38,275 research outputs found
A 3D Printed Toolbox for Opto-Mechanical Components
Nowadays is very common to find headlines in the media where it is stated
that 3D printing is a technology called to change our lives in the near future.
For many authors, we are living in times of a third industrial revolution.
Howerver, we are currently in a stage of development where the use of 3D
printing is advantageous over other manufacturing technologies only in rare
scenarios. Fortunately, scientific research is one of them. Here we present the
development of a set of opto-mechanical components that can be built easily
using a 3D printer based on Fused Filament Fabrication (FFF) and parts that can
be found on any hardware store. The components of the set presented here are
highly customizable, low-cost, require a short time to be fabricated and offer
a performance that compares favorably with respect to low-end commercial
alternatives.Comment: 9 pages, 9 figure
Genus and spot density in the COBE DMR first year anisotropy maps
A statistical analysis of texture on the {\it COBE}-DMR first year sky maps
based on the genus and spot number is presented. A generalized
statistic is defined in terms of ``observable'' quantities: the genus and spot
density that would be measured by different cosmic observers. This strategy
together with the use of Monte Carlo simulations of the temperature
fluctuations, including all the relevant experimental parameters, represent the
main difference with previous analyses. Based on the genus analysis we find a
strong anticorrelation between the quadrupole amplitude and the
spectral index of the density fluctuation power spectrum at recombination
of the form K for fixed
, consistent with previous works. The result obtained based on the spot
density is consistent with this relation. In addition to the
previous results we have determined, using Monte Carlo simulations, the minimum
uncertainty due to cosmic variance for the determination of the spectral index
with the genus analysis. This uncertainty is .Comment: 5 pages, uuencode file containing text and 1 figure. MNRAS in press
Thermodynamics of noncommutative quantum Kerr black holes
Thermodynamic formalism for rotating black holes, characterized by
noncommutative and quantum corrections, is constructed. From a fundamental
thermodynamic relation, equations of state and thermodynamic response functions
are explicitly given and the effect of noncommutativity and quantum correction
is discussed. It is shown that the well known divergence exhibited in specific
heat is not removed by any of these corrections. However, regions of
thermodynamic stability are affected by noncommutativity, increasing the
available states for which some thermodynamic stability conditions are
satisfied.Comment: 16 pages, 9 figure
HIPPARCOS Astrometric Orbit and Evolutionary Status of HR 6046
The previously known, 6-yr spectroscopic binary HR 6046 has been speculated
in the past to contain a compact object as the secondary. A recent study has
re-determined the orbit with great accuracy, and shown that the companion is an
evolved but otherwise normal star of nearly identical mass as the primary,
which is also a giant. The binary motion was detected by the Hipparcos mission
but was not properly accounted for in the published astrometric solution. Here
we use the Hipparcos intermediate data in combination with the spectroscopic
results to revise that solution and establish the orbital inclination angle for
the first time, and with it the absolute masses M(A) = 1.38 [-0.03,+0.09]
M(Sun) and M(B) = 1.36 [-0.02,+0.07] M(Sun). Aided by other constraints, we
investigate the evolutionary status and confirm that the primary star is
approaching the tip of the red-giant branch, while the secondary is beginning
its first ascent.Comment: To appear in The Astronomical Journal. 8 pages including tables and
figures, in emulateapj forma
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