10,680 research outputs found
Paleoseismic and Slip-Rate Observations along the Honey Lake Fault Zone, Northeastern California, USA
The Honey Lake fault is a major strike-slip fault in northeastern California that accommodates northwest-directed right-lateral shear in the northern Walker Lane. We reexamine the fault’s paleoseismic history and slip rate by evaluating a natural stream bank exposure of the fault and offset terrace riser. Structural and stratigraphic relations within the modern stream cut, radiocarbon ages, and a detailed topographic survey of the offset terrace riser are used to estimate a Holocene fault slip rate of 1.7–0.6 mm/yr or more. We also interpret the occurrence of at least four surface-rupturing earthquakes during the last 7025 calendar years before present (B.P.). Three of the surface-rupturing earthquakes occurred prior to 4670 calendar years B.P. and have interevent times that range between 730 and 990 yr. The stratigraphic record is limited after ~4670 calendar years B.P., and records evidence for at least one more subsequent surface-rupturing earthquake
Hearing new voices: re-viewing youth justice policy through practitioners’ relationships with young people
The relationship between young people and practitioners is the centre-piece of youth justice provision, yet little research-based knowledge has accumulated on its minutiae. After reviewing reforms affecting professional discretion, the paper draws on the concepts of dyadic relationships and praxis to reinvigorate a research agenda aimed at delineating a more nuanced understanding of practice relationships. Drawing on practice wisdom from across related social work fields, we argue that centralizing the practitioner-young person relationship remains the key to successful practice and thus needs greater, more detailed research attention. These claims are supported with a number of pilot interviews with youth justice workers about successful interventions that complement and extend related studies. The paper concludes with suggestions for research to enable joint activity between young people and practitioners to ‘rethink’ youth justice
From infall to rotation around young stellar objects: A transitional phase with a 2000 AU radius contracting disk?
Evidence for a transitional stage in the formation of a low-mass star is
reported, intermediate between the fully embedded and the T Tauri phases.
Millimeter aperture synthesis observations in the HCO+ J=1-0 and 3-2, HCN 1-0,
13CO 1-0, and C18O 1-0 transitions reveal distinctly different velocity fields
around two embedded, low-mass young stellar objects. The 0.6 M(sun) of material
around TMC 1 (IRAS 04381+2517) closely follows inside-out collapse in the
presence of a small amount of rotation (~3 km/s/pc), while L1489 IRS (IRAS
04016+2610) is surrounded by a 2000 AU radius, flared disk containing 0.02
M(sun). This disk shows Keplerian rotation around a ~0.65 M(sun) star and
infall at 1.3 (r/100 AU)^-0.5 km/s, or, equivalently, sub-Keplerian motions
around a central object between 0.65 and 1.4 M(sun). Its density is
characterized by a radial power law and an exponential vertical scale height.
The different relative importance of infall and rotation around these two
objects suggests that rotationally supported structures grow from collapsing
envelopes over a few times 10^5 yr to sizes of a few thousand AU, and then
decrease over a few times 10^4 yr to several hundred AU typical for T Tauri
disks. In this scenario, L1489 IRS represents a transitional phase between
embedded YSOs and T Tauri stars with disks. The expected duration of this phase
of ~5% of the embedded stage is consistent with the current lack of other known
objects like L1489 IRS. Alternative explanations cannot explain L1489 IRS's
large disk, such as formation from a cloud core with an unusually large
velocity gradient or a binary companion that prevents mass accretion onto small
scales. It follows that the transfer and dissipation of angular momentum is key
to understanding the formation of disks from infalling envelopes.Comment: Accepted ApJ. 33 pages, including 10 B/W figures and 1 color figure.
Uses AASTe
An XMM-Newton observation of the young open cluster NGC 2547: coronal activity at 30 Myr
We report XMM-Newton observations of the young open cluster NGC 2547 which
allow us to characterise coronal activity in solar-type stars at an age of 30
Myr. X-ray emission peaks among G-stars at luminosities (0.3-3keV) of
Lx~10^{30.5} erg/s and declines to Lx<=10^{29.0} erg/s among M-stars. Coronal
spectra show evidence for multi-temperature differential emission measures and
low coronal metal abundances (Z~0.3). The G- and K-type stars follow the same
relationship between X-ray activity and Rossby number established in older
clusters and field stars, although most solar-type stars in NGC 2547 exhibit
saturated/super-saturated X-ray activity levels. Median levels of Lx and
Lx/Lbol in the solar-type stars of NGC 2547 are similar to T-Tauri stars of the
Orion Nebula cluster (ONC), but an order of magnitude higher than in the older
Pleiades. The spread in X-ray activity levels among solar-type stars in NGC
2547 is much smaller than in older or younger clusters. Coronal temperatures
increase with Lx, Lx/Lbol and surface X-ray flux. Active solar-type stars in
NGC 2547 have coronal temperatures between those in the ONC and the most active
older ZAMS stars. A flaring rate (for total flare energies [0.3-3keV] >10^{34}
erg) of 1 every 350^{+350}_{-120} ks was found for solar-type stars, similar to
rates found in the ONC and Pleiades. Comparison with ROSAT HRI data taken 7
years previously reveals that only 10-15 percent of solar-type stars or stars
with Lx>3x10^{29} erg/s exhibit X-ray variability by more than a factor of two.
The similar levels of X-ray activity and rate of occurrence for large flares in
NGC 2547 and the ONC demonstrate that the X-ray radiation environment around
young solar-type stars remains relatively constant over their first 30 Myr
(abridged).Comment: Accepted for publication in MNRAS. Electronic tables available from
the autho
Load programmer, static switches, and annunciator for inverters and converters
Load programmer, switches, and annunciator for static inverters and converters operating in paralle
The Statistics of the BATSE Spectral Features
The absence of a BATSE line detection in a gamma-ray burst spectrum during
the mission's first six years has led to a statistical analysis of the
occurrence of lines in the BATSE burst database; this statistical analysis will
still be relevant if lines are detected. We review our methodology, and present
new simulations of line detectability as a function of the line parameters. We
also discuss the calculation of the number of ``trials'' in the BATSE database,
which is necessary for our line detection criteria.Comment: 5 pages, 2 figures, AIPPROC LaTeX, to appear in "Gamma-Ray Bursts,
4th Huntsville Symposium," eds. C. Meegan, R. Preece and T. Koshu
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