11,681 research outputs found
Properties of a cell line from human adenocarcinoma of the rectum.
A new, highly differentiated line of cells derived from adenocarcinoma of the rectum (HT55) is described. This line is noteworthy for the following features: 1. The role played in its development by the use of UV-inactivated Sendai virus to attach tumour cell clumps to plastic bottles. 2. Evidence that it produces RNA-containing material of density 1-5--1-16 g/ml. 3. Induction of bone formation in the stroma when grown in athymic mice. 4. Stimulation of primary CBA mouse embryo fibroblasts to form a transient nodule when mixed with them and injected into adult CBA mice. The karyotype and growth-cycle characteristics of the line are described
The Decay of Accreting Triple Systems as Brown Dwarf Formation Scenario
We investigate the dynamical decay of non-hierarchical accreting triple
systems and its implications on the ejection model as Brown Dwarf formation
scenario. A modified chain-regularization scheme is used to integrate the
equations of motion, that also allows for mass changes over time as well as for
momentum transfer from the accreted gas mass onto the bodies. We integrate an
ensemble of triple systems within a certain volume with different accretion
rates, assuming several prescriptions of how momentum is transferred onto the
bodies. We follow their evolution until the systems have decayed. We analyze
the end states and decay times of these systems and determine the fraction of
Brown Dwarfs formed, their escape speeds as well as the semi-major axis
distribution of the formed Brown Dwarf binaries. We find that the formation
probability of Brown Dwarfs depends strongly on the assumed momentum transfer
which is related to the motion of the gas. Due to ongoing accretion and
consequent shrinkage of the systems, the median escape velocity is increased by
a factor of 2 and the binary separations are decreased by a factor of 5
compared with non-accreting systems. Furthermore, the obtained semi-major axis
distribution drops off sharply to either side of the median, which is also
supported by observations. We conclude that accretion and momentum transfer of
accreted gas during the dynamical decay of triple systems is able to produce
the observed distribution of close binary Brown Dwarfs, making the ejection
model a viable option as Brown Dwarf formation scenario.Comment: 31 pages, 8 figures, accepted for publication in Ap
A Survey for Circumstellar Disks Around Young Substellar Objects
(Abridged) We have completed the first systematic survey for disks around
spectroscopically identified young brown dwarfs and very low mass stars. We
have obtained L'-band (3.8 um) imaging for 38 very cool objects in IC 348 and
Taurus. Our targets span spectral types from M6 to M9.5 (~100 to ~15 Mjup).
Using the objects' measured spectral types and extinctions, we find that most
of our sample (77%+/-15%) possess intrinsic IR excesses, indicative of disks.
Because the excesses are modest, conventional analyses using only IR colors
would have missed most of the sources with excesses. The observed IR excesses
are correlated with Halpha emission, consistent with a common accretion disk
origin. The excesses can be explained by disk reprocessing of starlight alone;
the implied accretion rates are at least an order of magnitude below typical
values for classical T Tauri stars. The observed distribution of IR excesses
suggests the presence of inner disk holes. The disk frequency appears to be
independent of the mass and age. In the same star-forming regions, disks around
brown dwarfs are at least as long-lived (~3 Myr) as disks around the T Tauri
stars. Altogether, the frequency and properties of young circumstellar disks
appear to be similar from the stellar regime down to the substellar and
planetary-mass regime. This provides prima facie evidence of a common origin
for most stars and brown dwarfs.Comment: ApJ, in press, 28 pages. Minor change to the online, abridged version
of the abstract. No change to the actual pape
First Detection of Millimeter Dust Emission from Brown Dwarf Disks
We report results from the first deep millimeter continuum survey targeting
Brown Dwarfs (BDs). The survey led to the first detection of cold dust in the
disks around two young BDs (CFHT-BD-Tau 4 and IC348 613), with deep JCMT and
IRAM observations reaching flux levels of a few mJy. The dust masses are
estimated to be a few Earth masses assuming the same dust opacities as usually
applied to TTauri stars.Comment: 5 pages, accepted for ApJ
Monitoring Breast Cancer Response to Neoadjuvant Chemotherapy Using Ultrasound Strain Elastography
© 2019 The Authors Strain elastography was used to monitor response to neoadjuvant chemotherapy (NAC) in 92 patients with biopsy-proven, locally advanced breast cancer. Strain elastography data were collected before, during, and after NAC. Relative changes in tumor strain ratio (SR) were calculated over time, and responder status was classified according to tumor size changes. Statistical analyses determined the significance of changes in SR over time and between response groups. Machine learning techniques, such as a naïve Bayes classifier, were used to evaluate the performance of the SR as a marker for Miller-Payne pathological endpoints. With pathological complete response (pCR) as an endpoint, a significant difference (P < .01) in the SR was observed between response groups as early as 2 weeks into NAC. Naïve Bayes classifiers predicted pCR with a sensitivity of 84%, specificity of 85%, and area under the curve of 81% at the preoperative scan. This study demonstrates that strain elastography may be predictive of NAC response in locally advanced breast cancer as early as 2 weeks into treatment, with high sensitivity and specificity, granting it the potential to be used for active monitoring of tumor response to chemotherapy
Effects of Spin on Tennis Ball Aerodynamics: An Experimental and Computational Study
The aerodynamic behaviour of a tennis ball is very complex and significantly differs from other sports balls due to its surface structures (fuzz, seam orientation etc). Relatively high rotational speeds (spin) make the aerodynamic properties of tennis balls even more complex. Although several studies have been conducted on drag and lift in steady state condition (no spin involved) by the author and others, little or no studies have been conducted on spin effects. The so called Magnus effect on a sphere is well known in fluid mechanics. It is believed that the spinning can affect aerodynamic drag and lift of a tennis ball thus the motion and flight path of the ball. Therefore, the primary objectives of this work are to study the spin effects using both experimental and computational methods. In order to achieve these objectives, a series of tennis balls were used to measure their aerodynamics forces as a function of wind speeds, seam orientation and spins. The experimental study was conducted in the RMIT Industrial Wind Tunnel. A computational study of a simplified tennis ball was also studied using commercial software ‘FLUENT’. The CFD results were compared with the experimental findings. Flow around the ball was visualised with smoke
Nominal Logic Programming
Nominal logic is an extension of first-order logic which provides a simple
foundation for formalizing and reasoning about abstract syntax modulo
consistent renaming of bound names (that is, alpha-equivalence). This article
investigates logic programming based on nominal logic. We describe some typical
nominal logic programs, and develop the model-theoretic, proof-theoretic, and
operational semantics of such programs. Besides being of interest for ensuring
the correct behavior of implementations, these results provide a rigorous
foundation for techniques for analysis and reasoning about nominal logic
programs, as we illustrate via examples.Comment: 46 pages; 19 page appendix; 13 figures. Revised journal submission as
of July 23, 200
- …