45,513 research outputs found
Preparation of high purity copper fluoride by fluorinating copper hydroxyfluoride
Copper fluoride containing no more than 50 ppm of any contaminating element was prepared by the fluorination of copper hydroxyfluoride. The impurity content was obtained by spark source mass spectrometry. High purity copper fluoride is needed as a cathode material for high energy density batteries
Copper emissions from a high volume air sampler
High volume air samplers (hi vols) are described which utilize a brush-type electric motor to power the fans used for pulling air through the filter. Anomalously high copper values were attributed to removal of copper from the commutator into the air stream due to arcing of the brushes and recirculation through the filter. Duplicate hi vols were set up under three operating conditions: (1) unmodified; (2) gasketed to prevent internal recirculation; and (3) gasketed and provided with a pipe to transport the motor exhaust some 20 feet away. The results of 5 days' operation demonstrate that hi vols can suddenly start emitting increased amounts of copper with no discernible operational indication, and that recirculation and capture on the filter can take place. Copper levels found with hi vols whose exhaust was discharged at a distance downwind were among the lowest found, and apparently provides a satisfactory solution to copper contamination
The Virtual Runner Learning Game
A learning game has been developed which allows learners to study and learn about the significance of three important variables in human physiology (lactate, glycogen, and hydration) and their influence on sports performance during running. The player can control the speed of the runner, and as a consequence the resulting physiological processes are simulated in real-time. The performance degradation of the runner due to these processes requires that different strategies for pacing the running speed are applied by the player, depending on the total length of the run. The game has been positively evaluated in a real learning context of academic physiology teaching
The ultimate outcome of black hole - neutron star mergers
We present a simple, semi--analytical description for the final stages of
mergers of black hole (BH) -- neutron star (NS) systems. Such systems are of
much interest as gravitational wave sources and gamma--ray burst progenitors.
Numerical studies show that in general the neutron star is not disrupted at the
first phase of mass transfer. Instead, what remains of the neutron star is left
on a wider, eccentric, orbit. We consider the evolution of such systems as they
lose angular momentum via gravitational radiation and come into contact for
further phases of mass transfer. During each mass transfer event the neutron
star mass is reduced until a critical value where mass loss leads to a rapid
increase in the stellar radius. At this point Roche lobe overflow shreds what
remains of the neutron star, most of the mass forming a disc around the black
hole. Such a disc may be massive enough to power a gamma--ray burst. The mass
of the neutron star at the time of disruption (and therefore the disc mass) is
largely independent of the initial masses of the black hole and neutron star,
indicating that BH--NS star mergers may be standard candles.Comment: MNRAS, in pres
Dielectric molding apparatus Patent
Dielectric apparatus for heating, fusing, and hardening of organic matrix to form plastic material into shaped produc
Neutron star binaries and long duration gamma-ray bursts
Cosmological long-duration gamma-ray bursts (LGRBs) are thought to originate
from the core collapse to black holes of stripped massive stars. Those with
sufficient rotation form a centrifugally-supported torus whose collapse powers
the GRB. We investigate the role of tidal locking within a tight binary as a
source of the necessary angular momentum. We find that the binary orbit must be
no wider than a few solar radii for a torus to form upon core collapse.
Comparing this criterion to the observed population of binaries containing two
compact objects suggests that rotation may have been important in the formation
of up to 50% of the observed systems. As these systems created a neutron star
and not a black hole they presumably did not produce highly luminous GRBs. We
suggest instead that they make the subset of GRBs in the relatively local
universe which have much lower luminosity.Comment: 7 pages, accepted for publication in MNRA
Rotating Metal Band Target for Pion Production at Muon Colliders and Neutrino Factories
A conceptual design is presented for a high power pion production target for
muon colliders and neutrino factories that is based around a rotating metal
band.Comment: 28 pages, 16 figures; to be published in Phys. Rev. ST Accel. Beam
Hopf algebras and characters of classical groups
Schur functions provide an integral basis of the ring of symmetric functions.
It is shown that this ring has a natural Hopf algebra structure by identifying
the appropriate product, coproduct, unit, counit and antipode, and their
properties. Characters of covariant tensor irreducible representations of the
classical groups GL(n), O(n) and Sp(n) are then expressed in terms of Schur
functions, and the Hopf algebra is exploited in the determination of
group-subgroup branching rules and the decomposition of tensor products. The
analysis is carried out in terms of n-independent universal characters. The
corresponding rings, CharGL, CharO and CharSp, of universal characters each
have their own natural Hopf algebra structure. The appropriate product,
coproduct, unit, counit and antipode are identified in each case.Comment: 9 pages. Uses jpconf.cls and jpconf11.clo. Presented by RCK at
SSPCM'07, Myczkowce, Poland, Sept 200
Filter cassette for high volume air sampler
Filter cassette eliminates or substantially reduces contamination of filter media by extraneous material and facilitates handling
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