552 research outputs found
Removing beam asymmetry bias in precision CMB temperature and polarisation experiments
Asymmetric beams can create significant bias in estimates of the power
spectra from CMB experiments. With the temperature power spectrum many orders
of magnitude stronger than the B-mode power spectrum any systematic error that
couples the two must be carefully controlled and/or removed. Here, we derive
unbiased estimators for the CMB temperature and polarisation power spectra
taking into account general beams and general scan strategies. A simple
consequence of asymmetric beams is that, even with an ideal scan strategy where
every sky pixel is seen at every orientation, there will be residual coupling
from temperature power to B-mode power if the orientation of the beam asymmetry
is not aligned with the orientation of the co-polarisation. We test our
correction algorithm on simulations of two temperature-only experiments and
demonstrate that it is unbiased. The simulated experiments use realistic scan
strategies, noise levels and highly asymmetric beams. We also develop a
map-making algorithm that is capable of removing beam asymmetry bias at the map
level. We demonstrate its implementation using simulations and show that it is
capable of accurately correcting both temperature and polarisation maps for all
of the effects of beam asymmetry including the effects of temperature to
polarisation leakage.Comment: 18 pages, 9 figure
Removing beam asymmetry bias in precision CMB temperature and polarisation experiments
Asymmetric beams can create significant bias in estimates of the power
spectra from CMB experiments. With the temperature power spectrum many orders
of magnitude stronger than the B-mode power spectrum any systematic error that
couples the two must be carefully controlled and/or removed. Here, we derive
unbiased estimators for the CMB temperature and polarisation power spectra
taking into account general beams and general scan strategies. A simple
consequence of asymmetric beams is that, even with an ideal scan strategy where
every sky pixel is seen at every orientation, there will be residual coupling
from temperature power to B-mode power if the orientation of the beam asymmetry
is not aligned with the orientation of the co-polarisation. We test our
correction algorithm on simulations of two temperature-only experiments and
demonstrate that it is unbiased. The simulated experiments use realistic scan
strategies, noise levels and highly asymmetric beams. We also develop a
map-making algorithm that is capable of removing beam asymmetry bias at the map
level. We demonstrate its implementation using simulations and show that it is
capable of accurately correcting both temperature and polarisation maps for all
of the effects of beam asymmetry including the effects of temperature to
polarisation leakage.Comment: 18 pages, 9 figure
Lateral patellar luxation in nine small breed dogs
The objective of this paper was to describe the clinical features, the management and the outcome of nine small breed dogs affected with lateral patella luxation referred during the period between January 2010 and December 2014. Patellar luxations were classified according to: breed, age, sex, weight, and grade of patellar luxation, as well as if unilateral or bilateral, and concurrent cranial cruciate ligament lesion. In affected dogs, surgical correction consisted in the combination of tibial tuberosity transposition and soft tissue procedure. Adjunctive condroplasty or trochleoplasty was performed as needing. The outcome was found positive after surgical management with low complication rate and complications have been easily managed with high success rate
Traumatic lumbosacral joint dislocation in 3 dogs: Clinical presentation, diagnosis, treatment and short-term follow-up
Traumatic lumbosacral joint dislocation (TLSJD) without L7 vertebral body fracture is a rare injury in dogs. This report describes clinical presentation, therapy and outcome in 3 dogs. Three crossbreed dogs with non-ambulatory paraparesis and lumbar pain were referred. Radiographs confirmed TLSJD and dorso-ventral displacement (DVD) was measured pre and postoperatively. Case 1 was treated by percutaneous transilial pinning. Cases 2 and 3 were treated by internal fixation with pins and PMMA. Within 72h after surgery all dogs were able to stand and walk, and faecal incontinence resolved. To the author's knowledge this is the first description of a case series of TLSJD in the dog. The biomechanics of TLSJD in animals have not been investigated. It is likely that a single trauma severely hyper-extends L7-S1 causing disruption of the supra and inter-spinous ligaments with simultaneous shear and compression forces that cause ventral slipping of the sacrum. Pins and PMMA compared to percutaneous transilial pinning, provided more strength and stability. In conclusion, TLSJD requires appropriate surgical reduction and stabilization to allow fibrous healing of the L7-S1 junction, resulting in satisfactory neurological recovery
Rotation in galaxy clusters from MUSIC simulations with the kinetic Sunyaev-Zel'dovich effect
We propose in this work its application for the detection of possible coherent rotational motions in the hot intra-cluster medium. We select a sample of massive, relaxed and rotating galaxy clusters from Marenostrum-mUltidark SImulations of galaxy Clusters (MUSIC), and we produce mock maps of the temperature distortion produced by the kinetic Sunyaev-Zel'dovich effect by exploring six different lines of sight, in the best observational condition. These maps are compared with the expected signal computed from a suitable theoretical model in two cases: (i) focusing only on the contribution from the rotation, and (ii) accounting also for the cluster bulk motion. We find that the parameters of the model assumed for the radial profile of the rotational velocity, averaged over the considered lines of sight, are in agreement within two standard deviations at most with independent estimates from the simulation data, without being significantly affected by the presence of the cluster bulk term. The amplitude of the rotational signal is, on average, of the order of 23 per cent of the total signal accounting also for the cluster bulk motion, and its values are consistent with the literature. The projected bulk velocity of the cluster is also recovered at the different lines of sight, with values in agreement with the simulation dataASB acknowledges funding from Sapienza Università di Roma - Progetti per Avvio alla Ricerca Anno 2017, prot. AR11715C82402BC
Constraining the evolution of the CMB temperature with SZ measurements from Planck data
The CMB temperature-redshift relation, T_CMB(z)=T_0(1+z), is a key prediction
of the standard cosmology, but is violated in many non standard models.
Constraining possible deviations to this law is an effective way to test the
LambdaCDM paradigm and to search for hints of new physics. We have determined
T_CMB(z), with a precision up to 3%, for a subsample (104 clusters) of the
Planck SZ cluster catalog, at redshift in the range 0.01-- 0.94, using
measurements of the spectrum of the Sunyaev Zel'dovich effect obtained from
Planck temperature maps at frequencies from 70 to 353 GHz. The method adopted
to provide individual determinations of T_CMB(z) at cluster redshift relies on
the use of SZ intensity change, Delta I_SZ(nu), at different frequencies, and
on a Monte-Carlo Markov Chain approach. By applying this method to the sample
of 104 clusters, we limit possible deviations of the form
T_CMB(z)=T_0(1+z)^(1-beta) to be beta= 0.022 +/- 0.018, at 1 sigma uncertainty,
consistent with the prediction of the standard model. Combining these
measurements with previously published results we get beta=0.016+/-0.012.Comment: submitted to JCAP, 21 pages, 8 figure
Congenital deformity of the distal extremities in three dogs
Congenital limb deformities are very rare conditions and the knowledge about etiology, pathogenesis, clinical presentation and treatment is still poor. Moreover, many defects are still not reported in veterinary literature. This report documents clinical and radiographic findings in three dogs with congenital deformity involving the distal extremities. Case 1 was affected with bilateral aphalangia of the pedes, case 2 presented a combination of brachydactyly and syndactyly, whereas in case 3 a unilateral ectrodactyly was observed. To the authors’ knowledge, brachydactyly, as well as aphalangia, are very uncommon anomalies and have been rarely documented. Moreover, association between syndactyly and brachydactyly has still not been reported
Absolute calibration and beam reconstruction of MITO (a ground-based instrument in the millimetric region)
An efficient sky data reconstruction derives from a precise characterization
of the observing instrument. Here we describe the reconstruction of
performances of a single-pixel 4-band photometer installed at MITO (Millimeter
and Infrared Testagrigia Observatory) focal plane. The strategy of differential
sky observations at millimeter wavelengths, by scanning the field of view at
constant elevation wobbling the subreflector, induces a good knowledge of beam
profile and beam-throw amplitude, allowing efficient data recovery. The
problems that arise estimating the detectors throughput by drift scanning on
planets are shown. Atmospheric transmission, monitored by skydip technique, is
considered for deriving final responsivities for the 4 channels using planets
as primary calibrators.Comment: 14 pages, 6 fiugres, accepted for pubblication by New Astronomy (25
March
Kinetic Inductance Detectors for the OLIMPO experiment: design and pre-flight characterization
We designed, fabricated, and characterized four arrays of horn--coupled,
lumped element kinetic inductance detectors (LEKIDs), optimized to work in the
spectral bands of the balloon-borne OLIMPO experiment. OLIMPO is a 2.6 m
aperture telescope, aimed at spectroscopic measurements of the
Sunyaev-Zel'dovich (SZ) effect. OLIMPO will also validate the LEKID technology
in a representative space environment. The corrected focal plane is filled with
diffraction limited horn-coupled KID arrays, with 19, 37, 23, 41 active pixels
respectively at 150, 250, 350, and 460GHz. Here we report on the full
electrical and optical characterization performed on these detector arrays
before the flight. In a dark laboratory cryostat, we measured the resonator
electrical parameters, such as the quality factors and the electrical
responsivities, at a base temperature of 300mK. The measured average
resonator s are 1.7, 7.0, 1.0, and
1.0 for the 150, 250, 350, and 460GHz arrays, respectively.
The average electrical phase responsivities on resonance are 1.4rad/pW,
1.5rad/pW, 2.1rad/pW, and 2.1rad/pW; the electrical noise
equivalent powers are 45, 160,
80, and 140, at 12 Hz. In the OLIMPO
cryostat, we measured the optical properties, such as the noise equivalent
temperatures (NET) and the spectral responses. The measured NETs are
, , ,
and , at 12 Hz; under 78, 88, 92, and 90 mK
Rayleigh-Jeans blackbody load changes respectively for the 150, 250, 350, and
460 GHz arrays. The spectral responses were characterized with the OLIMPO
differential Fourier transform spectrometer (DFTS) up to THz frequencies, with
a resolution of 1.8 GHz.Comment: Published on JCA
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