424 research outputs found
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
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
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
Millimeter and sub-millimeter atmospheric performance at Dome C combining radiosoundings and ATM synthetic spectra
The reliability of astronomical observations at millimeter and sub-millimeter
wavelengths closely depends on a low vertical content of water vapor as well as
on high atmospheric emission stability. Although Concordia station at Dome C
(Antarctica) enjoys good observing conditions in this atmospheric spectral
windows, as shown by preliminary site-testing campaigns at different bands and
in, not always, time overlapped periods, a dedicated instrument able to
continuously determine atmospheric performance for a wide spectral range is not
yet planned. In the absence of such measurements, in this paper we suggest a
semi-empirical approach to perform an analysis of atmospheric transmission and
emission at Dome C to compare the performance for 7 photometric bands ranging
from 100 GHz to 2 THz. Radiosoundings data provided by the Routine
Meteorological Observations (RMO) Research Project at Concordia station are
corrected by temperature and humidity errors and dry biases and then employed
to feed ATM (Atmospheric Transmission at Microwaves) code to generate synthetic
spectra in the wide spectral range from 100 GHz to 2 THz. To quantify the
atmospheric contribution in millimeter and sub-millimeter observations we are
considering several photometric bands in which atmospheric quantities are
integrated. The observational capabilities of this site at all the selected
spectral bands are analyzed considering monthly averaged transmissions joined
to the corresponding fluctuations. Transmission and pwv statistics at Dome C
derived by our semi-empirical approach are consistent with previous works. It
is evident the decreasing of the performance at high frequencies. We propose to
introduce a new parameter to compare the quality of a site at different
spectral bands, in terms of high transmission and emission stability, the Site
Photometric Quality Factor.Comment: accepted to MNRAS with minor revision
Bistability in the Tunnelling Current through a Ring of Coupled Quantum Dots
We study bistability in the electron transport through a ring of N coupled
quantum dots with two orbitals in each dot. One orbital is localized (called b
orbital) and coupling of the b orbitals in any two dots is negligible; the
other is delocalized in the plane of the ring (called d orbital), due to
coupling of the d orbitals in the neighboring dots, as described by a
tight-binding model. The d orbitals thereby form a band with finite width. The
b and d orbitals are connected to the source and drain electrodes with a
voltage bias V, allowing the electron tunnelling. Tunnelling current is
calculated by using a nonequilibrium Green function method recently developed
to treat nanostructures with multiple energy levels. We find a bistable effect
in the tunnelling current as a function of bias V, when the size N>50; this
effect scales with the size N and becomes sizable at N~100. The temperature
effect on bistability is also discussed. In comparison, mean-field treatment
tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte
Millimetric observations with a high-altitude 2.6-m ground based telescope
High atmospheric performances are necessary to ensure efficient sub/millimetre cosmological observations from ground. Low atmospheric components fluctuations along the line of sight are a must for best detector applications.
Such site constraints are attained only at in specific places around the world: highaltitude observatories or, equivalently, polar regions. We are currently involved in
cosmological observations with the MITO project from an Alpine ground station which satisfies such requirements: the Testa Grigia mountain at 3500 m a.s.l., AO—Italy. The Chacaltaya laboratory at 5200 m a.s.l. could also be an appropriate mm-site. One of the goals of MITO is the multifrequency observation of nearby rich clusters of galaxies for measuring the Sunyaev-Zel’dovich effect. Combined S-Z and X-ray measurements yield the Hubble constant and other cosmological information. A dedicated instrument has been designed to minimize spurious contaminations on the signals. The telescope is a 2.6 m Cassegrain with a wobbling subreflector and a 4-band single pixel photometer installed at the focal plane. The bolometric detectors are cooled down to 300 mK by a double stage He3-He4 fridge
Millimetric observations with a high-altitude 2.6-m ground based telescope
High atmospheric performances are necessary to ensure efficient sub/millimetre cosmological observations from ground. Low atmospheric components fluctuations along the line of sight are a must for best detector applications.
Such site constraints are attained only at in specific places around the world: highaltitude observatories or, equivalently, polar regions. We are currently involved in
cosmological observations with the MITO project from an Alpine ground station which satisfies such requirements: the Testa Grigia mountain at 3500 m a.s.l., AO—Italy. The Chacaltaya laboratory at 5200 m a.s.l. could also be an appropriate mm-site. One of the goals of MITO is the multifrequency observation of nearby rich clusters of galaxies for measuring the Sunyaev-Zel’dovich effect. Combined S-Z and X-ray measurements yield the Hubble constant and other cosmological information. A dedicated instrument has been designed to minimize spurious contaminations on the signals. The telescope is a 2.6 m Cassegrain with a wobbling subreflector and a 4-band single pixel photometer installed at the focal plane. The bolometric detectors are cooled down to 300 mK by a double stage He3-He4 fridge
The Large-Scale Polarization Explorer (LSPE)
The LSPE is a balloon-borne mission aimed at measuring the polarization of
the Cosmic Microwave Background (CMB) at large angular scales, and in
particular to constrain the curl component of CMB polarization (B-modes)
produced by tensor perturbations generated during cosmic inflation, in the very
early universe. Its primary target is to improve the limit on the ratio of
tensor to scalar perturbations amplitudes down to r = 0.03, at 99.7%
confidence. A second target is to produce wide maps of foreground polarization
generated in our Galaxy by synchrotron emission and interstellar dust emission.
These will be important to map Galactic magnetic fields and to study the
properties of ionized gas and of diffuse interstellar dust in our Galaxy. The
mission is optimized for large angular scales, with coarse angular resolution
(around 1.5 degrees FWHM), and wide sky coverage (25% of the sky). The payload
will fly in a circumpolar long duration balloon mission during the polar night.
Using the Earth as a giant solar shield, the instrument will spin in azimuth,
observing a large fraction of the northern sky. The payload will host two
instruments. An array of coherent polarimeters using cryogenic HEMT amplifiers
will survey the sky at 43 and 90 GHz. An array of bolometric polarimeters,
using large throughput multi-mode bolometers and rotating Half Wave Plates
(HWP), will survey the same sky region in three bands at 95, 145 and 245 GHz.
The wide frequency coverage will allow optimal control of the polarized
foregrounds, with comparable angular resolution at all frequencies.Comment: In press. Copyright 2012 Society of Photo-Optical Instrumentation
Engineers. One print or electronic copy may be made for personal use only.
Systematic reproduction and distribution, duplication of any material in this
paper for a fee or for commercial purposes, or modification of the content of
the paper are prohibite
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