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1.
Phys Rev Lett ; 124(23): 232502, 2020 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-32603173

RESUMO

We report on a comparison between the theoretically predicted and experimentally measured spectra of the first-forbidden nonunique ß-decay transition ^{137}Xe(7/2^{-})→^{137}Cs(7/2^{+}). The experimental data were acquired by the EXO-200 experiment during a deployment of an AmBe neutron source. The ultralow background environment of EXO-200, together with dedicated source deployment and analysis procedures, allowed for collection of a pure sample of the decays, with an estimated signal to background ratio of more than 99 to 1 in the energy range from 1075 to 4175 keV. In addition to providing a rare and accurate measurement of the first-forbidden nonunique ß-decay shape, this work constitutes a novel test of the calculated electron spectral shapes in the context of the reactor antineutrino anomaly and spectral bump.

2.
Phys Rev Lett ; 123(16): 161802, 2019 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-31702371

RESUMO

A search for neutrinoless double-ß decay (0νßß) in ^{136}Xe is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νßß and background events. Relative to previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of ^{136}Xe 0νßß has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νßß half-life sensitivity for this analysis is 5.0×10^{25} yr with a total ^{136}Xe exposure of 234.1 kg yr. No statistically significant evidence for 0νßß is observed, leading to a lower limit on the 0νßß half-life of 3.5×10^{25} yr at the 90% confidence level.

3.
Phys Rev Lett ; 120(7): 072701, 2018 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-29542972

RESUMO

Results from a search for neutrinoless double-beta decay (0νßß) of ^{136}Xe are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by EXO-200, the energy resolution of the detector has been improved to σ/E=1.23%, the electric field in the drift region has been raised by 50%, and a system to suppress radon in the volume between the cryostat and lead shielding has been implemented. In addition, analysis techniques that improve topological discrimination between 0νßß and background events have been developed. Incorporating these hardware and analysis improvements, the median 90% confidence level 0νßß half-life sensitivity after combining with the full data set acquired before the upgrade has increased twofold to 3.7×10^{25} yr. No statistically significant evidence for 0νßß is observed, leading to a lower limit on the 0νßß half-life of 1.8×10^{25} yr at the 90% confidence level.

4.
Phys Rev Lett ; 109(3): 032505, 2012 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-22861843

RESUMO

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3) kg(-1) yr(-1) keV(-1) in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νßß)(136Xe)>1.6×10(25) yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.

5.
Phys Rev Lett ; 107(21): 212501, 2011 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-22181874

RESUMO

We report the observation of two-neutrino double-beta decay in (136)Xe with T(1/2) = 2.11 ± 0.04(stat) ± 0.21(syst) × 10(21) yr. This second-order process, predicted by the standard model, has been observed for several nuclei but not for (136)Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrinoless double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale.

6.
Maturitas ; 50(3): 177-81, 2005 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-15734598

RESUMO

OBJECTIVES: The endometrium carcinoma is the most frequent malignancy of the female genital tract. Approximately, 10-20% of all patients with an endometrial carcinoma are free of symptoms until the time of diagnosis. The frequent occurrence of an endometrial carcinoma in connection with intrauterine cavity fluid collection (sero- or mucometra) has been discussed controversially in literature. What are the hysteroscopic and histological findings in patients with sonographically determined endometrial fluid in postmenopause, and how should these findings be interpreted? METHODS: 74 patients, in whom endometrial fluid without bleeding disorders had been diagnosed during routine transvaginal sonography, underwent hysteroscopy conducted with a 4.5 mm optics and dilatation and curettage (D&C). The median age of the patients was 68 years with a range of 32 years. RESULTS: The simple thickness of the endometrium, i.e. single layer measured sonographically at the point of maximal thickness, was on average 5.7 mm +/- 3.6 mm (2-15 mm). Hysteroscopically, an endometrium polyp was found in 23 cases (31.1%), endometrium hyperplasia in 12 (16.2%), and an atrophy in 35 cases (47.3%). In four cases (5.4%), an endometrial carcinoma was suspected. The histological results were consistent with the hysteroscopic findings. In all instances, in which the simple endometrial thickness amounted to 3 mm or less, an atrophic endometrium was found. The frequency of intrauterine pathologies increased significantly with a greater thickness of the endometrium. In 80% of patients, a cervical stenosis existed. CONCLUSIONS: Endometrial fluid by itself, without assessment of the endometrium, does not indicate the requirement for additional histological clarification. As diagnostics, the authors suggest especially the endometrial morphology.


Assuntos
Líquidos Corporais , Dilatação e Curetagem , Endométrio/patologia , Histeroscopia , Pós-Menopausa , Idoso , Idoso de 80 Anos ou mais , Atrofia/diagnóstico , Carcinoma/diagnóstico , Colo do Útero/patologia , Constrição Patológica/diagnóstico , Hiperplasia Endometrial/diagnóstico , Neoplasias do Endométrio/diagnóstico , Feminino , Humanos , Pessoa de Meia-Idade , Pólipos/diagnóstico , Sensibilidade e Especificidade
7.
Anticancer Res ; 20(6D): 5069-72, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11326670

RESUMO

The relationship between apoptosis and chemosensitivity remains complex. We tested the chemosensitivity of 45 patients with advanced breast cancer (BC) ex vivo against anthracyclines (A: doxorubicin, epirubicin), taxanes (T: paclitaxel, docetaxel), cisplatin (DDP) and CMF and any correlation with the expression of p53, Bcl-2 and apoptosis. Viable cells were processed for ex vivo ATP Tumor Chemosensitivity Assay (ATP-TCA). Immunohistochemistry was performed in corresponding tumor samples. Apoptosis prior to chemotherapy was assayed using a TUNEL Test. Of 45 BC tested, 18 (40%) were p53+ and 37 (82%) showed high Bcl-2 expression. Apoptosis was detected in 29 (64.4%) specimens. The Ex vivo Response Rate (EVRR) for T was 75.6% in all cases. This was the highest rate among the 4 drugs tested followed by CMF (66.7%). For A and DDP the positive rates were lower (27.6% and 10.6%, respectively). A significant correlation (r = 0.589, p < or = 0.01) was found between tumors which were sensitive to A and DDP. There was no association between chemosensitivity and apoptosis. Moreover tests for p53 and Bcl-2 did not show a correlation to ex vivo chemosensitivity. Pretreatment apoptotic parameters are unlikely to predict the individual response of breast cancer to antineoplastic agents.


Assuntos
Apoptose , Neoplasias da Mama/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/biossíntese , Proteína Supressora de Tumor p53/biossíntese , Antineoplásicos/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Feminino , Humanos , Estatística como Assunto
8.
Rev Sci Instrum ; 85(9): 095114, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25273779

RESUMO

We describe a system to transport and identify barium ions produced in liquid xenon, as part of R&D towards the second phase of a double beta decay experiment, nEXO. The goal is to identify the Ba ion resulting from an extremely rare nuclear decay of the isotope (136)Xe, hence providing a confirmation of the occurrence of the decay. This is achieved through Resonance Ionization Spectroscopy (RIS). In the test setup described here, Ba ions can be produced in liquid xenon or vacuum and collected on a clean substrate. This substrate is then removed to an analysis chamber under vacuum, where laser-induced thermal desorption and RIS are used with time-of-flight mass spectroscopy for positive identification of the barium decay product.

9.
Rev Sci Instrum ; 82(10): 105114, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22047336

RESUMO

A magnetically driven piston pump for xenon gas recirculation is presented. The pump is designed to satisfy extreme purity and containment requirements, as is appropriate for the recirculation of isotopically enriched xenon through the purification system and large liquid xenon time projection chamber of EXO-200. The pump, using sprung polymer gaskets, is capable of pumping more than 16 standard liters per minute of xenon gas with 750 Torr differential pressure.

10.
Rev Sci Instrum ; 81(11): 113301, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21133463

RESUMO

We describe a source capable of producing single barium ions through nuclear recoils in radioactive decay. The source is fabricated by electroplating (148)Gd onto a silicon α-particle detector and vapor depositing a layer of BaF(2) over it. (144)Sm recoils from the alpha decay of (148)Gd are used to dislodge Ba(+) ions from the BaF(2) layer and emit them in the surrounding environment. The simultaneous detection of an α particle in the substrate detector allows for tagging of the nuclear decay and of the Ba(+) emission. The source is simple, durable, and can be manipulated and used in different environments. We discuss the fabrication process, which can be easily adapted to emit most other chemical species, and the performance of the source.

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