169 research outputs found
Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber
Scintillation light produced in liquid xenon (LXe) by alpha particles,
electrons and gamma-rays was detected with a large area avalanche photodiode
(LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a
function of applied electric field. We estimate the quantum efficiency of the
LAAPD to be 45%. The best energy resolution from the light measurement at zero
electric field is 7.5%(sigma) for 976 keV internal conversion electrons from
Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector
used for these measurements was also operated as a gridded ionization chamber
to measure the charge yield. We confirm that using a LAAPD in LXe does not
introduce impurities which inhibit the drifting of free electrons.Comment: 13 pages, 8 figure
Secondary scintillation yield in high-pressure xenon gas for neutrinoless double beta decay (0νββ) search
AbstractThe search for neutrinoless double beta decay (0νββ) is an important topic in contemporary physics with many active experiments. New projects are planning to use high-pressure xenon gas as both source and detection medium. The secondary scintillation processes available in noble gases permit large amplification with negligible statistical fluctuations, offering the prospect of energy resolution approaching the Fano factor limit. This Letter reports results for xenon secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap for pressures ranging from 2 to 10 bar. A Large Area Avalanche Photodiode (LAAPD) collected the VUV secondary scintillation produced in the gas. X-rays directly absorbed in the LAAPD are used as a reference for determining the number of charge carriers produced by the scintillation pulse and, hence, the number of photons impinging the LAAPD. The number of photons produced per drifting electron and per kilovolt, the so-called scintillation amplification parameter, displays a small increase with pressure, ranging from 141±6 at 2 bar to 170±10 at 8 bar. In our setup, this parameter does not increase above 8 bar due to non-negligible electron attachment. The results are in good agreement with those presented in the literature in the 1 to 3 bar range. The increase of the scintillation amplification parameter with pressure for high gas densities has been also observed in former work at cryogenic temperatures
Influence of dietary Chlorella vulgaris and carbohydrate-active enzymes on growth performance, meat quality and lipid composition of broiler chickens
Article in pressHerein, we investigated the effect of
Chlorella vulgaris as ingredient (10% of incorporation) in
broiler diets, supplemented or not with 2 formulations of
Carbohydrate-Active enZymes (CAZymes; Rovabio
Excel AP and a mixture of recombinant CAZymes,
composed by an exo-b-glucosaminidase, an alginate
lyase, a peptidoglycan N-acetylmuramic acid deacetylase
and a lysozyme), on growth performance, meat quality,
fatty acid composition, oxidative stability, and sensory
traits. One hundred twenty 1-day-old Ross 308 male birds
were randomly assigned to one of the 4 experimental diets
(n 5 30): corn-soybean meal–basal diet (control), basal
diet with 10% C. vulgaris (CV), CV supplemented with
0.005% of a commercialCAZymecocktail (Rovabio Excel
AP), (CV1R), and CV supplemented with 0.01% of a 4-
CAZyme mixture previously selected (CV 1 M) during
the experimental period lasted from day 21 to day 35.
Body weight gain and feed conversion rate of broilers were
not affected by C. vulgaris but digesta viscosity increased more than 2-fold (P , 0.001) relative to the control. In
addition, neither cooking loss, shear force, juiciness, flavor
nor off-flavor was impaired by dietary treatments
(P.0.05). By contrast, the dietary C. vulgaris increased
tenderness, yellowness (b*) and total carotenoids in
breast and thigh meats. However, no additional protective
effect against lipid oxidation was observed in meat
with the inclusion of microalga. Chlorella vulgaris, independently
of CAZymes, had a minor impact on meat fatty
acid composition but improved the proportion of some
beneficial fatty acids. In summary, our data indicate a
slight improvement of broiler meat quality and lipid
nutritional value, without impairment of broilers’ growth
performance, thus supporting the usefulness of this
microalga in poultry diets, up to this high level of incorporation.
By contrast, the selected CAZyme mixtures
used do not significantly improve the release of microalga
nutrients in poultry diets, through the disruption of
microalga cell wall, which warrants further researchinfo:eu-repo/semantics/acceptedVersio
The scintillation and ionization yield of liquid xenon for nuclear recoils
XENON10 is an experiment designed to directly detect particle dark matter. It
is a dual phase (liquid/gas) xenon time-projection chamber with 3D position
imaging. Particle interactions generate a primary scintillation signal (S1) and
ionization signal (S2), which are both functions of the deposited recoil energy
and the incident particle type. We present a new precision measurement of the
relative scintillation yield \leff and the absolute ionization yield Q_y, for
nuclear recoils in xenon. A dark matter particle is expected to deposit energy
by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for
establishing the energy threshold of the experiment; this in turn determines
the sensitivity to particle dark matter. Our \leff measurement is in agreement
with recent theoretical predictions above 15 keV nuclear recoil energy, and the
energy threshold of the measurement is 4 keV. A knowledge of the ionization
yield \Qy is necessary to establish the trigger threshold of the experiment.
The ionization yield \Qy is measured in two ways, both in agreement with
previous measurements and with a factor of 10 lower energy threshold.Comment: 8 pages, 9 figures. To be published in Nucl. Instrum. Methods
Material screening and selection for XENON100
Results of the extensive radioactivity screening campaign to identify
materials for the construction of XENON100 are reported. This Dark Matter
search experiment is operated underground at Laboratori Nazionali del Gran
Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors
(HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been
applied for a few low mass plastic samples. Detailed tables with the
radioactive contaminations of all screened samples are presented, together with
the implications for XENON100.Comment: 8 pages, 1 figur
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
CsI-THGEM gaseous photomultipliers for RICH and noble-liquid detectors
The properties of UV-photon imaging detectors consisting of CsI-coated THGEM
electron multipliers are summarized. New results related to detection of
Cherenkov light (RICH) and scintillation photons in noble liquid are presented.Comment: 5 Pages, 10 Figures; Presented at the 7th International Workshop on
Ring Imaging Cherenkov Detectors (RICH 2010) RICH2010 - Cassis, Provence,
France, 3-7 May 201
Analysis of the XENON100 Dark Matter Search Data
The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso,
aims at the direct detection of dark matter in the form of weakly interacting
massive particles (WIMPs), based on their interactions with xenon nuclei in an
ultra low background dual-phase time projection chamber. This paper describes
the general methods developed for the analysis of the XENON100 data. These
methods have been used in the 100.9 and 224.6 live days science runs from which
results on spin-independent elastic, spin-dependent elastic and inelastic
WIMP-nucleon cross-sections have already been reported.Comment: 18 pages, 17 figures, information for the 224.6 live days run
include
The Lamb shift in muonic hydrogen and the proton radius
By means of pulsed laser spectroscopy applied to muonic hydrogen (μ− p) we have measured the 2S F = 1 1/2 − 2PF = 2 3/2 transition frequency to be 49881.88(76) GHz. By comparing this measurement with its theoretical prediction based on bound-state QED we have determined a proton radius value of rp = 0.84184 (67) fm. This new value is an order of magnitude preciser than previous results but disagrees by 5 standard deviations from the CODATA and the electronproton scattering values. An overview of the present effort attempting to solve the observed discrepancy is given. Using the measured isotope shift of the 1S-2S transition in regular hydrogen and deuterium also the rms charge radius of the deuteron rd = 2.12809 (31) fm has been determined. Moreover we present here the motivations for the measurements of the μ 4He + and μ 3He + 2S-2P splittings. The alpha and triton charge radii are extracted from these measurements with relative accuracies of few 10 − 4. Measurements could help to solve the observed discrepancy, lead to the best test of hydrogen-like energy levels and provide crucial tests for few-nucleon ab-initio theories and potentials
Impact of dietary incorporation of Spirulina (Arthrospira platensis) and exogenous enzymes on broiler performance, carcass traits and meat quality
This study assessed the effect of Spirulina
(Arthrospira platensis), individually and in combination
with exogenous enzymes, on growth
performance, carcass traits, and meat quality of broiler
chickens. One hundred and twenty Ross 308 male
chickens were allocated into 40 battery brooders, with 3
birds per cage, and fed ad libitum a corn-based diet
during the first 21 D of the trial. The experimental period
lasted from day 21 to 35, during which birds were fed 4
different diets: a corn-soybean basal diet, taken as the
control group, a basal diet containing 15% Spirulina
(MA), a basal diet containing 15% Spirulina plus 0.005%
Rovabio Excel AP (MAR), and a basal diet containing
15% Spirulina plus 0.01% lysozyme (MAL). Body weight
gain (P , 0.001) and feed conversion rate (P , 0.001)
were improved in control chickens, when compared with
those fed with Spirulina. In addition, Spirulina increased
the length of duodenum plus jejunum in relation to the
other treatment (P , 0.01). Chickens on the MAL diet showed a considerable increase in digesta viscosity
(P , 0.05) compared with the control group. Breast and
thigh meats from chickens fed with Spirulina, with or
without the addition of exogenous enzymes, had higher
values of yellowness (b*) (P , 0.001), total carotenoids
(P , 0.001), and saturated fatty acids (P , 0.001),
whereas n-3 polyunsaturated fatty acid (P , 0.01) and
a-tocopherol (P , 0.001) decreased, when compared
with the control. In conclusion, the incorporation of 15%
Spirulina in broiler diets, individually or combined with
exogenous enzymes, reduced birds’ performance through
a higher digesta viscosity, which is likely associated with
the gelation of microalga indigestible proteins. In addition,
cell wall of Spirulina was successfully broken by the
addition of lysozyme, but not by Rovabio Excel AP.
Therefore, we anticipate that the combination of lysozyme
with an exogenous specific peptidase could improve
the digestibility of proteins from this microalga and
avoid their detrimental gelationinfo:eu-repo/semantics/publishedVersio
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