7,790 research outputs found
Reactions of technetium hexafluoride with nitric acid, nitrosyl fluoride, and nitryl fluoride
Stoichiometry of technetium hexafluoride reactions is studied. Magnetic properties and infrared spectra of reaction products are studied and compared with those of analogous complexes of the hexafluorides of tungsten, rhenium, and osmium
Establishing confidence in CCV/ACT technology
Despite significant advancements in controls configured vehicles/active controls technology (CCV/ACT) in the past decade, few applications of this promising technology have appeared in recent aircraft designs. The status of CCV/ACT is summarized, and some of the constraints which are retarding its wider application are described. Suggestions toward establishing an increased level of confidence in the technology are given
Geopotential models in the Australian region
The ability of three high-order geopotential models (OSU81, GPM2 and OSU86E) to recover the gravity anomaly field (delta g) in the Australian region was tested. The region was divided into 2 x 2 deg blocks, and the mean and rms of the residual gravity (delta g measured - delta g modeled) was found to estimate the fit of the model to the point gravity data. The results showed that OSU81 and GPM2 performed similarly, recovering the delta g with a mean value of less than plus or minus 5 mGal in 63 and 70 percent of the blocks, respectively. However, both these models achieved a fit of worse that was plus or minus 13 mGal in 6 to 7 percent of cases. These were in areas either on or near the coast, or in the Central Australian region, inferring that for a precise geoid slope determination in these regions, a detailed analysis of delta g in region is needed. On the other hand, OSU86E produced a very good result, having a mean fit of less than plus or minus 5 mGal in 80 percent of the blocks, and worse than plus or minus 13 mGal in only 1 percent of cases. The rms values for this model were also improved over the other two models, indicating that for applications requiring highest precision, the preferred model is OSU86E
Ohmic contacts, irradiation effects, and thin film growth of GaAs and Al sub 1-x Ga sub x As
The effects of interfacial chemistry on the electrical properties of metal contacts to gallium arsenides and aluminum gallium arsenides are determined
Charge separation instability in an unmagnetized disk plasma around a Kerr black hole
In almost all of plasma theories for astrophysical objects, we have assumed
the charge quasi-neutrality of unmagnetized plasmas in global scales. This
assumption has been justified because if there is a charged plasma, it induces
electric field which attracts the opposite charge, and this opposite charge
reduces the charge separation. Here, we report a newly discovered instability
which causes a charge separation in a rotating plasma inside of an innermost
stable circular orbit (ISCO) around a black hole. The growth rate of the
instability is smaller than that of the disk instability even in the unstable
disk region and is forbidden in the stable disk region outside of the ISCO.
However, this growth rate becomes comparable to that of the disk instability
when the plasma density is much lower than a critical density inside of the
ISCO. In such case, the charge separation instability would become apparent and
cause the charged accretion into the black hole, thus charge the hole up.Comment: 15pages, 1 figur
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Magnetic characterization of perpendicular recording media
In this paper, we describe techniques for the magnetic characterization of perpendicular recording media. Such measurements made using traditional techniques, such as the vibrating sample magnetometry (VSM) and alternating gradient force magnetometer (AGFM), have to be corrected for the sample shape demagnetizing factor, which is often found not to be equal to -4p. For measurements other than the simple hysteresis loop, such as remanence curves, this correction must be carried out in real time and we describe the method by which this can be achieved and the process for achieving the correct demagnetization of perpendicular films prior to measurements of the isothermal remanent magnetization curve. A further complication is that real perpendicular media have a soft underlayer beneath the recording layer, which swamps and confuses signals from instruments such as VSM or AGFM. Hence, we describe the construction and use of a magnetooptical Kerr effect magnetometer, which does not penetrate significantly into the soft layer and enables the perpendicular layer to be measured independently. We describe the properties of a traditional alloy perpendicular medium and a Co-Pd multilayer system, which in the latter case exhibits multiple switching behavior. We also address the issue of the effect of the soft underlayer on the coupling in similar longitudinal films and find that the presence of the underlayer induces significant additional coupling effects that may well give rise to an increase in noise in recorded signal
Determinants of a transcriptionally competent environment at the GM-CSF promoter
Granulocyte macrophage-colony stimulating factor
(GM-CSF) is produced by T cells, but not B cells,
in response to immune signals. GM-CSF gene
activation in response to T-cell stimulation requires
remodelling of chromatin associated with the
gene promoter, and these changes do not occur in
B cells. While the CpG methylation status of the
murine GM-CSF promoter shows no correlation with
the ability of the gene to respond to activation, we
find that the basal chromatin environment of the
gene promoter influences its ability to respond to
immune signals. In unstimulated T cells but not B
cells, the GM-CSF promoter is selectively marked
by enrichment of histone acetylation, and association
of the chromatin-remodelling protein BRG1.
BRG1 is removed from the promoter upon activation
concomitant with histone depletion and BRG1
is required for efficient chromatin remodelling and
transcription. Increasing histone acetylation at
the promoter in T cells is paralleled by increased
BRG1 recruitment, resulting in more rapid chromatin
remodelling, and an associated increase in GM-CSF
mRNA levels. Furthermore, increasing histone
acetylation in B cells removes the block in chromatin
remodelling and transcriptional activation
of the GM-CSF gene. These data are consistent
with a model in which histone hyperacetylation
and BRG1 enrichment at the GM-CSF promoter,
generate a chromatin environment competent
to respond to immune signals resulting in gene
activation
Sodium, Potassium, Calcium and Magnesium Content of Northwest Arkansas Rain Water in 1973 and Trace Metal Analyses of 1974 Rains
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