5,005 research outputs found
Energy-stable linear schemes for polymer-solvent phase field models
We present new linear energy-stable numerical schemes for numerical
simulation of complex polymer-solvent mixtures. The mathematical model proposed
by Zhou, Zhang and E (Physical Review E 73, 2006) consists of the Cahn-Hilliard
equation which describes dynamics of the interface that separates polymer and
solvent and the Oldroyd-B equations for the hydrodynamics of polymeric
mixtures. The model is thermodynamically consistent and dissipates free energy.
Our main goal in this paper is to derive numerical schemes for the
polymer-solvent mixture model that are energy dissipative and efficient in
time. To this end we will propose several problem-suited time discretizations
yielding linear schemes and discuss their properties
Hydrogen safety Progress report no. 6, 1 Apr. - 30 Jun. 1965
Hydrogen safety hazards, storage, and handling - Hydrogen plume studies to determine quantity-distance criteria and guidelines for optimum placement of hydrogen detector
Hydrogen safety Progress report no. 7 1 Jul. - 30 Sep. 1965
Performance characteristics of two console-type hydrogen gas detectors sampling by diffusion and convectio
Hydrogen Flare Stack Diffusion Flames - Low and High Flow Instabilities, Burning Rates, Dilution Limits, Temperatures, and Wind Effects
Combustion characteristics and safety factors for hydrogen diffusion flames in flare stack operation
Distinct target genes and effector processes appear to be critical for p53-activated responses to acute DNA damage versus p53-mediated tumour suppression
The p53 tumour suppressor is the most frequently mutated gene in human cancer. This transcription factor can be activated by diverse cellular stresses, including DNA damage and oncogene activation. Through transcriptional induction of appropriate target genes, p53 can stimulate activity in a broad range of effector pathways, most notably cell cycle arrest, cellular senescence and apoptotic cell death. Insensitivity to cell death-inducing signals and deregulated proliferation are two key hallmarks of cancer cells. Given that p53 inhibits proliferation and induces apoptosis, it was widely believed that these processes are the most critical ones for p53-mediated tumour suppression. However, this dogma has been challenged. In striking contrast to p53-deficient mice, which all develop tumours before 250 days of age, mutant mice in which expression of the p53 target genes that are critical for induction of cell cycle arrest and apoptosis is impaired or abrogated are not cancer-prone. This demonstrates that distinct effector processes are critical for the p53-mediated acute response to DNA damage versus p53-mediated tumour suppression. The discovery that cell cycle arrest, senescence and apoptosis are not essential for p53-mediated tumour suppression re-launches the search for the p53 target genes and effector processes that are critical to prevent tumour development, with coordination of DNA repair being a leading contender
1420 MHz Continuum Absorption Towards Extragalactic Sources in the Galactic Plane
We present a 21-cm emission-absorption study towards extragalactic sources in
the Canadian Galactic Plane Survey (CGPS). We have analyzed HI spectra towards
437 sources with S > 150 mJy, giving us a source density of 0.6 sources per
square degree at arcminute resolution. We present the results of a first
analysis of the HI temperatures, densities, and feature statistics. Particular
emphasis is placed on 5 features with observed spin temperatures below 40 K. We
find most spin temperatures in the range from 40 K to 300 K. A simple HI
two-component model constrains the bulk of the cold component to temperatures
(T_c) between 40 K and 100 K. T_c peaks in the Perseus arm region and clearly
drops off with Galactocentric radius, R, beyond that. The HI density follows
this trend, ranging from a local value of 0.4 cm^{-3} to less than 0.1 cm^{-3}
at R = 20 kpc. We find that HI emission alone on average traces about 75% of
the total HI column density, as compared to the total inferred by the emission
and absorption. Comparing the neutral hydrogen absorption to CO emission no
correlation is found in general, but all strong CO emission is accompanied by a
visible HI spectral feature. Finally, the number of spectral HI absorption
features per kpc drop off exponentially with increasing R.Comment: 13 pages, 13 figures, Accepted for March 2004 Ap
- …