22,884 research outputs found
Stabilized lanthanum sulphur compounds
Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium, or strontium. This compound is an excellent thermoelectric material
Edge coating of flat wires
An apparatus and technique is described for the coating of the edge surfaces of flat ribbon conductors with an adherent coating of a dielectric insulating material. Means for passing the ribbon conductors between a pair of generally axially aligned rollers is provided. The edge surfaces of the conductor are disposed adjacent to and generally tangentially to the confronting surfaces of the roller so as to form a fillet of dielectric material along the edge surface of the conductor
Recommended from our members
Internalisation of membrane progesterone receptor-α after treatment with progesterone: Potential involvement of a clathrin-dependent pathway
This article has been made available through the Brunel Open Access Publishing Fund.Internalisation and recycling of seven trans-membrane domain receptors is a critical regulatory event for their signalling. The mechanism(s) by which membrane progesterone receptor-α (mPRα) number is regulated on the cell surface is unclear. In this study, we investigated the cellular distribution of mPRα and mechanisms of mPRα trafficking using a cell line derived from a primary culture of human myometrial cells (M11) as an experimental model. RT-PCR and immunofluorescent analysis demonstrated expression of mPRα in M11 cells with mPRα primarily distributed on the cell surface under basal conditions. For the first time, plasma membrane localisation of mPRα was confirmed using immuno-gold transmission electron microscopy. Stimulation of M11 cells with progesterone (P4, 100 nM) resulted in internalisation of mPRα from the plasma membrane to the cytoplasm (10 min) and subsequent partial translocation back to the cell surface (20 min). We investigated potential endocytotic pathways involved in trafficking of mPRα after its internalisation. Partial co-localisation of clathrin with mPRα was obvious after 10 min of P4 treatment. Of note, chlorpromazine (inhibitor of clathrin-mediated pathway) inhibited the endocytosis of mPRα, whereas treatment with nystatin (inhibitor of caveolae-mediated pathway) did not affect internalisation. Collectively, these data suggest that mPRα is expressed on the cell surface of M11 cells and undergoes endocytosis after P4 stimulation primarily via a clathrin-mediated pathway.This article is available through the Brunel Open Access Publishing Fun
Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies
Spatial variations of the [S II]/H-Alpha and [N II]/H-Alpha line intensity
ratios observed in the gaseous halo of the Milky Way and other galaxies are
inconsistent with pure photoionization models. They appear to require a
supplemental heating mechanism that increases the electron temperature at low
densities n_e. This would imply that in addition to photoionization, which has
a heating rate per unit volume proportional to n_e^2, there is another source
of heat with a rate per unit volume proportional to a lower power of n_e. One
possible mechanism is the dissipation of interstellar plasma turbulence, which
according to Minter & Spangler (1997) heats the ionized interstellar medium in
the Milky Way at a rate ~ 1x10^-25 n_e ergs cm^-3 s^-1. If such a source were
present, it would dominate over photoionization heating in regions where n_e <
0.1 cm^-3, producing the observed increases in the [S II]/H-Alpha and [N
II]/H-Alpha intensity ratios at large distances from the galactic midplane, as
well as accounting for the constancy of [S II]/[N II], which is not explained
by pure photoionization. Other supplemental heating sources, such as magnetic
reconnection, cosmic rays, or photoelectric emission from small grains, could
also account for these observations, provided they supply to the warm ionized
medium ~ 10^-5 ergs s^-1 per cm^2 of Galactic disk.Comment: 10 pages, 1 figur
Is Thermal Expansion Driving the Initial Gas Ejection in NGC 6251?
In this paper, we explore the possibility that the radiative properties of
the most compact region in NGC 6251* may be understood in the same sense as Sgr
A*, though with some telling differences that may hint at the nature of jet
formation. We show that observations of this object with ASCA, ROSAT, HST and
VLBI together may be hinting at a picture in which Bondi-Hoyle accretion from
an ambient ionized medium feeds a standard disk accreting at ~ 4.0*10^{22} g
s^{-1}. Somewhere near the event horizon, this plasma is heated to >10^{11} K,
where it radiates via thermal synchrotron (producing a radio component) and
self-Comptonization (accounting for a nonthermal X-ray flux). This temperature
is much greater than its virial value and the hot cloud expands at roughly the
sound speed (~0.1c), after which it begins to accelerate on a parsec scale to
relativistic velocities. In earlier work, the emission from the extended jet
has been modeled successfully using nonthermal synchrotron self-Compton
processes, with a self-absorbed inner core. In the picture we are developing
here, the initial ejection of matter is associated with a self-absorbed thermal
radio component that dominates the core emission on the smallest scales. The
nonthermal particle distributions responsible for the emission in the extended
jet are then presumably energized, e.g., via shock acceleration, within the
expanding, hot gas. The power associated with this plasma represents an
accretion efficiency of about 0.54, requiring dissipation in a prograde disk
around a rapidly spinning black hole (with spin parameter a~1).Comment: 17 pages, 1 figures, to appear in Ap
Count three for wear able computers
This paper is a postprint of a paper submitted to and accepted for publication in the Proceedings of the IEE Eurowearable 2003 Conference, and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.
A revised version of this paper was also published in Electronics Systems and Software, also subject to Institution of Engineering and Technology Copyright. The copy of record is also available at the IET Digital Library.A description of 'ubiquitous computer' is presented. Ubiquitous computers imply portable computers embedded into everyday objects, which would replace personal computers. Ubiquitous computers can be mapped into a three-tier scheme, differentiated by processor performance and flexibility of function. The power consumption of mobile devices is one of the most important design considerations. The size of a wearable system is often a design limitation
The high energy gamma-ray emission expected from Tycho's supernova remnant
A nonlinear kinetic model of cosmic ray (CR) acceleration in supernova
remnants (SNRs) is used to describe the properties of Tycho's SNR. Observations
of the expansion characteristics and of the nonthermal radio and X-ray emission
spectra, assumed to be of synchrotron origin, are used to constrain the overall
dynamical evolution and the particle acceleration parameters of the system, in
addition to what is known from independent estimates of the distance and
thermal X-ray observations. It is shown that a very efficient production of
nuclear cosmic rays, leading to strong shock modification, and a large
downstream magnetic field strength B_d approx 240muG are required to reproduce
the observed synchrotron emission from radio to X-ray frequencies. This field
strength is still well within the upper bound for the effective magnetic field,
consistent with the acceleration process. The pi^0-decay gamma-ray flux turns
out to be somewhat greater than the inverse Compton (IC) flux off the Cosmic
Microwave Background at energies below 1 TeV, dominating it strongly at 10 TeV.
The predicted TeV gamma-ray flux is consistent with but close to the very low
upper limit recently obtained by HEGRA. A future detection at E_gamma ~ 10 TeV
would clearly indicate hadronic emission.Comment: 8 pages, 6 figures. Accepted in Astronomy and Astrophyic
WHAM Observations of H-alpha from High-Velocity Clouds: Are They Galactic or Extragalactic?
It has been suggested that high velocity clouds may be distributed throughout
the Local Group and are therefore not in general associated with the Milky Way
galaxy. With the aim of testing this hypothesis, we have made observations in
the H-alpha line of high velocity clouds selected as the most likely candidates
for being at larger than average distances. We have found H-alpha emission from
4 out of 5 of the observed clouds, suggesting that the clouds under study are
being illuminated by a Lyman continuum flux greater than that of the
metagalactic ionizing radiation. Therefore, it appears likely that these clouds
are in the Galactic halo and not distributed throughout the Local Group.Comment: 12 pages, 5 eps figures, accepted for publication in ApJ Letter
On The Reddening in X-ray Absorbed Seyfert 1 Galaxies
There are several Seyfert galaxies for which there is a discrepancy between
the small column of neutral hydrogen deduced from X-ray observations and the
much greater column derived from the reddening of the optical/UV emission lines
and continuum. The standard paradigm has the dust within the highly ionized gas
which produces O~VII and O~VIII absorption edges (i.e., a ``dusty warm
absorber''). We present an alternative model in which the dust exists in a
component of gas in which hydrogen has been stripped, but which is at too low
an ionization state to possess significant columns of O~VII and O~VIII (i.e, a
``lukewarm absorber''). The lukewarm absorber is at sufficient radial distance
to encompass much of the narrow emission-line region, and thus accounts for the
narrow-line reddening, unlike the dusty warm absorber. We test the model by
using a combination of photoionization models and absorption edge fits to
analyze the combined ROSAT/ASCA dataset for the Seyfert 1.5 galaxy, NGC 3227.
We show that the data are well fit by a combination of the lukewarm absorber
and a more highly ionized component similar to that suggested in earlier
studies. We predict that the lukewarm absorber will produce strong UV
absorption lines of N V, C IV, Si IV and Mg II. Finally, these results
illustrate that singly ionized helium is an important, and often overlooked,
source of opacity in the soft X-ray band (100 - 500 eV).Comment: 17 pages, Latex, includes 1 figure (encapsulated postscript), one
additional table in Latex (landscape format), to appear in the Astrophysical
Journa
- …