分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: The neural correlates of associative memory in healthy older adults were investigated by examining the correlation of associative memory performance with spontaneous brain oscillations. Eighty healthy older adults underwent a resting-state functional MRI and took a paired-associative learning test (PALT). Correlations between the amplitude of low-frequency fluctuations (ALFF) as well as fractional ALFF (fALFF) in the whole brain and PALT scores were calculated. We found that spontaneous activity as indexed by both ALFF and fALFF in the parahippocampal gyrus (PHG) was significantly positively correlated with associative memory performance, suggesting that the PHG plays a critical role in associative memory in older people.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: Normal aging is associated with greater decline in associative memory relative to item memory due to impaired recollection. Familiarity may also contribute to associative recognition when stimuli are perceived as a 'unitized' representation. Given that familiarity is relatively preserved in older adults, we explored whether age-related associative memory deficits could be attenuated when associations were unitized (i.e., compounds) compared with those non-unitized (i.e., unrelated word pairs). Young and older adults performed an associative recognition task while electroencephalogram (EEG) was recorded. Behavioral results showed that age differences were smaller for recognition of compounds than for unrelated word pairs. ERP results indicated that only compounds evoked an early frontal old/new effect in older adults. Moreover, the early frontal old/new effect was positively correlated with associative discrimination accuracy. These findings suggest that reduced age-related associative deficits under unitized condition may be associated with the presence of familiarity-based retrieval of compounds in older adults. (C) 2015 Elsevier Inc. All rights reserved.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: We use the distance sum rule method to constrain the spatial curvature of the Universe with a large sample of 161 strong gravitational lensing systems, whose distances are calibrated from the Pantheon compilation of type Ia supernovae using deep learning. To investigate the possible influence of mass model of the lens galaxy on constraining the curvature parameter Ωk, we consider three different lens models. Results show that a flat Universe is supported in the singular isothermal sphere (SIS) model with the parameter
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We estimate the decay rate of the Ψ(2S) to J/Ψ(1S) + 2π and σ + 2π. This is based on the mixed hybrid theory that was developed for the Ψ(2S) and was used to estimate the ratio Ψ(2S)→J/Ψ(1S)+σ to Ψ(2S)→J/Ψ(1S)+2π in 2011. A main motivation of the present work is to predict the possible experimental detection of the decay of Ψ(2S) to J/Ψ(1S)+σ+2π, or possibly to J/Ψ(1S)+2π+glueball.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Molecularly thin water layer, with a hydrogen bonding network different from those in bulk water and ice, has unique properties and is generally involved in many important processes such as wetting, erosion, atmosphere chemical reaction, protein folding and biomolecular interaction. Here, we report a new water layer structure at room temperature, which is found inside nanobubbles by using synchrotron based scanning transmission soft X-ray microscopy (STXM). The three peaks 535.0, 536.8 and 540.9 eV at O K edge inside the nanobubbles show a novel characteristics of very thin water layers, which has never been observed before.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: For a high-energy electron facility, estimates of induced radioactivity in materials are of considerable importance to ensure that the exposure of personnel and the environment remains as low as reasonably achievable. In addition, accurate predictions of induced radioactivity are essential to the design, operation, and decommissioning of a high-energy electron linear accelerator. In the case of the 200-MeV electron linac of the National Synchrotron Radiation Laboratory (NSRL), the electrons are accelerated by five acceleration tubes and collimated by copper scrapers. The scrapers, which play a vital role in protecting the acceleration cavity, are bombarded by many electrons over a long-term operation, which causes a significant amount of induced radioactivity. Recently, the NSRL Linac is the first high-energy electron linear accelerator in China to be out of commission. Its decommissioning is highly significant for obtaining decommissioning experience. This paper focuses on the measurement of induced radioactivity on the fourth scraper, where the electron energy was 158 MeV. The radionuclides were classified according to their half-lives. Such a classification provides a reliable basis for the formulation of radiation protection and facility decommissioning. To determine the high-radioactivity area and to facilitate the decommissioning process, the slicing method was applied in this study. The specific activity of 60Co in each slice was measured at a cooling time of ten months, and the results were compared with the predictions generated by Monte Carlo program FLUKA. The trend of the measured results is in good agreement with the normalized simulation results. The slicing simulation using Monte Carlo method is useful for the determination of high-radiation areas and proper material handling protocols and, therefore, lays a foundation for the accumulation of decommissioning experience.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Heat accumulation is a severe problem for high-power light-emitting diodes (LEDs). Here, we introduce a thermostable and transparent lateral heat spreader as an additional heat-escaping channel of an LED chip to improve the thermal management of LED devices. The lateral heat spreader was prepared based on a silver nanowire (AgNW)/polyimide composite comprising a thin polyacrylate layer soldering a conductive AgNW network to confine the nanowires to the surface of a polyimide film and to obtain low contact resistance between the nanowires. The AgNW/polyimide composite film has a figure-of-merit sheet resistance of 7 ohm sq 1 with 76% transmittance at 550 nm. After heating at 200 C for 168 h, the sheet resistance increases to 16 ohm sq 1. The thermal conductivity and thermal diffusivity are 130.2 W m 1 K 1 and 60.5 mm2 s 1, respectively, which are comparable to those of a commercial copper foil. A demonstration shows the core temperature in a thermal diffusion apparatus can be lowered by 9 C. The experimental data combined with computational simulation indicate the Joule heating could be drawn away efficiently along the lateral heat spreader.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: The ability of animals to respond to life-threatening stimuli is essential for survival. Although vision provides one of the major sensory inputs for detecting threats across animal species, the circuitry underlying defensive responses to visual stimuli remains poorly defined. Here, we investigate the circuitry underlying innate defensive behaviours elicited by predator-like visual stimuli in mice. Our results demonstrate that neurons in the superior colliculus (SC) are essential for a variety of acute and persistent defensive responses to overhead looming stimuli. Optogenetic mapping revealed that SC projections to the lateral posterior nucleus (LP) of the thalamus, a non-canonical polymodal sensory relay, are sufficient to mimic visually evoked fear responses. In vivo electrophysiology experiments identified a di-synaptic circuit from SC through LP to the lateral amygdale (Amg), and lesions of the Amg blocked the full range of visually evoked defensive responses. Our results reveal a novel collicular-thalamic-Amg circuit important for innate defensive responses to visual threats.