4,028 research outputs found
Adsorption of a binary mixture of monomers with nearest-neighbour cooperative effects
A model for the adsorption of a binary mixture on a one-dimensional infinite
lattice with nearest neighbour cooperative effects is considered. The particles
of the two species are both monomers but differ in the repulsive interaction
experienced by them when trying to adsorb. An exact expression for the coverage
of the lattice is derived. In the jamming limit, it is a monotonic function of
the ratio between the attempt frequencies of the two species, varying between
the values corresponding to each of the two single species. This is in contrast
with the results obtained in other models for the adsorption of particles of
different sizes. The structure of the jamming state is also investigated.Comment: v2: Errors in the figures fixed; same text; 23 pages, 5 figures.
Accepted for publication in Journal of Physics A: Mathematical and Genera
Prostaglandins in breast cancer: relationship to disease stage and hormone status.
Tissue prostaglandin (PG) content and production by human breast cancers were measured in 24 human mammary carcinoma specimens. The 5 compounds studied were PGE1, PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and TXB2. The tissue content of all 5 compounds was higher in neoplastic tissue in comparison with the paired noncancerous breast tissue. However, microsomal PG synthetase activity in vitro in noncancerous and neoplastic breast tissue was comparable. Increased thromboxane formation was associated with three clinical variables--tumour size, axillary lymph node metastases and distant metastasis. A lesion negative for either oestrogen or progesterone receptor content tended to produce more TXB2 but lower PGE2 and 6-keto-PGF1 alpha. Results obtained in this pilot study may provide clues as to what direction future larger studies could take in the search for reliable prognostic indicators for breast cancer
Solar-like oscillations in a massive star
Seismology of stars provides insight into the physical mechanisms taking
place in their interior, with modes of oscillation probing different layers.
Low-amplitude acoustic oscillations excited by turbulent convection were
detected four decades ago in the Sun and more recently in low-mass
main-sequence stars. Using data gathered by the Convection Rotation and
Planetary Transits mission, we report here on the detection of solar-like
oscillations in a massive star, V1449 Aql, which is a known large-amplitude (b
Cephei) pulsator.Comment: Published in Sience, 19 June 2009, vol. 324, p. 154
A New Method to Extract Piezoresistive Coefficients in Polysilicon Through Gauges Placed on a MEMS Membrane
AbstractThis paper presents a new method to evaluate piezoresistive coefficients of polysilicon in the case of N-doping but valid for other types. We measured and simulated the mechanical stress profile distribution along a bossed membrane using several gauges placed along the radial axis of round membranes. Pressure was applied to the membrane. The electromechanical characterizations of the MEMS membrane are in accordance with the simulations and allowed to extract piezoresistive coefficients of the heavily doped polysilicon
2-Dust : a Dust Radiative Transfer Code for an Axisymmetric System
We have developed a general purpose dust radiative transfer code for an
axisymmetric system, 2-Dust, motivated by the recent increasing availability of
high-resolution images of circumstellar dust shells at various wavelengths.
This code solves the equation of radiative transfer following the principle of
long characteristic in a 2-D polar grid while considering a 3-D radiation field
at each grid point. A solution is sought through an iterative scheme in which
self-consistency of the solution is achieved by requiring a global luminosity
constancy throughout the shell. The dust opacities are calculated through Mie
theory from the given size distribution and optical properties of the dust
grains. The main focus of the code is to obtain insights on (1) the global
energetics of dust grains in the shell (2) the 2-D projected morphologies that
are strongly dependent on the mixed effects of the axisymmetric dust
distribution and inclination angle of the shell. Here, test models are
presented with discussion of the results. The code can be supplied with a
user-defined density distribution function, and thus, is applicable to a
variety of dusty astronomical objects possessing the axisymmetric geometry.Comment: To be published in ApJ, April 2003 issue; 13 pages, 4 tables, 17
figures, 5-page appendix (no figures for the main text included in this
preprint). For the complete preprint and code distribution, contact the
author
Monotremes and marsupials : comparative models to better understand the function of milk
Analytical solution of a one-dimensional Ising model with zero temperature dynamics
The one-dimensional Ising model with nearest neighbour interactions and the
zero-temperature dynamics recently considered by Lefevre and Dean -J. Phys. A:
Math. Gen. {\bf 34}, L213 (2001)- is investigated. By introducing a
particle-hole description, in which the holes are associated to the domain
walls of the Ising model, an analytical solution is obtained. The result for
the asymptotic energy agrees with that found in the mean field approximation.Comment: 6 pages, no figures; accepted in J. Phys. A: Math. Gen. (Letter to
the Editor
Individual and collective stock dynamics: intra-day seasonalities
We establish several new stylised facts concerning the intra-day
seasonalities of stock dynamics. Beyond the well known U-shaped pattern of the
volatility, we find that the average correlation between stocks increases
throughout the day, leading to a smaller relative dispersion between stocks.
Somewhat paradoxically, the kurtosis (a measure of volatility surprises)
reaches a minimum at the open of the market, when the volatility is at its
peak. We confirm that the dispersion kurtosis is a markedly decreasing function
of the index return. This means that during large market swings, the
idiosyncratic component of the stock dynamics becomes sub-dominant. In a
nutshell, early hours of trading are dominated by idiosyncratic or sector
specific effects with little surprises, whereas the influence of the market
factor increases throughout the day, and surprises become more frequent.Comment: 9 pages, 7 figure
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