2,280 research outputs found
Photodegradation Mechanisms of Tetraphenyl Butadiene Coatings for Liquid Argon Detectors
We report on studies of degradation mechanisms of tetraphenyl butadiene (TPB)
coatings of the type used in neutrino and dark matter liquid argon experiments.
Using gas chromatography coupled to mass spectrometry we have detected the
ultraviolet-blocking impurity benzophenone (BP). We monitored the drop in
performance and increase of benzophenone concentration in TPB plates with
exposure to ultraviolet (UV) light, and demonstrate the correlation between
these two variables. Based on the presence and initially exponential increase
in the concentration of benzophenone observed, we propose that TPB degradation
is a free radical-mediated photooxidation reaction, which is subsequently
confirmed by displaying delayed degradation using a free radical inhibitor.
Finally we show that the performance of wavelength-shifting coatings of the
type envisioned for the LBNE experiment can be improved by 10-20%, with
significantly delayed UV degradation, by using a 20% admixture of
4-tert-Butylcatechol.Comment: 12 pages, 9 figures. Submitted to JINS
An efficient technique of texture representation in segmentation-based image coding schemes
In segmentation-based image coding techniques the image to be compressed is first segmented. Then, the information is coded describing the shape and the interior of the regions. A new method to encode the texture obtained in segmentation-based coding schemes is presented. The approach combines 2-D linear prediction and stochastic vector quantization. To encode a texture, a linear predictor is computed first. Next, a codebook following the prediction error model is generated and the prediction error is encoded with VQ. In the decoder, the error image is decoded first and then filtered as a whole, using the prediction filter. Hence, correlation between pixels is not lost from one block to another and a good reproduction quality can be achieved.Peer ReviewedPostprint (published version
Snake Venomics and Antivenomics of Bothrops diporus, a Medically Important Pitviper in Northeastern Argentina
Snake species within genus Bothrops are responsible for more than 80% of the snakebites occurring in South America. The species that cause most envenomings in Argentina, B. diporus, is widely distributed throughout the country, but principally found in the Northeast, the region with the highest rates of snakebites. The venom proteome of this medically relevant snake was unveiled using a venomic approach. It comprises toxins belonging to fourteen protein families,be ing dominated by PI- and PIII-SVMPs, PLA2 molecules, BPP-like peptides, L-amino acid oxidase and serine proteinases. This toxin profile largely explains the characteristic pathophysiological effects of bothropic snakebites observed in patients envenomed by B. diporus. Antivenomic analysis of the SAB antivenom (Instituto Vital Brazil) against the venom of B. diporus showed that this pentabothropic antivenom efficiently recognized all the venom proteins and exhibited poor affinity towards the small peptide (BPPs and tripeptide inhibitors of PIII-SVMPs) components of the venom.Fil: Gay, Claudia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; ArgentinaFil: Sanz, Libia. Instituto de Biomedicina de Valencia; EspañaFil: Calvete, Juan J.. Instituto de Biomedicina de Valencia; EspañaFil: Pla, Davinia. Instituto de Biomedicina de Valencia; Españ
Statistical Analysis of Genealogical Trees for Polygamic Species
Repetitions within a given genealogical tree provides some information about
the degree of consanguineity of a population. They can be analyzed with
techniques usually employed in statistical physics when dealing with fixed
point transformations. In particular we show that the tree features strongly
depend on the fractions of males and females in the population, and also on the
offspring probability distribution. We check different possibilities, some of
them relevant to human groups, and compare them with simulations.Comment: 2 eps figs, Fig.2 changed to meet cond-mat size criteri
Bartolomé de las CASAS: Brevísima relación de la destruición de las Indias. (Edición, estudio y notas de José Miguel Martínez Torrejón)
Exploring quantum chaos with a single nuclear spin
Most classical dynamical systems are chaotic. The trajectories of two
identical systems prepared in infinitesimally different initial conditions
diverge exponentially with time. Quantum systems, instead, exhibit
quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of
quantum systems whose classical counterparts are chaotic are expected to show
some features that resemble chaotic motion. Among the many controversial
aspects of the quantum-classical boundary, the emergence of chaos remains among
the least experimentally verified. Time-resolved observations of quantum
chaotic dynamics are particularly rare, and as yet unachieved in a single
particle, where the subtle interplay between chaos and quantum measurement
could be explored at its deepest levels. We present here a realistic proposal
to construct a chaotic driven top from the nuclear spin of a single donor atom
in silicon, in the presence of a nuclear quadrupole interaction. This system is
exquisitely measurable and controllable, and possesses extremely long intrinsic
quantum coherence times, allowing for the observation of subtle dynamical
behavior over extended periods. We show that signatures of chaos are expected
to arise for experimentally realizable parameters of the system, allowing the
study of the relation between quantum decoherence and classical chaos, and the
observation of dynamical tunneling.Comment: revised and published versio
The Golden Channel at a Neutrino Factory revisited: improved sensitivities from a Magnetised Iron Neutrino Detector
This paper describes the performance and sensitivity to neutrino mixing
parameters of a Magnetised Iron Neutrino Detector (MIND) at a Neutrino Factory
with a neutrino beam created from the decay of 10 GeV muons. Specifically, it
is concerned with the ability of such a detector to detect muons of the
opposite sign to those stored (wrong-sign muons) while suppressing
contamination of the signal from the interactions of other neutrino species in
the beam. A new more realistic simulation and analysis, which improves the
efficiency of this detector at low energies, has been developed using the GENIE
neutrino event generator and the GEANT4 simulation toolkit. Low energy neutrino
events down to 1 GeV were selected, while reducing backgrounds to the
level. Signal efficiency plateaus of ~60% for and ~70% for
events were achieved starting at ~5 GeV. Contamination from the
oscillation channel was studied for the first
time and was found to be at the level between 1% and 4%. Full response matrices
are supplied for all the signal and background channels from 1 GeV to 10 GeV.
The sensitivity of an experiment involving a MIND detector of 100 ktonnes at
2000 km from the Neutrino Factory is calculated for the case of . For this value of , the accuracy in the
measurement of the CP violating phase is estimated to be , depending on the value of ,
the CP coverage at is 85% and the mass hierarchy would be determined
with better than level for all values of
Seawater intrusion and coastal groundwater resources management. Examples from two Mediterranean regions: Catalonia and Sardinia
Seawater intrusion is a natural phenomenon that allows the encroachment of saline water into aquifers. Nevertheless, many human actions along the coastline, in particular groundwater withdrawal, enhance this process and finally cause the salinization of groundwater resources. Here we review the hydrogeological basis of seawater intrusion and describe specific cases in Catalonia and Sardinia, as examples of environmental problems and water management actions. We emphasize the origin of salinization and the hydrogeological details of each case, as well as the solutions that have been implemented to prevent groundwater salinization
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