369 research outputs found
Knot invariants in lens spaces
In this survey we summarize results regarding the Kauffman bracket, HOMFLYPT,
Kauffman 2-variable and Dubrovnik skein modules, and the Alexander polynomial
of links in lens spaces, which we represent as mixed link diagrams. These
invariants generalize the corresponding knot polynomials in the classical case.
We compare the invariants by means of the ability to distinguish between some
difficult cases of knots with certain symmetries
An Evolving Entropy Floor in the Intracluster Gas?
Non-gravitational processes, such as feedback from galaxies and their active
nuclei, are believed to have injected excess entropy into the intracluster gas,
and therefore to have modified the density profiles in galaxy clusters during
their formation. Here we study a simple model for this so-called preheating
scenario, and ask (i) whether it can simultaneously explain both global X-ray
scaling relations and number counts of galaxy clusters, and (ii) whether the
amount of entropy required evolves with redshift. We adopt a baseline entropy
profile that fits recent hydrodynamic simulations, modify the hydrostatic
equilibrium condition for the gas by including approx. 20% non-thermal pressure
support, and add an entropy floor K_0 that is allowed to vary with redshift. We
find that the observed luminosity-temperature (L-T) relations of low-redshift
(z=0.05) HIFLUGCS clusters and high-redshift (z=0.8) WARPS clusters are best
simultaneously reproduced with an evolving entropy floor of
K_0(z)=341(1+z)^{-0.83}h^{-1/3} keV cm^2. If we restrict our analysis to the
subset of bright (kT > 3 keV) clusters, we find that the evolving entropy floor
can mimic a self-similar evolution in the L-T scaling relation. This degeneracy
with self-similar evolution is, however, broken when (0.5 < kT < 3 keV)
clusters are also included. The approx. 60% entropy increase we find from z=0.8
to z=0.05 is roughly consistent with that expected if the heating is provided
by the evolving global quasar population. Using the cosmological parameters
from the WMAP 3-year data with sigma_8=0.76, our best-fit model underpredicts
the number counts of the X-ray galaxy clusters compared to those derived from
the 158 deg^2 ROSAT PSPC survey. Treating sigma_8 as a free parameter, we find
a best-fit value of sigma_8=0.80+/- 0.02.Comment: 14 emulateapj pages with 9 figures, submitted to Ap
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Electron capture by Ne2+ ions from atomic hydrogen
Using a merged-beam technique, the absolute, total electron-capture cross section has been measured for collisions of Ne2+ ions with hydrogen (deuterium) atoms at collision energies between 139 and 1490 eV/u. These data are compared to three other published measurements, two of which differ from one another by a factor greater than two. Early quantal rate coefficient calculations for Ne2+ ions with hydrogen at eV/u energies predict a cross section many orders of magnitude below the previously measured cross section at 40 eV/u. A possible explanation is given for the discrepancy between theory and experiment
Galaxy Cluster Scaling Relations between Bolocam Sunyaev-Zel'dovich Effect and Chandra X-ray Measurements
We present scaling relations between the integrated Sunyaev-Zel'dovich Effect
(SZE) signal, , its X-ray analogue, , and total mass, , for the 45 galaxy clusters in
the Bolocam X-ray-SZ (BOXSZ) sample. All parameters are integrated within
. values are measured using SZE data collected with
Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory (CSO).
The temperature, , and mass, , of the intracluster
medium are determined using X-ray data collected with Chandra, and is derived from assuming a constant gas mass fraction. Our
analysis accounts for several potential sources of bias, including: selection
effects, contamination from radio point sources, and the loss of SZE signal due
to noise filtering and beam-smoothing effects. We measure the
-- scaling to have a power-law index of , and
a fractional intrinsic scatter in of at fixed , both of which are consistent with previous analyses. We also measure the
scaling between and , finding a power-law index of
and a fractional intrinsic scatter in at fixed mass of
. While recent SZE scaling relations using X-ray mass proxies have
found power-law indices consistent with the self-similar prediction of 5/3, our
measurement stands apart by differing from the self-similar prediction by
approximately 5. Given the good agreement between the measured
-- scalings, much of this discrepancy appears to be caused
by differences in the calibration of the X-ray mass proxies adopted for each
particular analysis.Comment: 31 pages, 15 figures, accepted by ApJ 04/11/2015. This version is
appreciably different from the original submission: it includes an entirely
new appendix, extended discussion, and much of the material has been
reorganize
Pancreatic remnant fate
There is eternal discussion on the best surgical method of pancreatoduodenectomy and reconstruction method. Several different methods of pancreatic stump anastomosis exist. The most popular argument taken into account in the discussion is the frequency of early postoperative complications. Relatively fewer papers analyse the late functional outcome of pancreatic surgery and the method of anastomosis employed. Authors presented short series of 12 patients after pancreatic surgery with analysis of pancreatic remnant morphology and function. Pancreatic remnant volume, pancreatic duct distension and stool elastase-1 test were analysed. There was no correlation of pancreatic exo- or endocrine insufficiency with the volume of pancreatic remnant or the kind of surgery or anastomosis performed
A Titanium Nitride Absorber for Controlling Optical Crosstalk in Horn-Coupled Aluminum LEKID Arrays for Millimeter Wavelengths
We discuss the design and measured performance of a titanium nitride (TiN)
mesh absorber we are developing for controlling optical crosstalk in
horn-coupled lumped-element kinetic inductance detector arrays for
millimeter-wavelengths. This absorber was added to the fused silica
anti-reflection coating attached to previously-characterized, 20-element
prototype arrays of LEKIDs fabricated from thin-film aluminum on silicon
substrates. To test the TiN crosstalk absorber, we compared the measured
response and noise properties of LEKID arrays with and without the TiN mesh.
For this test, the LEKIDs were illuminated with an adjustable, incoherent
electronic millimeter-wave source. Our measurements show that the optical
crosstalk in the LEKID array with the TiN absorber is reduced by 66\% on
average, so the approach is effective and a viable candidate for future
kilo-pixel arrays.Comment: 7 pages, 5 figures, accepted for publication in the Journal of Low
Temperature Physic
Galaxy Cluster Pressure Profiles as Determined by Sunyaev Zel'dovich Effect Observations with MUSTANG and Bolocam I: Joint Analysis Technique
We present a technique to constrain galaxy cluster pressure profiles by
jointly fitting Sunyaev-Zel'dovich effect (SZE) data obtained with MUSTANG and
Bolocam for the clusters Abell 1835 and MACS0647. Bolocam and MUSTANG probe
different angular scales and are thus highly complementary. We find that the
addition of the high resolution MUSTANG data can improve constraints on
pressure profile parameters relative to those derived solely from Bolocam. In
Abell 1835 and MACS0647, we find gNFW inner slopes of and , respectively when
and are constrained to 0.86 and 4.67 respectively. The fitted
SZE pressure profiles are in good agreement with X-ray derived pressure
profiles.Comment: 12 pages, 12 figures. Submitted to Ap
Thermodynamic evolution of the galaxy cluster IDCS J1426.5+3508
We present resolved thermodynamic profiles out to 500 kpc, about ,
of the galaxy cluster IDCS J1426.5+3508 with 40 kpc resolution. Thanks
to the combination of Sunyaev-Zel'dovich and X-ray datasets, IDCS J1426.5+3508
becomes the most distant cluster with resolved thermodynamic profiles. These
are derived assuming a non-parametric pressure profile and a very flexible
model for the electron density profile. The shape of the pressure profile is
flatter than the universal pressure profile. The IDCS J1426.5+3508 temperature
profile is increasing radially out to 500 kpc. To identify the possible future
evolution of IDCS J1426.5+3508 , we compared it with its local descendants that
numerical simulations show to be dex more massive. We found no
evolution at 30 kpc, indicating a fine tuning between cooling and heating at
small radii. At kpc, our observations show that entropy and heat
must be deposited with little net gas transfer, while at 500 kpc the gas need
to be replaced by a large amount of cold, lower entropy gas, consistent with
theoretical expectation of a filamentary gas stream, which brings low entropy
gas to 500 kpc and energy at even smaller radii. At kpc the
polytropic index takes a low value, which indicates the presence of a large
amount of non-thermal pressure. Our work also introduces a new definition of
the evolutionary rate, which uses unscaled radii, unscaled thermodynamic
quantities, and different masses at different redshifts to compare ancestors
and descendants. It has the advantage of separating cluster evolution,
dependence on mass, pseudo-evolution and returns a number with unique
interpretation, unlike other definitions used in literature.Comment: MNRAS, in press. In v2 we only corrected author affiliations and
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