7,544 research outputs found
RXTE and BeppoSAX Observations of MCG -5-23-16: Reflection From Distant Cold Material
We examine the spectral variability of the Seyfert 1.9 galaxy MCG -5-23-16
using RXTE and BeppoSAX observations spanning 2 years from April 1996 to April
1998. During the first year the X-ray source brightens by a factor of ~25% on
timescales of days to months. During this time, the reprocessed continuum
emission seen with RXTE does not respond measurably to the continuum increase.
However, by the end of the second year during the BeppoSAX epoch the X-ray
source has faded again. This time, the reprocessed emission has also faded,
indicating that the reprocessed flux has responded to the continuum. If these
effects are caused by time delays due to the distance between the X-ray source
and the reprocessing region, we derive a light crossing time of between ~1
light day and ~1.5 light years. This corresponds to a distance of 0.001 pc to
0.55 pc, which implies that the reprocessed emission originates between 3x10^15
cm and 1.6x10^18 cm from the X-ray source. In other words, the reprocessing in
MCG -5-23-16 is not dominated by the inner regions of a standard accretion
disk.Comment: Accepted for publication in ApJ. 17 pages, 8 figure
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Bioaccumulation of PCB & DDE methyl sulfones in marine mammals and their interactions with receptor proteins
PCB and DDE-Methyl sulphone metabolites are the product of enzymatic and bile acid entero hepatic metabolism in the final phase (III) of PCB and DDE detoxification in mammals following hepatic microsomal cytochrome P450-dependent metabolism (phase I) and conjugation (phase II). There is good evidence that PCB and DDE methyl sulphone (MSF) metabolites interfere with steroid binding to a receptor protein in uterine epithelium (uteroglobin - UG2 and bronchial epithelium (clara cell secretory protein - CCSP). UG and CCSP are homologous 16,000 Da proteins with different tissue-specific functions. UG binds progesterone in the pre-implantation uterus to signal localised endometrial thickening and capillary formation, vital for successful attachment of the fertilised embryo. PCB-MSFs can displace progesterone in the mammalian uterus due to their higher affinity for UG, resulting in implantation failure or early fetal death. CCSP however, functions to sequester phospholipase A2 (PLA2) released in response to stress (pathogenic infection / injury) to suppress inflammatory responses triggered by PLA2 in bronchial epithelium. CCSP is also known as retinol-binding protein (RBP) transporting retinol (vit A) to target epithelia for a functional immune response*. Studies with Harbour Seals demonstrated displacement of retinol from RBP by hydroxy-PCB metabolites resulting in immunosuppression. PCB-MSFs have been shown to accumulate in clara cells and uterine epithelium in laboratory radioactive tracer studies and CCSP-knock out studies with mice. PCB and DDE -MSFs burdens have been found in marine mammals, suggesting they may be subject to reproductive and immuno-toxic effects of these metabolites. This study determines PCB and DDE-MSFs burdens in tissues (including lung & uterus) of Harbour Seal (Phoca vitulina) and Striped Dolphin (Stenella coeruleoalba) morbillivirus victims and characterises the marine mammalian UG/CCSP protein
\u3ci\u3eLeucanthiza Dircella\u3c/i\u3e (Lepidoptera: Gracillariidae): A Leafminer of Leatherwood, \u3ci\u3eDirca Palustris\u3c/i\u3e
Leatherwood, Dirca palustris (Thymelaeaceae), is an understory shrub ranging throughout most of the eastern and central United States and adjacent Canada. During 1997-1999, we conducted studies to identify and assess the impact of a leafminer that was causing significant damage to leather- wood plants in eastern Gogebic County, Michigan. Leucanthiza dircella was identified as the only insect responsible for the leaf mining activity on leatherwood. In northern Michigan, L. dircella completed one generation per year. Adult moths were captured on yellow sticky panels suspended from leatherwood branches. In 1997 and 1998, most adults were captured during the first sampling period of each year: 6-12 June 1997 and 3-19 May 199B. In 1999, no moths were collected during 5-29 April but adults were collected between 30 April and 22 June 1999. In 1999, initiation of adult flight coincided with D. palustris leaf flush. In 1997, leaf mines were very noticeable by 30 June. The mean number of live L. dircella larvae per mine was 3.5 on 17 July 1997 and then decreased as the season progressed, with most larvae having exited the mines by late August to pupate in the soil. In late August 1997, the mean surface area of a single leaf was 17.8 cm2 and the mean surface area of a single mine was 5.9 cm2. At the end of the 1997 growing seaÂson, 31% of the leatherwood leaves contained L. dircella mines, and 11% of the total leaf surface area had been mined. In 1999, only 8% of the leaves in the study area contained L. dircella mines. No leatherwood mortality was evident as a result of L. dircella leaf mining. Seven species of hymenopteran parasitoids were reared from L. dircella larvae, including one braconid in the genus Pholetesor and six eulophids in the genera Chrysocharis, Closterocerus, Pnigalio, and Sympiesis. Three coleopterans that were commonly observed on leatherwood plants during all years included: Glyptina brunnea (Chrysomelidae), Phyllobius oblongus (Curculionidae) and Polydrusus sericeus (Curculionidae)
Hate Crimes Against LGBTQ Communities and Persons
This section focuses on scholarship surrounding hate crimes—in particular hate crimes relating to LGBTQ communities. The scholarship spans the last decade, a decade that has seen significant progress. As such, early articles discuss marriage equality and suggest that hate crimes would significantly decrease if marriage equality passed at a federal level. Other articles focus on the Hate Crimes Statistics Act, Pub. L. No. 101-275, 28 U.S.C. § 534, and suggest that Congress should enact more, better antihate crime legislation that includes sexual orientation and gender identity as protected classes. After the passage of the Hate Crimes Prevention Act, Pub. L. No. 111-84, 18 U.S.C. § 249, 1389; 42 U.S.C. § 3716, 3716a, scholars focus on the Act’s deficiencies and the need for consistent and strong state laws prohibiting hate crimes. Still other scholars discuss the intersection of communities of color and LGBTQ communities in common oppression and as victims of hate crimes. As evidenced by the Pulse nightclub massacre in 2016, Latinx and LGBTQ communities intersected as victims of a common attack. At least one article discusses the complexities of such an intersection and why the threads of oppression cannot be untangled
Epitaxial Growth of an n-type Ferromagnetic Semiconductor CdCr2Se4 on GaAs(001) and GaP(001)
We report the epitaxial growth of CdCr2Se4, an n-type ferromagnetic
semiconductor, on both GaAs and GaP(001) substrates, and describe the
structural, magnetic and electronic properties. Magnetometry data confirm
ferromagnetic order with a Curie temperature of 130 K, as in the bulk material.
The magnetization exhibits hysteretic behavior with significant remanence, and
an in-plane easy axis with a coercive field of ~125 Oe. Temperature dependent
transport data show that the films are semiconducting in character and n-type
as grown, with room temperature carrier concentrations of n ~ 1 x 10^18 cm-3.Comment: 12 pages, 3 figure
Characterization of Dredged Sediment Used in Coastal Restoration and Marsh Creation Projects
To minimize coastal land loss and create new land, dredged sediment has been in use in coastal Louisiana during the last several years. Engineering properties and material characteristics of dredged material are input parameters in several mathematical models used to predict the long-term hydrodynamic behavior of the coast. Therefore, proper characterization of the dredged material is of utmost importance in the correct design of coastal restoration and land creation projects. The sedimentation characteristics of the dredged material, among other factors, depends on the (a) grain size distribution of the dredged material, (b) salinity (fresh, brackish, or saltwater environment) of the composite slurry, and (c) concentration of the solid particles in the slurry. In this research, dredged sediments obtained from actual coastal restoration projects were characterized. Furthermore, the effects of grain size distribution, salinity and solid particle concentration on sedimentation characteristics have been evaluated
Earth-like sand fluxes on Mars
Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models, raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies showed sand activity, but could not determine whether entire dunes were moving—implying large sand fluxes—or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar
Introducing the Quantum Research Kernels: Lessons from Classical Parallel Computing
Quantum computing represents a paradigm shift for computation requiring an
entirely new computer architecture. However, there is much that can be learned
from traditional classical computer engineering. In this paper, we describe the
Parallel Research Kernels (PRK), a tool that was very useful for designing
classical parallel computing systems. The PRK are simple kernels written to
expose bottlenecks that limit classical parallel computing performance. We
hypothesize that an analogous tool for quantum computing, Quantum Research
Kernels (QRK), may similarly aid the co-design of software and hardware for
quantum computing systems, and we give a few examples of representative QRKs.Comment: 2 page
Magnetic Properties of Epitaxial and Polycrystalline Fe/Si Multilayers
Fe/Si multilayers with antiferromagnetic interlayer coupling have been grown
via ion-beam sputtering on both glass and single-crystal substrates. High-angle
x-ray diffraction measurements show that both sets of films have narrow Fe
peaks, implying a large crystallite size and crystalline iron silicide spacer
layers. Low-angle x-ray diffraction measurements show that films grown on glass
have rougher interfaces than those grown on single-crystal substrates. The
multilayers grown on glass have a larger remanent magnetization than the
multilayers grown on single-crystal substrates. The observation of
magnetocrystalline anisotropy in hysteresis loops and peaks in x-ray
diffraction demonstrates that the films grown on MgO and Ge are epitaxial. The
smaller remanent magnetization in Fe/Si multilayers with better layering
suggests that the remanence is not an intrinsic property.Comment: 9 pages, RevTex, 4 figures available by fax. Send email to
[email protected] for more info. Submitted to '95 MMM proceeding
Surface ozone in the Colorado northern Front Range and the influence of oil and gas development during FRAPPE/DISCOVER-AQ in summer 2014
High mixing ratios of ozone (O3) in the northern Front Range (NFR) of Colorado are not limited to the urban Denver area but were also observed in rural areas where oil and gas activity is the primary source of O3 precursors. On individual days, oil and gas O3 precursors can contribute in excess of 30 ppb to O3 growth and can lead to exceedances of the EPA O3 National Ambient Air Quality Standard. Data used in this study were gathered from continuous surface O3 monitors for June–August 2013–2015 as well as additional flask measurements and mobile laboratories that were part of the FRAPPE/DISCOVER-AQ field campaign of July–August 2014. Overall observed O3 levels during the summer of 2014 were lower than in 2013, likely due to cooler and damper weather than an average summer. This study determined the median hourly surface O3 mixing ratio in the NFR on summer days with limited photochemical production to be approximately 45–55 ppb. Mobile laboratory and flask data collected on three days provide representative case studies of different O3 formation environments in and around Greeley, Colorado. Observations of several gases (including methane, ethane, CO, nitrous oxide) along with O3 are used to identify sources of O3 precursor emissions. A July 23 survey demonstrated low O3 (45–60 ppb) while August 3 and August 13 surveys recorded O3 levels of 75–80 ppb or more. August 3 exemplifies influence of moderate urban and high oil and gas O3 precursor emissions. August 13 demonstrates high oil and gas emissions, low agricultural emissions, and CO measurements that were well correlated with ethane from oil and gas, suggesting an oil and gas related activity as a NOx and O3 precursor source. Low isoprene levels indicated that they were not a significant contributor to O3 precursors measured during the case studies
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