3,010 research outputs found
BVR photometry of the resolved dwarf galaxy Ho IX
We present BVR CCD photometry down to limiting magnitude B=23.5 mag for 232
starlike objects and 11 diffuse objects in a 5.4' x 5.4' field of Ho IX. The
galaxy is a gas-rich irregular dwarf galaxy possibly very close to M 81, which
makes it especially interesting in the context of the evolution of satellite
galaxies and the accretion of dwarf galaxies. Investigations of Ho IX were
hampered by relatively large contradictions in the magnitude scale between
earlier studies. With our new photometry we resolved these discrepancies. The
color magnitude diagram (CMD) of Ho IX is fairly typical of a star-forming
dwarf irregular, consistent with earlier results. Distance estimates from our
new CMD are consistent with Ho IX being very close to M 81 and therefore being
a definite member of the M 81 group, apparently in very close physical
proximity to M 81.Comment: 9 pages, 8 figures, uses aa.cls, A&A in pres
Model turbulent floods with the Smagorinski large eddy closure
Floods, tides and tsunamis are turbulent, yet conventional models are based
upon depth averaging inviscid irrotational flow equations. We propose to change
the base of such modelling to the Smagorinksi large eddy closure for turbulence
in order to appropriately match the underlying fluid dynamics. Our approach
allows for large changes in fluid depth to cater for extreme inundations. The
key to the analysis underlying the approach is to choose surface and bed
boundary conditions that accommodate a constant turbulent shear as a nearly
neutral mode. Analysis supported by slow manifold theory then constructs a
model for the coupled dynamics of the fluid depth and the mean turbulent
lateral velocity. The model resolves the internal turbulent shear in the flow
and thus may be used in further work to rationally predict erosion and
transport in turbulent floods
The catalogue of OB associations in IC 1613
We present a catalogue of OB associations in IC 1613. Using an automatic and
objective method (Battinelli's 1991 technique) 60 objects were found. The size
distribution reveals a significant peak at about 60 parsecs if a distance
modulus of 24.27 mag is assumed. Spatial distributions of the detected
associations and H II regions are strongly correlated.Comment: 5 pages, 3 figures, A&A accepte
Computational equivalence of the two inequivalent spinor representations of the braid group in the Ising topological quantum computer
We demonstrate that the two inequivalent spinor representations of the braid
group \B_{2n+2}, describing the exchanges of 2n+2 non-Abelian Ising anyons in
the Pfaffian topological quantum computer, are equivalent from computational
point of view, i.e., the sets of topologically protected quantum gates that
could be implemented in both cases by braiding exactly coincide. We give the
explicit matrices generating almost all braidings in the spinor representations
of the 2n+2 Ising anyons, as well as important recurrence relations. Our
detailed analysis allows us to understand better the physical difference
between the two inequivalent representations and to propose a process that
could determine the type of representation for any concrete physical
realization of the Pfaffian quantum computer.Comment: 9 pages, 2 figures, published versio
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The Use of a Solid Hydrocarbon as a Graphite Substitute for Astaloy CrM Sintered Steel
YesAbstract
Höganäs Astaloy CrM powder was used to prepare mixtures with 0.3-1.6 % carbon contents, both with and without 1 wt.% manganese additions. The carbon was added in three ways: as a graphite powder, as a solid CnHm hydrocarbon powder, and as a mixture of both. Green compacts were pressed at 300 - 800 MPa and sintered isothermally at temperatures in the range 1170 - 1295°C under flowing high purity nitrogen or nitrogen/hydrogen (9:1) atmosphere. Compressibility of the powder mixtures was investigated. Carbon loss occurring during sintering was carefully monitored. Sintering behaviour of numerous combinations of carbon content was investigated by dilatometry. For high carbon contents and high sintering temperatures, densification resulted from controlled generation of a liquid phase. Advantages of using solid hydrocarbon as a carbon donor and of Mn addition in powder metallurgy processing of steels are indicated
On a Calderon-Zygmund commutator-type estimate
In this paper we extend a Calderon-Zygmund commutator-type estimate. This
estimate enables us to prove an embedding result concerning weighted function
spaces.Comment: 20 pages, no figure
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