8,465 research outputs found
The effect of stress on paleomagnetic signals: A micromagnetic study of magnetiteâs single-vortex response
In this study we use micromagnetic modeling to show that the magnetizations of magnetically single-vortex particles rotate toward the stress axis on the application of a differential compression stress. This is the exact opposite response to magnetically single-domain particles, which previously provided the theoretical underpinning of the effect of stress on the magnetic signals of rocks. We show that the magnetization directions of single-vortex and equant single-domain particles are altered by much lower stresses than previously predicted, c.f., 100 versus 1,000 MPa; where a change in magnetization is defined as a rotation of >3° after the removal of stress. The magnetization intensity of assemblages also drops by âŒ20%â30% on the application and removal of stress of âŒ100 MPa. Given that single-vortex particles are now thought to dominate the magnetization of most rocks, future studies should account for paleomagnetic directional uncertainties and potential underestimation of the ancient magnetic field intensity
The star-forming content of the W3 giant molecular cloud
We have surveyed a ~0.9-square-degree area of the W3 giant molecular cloud
and star-forming region in the 850-micron continuum, using the SCUBA bolometer
array on the James Clerk Maxwell Telescope. A complete sample of 316 dense
clumps was detected with a mass range from around 13 to 2500 Msun. Part of the
W3 GMC is subject to an interaction with the HII region and fast stellar winds
generated by the nearby W4 OB association. We find that the fraction of total
gas mass in dense, 850-micron traced structures is significantly altered by
this interaction, being around 5% to 13% in the undisturbed cloud but ~25 - 37%
in the feedback-affected region. The mass distribution in the detected clump
sample depends somewhat on assumptions of dust temperature and is not a simple,
single power law but contains significant structure at intermediate masses.
This structure is likely to be due to crowding of sources near or below the
spatial resolution of the observations. There is little evidence of any
difference between the index of the high-mass end of the clump mass function in
the compressed region and in the unaffected cloud. The consequences of these
results are discussed in terms of current models of triggered star formation.Comment: 13 pages, 8 figures, 1 table (full source table available on
request). Accepted for publication in Monthly Notices of the Royal
Astronomical Society (Main Journal
High-Resolution Continuum Imaging at 1.3 and 0.7 cm of the W3 IRS 5 Region
High-resolution images of the hypercompact HII regions (HCHII) in W3 IRS 5
taken with the Very Large Array (VLA) at 1.3 and 0.7 cm are presented. Four
HCHII regions were detected with sufficient signal-to-noise ratios to allow the
determination of relevant parameters such as source position, size and flux
density. The sources are slightly extended in our ~0.2 arcsecond beams; the
deconvolved radii are less than 240 AU. A comparison of our data with VLA
images taken at epoch 1989.1 shows proper motions for sources IRS 5a and IRS
5f. Between 1989.1 and 2002.5, we find a proper motion of 210 mas at a position
angle of 12 deg for IRS 5f and a proper motion of 190 mas at a position angle
of 50 deg for IRS 5a. At the assumed distance to W3 IRS 5, 1.83 +/- 0.14 kpc,
these offsets translate to proper motions of ~135 km/s and ~122 km/s$
respectively. These sources are either shock ionized gas in an outflow or
ionized gas ejected from high mass stars. We find no change in the positions of
IRS 5d1/d2 and IRS 5b; and we show through a comparison with archival NICMOS
2.2 micron images that these two radio sources coincide with the infrared
double constituting W3 IRS 5. These sources contain B or perhaps O stars. The
flux densities of the four sources have changed compared to the epoch 1989.1
results. In our epoch 2002.5 data, none of the spectral indicies obtained from
flux densities at 1.3 and 0.7 cm are consistent with optically thin free-free
emission; IRS 5d1/d2 shows the largest increase in flux density from 1.3 cm to
0.7 cm. This may be an indication of free-free optical depth within an ionized
wind, a photoevaporating disk, or an accretion flow. It is less likely that
this increase is caused by dust emission at 0.7 cm.Comment: 13 pages, 3 figures To be published in The Astrophysical Journa
Radio Observations of the Hubble Deep Field South region: I. Survey Description and Initial Results
This paper is the first of a series describing the results of the Australia
Telescope Hubble Deep Field South (ATHDFS) radio survey. The survey was
conducted at four wavelengths - 20, 11, 6, and 3 cm, over a 4-year period, and
achieves an rms sensitivity of about 10 microJy at each wavelength. We describe
the observations and data reduction processes, and present data on radio
sources close to the centre of the HDF-S. We discuss in detail the properties
of a subset of these sources. The sources include both starburst galaxies and
galaxies powered by an active galactic nucleus, and range in redshift from 0.1
to 2.2. Some of them are characterised by unusually high radio-to-optical
luminosities, presumably caused by dust extinction.Comment: Accepted by AJ. 32 pages, 4 tables, 3 figures. PDF with
full-resolution figures is on
http://www.atnf.csiro.au/people/rnorris/N197.pd
GCIP water and energy budget synthesis (WEBS)
As part of the World Climate Research Program\u27s (WCRPs) Global Energy and Water-Cycle Experiment (GEWEX) Continental-scale International Project (GCIP), a preliminary water and energy budget synthesis (WEBS) was developed for the period 1996â1999 from the âbest availableâ observations and models. Besides this summary paper, a companion CD-ROM with more extensive discussion, figures, tables, and raw data is available to the interested researcher from the GEWEX project office, the GAPP project office, or the first author. An updated online version of the CD-ROM is also available at http://ecpc.ucsd.edu/gcip/webs.htm/. Observations cannot adequately characterize or âcloseâ budgets since too many fundamental processes are missing. Models that properly represent the many complicated atmospheric and near-surface interactions are also required. This preliminary synthesis therefore included a representative global general circulation model, regional climate model, and a macroscale hydrologic model as well as a global reanalysis and a regional analysis. By the qualitative agreement among the models and available observations, it did appear that we now qualitatively understand water and energy budgets of the Mississippi River Basin. However, there is still much quantitative uncertainty. In that regard, there did appear to be a clear advantage to using a regional analysis over a global analysis or a regional simulation over a global simulation to describe the Mississippi River Basin water and energy budgets. There also appeared to be some advantage to using a macroscale hydrologic model for at least the surface water budgets
Finite size scaling in neural networks
We demonstrate that the fraction of pattern sets that can be stored in
single- and hidden-layer perceptrons exhibits finite size scaling. This feature
allows to estimate the critical storage capacity \alpha_c from simulations of
relatively small systems. We illustrate this approach by determining \alpha_c,
together with the finite size scaling exponent \nu, for storing Gaussian
patterns in committee and parity machines with binary couplings and up to K=5
hidden units.Comment: 4 pages, RevTex, 5 figures, uses multicol.sty and psfig.st
NCI-MATCH Arms N & P: Phase II study of PI3K beta inhibitor GSK2636771 in patients (pts) with cancers (ca) with PTEN mutation/deletion (mut/del) or PTEN protein loss
Background: The NCI-MATCH trial is the largest national study (1173 sites) for ptswith relapsed/ refractory solid tumors, lymphomas and myeloma, which assigns tar-geted therapies based on individual tumor molecular alterations detected using theadapted Oncomine AmpliSeq panel (143 genes) and immunohistochemistry (IHC).We hypothesized that patients with PTEN-deficient cancers enrolled to Arms N and Pmay benefit from treatment with the PI3K beta-selective inhibitor GSK2636771.
Methods: Eligibility: relapsed/refractory ca, good end-organ function, and ECOG PSâ
â€â
1. Pts were screened for molecular alterations by centralized testing on fresh tumor biopsy and had deleterious PTEN mut/del without loss of expression (Arm N) or complete loss of cytoplasmic and nuclear PTEN staining on IHC (Arm P), and no other aberrations activating the PI3K/MTOR and MAPK pathways (mut in PIK3CA, PIK3R1, BRAF, KRAS, AKT1, TSC1/2, mTOR, RHEB, NF2, NRAS, HRAS). Pts received GSK2636771 400mg/day (28-days cycles). RECIST 1.1 overall response rate (ORR) was the primary endpoint.
Results: Of 59 enrolled pts, 56 were eligible and received treatment. Of 22 pts with PTEN mut/del (Arm N: 6 uterine, 2 breast, 2 prostate, 2 head/neck ca, 10 other), all are off treatment as of analysis (14 disease progression, 4 for adverse events [AEs], 4 other). One pt (4.5%) with prostate ca (PTEN deletion, MPRSS2-ERG fusion) attained a partial response (-42%). Of 7 (32%) pts with stable disease (SD), 2 had SDâ
\u3eâ
6 months (uterine leiomyosarcoma; endometrial carcinoma). Of 34 pts with loss of PTEN protein by IHC (Arm P: 7 prostate, 6 breast, 3 squamous anal ca, 2 cholangiocarcinoma, 16 other), all are off treatment as of analysis (26 disease progression, 4 for AE, 4 other). Of 9 (37.5%) pts with SD, 3 had SDâ
\u3eâ
6 months (prostate cancer; squamous bladder cancer, squamous anal cancer). Median progression-free survival was 1.8 months for both arms. Grâ
â„â
3 treatment-related (tr) reversible toxicities were experienced by 30% (7) and 20% (7) of pts in arms N and P, respectively. No tr Gr 5 toxicities were observed in either arm.
Conclusions: Single agent GSK2636771 has very modest activity in ca with PTEN gene mutation/deletion and/or PTEN protein loss
Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array
We apply two methods to estimate the 21~cm bispectrum from data taken within
the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA).
Using data acquired with the Phase II compact array allows a direct bispectrum
estimate to be undertaken on the multiple redundantly-spaced triangles of
antenna tiles, as well as an estimate based on data gridded to the -plane.
The direct and gridded bispectrum estimators are applied to 21 hours of
high-band (167--197~MHz; =6.2--7.5) data from the 2016 and 2017 observing
seasons. Analytic predictions for the bispectrum bias and variance for point
source foregrounds are derived. We compare the output of these approaches, the
foreground contribution to the signal, and future prospects for measuring the
bispectra with redundant and non-redundant arrays. We find that some triangle
configurations yield bispectrum estimates that are consistent with the expected
noise level after 10 hours, while equilateral configurations are strongly
foreground-dominated. Careful choice of triangle configurations may be made to
reduce foreground bias that hinders power spectrum estimators, and the 21~cm
bispectrum may be accessible in less time than the 21~cm power spectrum for
some wave modes, with detections in hundreds of hours.Comment: 19 pages, 10 figures, accepted for publication in PAS
Ground-state Spectrum of Light-quark Mesons
A confining, Goldstone theorem preserving, separable Ansatz for the ladder
kernel of the two-body Bethe-Salpeter equation is constructed from
phenomenologically efficacious , and dressed-quark propagators. The
simplicity of the approach is its merit. It provides a good description of the
ground-state isovector-pseudoscalar, vector and axial-vector meson spectrum;
facilitates an exploration of the relative importance of various components of
the two-body Bethe-Salpeter amplitudes, showing that sub-leading Dirac
components are quantitatively important in the isovector-pseudoscalar meson
channels; and allows a scrutiny of the domain of applicability of ladder
truncation studies. A colour-antitriplet diquark spectrum is obtained.
Shortcomings of separable Ans\"atze and the ladder kernel are highlighted.Comment: 30 pages, LaTeX/REVTEX 3.0, no figure
- âŠ