A
bstract
The
Neutrino Experiment with a Xenon TPC
(NEXT) searches for the neutrinoless double-beta (0
νββ
) decay of
136
Xe using high-pressure xenon gas TPCs with electroluminescent amplification. ...A scaled-up version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0
νββ
decay better than 10
27
years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
The present study aimed to analyze the behavior of different activated carbons in the adsorption and removal of bisphenol A (2−2-bis-4-hydroxypheniyl propane) from aqueous solutions in order to ...identify the parameters that determine this process. Two commercial activated carbons and one prepared in our laboratory from almond shells were used; they were texturally and chemically characterized, obtaining the surface area, pore size distribution, mineral matter content, elemental analysis, oxygen surface groups, and pH of the point of zero charge (pHPZC), among other parameters. Adsorption isotherms of bisphenol A and adsorption capacities were obtained. The capacity of the carbons to remove bisphenol A was related to their characteristics. Thus, the adsorption of bisphenol A on activated carbon fundamentally depends on the chemical nature of the carbon surface and the pH of the solution. The most favorable experimental conditions for this process are those in which the net charge density of the carbon is zero and the bisphenol A is in molecular form. Under these conditions, the adsorbent−adsorbate interactions that govern the adsorption mechanism are enhanced. Influences of the mineral matter present in the carbon samples and the solution chemistry (pH and ionic strength) were also analyzed. The presence of mineral matter in carbons reduces their adsorption capacity because of the hydrophilic nature of the matter. The presence of electrolytes in the solution favor the adsorption process because of the screening effect produced between the positively charged carbon surface and the bisphenol A molecules, with a resulting increase in adsorbent−adsorbate interactions.
A
bstract
The NEXT experiment aims at searching for the hypothetical neutrinoless double-beta decay from the
136
Xe isotope using a high-purity xenon TPC. Efficient discrimination of the events ...through pattern recognition of the topology of primary ionisation tracks is a major requirement for the experiment. However, it is limited by the diffusion of electrons. It is known that the addition of a small fraction of a molecular gas to xenon reduces electron diffusion. On the other hand, the electroluminescence (EL) yield drops and the achievable energy resolution may be compromised. We have studied the effect of adding several molecular gases to xenon (CO
2
, CH
4
and CF
4
) on the EL yield and energy resolution obtained in a small prototype of driftless gas proportional scintillation counter. We have compared our results on the scintillation characteristics (EL yield and energy resolution) with a microscopic simulation, obtaining the diffusion coefficients in those conditions as well. Accordingly, electron diffusion may be reduced from about 10 mm/
m
for pure xenon down to 2.5 mm/
m
using additive concentrations of about 0.05%, 0.2% and 0.02% for CO
2
, CH
4
and CF
4
, respectively. Our results show that CF
4
admixtures present the highest EL yield in those conditions, but very poor energy resolution as a result of huge fluctuations observed in the EL formation. CH
4
presents the best energy resolution despite the EL yield being the lowest. The results obtained with xenon admixtures are extrapolated to the operational conditions of the NEXT-100 TPC. CO
2
and CH
4
show potential as molecular additives in a large xenon TPC. While CO
2
has some operational constraints, making it difficult to be used in a large TPC, CH
4
shows the best performance and stability as molecular additive to be used in the NEXT-100 TPC, with an extrapolated energy resolution of 0.4% at 2.45 MeV for concentrations below 0.4%, which is only slightly worse than the one obtained for pure xenon. We demonstrate the possibility to have an electroluminescence TPC operating very close to the thermal diffusion limit without jeopardizing the TPC performance, if CO
2
or CH
4
are chosen as additives.
A
bstract
The measurement of the internal
222
Rn activity in the NEXT-White detector during the so-called Run-II period with
136
Xe-depleted xenon is discussed in detail, together with its ...implications for double beta decay searches in NEXT. The activity is measured through the alpha production rate induced in the fiducial volume by
222
Rn and its alpha-emitting progeny. The specific activity is measured to be (38.1 ± 2.2 (stat.) ± 5.9 (syst.)) mBq/m
3
. Radon-induced electrons have also been characterized from the decay of the
214
Bi daughter ions plating out on the cathode of the time projection chamber. From our studies, we conclude that radon-induced backgrounds are sufficiently low to enable a successful NEXT-100 physics program, as the projected rate contribution should not exceed 0.1 counts/yr in the neutrinoless double beta decay sample.
A
bstract
Natural radioactivity represents one of the main backgrounds in the search for neutrinoless double beta decay. Within the NEXT physics program, the radioactivity- induced backgrounds are ...measured with the NEXT-White detector. Data from 37.9 days of low-background operations at the Laboratorio Subterráneo de Canfranc with xenon depleted in
136
Xe are analyzed to derive a total background rate of (0.84
±
0.02) mHz above 1000 keV. The comparison of data samples with and without the use of the radon abatement system demonstrates that the contribution of airborne-Rn is negligible. A radiogenic background model is built upon the extensive radiopurity screening campaign conducted by the NEXT collaboration. A spectral fit to this model yields the specific contributions of
60
Co,
40
K,
214
Bi and
208
Tl to the total background rate, as well as their location in the detector volumes. The results are used to evaluate the impact of the radiogenic backgrounds in the double beta decay analyses, after the application of topological cuts that reduce the total rate to (0.25
±
0.01) mHz. Based on the best-fit background model, the NEXT-White median sensitivity to the two-neutrino double beta decay is found to be 3.5
σ
after 1 year of data taking. The background measurement in a Q
ββ
±
100 keV energy window validates the best-fit background model also for the neutrinoless double beta decay search with NEXT-100. Only one event is found, while the model expectation is (0.75
±
0.12) events.
A
bstract
In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore ...improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a
228
Th calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of 71
.
6
±
1
.
5
stat
±
0
.
3
sys
% for a background acceptance of 20
.
6
±
0
.
4
stat
±
0
.
3
sys
% is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies.
We report a series of 1,3-diphenylureido hydroxamate HDAC inhibitors evaluated against sensitive and drug-resistant P. falciparum strains. Compounds 8a-d show potent antiplasmodial activity, ...indicating that a phenyl spacer allows improved potency relative to cinnamyl and di-hydrocinnamyl linkers. In vitro, mechanistic studies demonstrated target activity for PfHDAC1 on a recombinant level, which agreed with cell quantification of the acetylated histone levels. Compounds 6c, 7c, and 8c, identified as the most active in phenotypic assays and PfHDAC1 enzymatic inhibition. Compound 8c stands out as a remarkable inhibitor, displaying an impressive 85% inhibition of PfHDAC1, with an IC
value of 0.74 µM in the phenotypic screening on Pf3D7 and 0.8 µM against multidrug-resistant PfDd2 parasites. Despite its potent inhibition of PfHDAC1, 8c remains the least active on human HDAC1, displaying remarkable selectivity. In silico studies suggest that the phenyl linker has an ideal length in the series for permitting effective interactions of the hydroxamate with PfHDAC1 and that this compound series could bind as well as in HsHDAC1. Taken together, these results highlight the potential of diphenylurea hydroxamates as a privileged scaffold for the generation of potent antimalarial HDAC inhibitors with improved selectivity over human HDACs.
A
bstract
The NEXT experiment aims at the sensitive search of the neutrinoless double beta decay in
136
Xe, using high-pressure gas electroluminescent time projection chambers. The NEXT-White ...detector is the first radiopure demonstrator of this technology, operated in the Laboratorio Subterráneo de Canfranc. Achieving an energy resolution of 1% FWHM at 2.6 MeV and further background rejection by means of the topology of the reconstructed tracks, NEXT-White has been exploited beyond its original goals in order to perform a neu- trinoless double beta decay search. The analysis considers the combination of 271.6 days of
136
Xe-enriched data and 208.9 days of
136
Xe-depleted data. A detailed background modeling and measurement has been developed, ensuring the time stability of the radiogenic and cosmogenic contributions across both data samples. Limits to the neutrinoless mode are obtained in two alternative analyses: a background-model-dependent approach and a novel direct background-subtraction technique, offering results with small dependence on the background model assumptions. With a fiducial mass of only 3.50 ± 0.01 kg of
136
Xe-enriched xenon, 90% C.L. lower limits to the neutrinoless double beta decay are found in the
T
1
/
2
0
ν
> 5
.
5
×
10
23
−
1
.
3
×
10
24
yr range, depending on the method. The presented techniques stand as a proof-of-concept for the searches to be implemented with larger NEXT detectors.
A
bstract
The NEXT experiment aims to observe the neutrinoless double beta decay of
136
Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. One ...of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to
Q
ββ
. This paper presents the first demonstration that the topology provides extra handles to reject background events using data obtained with the NEXT-DEMO prototype.
Single electrons resulting from the interactions of
22
Na 1275 keV gammas and electronpositron pairs produced by conversions of gammas from the
228
Th decay chain were used to represent the background and the signal in a double beta decay. These data were used to develop algorithms for the reconstruction of tracks and the identification of the energy deposited at the end-points, providing an extra background rejection factor of 24
.
3 ± 1
.
4 (stat.)%, while maintaining an efficiency of 66
.
7 ± 1
.
% for signal events.
Peru had the second-highest number of COVID-19 cases in Latin America. After the first wave, Peru registered more than 900,000 cases of COVID-19 and more than 36,000 confirmed deaths from the ...disease. Tumbes, a border area with poor sanitation and not enough water, had the fifth highest death rate. The cross-sectional analytic study aimed: a) to assess seroprevalence of COVID-19 after the first wave; b) to assess sociodemographic determinants and symptoms associated with a positive COVID-19 antibody lateral flow test.
We performed this study between November 11th and November 30th, 2020, in an informal settlement in Tumbes. Individuals older than two years were invited to participate in a systematic random sample from one in every four households. Finger-prick blood samples were collected, and a census and symptom survey were applied. Within the chosen house, one adult over 18 years of age was chosen for a PCR-RT molecular test. Overall seroprevalence was 25.59%, adjusted seroprevalence was 24.82% (95%CI 22.49-27.25). Women had higher adjusted seroprevalence (28.03% vs 21.11%; 95% CI 24.83-31.41, p = 0.002). Symptoms as fever (PR 1.89: 95% CI 1.44-2.48, p<0.001), general discomfort (PR 1.67; 95% CI 1.23-2.26, p = 0.001), cough (PR 2.0; 95% CI 1.60-2.50, p<0.001), nasal congestion (PR 1.46; 95% CI 1.03-2.09, p = 0.036), respiratory distress (PR 1.64; 95% CI 1.04-2.56, p = 0.031), headache (PR 1.54; 95% CI 1.09-2.17, p = 0.014), anosmia (PR 1.78; 95% CI 1.01-3.14, p = 0.046) and ageusia (PR 2.31; 95% CI 1.48-3.61, p<0.001) were associated with a positive covid-19 antibody lateral flow test.
The COVID-19 transmission and distribution were highlighted by this cross-sectional study. The data will help the Ministry of Health improve its monitoring, surveillance, and monitoring of respiratory community sequelae in the future.
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