1,507 research outputs found
Vast planes of satellites in a high resolution simulation of the Local Group: comparison to Andromeda
We search for vast planes of satellites (VPoS) in a high resolution
simulation of the Local Group performed by the CLUES project, which improves
significantly the resolution of former similar studies. We use a simple method
for detecting planar configurations of satellites, and validate it on the known
plane of M31. We implement a range of prescriptions for modelling the satellite
populations, roughly reproducing the variety of recipes used in the literature,
and investigate the occurence and properties of planar structures in these
populations. The structure of the simulated satellite systems is strongly
non-random and contains planes of satellites, predominantly co-rotating, with,
in some cases, sizes comparable to the plane observed in M31 by Ibata et al..
However the latter is slightly richer in satellites, slightly thinner and has
stronger co-rotation, which makes it stand out as overall more exceptional than
the simulated planes, when compared to a random population. Although the
simulated planes we find are generally dominated by one real structure, forming
its backbone, they are also partly fortuitous and are thus not kinematically
coherent structures as a whole. Provided that the simulated and observed planes
of satellites are indeed of the same nature, our results suggest that the VPoS
of M31 is not a coherent disc and that one third to one half of its satellites
must have large proper motions perpendicular to the plane
The structure of radiative shock waves. V. Hydrogen emission lines
We considered the structure of steady-state plane-parallel radiative shock
waves propagating through the partially ionized hydrogen gas of temperature T_1
= 3000K and density 1e-12 gm/cm^3 <= \rho_1 <= 1e-9 gm/cm^3. The upstream Mach
numbers range within 6 <= M_1 <= 14. In frequency intervals of hydrogen lines
the radiation field was treated using the transfer equation in the frame of the
observer for the moving medium, whereas the continuum radiation was calculated
for the static medium. Doppler shifts in Balmer emission lines of the radiation
flux emerging from the upstream boundary of the shock wave model were found to
be roughly one-third of the shock wave velocity. The gas emitting the Balmer
line radiation is located at the rear of the shock wave in the hydrogen
recombination zone where the gas flow velocity in the frame of the observer is
approximately one-half of the shock wave velocity. The ratio of the Doppler
shift to the gas flow velocity of 0.7 results both from the small optical
thickness of the shock wave in line frequencies and the anisotropy of the
radiation field typical for the slab geometry. In the ambient gas with density
of \rho_1 >= 1e-11 gm/cm^3 the flux in the H-alpha frequency interval reveals
the double structure of the profile. A weaker H-beta profile doubling was found
for \rho_1 >= 1e-10 gm/cm^3 and U_1 <= 50 km/s. The unshifted redward component
of the double profile is due to photodeexcitation accompanying the rapid growth
of collisional ionization in the narrow layer in front of the discontinuous
jump.Comment: 13 pages, 13 figures, LaTeX, accepted for publication in A
Expanding Autonomy Psychological Need States From Two (Satisfaction, Frustration) to Three (Dissatisfaction): A Classroom-Based Intervention Study
We propose that students experience "autonomy dissatisfaction" when the learning environment is indifferent to their psychological need for autonomy. We hypothesized that (a) students could distinguish this newly proposed need state from both autonomy satisfaction and autonomy frustration, (b) autonomy dissatisfaction would explain unique and rather substantial variance in students' classroom disengagement, and (c) a full understanding of the psychological need for autonomy necessitates expanding the current emphasis from two need states (satisfaction, frustration) to three (dissatisfaction). In the experimental condition, 20 secondaryschool physical education (PE) teachers learned how to teach in an autonomy-supportive way; in the control condition, 17 PE teachers taught using "practice as usual." Their 2,669 students (1,180 females, 1,489 males) self-reported their autonomy satisfaction, autonomy dissatisfaction, autonomy frustration, engagement, and disengagement throughout a semester. Objective raters scored the manipulation check (teachers' autonomysupportive instructional behaviors) and the engagement-disengagement outcome measure. Autonomy dissatisfaction longitudinally increased in the control group and longitudinally decreased in the experimental group. Most importantly, intervention-enabled decreases in autonomy dissatisfaction decreased students' end-ofsemester disengagement, even after controlling for midsemester changes in autonomy satisfaction and autonomy frustration. We discuss the theoretical and practical benefits of adding autonomy dissatisfaction to the self-determination theory explanatory framework
WHOOPING CRANE NEST BUILDING IN SOUTHWEST INDIANA
The first documented case of whooping crane (Grus americana) nest building in Indiana is described. During spring 2015, a pair of whooping cranes did not leave their wintering grounds in Gibson County, Indiana, to return to their summering area in Wisconsin. Three nest platforms were discovered after the death of the female crane. To date, this is the only documented example of a whooping crane pair in the reintroduced Eastern Migratory Population (EMP) building nest platforms outside of Wisconsin. Although fidelity to the core nesting areas in Wisconsin is strong, and natal dispersal is usually \u3c30 km, this example from Indiana shows that whooping cranes in the EMP may have the potential to pioneer nesting areas far outside of core reintroduction areas
Big Line Bundles over Arithmetic Varieties
We prove a Hilbert-Samuel type result of arithmetic big line bundles in
Arakelov geometry, which is an analogue of a classical theorem of Siu. An
application of this result gives equidistribution of small points over
algebraic dynamical systems, following the work of Szpiro-Ullmo-Zhang. We also
generalize Chambert-Loir's non-archimedean equidistribution
Genome-wide Determinants of Proviral Targeting, Clonal Abundance and Expression in Natural HTLV-1 Infection
The regulation of proviral latency is a central problem in retrovirology. We postulate that the genomic integration site of human T lymphotropic virus type 1 (HTLV-1) determines the pattern of expression of the provirus, which in turn determines the abundance and pathogenic potential of infected T cell clones in vivo. We recently developed a high-throughput method for the genome-wide amplification, identification and quantification of proviral integration sites. Here, we used this protocol to test two hypotheses. First, that binding sites for transcription factors and chromatin remodelling factors in the genome flanking the proviral integration site of HTLV-1 are associated with integration targeting, spontaneous proviral expression, and in vivo clonal abundance. Second, that the transcriptional orientation of the HTLV-1 provirus relative to that of the nearest host gene determines spontaneous proviral expression and in vivo clonal abundance. Integration targeting was strongly associated with the presence of a binding site for specific host transcription factors, especially STAT1 and p53. The presence of the chromatin remodelling factors BRG1 and INI1 and certain host transcription factors either upstream or downstream of the provirus was associated respectively with silencing or spontaneous expression of the provirus. Cells expressing HTLV-1 Tax protein were significantly more frequent in clones of low abundance in vivo. We conclude that transcriptional interference and chromatin remodelling are critical determinants of proviral latency in natural HTLV-1 infection
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