367 research outputs found
Development of Lumped Element Kinetic Inductance Detectors for the W-Band
We are developing a Lumped Element Kinetic Inductance Detector (LEKID) array
able to operate in the W-band (75-110 GHz) in order to perform ground-based
Cosmic Microwave Background (CMB) and mm-wave astronomical observations. The
W-band is close to optimal in terms of contamination of the CMB from Galactic
synchrotron, free-free, and thermal interstellar dust. In this band, the
atmosphere has very good transparency, allowing interesting ground-based
observations with large (>30 m) telescopes, achieving high angular resolution
(<0.4 arcmin). In this work we describe the startup measurements devoted to the
optimization of a W-band camera/spectrometer prototype for large aperture
telescopes like the 64 m SRT (Sardinia Radio Telescope). In the process of
selecting the best superconducting film for the LEKID, we characterized a 40 nm
thick Aluminum 2-pixel array. We measured the minimum frequency able to break
CPs (i.e. ) obtaining
GHz, that corresponds to a critical temperature of 1.31 K. This is not suitable
to cover the entire W-band. For an 80 nm layer the minimum frequency decreases
to 93.2 GHz, which corresponds to a critical temperature of 1.28 K; this value
is still suboptimal for W-band operation. Further increase of the Al film
thickness results in bad performance of the detector. We have thus considered a
Titanium-Aluminum bi-layer (10 nm thick Ti + 25 nm thick Al, already tested in
other laboratories), for which we measured a critical temperature of 820 mK and
a cut-on frequency of 65 GHz: so this solution allows operation in the entire
W-band.Comment: 16th International Workshop on Low Temperature Detectors, Grenoble
20-24 July 2015, Journal of Low Temperature Physics, Accepte
Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms
Leaching experiments were carried out on fresh ash samples from Popocatépetl 2012, Etna 2011, and Etna 2012 eruptions, in order to investigate the release of compounds in both double-deionized and lake (Lake Ohrid, FYR of Macedonia) waters. The experiments were carried out using different grain sizes and variable stirring times (from 30 min to 7 days). Results were discussed in the light of changing pH and release of compounds for the different leachates. In particular, Etna samples induced alkalinization, and Popocatépetl samples induced acidification of the corresponding leachates. The release of different elements does not show correlation with the stirring time, with the measured maximum concentrations reached in the first hours of washing. General inverse correlation with grain size was observed only for Na+, K+, Cl-, Ca2+, Mg2+, SO2-4 , and Mn2+, while the other analysed elements show a complex, scattering relationship with grain size. Geochemical modelling highlights leachates' saturation only for F and Si, with Popocatépetl samples sometimes showing saturation in Fe. The analysed leachates are classified as undrinkable for humans on the basis of European laws, due to excess in F-, Mn2+, Fe, and SO2-4 (the latter only for Popocatépetl samples). Finally, the Etna 2012 and Popocatépetl leachates were used for toxicity experiments on living biota (Xenopus laevis). They are mildly toxic, and no significant differences exist between the toxic profiles of the two leachates. In particular, no significant embryo mortality was observed; while even at high dilutions, the leachates produced more than 20% of malformed larvae
Lumped element kinetic inductance detectors maturity for space-borne instruments in the range between 80 and 180 GHz
This work intends to give the state-of-the-art of our knowledge of the
performance of LEKIDs at millimetre wavelengths (from 80 to 180~GHz). We
evaluate their optical sensitivity under typical background conditions and
their interaction with ionising particles. Two LEKID arrays, originally
designed for ground-based applications and composed of a few hundred pixels
each, operate at a central frequency of 100, and 150~GHz (
about 0.3). Their sensitivities have been characterised in the laboratory using
a dedicated closed-circle 100~mK dilution cryostat and a sky simulator,
allowing for the reproduction of realistic, space-like observation conditions.
The impact of cosmic rays has been evaluated by exposing the LEKID arrays to
alpha particles (Am) and X sources (Cd) with a readout sampling
frequency similar to the ones used for Planck HFI (about 200~Hz), and also with
a high resolution sampling level (up to 2~MHz) in order to better characterise
and interpret the observed glitches. In parallel, we have developed an
analytical model to rescale the results to what would be observed by such a
LEKID array at the second Lagrangian point.Comment: 7 pages, 2 tables, 13 figure
Analysis of four new enterococcus faecalis phages and modeling of a hyaluronidase catalytic domain from saphexavirus
Background: Phage therapy (PT), as a method to treat bacterial infections, needs identification of bacteriophages targeting specific pathogenic host. Enterococcus faecalis, a Gram-positive coccus resident in the human gastrointestinal tract, may become pathogenic in hospitalized patients showing acquired resistance to vancomycin and thus representing a possible target for PT. Materials and Methods: We isolated four phages that infect E. faecalis and characterized them by host range screening, transmission electron microscopy, and genome sequencing. We also identified and three-dimensional modeled a new hyaluronidase enzyme. Results: The four phages belong to Siphoviridae family: three Efquatrovirus (namely vB_EfaS_TV51, vB_EfaS_TV54, and vB_EfaS_TV217) and one Saphexavirus (vB_EfaS_TV16). All of them are compatible with lytic cycle. vB_EfaS_TV16 moreover presents a gene encoding for a hyaluronidase enzyme. Conclusions: The identified phages show features suggesting their useful application in PT, particularly the Saphexavirus that may be of enhanced relevance in PT because of its potential biofilm-digestion capability
The genomic organisation of the tra/trd locus validates the peculiar characteristics of dromedary δ-chain expression
The role of γδ T cells in vertebrate immunity is still an unsolved puzzle. Species such as humans and mice display a low percentage of these T lymphocytes (i.e., “γδ low species”) with a restricted diversity of γδ T cell receptors (TR). Conversely, artiodactyl species (i.e., “γδ high species”) account for a high proportion of γδ T cells with large γ and δ chain repertoires. The genomic organisation of the TR γ (TRG) and δ (TRD) loci has been determined in sheep and cattle, noting that a wide number of germline genes that encode for γ and δ chains characterise their genomes. Taking advantage of the current improved version of the genome assembly, we have investigated the genomic structure and gene content of the dromedary TRD locus, which, as in the other mammalian species, is nested within the TR α (TRA) genes. The most remarkable finding was the identification of a very limited number of variable germline genes (TRDV) compared to sheep and cattle, which supports our previous expression analyses for which the somatic hypermutation mechanism is able to enlarge and diversify the primary repertoire of dromedary δ chains. Furthermore, the comparison between genomic and expressed sequences reveals that D genes, up to four incorporated in a transcript, greatly contribute to the increased diversity of the dromedary δ chain antigen binding-site
New application of superconductors: high sensitivity cryogenic light detectors
In this paper we describe the current status of the CALDER project, which is
developing ultra-sensitive light detectors based on superconductors for
cryogenic applications. When we apply an AC current to a superconductor, the
Cooper pairs oscillate and acquire kinetic inductance, that can be measured by
inserting the superconductor in a LC circuit with high merit factor.
Interactions in the superconductor can break the Cooper pairs, causing sizable
variations in the kinetic inductance and, thus, in the response of the LC
circuit. The continuous monitoring of the amplitude and frequency modulation
allows to reconstruct the incident energy with excellent sensitivity. This
concept is at the basis of Kinetic Inductance Detectors (KIDs), that are
characterized by natural aptitude to multiplexed read-out (several sensors can
be tuned to different resonant frequencies and coupled to the same line),
resolution of few eV, stable behavior over a wide temperature range, and ease
in fabrication. We present the results obtained by the CALDER collaboration
with 2x2 cm2 substrates sampled by 1 or 4 Aluminum KIDs. We show that the
performances of the first prototypes are already competitive with those of
other commonly used light detectors, and we discuss the strategies for a
further improvement
Characterization of the KID-Based Light Detectors of CALDER
The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution
(CALDER) project is the development of light detectors with active area of
cm and noise energy resolution smaller than 20 eV RMS,
implementing phonon-mediated kinetic inductance detectors. The detectors are
developed to improve the background suppression in large-mass bolometric
experiments such as CUORE, via the double read-out of the light and the heat
released by particles interacting in the bolometers. In this work, we present
the characterization of the first light detectors developed by CALDER. We
describe the analysis tools to evaluate the resonator parameters (resonant
frequency and quality factors) taking into account simultaneously all the
resonance distortions introduced by the read-out chain (as the feed-line
impedance and its mismatch) and by the power stored in the resonator itself. We
detail the method for the selection of the optimal point for the detector
operation (maximizing the signal-to-noise ratio). Finally, we present the
response of the detector to optical pulses in the energy range of 0-30 keV
Genomic segmental duplications on the basis of the t(9;22) rearrangement in chronic myeloid leukemia
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High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out
The development of wide-area cryogenic light detectors with good energy
resolution is one of the priorities of next generation bolometric experiments
searching for rare interactions, as the simultaneous read-out of the light and
heat signals enables background suppression through particle identification.
Among the proposed technological approaches for the phonon sensor, the
naturally-multiplexed Kinetic Inductance Detectors (KIDs) stand out for their
excellent intrinsic energy resolution and reproducibility. To satisfy the large
surface requirement (several cm) KIDs are deposited on an insulating
substrate that converts the impinging photons into phonons. A fraction of
phonons is absorbed by the KID, producing a signal proportional to the energy
of the original photons. The potential of this technique was proved by the
CALDER project, that reached a baseline resolution of 1547 eV RMS by
sampling a 22 cm Silicon substrate with 4 Aluminum KIDs. In this
paper we present a prototype of Aluminum KID with improved geometry and quality
factor. The design improvement, as well as the combined analysis of amplitude
and phase signals, allowed to reach a baseline resolution of 824 eV by
sampling the same substrate with a single Aluminum KID
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