722 research outputs found
Wyoming v. Zinke
In Wyoming v. Zinke, the Bureau of Land Management attempted to update a regulation governing hydraulic fracturing from the 1980s, but oil and gas industry companies opposed, and brought suit. The district court held in favor of the industry petitioners, and the Bureau of Land Management and citizen group intervenors appealed. In the wake of appeal, Donald J. Trump became President of the United States. The administration change caused the Bureau of Land Management to alter its position and align with the new administration. Secretary of the Interior, Ryan Zinke, via executive order, began rescinding the new fracking regulation, which rendered the issues prudentially unripe for review
Navajo Nation v. Department of the Interior
In Navajo Nation v. Department of the Interior, the Navajo Nation challenged the Department of the Interior’s 2001 and 2008 water allocation guidelines and asserted that under NEPA and the APA the guidelines violated the Navajo Nation’s water rights. The Navajo Nation also asserted a breach of trust claim against the United States. After nearly a decade of attempted settlement negotiations, the Navajo Nation reasserted its complaints. The District Court for the District of Arizona denied the Navajo Nation’s motions, and the Navajo Nation appealed to the Ninth Circuit Court of Appeals, which determined the Navajo Nation lacked standing, leaving the Navajo Nation’s water rights unadjudicated and unquantified
Student perceptions of the English for Native Speakers of Other Languages (ENSOL) Program at Iowa State University
Association of Retinal Vascular Caliber and Age-Related Macular Degeneration in Patients With the Acquired Immunodeficiency Syndrome.
PurposeTo evaluate the relationship between retinal vascular caliber and AMD in patients with AIDS.MethodsParticipants enrolled in the Longitudinal Study of the Ocular Complications of AIDS had retinal photographs taken at enrollment. Retinal vascular caliber (central retinal artery equivalent [CRAE] and central retinal vein equivalent [CRVE]) and intermediate-stage AMD were determined from these retinal photographs. Photographs were evaluated by graders at a centralized reading center, using the Age-Related Eye Disease Study grading system for AMD and semiautomated techniques for evaluating retinal vascular caliber.ResultsOf the 1171 participants evaluated, 110 (9.4%) had AMD and 1061 (90.6%) did not. Compared with participants without AMD, participants with AMD had larger mean CRAEs (151 ± 16 μm versus 147 ± 16 μm; P = 0.009) and mean CRVEs (228 ± 24 μm versus 223 ± 25 μm; P = 0.02). The unadjusted differences were: CRAE, 4.3 μm (95% confidence interval [CI] 1.1-7.5; P = 0.009) and CRVE, 5.5 μm (95% CI 0.7-10.3; P = 0.02). After adjustment for age, race/ethnicity, sex, human immunodeficiency syndrome (HIV) transmission category, smoking, enrollment and nadir CD4+ T cells, and enrollment and maximum HIV load, the differences between patients with and without AMD were as follows: CRAE, 5.4 μm (95% CI 2.3-8.5; P = 0.001) and CRVE, 6.0 μm (95% CI 1.4-10.6; P = 0.01).ConclusionsIn patients with AIDS, AMD is associated with greater retinal arteriolar and venular calibers, suggesting a role for shared pathogenic mechanisms, such as persistent systemic inflammation
Vertical structure models of T Tauri and Herbig Ae/Be disks
In this paper we present detailed models of the vertical structure
(temperature and density) of passive irradiated circumstellar disks around T
Tauri and Herbig Ae/Be stars. In contrast to earlier work, we use full
frequency- and angle-dependent radiative transfer instead of the usual moment
equations. We find that this improvement of the radiative transfer has strong
influence on the resulting vertical structure of the disk, with differences in
temperature as large as 70 %. However, the spectral energy distribution (SED)
is only mildly affected by this change. In fact, the SED compares reasonably
well with that of improved versions of the Chiang & Goldreich (CG) model. This
shows that the latter is a reasonable model for the SED, in spite of its
simplicity. It also shows that from the SED alone, little can be learned about
the vertical structure of a passive circumstellar disk. The molecular line
emission from these disks is more sensitive to the vertical temperature and
density structure, and we show as an example how the intensity and profiles of
various CO lines depend on the adopted disk model. The models presented in this
paper can also serve as the basis of theoretical studies of e.g. dust
coagulation and settling in disks.Comment: 12 pages, 15 figures, accepted for publication in A&
Grain growth and dust settling in a brown dwarf disk: Gemini/T-ReCS observations of CFHT-BD-Tau 4
We present accurate mid-infrared observations of the disk around the young,
bona-fide brown dwarf CFHT-BD-Tau 4. We report GEMINI/T-ReCS measurements in
the 7.9, 10.4 and 12.3 micron filters, from which we infer the presence of a
prominent, broad silicate emission feature. The shape of the silicate feature
is dominated by emission from 2 micron amorphous olivine grains. Such grains,
being an order of magnitude larger than those in the interstellar medium, are a
first proof of dust processing and grain growth in disks around brown dwarfs.
The object's spectral energy distribution is below the prediction of the
classical flared disk model but higher than that of the two-layer flat disk. A
good match can be achieved by using an intermediate disk model with strongly
reduced but non-zero flaring. Grain growth and dust settling processes provide
a natural explanation for this disk geometry and we argue that such
intermediate flaring might explain the observations of several other brown
dwarf disks as well.Comment: Accepted for publication in Astronomy & Astrophysics Letters, 4.5
pages with 1 figur
Accretion Rates in Herbig Ae stars
Accretion rates from disks around pre-main sequence stars are of importance
for our understanding of planetary formation and disk evolution. We provide in
this paper estimates of the mass accretion rates in the disks around a large
sample of Herbig Ae stars. We obtained medium resolution 2 micron spectra and
used the results to compute values of Macc from the measured luminosity of the
Br_gamma emission line, using a well established correlation between
L(Br_gamma) and the accretion luminosity Lacc. We find that 80% of the stars,
all of which have evidence of an associated circumstellar disk, are accreting
matter, with rates 3x10^{-9} < Macc} < 10^{-6} Msun/yr; for 7 objects, 6 of
which are located on the ZAMS in the HR diagram, we do not detect any line
emission. Few HAe stars (25%) have Macc>10^{-7} Msun/yr. In most HAe stars the
accretion rate is sufficiently low that the gas in the inner disk, inside the
dust evaporation radius, is optically thin and does not prevent the formation
of a puffed-up rim, where dust is directly exposed to the stellar radiation.
When compared to the Macc values found for lower-mass stars in the star forming
regions Taurus and Ophiuchus, HAe stars have on average higher accretion rates
than solar-mass stars; however, there is a lack of very strong accretors among
them, probably due to the fact that they are on average older.Comment: To be published in Astronomy & Astrophysic
The IC1396N proto-cluster at a scale of 250 AU
We investigate the mm-morphology of IC1396N with unprecedented spatial
resolution to analyze its dust and molecular gas properties, and draw
comparisons with objects of similar mass. We have carried out sensitive
observations in the most extended configurations of the IRAM Plateau de Bure
interferometer, to map the thermal dust emission at 3.3 and 1.3mm, and the
emission from the =13 hyperfine transitions of methyl cyanide
(CHCN). We unveil the existence of a sub-cluster of hot cores in IC1396N,
distributed in a direction perpendicular to the emanating outflow. The cores
are embedded in a common envelope of extended and diffuse dust emission. We
find striking differences in the dust properties of the cores ( 0)
and the surrounding envelope ( 1), very likely testifying to
differences in the formation and processing of dust material. The CHCN
emission peaks towards the most massive hot core and is marginally extended in
the outflow direction
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