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The sensory neocortex has been suggested to be a substrate for long-term memory storage, yet which exact single cells could be specific candidates underlying such long-term memory storage remained neither known nor visible for over a century. Here, using a combination of day-by-day two-photon Ca 2+ imaging and targeted single-cell loose-patch recording in an auditory associative learning paradigm with composite sounds in male mice, we reveal sparsely distributed neurons in layer 2/3 of auditory cortex emerged step-wise from quiescence into bursting mode, which then invariably expressed holistic information of the learned composite sounds, referred to as holistic bursting (HB) cells. Notably, it was not shuffled populations but the same sparse HB cells that embodied the behavioral relevance of the learned composite sounds, pinpointing HB cells as physiologically-defined single-cell candidates of an engram underlying long-term memory storage in auditory cortex. Previous work has identified cells in L2/3 of auditory cortex which strongly respond with bursting to a specific learned chord, but not to single component tones in an auditory task. Here the authors show that these cells correlate with the behavioral relevance of the learned composite sounds.

Sound‐evoked wakefulness from sleep is crucial in daily life, yet its neural mechanisms remain poorly understood. It is found that CaMKIIα+ neurons in the temporal association cortex (TeA) of mice are not essential for natural awakening from sleep. However, optogenetic activation of these neurons reliably induces wakefulness from non‐rapid eye movement (NREM) sleep but not from rapid eye movement (REM) sleep. In vivo electrophysiological and calcium recordings further demonstrated that TeA neurons are monotonically tuned to sound intensity but not frequency. More importantly, it is found that the activity of CaMKIIα+ neurons in TeA can gate sound‐evoked arousal from NREM sleep, which is further confirmed by optogenetic manipulations. Further investigation reveals that the baseline excitability of TeA CaMKIIα+ neurons and the delta oscillations in the electroencephalogram are particularly important in regulating the evoked activity of TeA neurons. Anatomical and functional screening of downstream targets of TeA reveals that excitatory projections from TeA glutamatergic neurons to glutamatergic neurons in the basolateral/lateral amygdala are critical for modulating sound‐evoked arousal from NREM sleep. These findings uncover a top‐down regulatory circuit that selectively governs sound‐evoked arousal from NREM sleep, with the TeA functioning as a key connecting cortex to subcortical regions. It is often wondered why some sounds wake people while others don't. Researchers have discovered that the temporal association cortex plays a key role in this during NREM sleep. Neurons in this region work with the amygdala to decide which sounds are important enough to interrupt sleep, providing a balance between rest and responsiveness.

A bstract We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.

A bstract JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day (cpd), therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration to reduce at minimum the impact of natural radioactivity. We describe our efforts for an optimized experimental design, a careful material screening and accurate detector production handling, and a constant control of the expected results through a meticulous Monte Carlo simulation program. We show that all these actions should allow us to keep the background count rate safely below the target value of 10 Hz (i.e. ∼ 1 cpd accidental background) in the default fiducial volume, above an energy threshold of 0.7 MeV.

This article presents the design and implementation of a soft X-ray polarized calibration platform based on Bragg’s Law and Fresnel’s Law, which is used to calibrate low-energy polarization detector(LPD/POLAR-2) that has potential deployment onboard the China Space Station. The platform is equipped with versatile equipment that can generate both completely and partially polarized X-ray beams, and provides precise control over the diffraction angle, achieving the desired polarization degree. It covers the 3–8 keV energy band, with a high fraction of monochromatic light (>93%)(The proportion of monochromatic light is defined as the ratio of the number of photons falling within three times the sigma of the target peak centre value to the total photons.) and good monochromaticity(In this article, we evaluate the monochromaticity of the polarized source using the Full Width at Half Maximum (FWHM) of its all-in-one peak.), and is suitable for calibrating LPD’s large-field-of-view soft X-ray polarization detector using its vertically incident and obliquely incident polarized X-rays. The completely and partially polarized X-ray beams generated at 8.0 keV by the calibration platform are used to test the polarization measurement capabilities of the soft X-ray polarized detector and verify the linearity between the calibration source’s polarization and the measurable modulation of the polarimeter.

The OSIRIS detector is a subsystem of the liquid scintillator filling chain of the JUNO reactor neutrino experiment. Its purpose is to validate the radiopurity of the scintillator to assure that all components of the JUNO scintillator system work to specifications and only neutrino-grade scintillator is filled into the JUNO Central Detector. The aspired sensitivity level of 10-16g/g of 238U and 232Th requires a large (∼20m3) detection volume and ultralow background levels. The present paper reports on the design and major components of the OSIRIS detector, the detector simulation as well as the measuring strategies foreseen and the sensitivity levels to U/Th that can be reached in this setup.

Observation of X-ray counterpart produced by the merger of binary compact star system is of great significance for studying their physical mechanisms. Based on the application requirements of the X-ray counterpart collection device, ring-welded samples of 316L stainless steel and UNS K94610 Kovar alloy were investigated using a continuous wave laser. The effects of heat input on the weld formation, microstructure, mechanical properties, and sealing performance were studied. It was shown that because of the different heat distributions inside and outside the ring weld, the internal profile of the weld cross-section was closer to the circular shape and the columnar crystal growth near the fusion line was longer. Specially, the epitaxial growth was found on the K alloy side. However, the element distribution of the weld was uniform and its crystal structure was austenitic phase. When the heat input was greater than 11.88 J/mm, the tensile strength of the weld was higher than that of the K alloy. The tensile failure locations were at the K alloy BM zone, except for samples with heat input less than 7.92 J/mm. However, when the heat input was greater than 37.50 J/mm, the weld had better sealing performance, and the minimum leak rate could reach 4 × 10 −10 Pa·mm 3 /s.

Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric νe and νμ fluxes is presented in this paper. In this study, a sample of atmospheric neutrino Monte Carlo events has been generated, starting from theoretical models, and then processed by the detector simulation. The excellent timing resolution of the 3” PMT light detection system of JUNO detector and the much higher light yield for scintillation over Cherenkov allow to measure the time structure of the scintillation light with very high precision. Since νe and νμ interactions produce a slightly different light pattern, the different time evolution of light allows to discriminate the flavor of primary neutrinos. A probabilistic unfolding method has been used, in order to infer the primary neutrino energy spectrum from the detector experimental observables. The simulated spectrum has been reconstructed between 100 MeV and 10 GeV, showing a great potential of the detector in the atmospheric low energy region.

Large-scale organic liquid scintillator detectors are highly efficient in the detection of MeV-scale electron antineutrinos. These signal events can be detected through inverse beta decay on protons, which produce a positron accompanied by a neutron. A noteworthy background for antineutrinos coming from nuclear power reactors and from the depths of the Earth (geoneutrinos) is generated by ( α , n ) reactions. In organic liquid scintillator detectors, α particles emitted from intrinsic contaminants such as 238 U, 232 Th, and 210 Pb/ 210 Po, can be captured on 13 C nuclei, followed by the emission of a MeV-scale neutron. Three distinct interaction mechanisms can produce prompt energy depositions preceding the delayed neutron capture, leading to a pair of events correlated in space and time within the detector. Thus, ( α , n ) reactions represent an indistinguishable background in liquid scintillator-based antineutrino detectors, where their expected rate and energy spectrum are typically evaluated via Monte Carlo simulations. This work presents results from the open-source SaG4n software, used to calculate the expected energy depositions from the neutron and any associated de-excitation products. Also simulated is a detailed detector response to these interactions, using a dedicated Geant4-based simulation software from the JUNO experiment. An expected measurable 13 C ( α , n ) 16 O event rate and reconstructed prompt energy spectrum with associated uncertainties, are presented in the context of JUNO, however, the methods and results are applicable and relevant to other organic liquid scintillator neutrino detectors.

Large-scale organic liquid scintillator detectors are highly efficient in the detection of MeV-scale electron antineutrinos. These signal events can be detected through inverse beta decay on protons, which produce a positron accompanied by a neutron. A noteworthy background for antineutrinos coming from nuclear power reactors and from the depths of the Earth (geoneutrinos) is generated by ($$\\alpha ,\\,n$$α , n ) reactions. In organic liquid scintillator detectors,$$\\alpha $$α particles emitted from intrinsic contaminants such as$$^{238}$$238 U,$$^{232}$$232 Th, and$$^{210}$$210 Pb/$$^{210}$$210 Po, can be captured on$$^{13}$$13 C nuclei, followed by the emission of a MeV-scale neutron. Three distinct interaction mechanisms can produce prompt energy depositions preceding the delayed neutron capture, leading to a pair of events correlated in space and time within the detector. Thus, ($$\\alpha ,\\,n$$α , n ) reactions represent an indistinguishable background in liquid scintillator-based antineutrino detectors, where their expected rate and energy spectrum are typically evaluated via Monte Carlo simulations. This work presents results from the open-source SaG4n software, used to calculate the expected energy depositions from the neutron and any associated de-excitation products. Also simulated is a detailed detector response to these interactions, using a dedicated Geant4-based simulation software from the JUNO experiment. An expected measurable$$^{13}$$13 C$$(\\alpha ,\\,n)^{16}$$( α , n ) 16 O event rate and reconstructed prompt energy spectrum with associated uncertainties, are presented in the context of JUNO, however, the methods and results are applicable and relevant to other organic liquid scintillator neutrino detectors.