1,112 research outputs found
Multi-mode TES bolometer optimization for the LSPE-SWIPE instrument
In this paper we explore the possibility of using transition edge sensor
(TES) detectors in multi-mode configuration in the focal plane of the Short
Wavelength Instrument for the Polarization Explorer (SWIPE) of the
balloon-borne polarimeter Large Scale Polarization Explorer (LSPE) for the
Cosmic Microwave Background (CMB) polarization. This study is motivated by the
fact that maximizing the sensitivity of TES bolometers, under the augmented
background due to the multi-mode design, requires a non trivial choice of
detector parameters. We evaluate the best parameter combination taking into
account scanning strategy, noise constraints, saturation power and operating
temperature of the cryostat during the flight.Comment: in Journal of Low Temperature Physics, 05 January 201
Geometric transport along circular orbits in stationary axisymmetric spacetimes
Parallel transport along circular orbits in orthogonally transitive
stationary axisymmetric spacetimes is described explicitly relative to Lie
transport in terms of the electric and magnetic parts of the induced
connection. The influence of both the gravitoelectromagnetic fields associated
with the zero angular momentum observers and of the Frenet-Serret parameters of
these orbits as a function of their angular velocity is seen on the behavior of
parallel transport through its representation as a parameter-dependent Lorentz
transformation between these two inner-product preserving transports which is
generated by the induced connection. This extends the analysis of parallel
transport in the equatorial plane of the Kerr spacetime to the entire spacetime
outside the black hole horizon, and helps give an intuitive picture of how
competing "central attraction forces" and centripetal accelerations contribute
with gravitomagnetic effects to explain the behavior of the 4-acceleration of
circular orbits in that spacetime.Comment: 33 pages ijmpd latex article with 24 eps figure
Detailed study of the microwave emission of the supernova remnant 3C 396
We have observed the supernova remnant 3C~396 in the microwave region using
the Parkes 64-m telescope. Observations have been made at 8.4 GHz, 13.5 GHz,
and 18.6 GHz and in polarisation at 21.5 GHz. We have used data from several
other observatories, including previously unpublished observations performed by
the Green Bank Telescope at 31.2 GHz, to investigate the nature of the
microwave emission of 3C 396. Results show a spectral energy distribution
dominated by a single component power law emission with . Data do not favour the presence of anomalous microwave emission coming
from the source. Polarised emission at 21.5 GHz is consistent with
synchrotron-dominated emission. We present microwave maps and correlate them
with infrared (IR) maps in order to characterise the interplay between thermal
dust and microwave emission. IR vs. microwave TT plots reveal poor correlation
between mid-infrared and microwave emission from the core of the source. On the
other hand, a correlation is detected in the tail emission of the outer shell
of 3C 396, which could be ascribed to Galactic contamination.Comment: published in MNRA
Physico-Mechanical Performances of Mortars Prepared with Sorted Earthquake Rubble: The Role of CDW Type and Contained Crystalline Phases
Construction and demolition waste (CDW) from earthquake rubbles was used here as recycled aggregates (RA) in cementitious binders. The materials were sorted in six groups: concrete (CO), natural stone (NS), tile (TI), brick (BR), perforated brick (PF) and roof tile (RT). The abundance (wt.%) of crystalline phases in each RA type was determined by X-ray Powder Diffraction (XRPD). Each group of RAs was used alone (100 wt.% of RA) and mixed with quartz-rich virgin aggregates (VA) to prepare 13 types of mortars (12 specimens per type): one reference mortar (RM) with only VA, six recycled aggregate mortars (RAM) and six recycled-plus-virgin aggregate mortars (RVAM). The physical and mechanical properties of aggregates and mortars reflect the type and abundance of crystalline phases in each CDW group. Recycled mortars rich in concrete, natural stones and tiles have better mechanical performance than mortars prepared with recycled bricks, perforated bricks and roof tiles. For each RA, RVAMs have superior mechanical characteristics than the corresponding RAM. Since the type and amount of phases contained in recycled aggregates strongly control the mechanical performance of new construction materials, they should be routinely quantified as reported here, in addition to other physical features (water absorption, density, etc.). The separation of heterogeneous CDW into homogeneous RA groups is necessary for the production of new construction materials with stable and predictable performances to ensure CDW recycling, especially in areas hit by major adverse events, where large amounts of still valuable materials could be used for reconstruction processes
Energy resolution and efficiency of phonon-mediated Kinetic Inductance Detectors for light detection
The development of sensitive cryogenic light detectors is of primary interest
for bolometric experiments searching for rare events like dark matter
interactions or neutrino-less double beta decay. Thanks to their good energy
resolution and the natural multiplexed read-out, Kinetic Inductance Detectors
(KIDs) are particularly suitable for this purpose. To efficiently couple
KIDs-based light detectors to the large crystals used by the most advanced
bolometric detectors, active surfaces of several cm are needed. For this
reason, we are developing phonon-mediated detectors. In this paper we present
the results obtained with a prototype consisting of four 40 nm thick aluminum
resonators patterned on a 22 cm silicon chip, and calibrated with
optical pulses and X-rays. The detector features a noise resolution
eV and an (182) efficiency.Comment: 5 pages, 5 figure
Electronics and data acquisition demonstrator for a kinetic inductance camera
A prototype of digital frequency multiplexing electronics allowing the real
time monitoring of kinetic inductance detector (KIDs) arrays for mm-wave
astronomy has been developed. It requires only 2 coaxial cables for
instrumenting a large array. For that, an excitation comb of frequencies is
generated and fed through the detector. The direct frequency synthesis and the
data acquisition relies heavily on a large FPGA using parallelized and
pipelined processing. The prototype can instrument 128 resonators (pixels) over
a bandwidth of 125 MHz. This paper describes the technical solution chosen, the
algorithm used and the results obtained
Activated biochars as sustainable and effective supports for hydrogenations
Activated biochars were obtained from pyrolysis and CO2-physical activation of four different biomasses including tannery shaving waste (T), vine wood waste (W), barley waste (B) and Sargassum, brown macroalgae of Venice lagoon (A). The potential of obtained carbonaceous materials as the supports of Ni,Al catalysts was investigated in levulinic acid (LA) conversion to γ-valerolactone (GVL) as a model hydrogenation reaction. Al-containing species as the Lewis acid sites for the dehydration step were incorporated to the supports using wet impregnation or precipitation. Ni as a hydrogenation active phase was added to the supports via wet impregnation. Biochar-based supports and catalysts were characterized by AAS, elemental analysis, FTIR, N2 physisorption, XRD, SEM, EDS, TEM, He-TPD, NH3-TPD and TPR techniques. The catalysts were tested for LA hydrogenation to GVL in a batch system and aqueous medium. The results showed that Ni supported on activated biochar was not active due to a lack of Lewis acid sites for dehydration. Precipitated Al-containing species on the biochar-based supports demonstrated a better catalytic performance in the reaction compared to impregnated one because of different interactions with the support and Ni species. Among different supports, the activated biochars obtained from T and W acted as the best ones. A higher catalytic efficiency was strongly influenced by the chemical (aromaticity and stability, presence of N,O-doped and functional groups), textural (the porous texture and surface area), and morphological (higher dispersion of active phases) properties of activated biochars obtained from different biomasses with different natures
Erythromycin resistance in Streptococcus pyogenes in Italy.
In a prospective study of acute pharyngitis in Italian children, 69 (38.3%) of 180 isolates of Streptococcus pyogenes were resistant to macrolides. S. pyogenes was eradicated in 12 (63.1%) of 19 patients with erythromycin-resistant S. pyogenes treated with clarithromycin and in 22 (88%) of 25 patients with erythromycin-susceptible strains. The constitutive-resistant phenotype was correlated with failure of macrolide treatment
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