVD risk factor characterization was determined by creating CVD risk factor profiles (i.e., the total number of CVD risk factors an individual possesses), then separating participants into low (0-2 CVD risk factors), moderate (3-5), and high (6-8) risk groups. Muscular strength was determined by isokinetic maximal peak force (PF) of the leg extensors, both raw and normalized to body mass. Normalized, but not raw, muscular strength was shown to be significantly inversely associated with CVD risk factor characterization for both males and females (Phttps://digitalcommons.odu.edu/gradposters2022_education/1002/thumbnail.jp
Revealing the Dusty Warm Absorber in MCG--6-30-15 with the Chandra HETG
We present detailed evidence for a warm absorber in the Seyfert 1 galaxy
MCG--6-30-15 and dispute earlier claims for relativistic O line emission. The
HETG spectra show numerous narrow, unresolved (FWHM < 200 km/s) absorption
lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and
Fe. The O VII edge and 1s^2--1snp resonance line series to n=9 are clearly
detected at rest in the AGN frame. We attribute previous reports of an
apparently highly redshifted O VII edge to the 1s^2--1snp (n > 5) O VII
resonance lines, and a neutral Fe L absorption complex. The shape of the Fe L
feature is nearly identical to that seen in the spectra of several X-ray
binaries, and in laboratory data. The implied dust column density agrees with
that obtained from reddening studies, and gives the first direct X-ray evidence
for dust embedded in a warm absorber. The O VIII resonance lines and weak edge
are also detected, and the spectral rollover below 2 keV is explained by the
superposition of numerous absorption lines and edges. We identify, for the
first time, a KLL resonance in the O VI photoabsorption cross section, giving a
measure of the O VI column density. The O VII (f) emission detected at the
systemic velocity implies a covering fraction of ~5% (depending on the observed
vs. time-averaged ionizing flux). Our observations show that a dusty warm
absorber model is not only adequate to explain all the spectral features > 0.48
keV (< 26 \AA) the data REQUIRE it. This contradicts the interpretation of
Branduardi-Raymont et al. (2001) that this spectral region is dominated by
highly relativistic line emission from the vicinity of the black hole.Comment: 4.5 pages, 1 color figure, accepted (April 2001) for publication in
ApJL, not many changes from the initial submission - updated/added some
measuements for the O VII resonance series, and added a discussion about FeO2
grain
A Single Bout of Breast Milk Expression Does Not Increase Resting Metabolic Rate
Introduction: Breastfeeding women have elevated resting metabolic rate (RMR); however, whether a single bout of lactation increases RMR is unknown. This study aimed to determine if a single bout of lactation acutely increased RMR.
Methods: Twenty-two lactating women (age: 31 ± 0.9 year, body mass index: 27.3 ± 1.2 kg/m2) were recruited. RMR was assessed at baseline and at 1- and 2-h following breast milk expression.
Results: RMR was unchanged in lactating women following a single bout of lactation (baseline: 1437 ± 39; 1 h: 1425 ± 37 2 h: 1440 ± 31 kcal/day) (p \u3e .05). RMR was not correlated to daily milk produced (r = 0.05, p \u3e .05), but was correlated to body mass (r = 0.74, p \u3c .001), fat-free mass (kg) (r = 0.61, p \u3c .01), and fat mass (kg) (r = 0.71, p \u3c .01).
Conclusion: RMR in lactating women appears to be more related to body mass or composition in the postpartum period rather than lactation
Shocked Molecular Hydrogen in the 3C 326 Radio Galaxy System
The Spitzer spectrum of the giant FR II radio galaxy 3C 326 is dominated by
very strong molecular hydrogen emission lines on a faint IR continuum. The H2
emission originates in the northern component of a double-galaxy system
associated with 3C 326. The integrated luminosity in H2 pure-rotational lines
is 8.0E41 erg/s, which corresponds to 17% of the 8-70 micron luminosity of the
galaxy. A wide range of temperatures (125-1000 K) is measured from the H2 0-0
S(0)-S(7) transitions, leading to a warm H2 mass of 1.1E9 Msun. Low-excitation
ionic forbidden emission lines are consistent with an optical LINER
classification for the active nucleus, which is not luminous enough to power
the observed H2 emission. The H2 could be shock-heated by the radio jets, but
there is no direct indication of this. More likely, the H2 is shock-heated in a
tidal accretion flow induced by interaction with the southern companion galaxy.
The latter scenario is supported by an irregular morphology, tidal bridge, and
possible tidal tail imaged with IRAC at 3-9 micron. Unlike ULIRGs, which in
some cases exhibit H2 line luminosities of comparable strength, 3C 326 shows
little star-formation activity (~0.1 Msun/yr). This may represent an important
stage in galaxy evolution. Starburst activity and efficient accretion onto the
central supermassive black hole may be delayed until the shock-heated H2 can
kinematically settle and coolComment: 27 pages, 7 figures, accepted for publication in the Astrophysical
Journa
Intrinsic Absorption in the Spectrum of NGC 7469: Simultaneous Chandra, FUSE, and STIS Observations
We present simultaneous X-ray, far-ultraviolet, and near-ultraviolet spectra
of the Seyfert 1 galaxy NGC 7469 obtained with the Chandra X-Ray Observatory,
the Far Ultraviolet Spectroscopic Explorer, and the Space Telescope Imaging
Spectrograph on the Hubble Space Telescope. Previous non-simultaneous
observations of this galaxy found two distinct UV absorption components, at
-560 and -1900 km/s, with the former as the likely counterpart of the X-ray
absorber. We confirm these two absorption components in our new UV
observations, in which we detect prominent O VI, Ly alpha, N V, and C IV
absorption. In our Chandra spectrum we detect O VIII emission, but no
significant O VIII or O VII absorption. We also detect a prominent Fe K alpha
emission line in the Chandra spectrum, as well as absorption due to
hydrogen-like and helium-like neon, magnesium, and silicon at velocities
consistent with the -560 km/s UV absorber. The FUSE and STIS data reveal that
the H I and C IV column densities in this UV- and X-ray- absorbing component
have increased over time, as the UV continuum flux decreased. We use measured H
I, N V, C IV, and O VI column densities to model the photoionization state of
both absorbers self-consistently. We confirm the general physical picture of
the outflow in which the low velocity component is a highly ionized, high
density absorber with a total column density of 10^20 cm^-2, located near the
broad emission line region, although due to measurable columns of N V and C IV,
we assign it a somewhat smaller ionization parameter than found previously,
U~1. The high velocity UV component is of lower density, log N=18.6, and likely
resides farther from the central engine as we find its ionization parameter to
be U=0.08.Comment: Minor correction to abstract; STScI eprint #1683; 50 pages, incl. 19
figures, 4 tables; Accepted to Ap
Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites
Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species
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