15,642 research outputs found
Hydrogen in Type Ic Supernovae?
By definition, a Type Ic supernova (SN Ic) does not have conspicuous lines of
hydrogen or helium in its optical spectrum. SNe Ic usually are modelled in
terms of the gravitational collapse of bare carbon-oxygen cores. We consider
the possibility that the spectra of ordinary (SN 1994I-like) SNe Ic have been
misinterpreted, and that SNe Ic eject hydrogen. An absorption feature usually
attributed to a blend of Si II 6355 and C II 6580 may be produced by H-alpha.
If SN 1994I-like SNe Ic eject hydrogen, the possibility that hypernova (SN
1998bw-like) SNe Ic, some of which are associated with gamma-ray bursts, also
eject hydrogen should be considered. The implications of hydrogen for SN Ic
progenitors and explosion models are briefly discussed.Comment: Accepted by PASP. Several significant changes including one
additional figur
Are you a researcher as well as a medical illustrator?
When we list the areas of practice for medical illustrators we always include research, but how involved in research are we? The aim of this activity is to encourage your professional development not just as a medical illustrator but your involvement with research whether that is undertaking your own research, undertaking evidence based practice (1) , working as part of a research team, advising researchers on the value of medical illustration or supporting a student undertaking a research project for their degree or post-graduate qualification
Implications for the U.S. of Anglo-French Defense Cooperation
The paper analyzes, from a predominantly UK perspective, the implications for
the U.S. of the November 2, 2010, Anglo-French Defence Cooperation Treaty. The
current pressures on British and French defence budgets were the primary driving
force behind this cooperative effort. London and Paris have made steps toward
improving joint efforts in a number of areas, with defence acquisition and
industrial cooperation being prominent. In the UK, there appears to be strong
political support at the highest levels, which has permeated to lower levels in
the bureaucracy, while the UK defence industry appears to be cautiously
optimistic about future business opportunities.
The impact of enhanced Anglo-French cooperation on the U.S. would appear to be
largely favourable for Washington. Rather than providing a basis for weakened UK
attention to the U.S., as some fear, the efforts by London and Paris will
potentially generate greater national military capability from scarce resources
and could serve as a vehicle for broader European efforts to enhance their
defence capabilities. While multinational European military development projects
are viewed with scepticism in the UK, the Anglo-French arrangement could
strengthen the prospects for bilateral projects in which other European states
may elect to participate
Producing High Concentrations of Hydrogen in Palladium via Electrochemical Insertion from Aqueous and Solid Electrolytes
Metal hydrides are critical materials in numerous technologies including
hydrogen storage, gas separation, and electrocatalysis. Here, using Pd-H as a
model metal hydride, we perform electrochemical insertion studies of hydrogen
via liquid and solid state electrolytes at 1 atm ambient pressure, and achieve
H:Pd ratios near unity, the theoretical solubility limit. We show that the
compositions achieved result from a dynamic balance between the rate of
hydrogen insertion and evolution from the Pd lattice, the combined kinetics of
which are sufficiently rapid that operando experiments are necessary to
characterize instantaneous PdHx composition. We use simultaneous
electrochemical insertion and X-ray diffraction measurements, combined with a
new calibration of lattice parameter versus hydrogen concentration, to enable
accurate quantification of the composition of electrochemically synthesized
PdHx. Furthermore, we show that the achievable hydrogen concentration is
severely limited by electrochemomechanical damage to the palladium and/or
substrate. The understanding embodied in these results helps to establish new
design rules for achieving high hydrogen concentrations in metal hydrides.Comment: 38 page
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