5,758 research outputs found
Exploring New Ultrafast Operation Regimes in Quantum Dot Lasers and Amplifiers
We will present our recent results, harnessing the flexibility of quantum dot materials towards the development of increasingly versatile regimes of ultrashort pulse generation and amplification in edge-emitting devices
Reproducibility of measurements of oestrogen-receptor concentration in breast cancer.
The reproducibility of measurements of oestrogen-receptor activity has been examined in multiple specimens from a rabbit uterus, a rat mammary tumour and human breast tumours. The relationship between receptor concentration and tumour histology has also been investigated in 11 large primary tumours. In the animal tissues, receptor measurements were relatively reproducible (coefficient of variance: wet wt. basis 16-17%, protein basis 16-21%) but in human breast tumours receptor activity varied considerably (c.v.: wet wt. basis, 22-125%; protein basis, 28-72%). In addition to these variations in receptor activity within tumours, there was a difference between tumours, as demonstrated by an analysis of variance (P less than 0.01). In the 11 primary breast cancers selected for study, the level of receptor activity was related to menopausal status and the tumour content of the specimen. We conclude that the receptor activity detected varies within a tumour and depends upon the tumour content of the biopsy specimen. Predictions based on precise quantitation of receptor concentrations may therefore necessitate replicate tumour sampling and correction for the fraction of non-tumour tissue in each sample
Slow dynamics near glass transitions in thin polymer films
The -process (segmental motion) of thin polystyrene films supported
on glass substrate has been investigated in a wider frequency range from
10 Hz to 10 Hz using dielectric relaxation spectroscopy and thermal
expansion spectroscopy. The relaxation rate of the -process increases
with decreasing film thickness at a given temperature above the glass
transition. This increase in the relaxation rate with decreasing film thickness
is much more enhanced near the glass transition temperature. The glass
transition temperature determined as the temperature at which the relaxation
time of the -process becomes a macroscopic time scale shows a distinct
molecular weight dependence. It is also found that the Vogel temperature has
the thickness dependence, i.e., the Vogel temperature decreases with decreasing
film thickness. The expansion coefficient of the free volume is
extracted from the temperature dependence of the relaxation time within the
free volume theory. The fragility index is also evaluated as a function of
thickness. Both and are found to decrease with decreasing film
thickness.Comment: 9 pages, 7 figures, and 2 table
Report of the direct infrared sensors panel
The direct infrared sensors panel considered a wide range of options for technologies relevant to the science goals of the Astrotech 21 mission set. Among the technologies assessed are: large format arrays; photon counting detectors; higher temperature 1 to 10 micro-m arrays; impurity band conduction (IBC) or blocked impurity band (BIB) detectors; readout electronics; and adapting the Space Infrared Telescope Facility and Hubble Space Telescope. Detailed development plans were presented for each of these technology areas
Fully Sampled Maps of Ices and Silicates in Front of Cepheus A East with Spitzer
We report the first fully sampled maps of the distribution of interstellar
CO2 ices, H2O ices and total hydrogen nuclei, as inferred from the 9.7 micron
silicate feature, toward the star-forming region Cepheus A East with the IRS
instrument onboard the Spitzer Space Telescope. We find that the column density
distributions for these solid state features all peak at, and are distributed
around, the location of HW2, the protostar believed to power one of the
outflows observed in this star-forming region. A correlation between the column
density distributions of CO2 and water ice with that of total hydrogen
indicates that the solid state features we mapped mostly arise from the same
molecular clumps along the probed sight lines. We therefore derive average CO2
ice and water ice abundances with respect to the total hydrogen column density
of X(CO2)_ice~1.9x10^-5 and X(H2O)_ice~7.5x10^-5. Within errors, the abundances
for both ices are relatively constant over the mapped region exhibiting both
ice absorptions. The fraction of CO2 ice with respect to H2O ice is also
relatively constant at a value of 22% over that mapped region. A clear
triple-peaked structure is seen in the CO2 ice profiles. Fits to those profiles
using current laboratory ice analogs suggest the presence of both a
low-temperature polar ice mixture and a high-temperature methanol-rich ice
mixture along the probed sightlines. Our results further indicate that thermal
processing of these ices occurred throughout the sampled region.Comment: 26 pages, 8 figures, accepted for publication in Ap
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