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This Letter presents results of a search for the mixing of a sub-eV sterile neutrino with three active neutrinos based on the full data sample of the Daya Bay Reactor Neutrino Experiment, collected during 3158 days of detector operation, which contains 5.55×10^{6} reactor ν[over ¯]_{e} candidates identified as inverse beta-decay interactions followed by neutron capture on gadolinium. The analysis benefits from a doubling of the statistics of our previous result and from improvements of several important systematic uncertainties. No significant oscillation due to mixing of a sub-eV sterile neutrino with active neutrinos was found. Exclusion limits are set by both Feldman-Cousins and CLs methods. Light sterile neutrino mixing with sin^{2}2θ_{14}â³0.01 can be excluded at 95% confidence level in the region of 0.01 eV^{2}â²|Δm_{41}^{2}|â²0.1 eV^{2}. This result represents the world-leading constraints in the region of 2×10^{-4} eV^{2}â²|Δm_{41}^{2}|â²0.2 eV^{2}.
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Reactor neutrino experiments play a crucial role in advancing our knowledge of neutrinos. In this Letter, the evolution of the flux and spectrum as a function of the reactor isotopic content is reported in terms of the inverse-beta-decay yield at Daya Bay with 1958 days of data and improved systematic uncertainties. These measurements are compared with two signature model predictions: the Huber-Mueller model based on the conversion method and the SM2018 model based on the summation method. The measured average flux and spectrum, as well as the flux evolution with the ^{239}Pu isotopic fraction, are inconsistent with the predictions of the Huber-Mueller model. In contrast, the SM2018 model is shown to agree with the average flux and its evolution but fails to describe the energy spectrum. Altering the predicted inverse-beta-decay spectrum from ^{239}Pu fission does not improve the agreement with the measurement for either model. The models can be brought into better agreement with the measurements if either the predicted spectrum due to ^{235}U fission is changed or the predicted ^{235}U, ^{238}U, ^{239}Pu, and ^{241}Pu spectra are changed in equal measure.
Assuntos
Reatores Nucleares , UrânioRESUMO
We present a new determination of the smallest neutrino mixing angle θ_{13} and the mass-squared difference Δm_{32}^{2} using a final sample of 5.55×10^{6} inverse beta-decay (IBD) candidates with the final-state neutron captured on gadolinium. This sample is selected from the complete dataset obtained by the Daya Bay reactor neutrino experiment in 3158 days of operation. Compared to the previous Daya Bay results, selection of IBD candidates has been optimized, energy calibration refined, and treatment of backgrounds further improved. The resulting oscillation parameters are sin^{2}2θ_{13}=0.0851±0.0024, Δm_{32}^{2}=(2.466±0.060)×10^{-3} eV^{2} for the normal mass ordering or Δm_{32}^{2}=-(2.571±0.060)×10^{-3} eV^{2} for the inverted mass ordering.
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This Letter reports the first measurement of high-energy reactor antineutrinos at Daya Bay, with nearly 9000 inverse beta decay candidates in the prompt energy region of 8-12 MeV observed over 1958 days of data collection. A multivariate analysis is used to separate 2500 signal events from background statistically. The hypothesis of no reactor antineutrinos with neutrino energy above 10 MeV is rejected with a significance of 6.2 standard deviations. A 29% antineutrino flux deficit in the prompt energy region of 8-11 MeV is observed compared to a recent model prediction. We provide the unfolded antineutrino spectrum above 7 MeV as a data-based reference for other experiments. This result provides the first direct observation of the production of antineutrinos from several high-Q_{ß} isotopes in commercial reactors.
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A joint determination of the reactor antineutrino spectra resulting from the fission of ^{235}U and ^{239}Pu has been carried out by the Daya Bay and PROSPECT Collaborations. This Letter reports the level of consistency of ^{235}U spectrum measurements from the two experiments and presents new results from a joint analysis of both data sets. The measurements are found to be consistent. The combined analysis reduces the degeneracy between the dominant ^{235}U and ^{239}Pu isotopes and improves the uncertainty of the ^{235}U spectral shape to about 3%. The ^{235}U and ^{239}Pu antineutrino energy spectra are unfolded from the jointly deconvolved reactor spectra using the Wiener-SVD unfolding method, providing a data-based reference for other reactor antineutrino experiments and other applications. This is the first measurement of the ^{235}U and ^{239}Pu spectra based on the combination of experiments at low- and highly enriched uranium reactors.
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Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the θ_{µe} mixing angle are derived that constitute the most constraining limits to date over five orders of magnitude in the mass-squared splitting Δm_{41}^{2}, excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CL_{s} for Δm_{41}^{2}<13 eV^{2}. Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CL_{s} for Δm_{41}^{2}<1.6 eV^{2}.
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This Letter reports the first extraction of individual antineutrino spectra from ^{235}U and ^{239}Pu fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses 3.5×10^{6} inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, ^{235}U and ^{239}Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4-6 MeV, a 7% (9%) excess of events is observed for the ^{235}U (^{239}Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0σ for ^{235}U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3σ. In the energy range of 4-6 MeV, a maximal local discrepancy of 6.3σ is observed.
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We report a measurement of electron antineutrino oscillation from the Daya Bay Reactor Neutrino Experiment with nearly 4 million reactor ν[over ¯]_{e} inverse ß decay candidates observed over 1958 days of data collection. The installation of a flash analog-to-digital converter readout system and a special calibration campaign using different source enclosures reduce uncertainties in the absolute energy calibration to less than 0.5% for visible energies larger than 2 MeV. The uncertainty in the cosmogenic ^{9}Li and ^{8}He background is reduced from 45% to 30% in the near detectors. A detailed investigation of the spent nuclear fuel history improves its uncertainty from 100% to 30%. Analysis of the relative ν[over ¯]_{e} rates and energy spectra among detectors yields sin^{2}2θ_{13}=0.0856±0.0029 and Δm_{32}^{2}=(2.471_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the normal hierarchy, and Δm_{32}^{2}=-(2.575_{-0.070}^{+0.068})×10^{-3} eV^{2} assuming the inverted hierarchy.
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The Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW_{th} reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective ^{239}Pu fission fractions F_{239} from 0.25 to 0.35, Daya Bay measures an average IBD yield σ[over ¯]_{f} of (5.90±0.13)×10^{-43} cm^{2}/fission and a fuel-dependent variation in the IBD yield, dσ_{f}/dF_{239}, of (-1.86±0.18)×10^{-43} cm^{2}/fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the ^{239}Pu fission fraction at 10 standard deviations. The variation in IBD yield is found to be energy dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1σ. This discrepancy indicates that an overall deficit in the measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes ^{235}U, ^{239}Pu, ^{238}U, and ^{241}Pu. Based on measured IBD yield variations, yields of (6.17±0.17) and (4.27±0.26)×10^{-43} cm^{2}/fission have been determined for the two dominant fission parent isotopes ^{235}U and ^{239}Pu. A 7.8% discrepancy between the observed and predicted ^{235}U yields suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.
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Opioids are increasingly used to control chronic non-cancer pain globally. International opioid guidelines have been issued in many different countries but a similar document is not generally available in Hong Kong. Chronic opioid therapy has a role in multidisciplinary management of chronic non-cancer pain despite insufficient evidence for its effectiveness and safety for long-term use. This document reviews the current literature to inform Hong Kong practitioners about the rational use of chronic opioid therapy in chronic non-cancer pain. It also aims to provide useful recommendations for the appropriate, effective, and safe use of such therapy in the management of chronic non-cancer pain in adults. Physicians should conduct a comprehensive biopsychosocial evaluation of patients prior to the commencement of opioid therapy. When opioid use is deemed appropriate, the patient should provide informed consent within an agreement that specifies treatment goals and expectations. A trial of opioid can be commenced and, provided there is progress towards treatment goals, then chronic therapy can be considered at a dose that minimises harm. Monitoring of effectiveness, safety, and drug misuse should be continued. Treatment should be stopped when opioids become ineffective, intolerable, or misused. The driving principles for opioid prescription in chronic pain management should be: start with a low dose, titrate slowly, and maintain within the shortest possible time.
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Analgésicos Opioides/administração & dosagem , Dor Crônica/tratamento farmacológico , Guias de Prática Clínica como Assunto , Adulto , Analgésicos Opioides/efeitos adversos , Relação Dose-Resposta a Droga , Hong Kong , Humanos , Consentimento Livre e Esclarecido , Transtornos Relacionados ao Uso de Opioides/prevenção & controleRESUMO
This Letter reports an improved search for light sterile neutrino mixing in the electron antineutrino disappearance channel with the full configuration of the Daya Bay Reactor Neutrino Experiment. With an additional 404 days of data collected in eight antineutrino detectors, this search benefits from 3.6 times the statistics available to the previous publication, as well as from improvements in energy calibration and background reduction. A relative comparison of the rate and energy spectrum of reactor antineutrinos in the three experimental halls yields no evidence of sterile neutrino mixing in the 2×10^{-4}â²|Δm_{41}^{2}|â²0.3 eV^{2} mass range. The resulting limits on sin^{2}2θ_{14} are improved by approx imately a factor of 2 over previous results and constitute the most stringent constraints to date in the |Δm_{41}^{2}|â²0.2 eV^{2} region.
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Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^{2}2θ_{µe} are set over 6 orders of magnitude in the sterile mass-squared splitting Δm_{41}^{2}. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm_{41}^{2}<0.8 eV^{2} at 95% CL_{s}.
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This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GWth nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse ß decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55±0.04) ×10(-18) cm(2) GW(-1) day(-1) or (5.92±0.14) ×10(-43) cm(2) fission(-1). This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946±0.022 (0.991±0.023) relative to the flux predicted with the Huber-Mueller (ILL-Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2σ over the full energy range with a local significance of up to â¼4σ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.
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We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9×10^{5} GW_{th} ton days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six ^{241}Am-^{13}C radioactive calibration sources reduced the background by a factor of 2 for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of sin^{2}2θ_{13} and |Δm_{ee}^{2}| were halved as a result of these improvements. An analysis of the relative antineutrino rates and energy spectra between detectors gave sin^{2}2θ_{13}=0.084±0.005 and |Δm_{ee}^{2}|=(2.42±0.11)×10^{-3} eV^{2} in the three-neutrino framework.
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OBJECTIVES: To review the clinical and social benefits of a pain management programme in Hong Kong. DESIGN: Prospective cohort study. SETTING: Tertiary out-patient clinic, Hong Kong. PARTICIPANTS: Patients with chronic non-cancer pain and prolonged (mean, 46 months) psychosocial disability who joined the Comprehensive Outpatient Pain Engagement programme between 2002 and 2012. INTERVENTION: A structured 6-week out-patient pain rehabilitation course designed to improve function and reduce disability, regardless of the cause or severity of pain. MAIN OUTCOME MEASURES: Social outcomes included return-to-work rate, hospital admissions, and out-patient visits. Physical outcomes included tolerance to sitting and standing. Psychological constructs such as mood, catastrophisation, self-efficacy, quality of life, and perceived performances were used. Each measure was taken before and 1 year after the programme. RESULTS: There was significant increase in return-to-work rate 1 year after commencement of the programme (35% after vs 17% before the programme; odds ratio=3.01), reduction in medical utilisation, and improvement in all physical and psychological measures. Pain intensity, psychological distress, and history of work-related injuries were not related to the likelihood of return to work. Shorter duration of pain and higher physical functioning score in 36-Item Short-Form Health Survey were prognostic indicators. CONCLUSIONS: Patients with chronic pain who joined the Comprehensive Outpatient Pain Engagement programme showed significant functional improvement despite the long history of pain.
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Dor Crônica/reabilitação , Avaliação da Deficiência , Avaliação de Resultados em Cuidados de Saúde/estatística & dados numéricos , Manejo da Dor/métodos , Avaliação de Programas e Projetos de Saúde/estatística & dados numéricos , Adulto , Povo Asiático , Dor Crônica/psicologia , Feminino , Hong Kong , Humanos , Masculino , Pessoa de Meia-Idade , Visita a Consultório Médico/estatística & dados numéricos , Pacientes Ambulatoriais/psicologia , Pacientes Ambulatoriais/estatística & dados numéricos , Manejo da Dor/estatística & dados numéricos , Medição da Dor/psicologia , Medição da Dor/estatística & dados numéricos , Admissão do Paciente/estatística & dados numéricos , Estudos Prospectivos , Qualidade de Vida , Retorno ao Trabalho/estatística & dados numéricos , Adulto JovemRESUMO
A search for light sterile neutrino mixing was performed with the first 217 days of data from the Daya Bay Reactor Antineutrino Experiment. The experiment's unique configuration of multiple baselines from six 2.9 GW(th) nuclear reactors to six antineutrino detectors deployed in two near (effective baselines 512 m and 561 m) and one far (1579 m) underground experimental halls makes it possible to test for oscillations to a fourth (sterile) neutrino in the 10(-3) eV(2)<|Δm(41)(2) |< 0.3 eV(2) range. The relative spectral distortion due to the disappearance of electron antineutrinos was found to be consistent with that of the three-flavor oscillation model. The derived limits on sin(2) 2θ(14) cover the 10(-3) eV(2) â² |Δm(41)(2)| â² 0.1 eV(2) region, which was largely unexplored.
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A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9 GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3) eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(µµ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
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The Daya Bay Reactor Neutrino Experiment has measured a nonzero value for the neutrino mixing angle θ(13) with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GWth-day live-time exposure in 55 days, 10,416 (80,376) electron-antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R=0.940±0.011(stat.)±0.004(syst.). A rate-only analysis finds sin(2)2θ(13)=0.092±0.016(stat.)±0.005(syst.) in a three-neutrino framework.
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OBJECTIVE: To describe experience with a chronic pain management programme in Hong Kong Chinese patients. DESIGN: Prospective study. SETTING: Regional hospital, Hong Kong. PARTICIPANTS: Patients with chronic pain who participated in the first six Comprehensive Out-patient Pain Engagement programmes between 2002 and 2005. INTERVENTION: Comprehensive Out-patient Pain Engagement is a 14-day structured, multidisciplinary out-patient programme conducted over 6 weeks. It includes pain education, cognitive re-conceptualisation, training in communication skills and coping strategies, graded physical exercises and functional activities training. It aims to improve patient function and quality of life, despite persistent pain. MAIN OUTCOME MEASURES: Changes in scores from baseline values after joining the programme, with respect to several assessment tools. These included the following: visual analogue pain scale, Pain Catastrophizing Scale, Patient Self-efficacy Questionnaire, Canadian Occupational Performance Measure, Medical Outcome Survey-Short Form 36 Questionnaire, and duration of physical tolerances, medication utilisation, and work status records. RESULTS: Forty-five patients were available for analysis. After the Comprehensive Out-patient Pain Engagement programme, improvements in Medical Outcome Survey-Short Form 36 Questionnaire (role physical and vitality), Pain Catastrophizing Scale, Patient Self-efficacy Questionnaire, and Canadian Occupational Performance Measure were demonstrated (P<0.05). The duration of standing and sitting tolerances increased (P<0.05). An improvement in employment rate was also evident (P=0.01). CONCLUSION: The initial results of our management programme in Chinese patients with chronic pain are encouraging. This type of programme should be promoted more widely in this group of patients, as it appears to improve physical function, psychological well-being, and productivity.
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Terapia Cognitivo-Comportamental/métodos , Manejo da Dor , Medição da Dor , Qualidade de Vida , Adulto , Assistência Ambulatorial , China/etnologia , Doença Crônica , Comunicação , Exercício Físico , Feminino , Hong Kong , Humanos , Masculino , Pessoa de Meia-Idade , Ambulatório Hospitalar , Dor/etnologia , Educação de Pacientes como Assunto , Estudos ProspectivosRESUMO
OBJECTIVES: To examine the demographics, process indicators of adult in-hospital cardiopulmonary arrest resuscitation, and outcomes in a teaching hospital in Hong Kong. DESIGN: Retrospective study. SETTING: A university-affiliated tertiary referral hospital with 997 acute adult beds in Hong Kong. PATIENTS: Those who suffered a cardiopulmonary resuscitation event, as documented in retrieved records of all in-patients during the inclusive period January 2002 to December 2005. RESULTS: There were 531 resuscitation events; the mean (standard deviation) age of the corresponding patients was 70.7 (15.4) years. Most (83%) occurred in non-monitored areas and most (97%) were cardiopulmonary arrests. The predominant initial rhythm was asystole (52%); only 8% of patients had ventricular tachycardia/fibrillation. All the resuscitations were initiated by on-site first responders. The median times from collapse to arrival of the resuscitation team, to defibrillation, to administration of adrenaline, and to intubation were: 5 (interquartile range, 2-6) minutes, 5 (1-7) minutes, 5 (3-10) minutes, and 9 (5-13) minutes, respectively. The overall hospital survival (discharge) rate was 5%. The survival rate was higher among patients in monitored areas (9 vs 4%, P=0.046), among patients with isolated respiratory arrests (61 vs 3%, P<0.001), primary ventricular tachycardia/fibrillation arrests (13 vs 4%, P<0.001), shorter interval times from collapse to medication (1.5 vs 5 min, P=0.013), and longer interval times to intubation (12 vs 8 min, P=0.013). CONCLUSION: Hospital survival after in-hospital cardiopulmonary arrests was poor. Possible strategies to improve survival include shorten time interval to defibrillation, and provision of more monitored beds.