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 β 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 ∼4σ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.
A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and ...detected by eight antineutrino detectors deployed in two near（560 m and 600 m flux-weighted baselines） and one far（1640 m flux-weighted baseline） underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay（IBD） candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946±0.020（0.992±0.021） for the Huber＋Mueller（ILL＋Vogel） model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4–6 MeV was found in the measured spectrum, with a local significance of 4.4σ. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
This work reports a precise measurement of the reactor antineutrino flux using 2.2 million inverse beta decay (IBD) events collected with the Daya Bay near detectors in 1230 days. The dominant ...uncertainty on the neutron detection efficiency is reduced by 56% with respect to the previous measurement through a comprehensive neutron calibration and detailed data and simulation analysis. The new average IBD yield is determined to be (5.91±0.09)×10−43 cm2/fission with total uncertainty improved by 29%. The corresponding mean fission fractions from the four main fission isotopes U235, U238, Pu239, and Pu241 are 0.564, 0.076, 0.304, and 0.056, respectively. The ratio of measured to predicted antineutrino yield is found to be 0.952±0.014±0.023 (1.001±0.015±0.027) for the Huber-Mueller (ILL-Vogel) model, where the first and second uncertainty are experimental and theoretical model uncertainty, respectively. This measurement confirms the discrepancy between the world average of reactor antineutrino flux and the Huber-Mueller model.
Reward-based decision-learning refers to the process of learning to select those actions that lead to rewards while avoiding actions that lead to punishments. This process, known to rely on ...dopaminergic activity in striatal brain regions, is compromised in Parkinson's disease (PD). We hypothesized that such decision-learning deficits are alleviated by induced positive affect, which is thought to incur transient boosts in midbrain and striatal dopaminergic activity. Computational measures of probabilistic reward-based decision-learning were determined for 51 patients diagnosed with PD. Previous work has shown these measures to rely on the nucleus caudatus (outcome evaluation during the early phases of learning) and the putamen (reward prediction during later phases of learning). We observed that induced positive affect facilitated learning, through its effects on reward prediction rather than outcome evaluation. Viewing a few minutes of comedy clips served to remedy dopamine-related problems associated with frontostriatal circuitry and, consequently, learning to predict which actions will yield reward.
Cognitive training is not always effective. This is also the case for the form of cognitive training that this Research Topic focuses on: prolonged performance on game-like cognitive tasks. The ...ultimate goal of this cognitive training is to improve ecologically-valid target functions. For example, cognitive training should help children with ADHD to stay focused at school, or help older adults to manage the complexity of daily life. However, so far this goal has proven too ambitious. Transfer from trained to non-trained tasks is not even guaranteed in a laboratory, so there is a strong need for understanding how, when and for how long cognitive training has effect. Which cognitive functions are amenable to game training, for whom, and how? Are there mediating factors for success, such as motivation, attention, or age? Are the improvements real, or can they be attributed to nonspecific factors, such as outcome expectancy or demand characteristics? Are there better strategies to improve cognitive functions through game training? This Research Topic of Frontiers in Human Neuroscience charts current insights in the determinants of success of game training.
The spin structure function of the neutron ital gsub 1sup ital n has been determined over the range 0.03ltital xlt0.6 at an average ital Qsup 2 of 2 (GeV/ital c)sup 2 by measuring the asymmetry in ...deep inelastic scattering of polarized electrons from a polarized sup 3He target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be integralsub 0sup 1ital gsub 1sup ital n(ital x)ital dx=minus0.022plus minus0.011. Earlier reported proton results together with the Bjorken sum rule predict integralsub 0sup 1ital gsub 1sup ital n(ital x)ital dx=minus0.059plus minus0.019.
Negative affect in healthy populations regulates the appraisal of demanding situations, which tunes subsequent effort mobilization and adjustments in cognitive control. In the present study, we ...hypothesized that dysphoria in depressed individuals similarly modulates this adaptation, possibly through a neural mechanism involving serotonergic regulation. We tested the effect of dysphoria induced by acute tryptophan depletion (ATD) in remitted depressed patients on conflict adaptation in a Simon task. ATD temporarily lowers the availability of the serotonin precursor L-Tryptophan and is known to increase depressive symptoms in approximately half of remitted depressed participants. We found that depressive symptoms induced by ATD were associated with increased conflict adaptation. Our finding extends recent observations implying an important role of affect in regulating conflict-driven cognitive control.
Abstract This study investigated the role of arousal and effort costs in the cognitive benefits of alternating between sitting and standing postures using a sit‐stand desk, while measuring executive ...functions, self‐reports, physiology, and neural activity in a 2‐h laboratory session aimed to induce mental fatigue. Two sessions were conducted with a one‐week gap, during which participants alternated between sitting and standing postures each 20‐min block in one session and remained seated in the other. In each block, inhibition, switching, and updating were assessed. We examined effects of time‐on‐task, acute (local) effects of standing versus sitting posture, and cumulative (global) effects of a standing posture that generalize to the subsequent block in which participants sit. Results ( N = 43) confirmed that time‐on‐task increased mental fatigue and decreased arousal. Standing (versus sitting) led to acute increases in arousal levels, including self‐reports, alpha oscillations, and cardiac responses. Standing also decreased physiological and perceived effort costs. Standing enhanced processing speed in the flanker task, attributable to shortened nondecision time and speeded evidence accumulation processes. No significant effects were observed on higher‐level executive functions. Alternating postures also increased heart rate variability cumulatively over time. Exploratory mediation analyses indicated that the positive impact of acute posture on enhanced drift rate was mediated by self‐reported arousal, whereas decreased nondecision time was mediated by reductions in alpha power. In conclusion, alternating between sitting and standing postures can enhance arousal, decrease effort costs, and improve specific cognitive and physiological outcomes.
We studied the impact of standing on executive functions and physiology using a unique multi‐method approach that investigated the effect of alternating between sitting and standing on cardiac physiology, neural oscillations, and executive functions. Standing improved neural and physiological arousal, enhanced overall task performance in a flanker task, while also decreasing physiological and perceived effort costs, and increasing heart rate variability over time. These findings emphasize the benefits of alternating between seated and standing postures for the body and the brain.
There is a demand for ways to enhance cognitive flexibility, as it can be a limiting factor for performance in daily life. Video game training has been linked to advantages in cognitive functioning, ...raising the question if training with video games can promote cognitive flexibility. In the current study, we investigated if game-based computerized cognitive training (GCCT) could enhance cognitive flexibility in a healthy young adult sample (N = 72), as measured by task-switch performance. Three GCCT schedules were contrasted, which targeted: (1) cognitive flexibility and task switching, (2) attention and working memory, or (3) an active control involving basic math games, in twenty 45-min sessions across 4–6 weeks. Performance on an alternating-runs task-switch paradigm during pretest and posttest sessions indicated greater overall reaction time improvements after both flexibility and attention training as compared to control, although not related to local switch cost. Flexibility training enhanced performance in the presence of distractor-related interference. In contrast, attention training was beneficial when low task difficulty undermined sustained selective attention. Furthermore, flexibility training improved response selection as indicated by a larger N2 amplitude after training as compared to control, and more efficient conflict monitoring as indicated by reduced Nc/CRN and larger Pe amplitude after training. These results provide tentative support for the efficacy of GCCT and suggest that an ideal training might include both task switching and attention components, with maximal task diversity both within and between training games.
To maximize the light yield of the liquid scintillator (LS) for the Jiangmen Underground Neutrino Observatory (JUNO), a 20 t LS sample was produced in a pilot plant at Daya Bay. The optical ...properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector. The concentrations of the fluor, PPO, and the wavelength shifter, bis-MSB, were increased in 12 steps from 0.5 g/L and <0.01 mg/L to 4 g/L and 13 mg/L, respectively. The numbers of total detected photoelectrons suggest that, with the optically purified solvent, the bis-MSB concentration does not need to be more than 4 mg/L. To bridge the one order of magnitude in the detector size difference between Daya Bay and JUNO, the Daya Bay data were used to tune the parameters of a newly developed optical model. Then, the model and tuned parameters were used in the JUNO simulation. This enabled to determine the optimal composition for the JUNO LS: purified solvent LAB with 2.5 g/L PPO, and 1 to 4 mg/L bis-MSB.
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