Single Photon Emission from Single Perovskite Nanocrystals of Cesium Lead Bromide

The power conversion efficiency of photovoltaic devices based on semiconductor perovskites has reached ~20% after just several years of research efforts. With concomitant discoveries of other promising applications in lasers, light-emitting diodes and photodetectors, it is natural to anticipate what further excitements these exotic perovskites could bring about. Here we report on the observation of single photon emission from single CsPbBr3 perovskite nanocrystals (NCs) synthesized from a facile colloidal approach. Compared with traditional metal-chalcogenide NCs, these CsPbBr3 NCs exhibit nearly two orders of magnitude increase in their absorption cross sections at similar emission colors. Moreover, the radiative lifetime of CsPbBr3 NCs is greatly shortened at both room and cryogenic temperatures to favor an extremely fast output of single photons. The above findings have not only added a novel member to the perovskite family for the integration into current optoelectronic architectures, but also paved the way towards quantum-light applications of single perovskite NCs in various quantum information processing schemes

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

Exciton polaritons (EPs) are half‐light, half‐matter quasiparticles formed due to the coupling between photons and excitons in semiconductors. Their uniqueness lies at the strong light–matter interactions and long‐distance transport, thus promising for many novel applications in photonics, information, and quantum technologies. Recently, EPs in group‐VI transition‐metal dichalcogenides (TMDs) have attracted a lot of research interest due to their room‐temperature stability, long‐distance propagation, and controllability through electric gating, valley‐selective optical pumping, and precise thickness control. In this progress report, recent studies of EPs in TMDs are reviewed, highlighting their key properties and functionalities, and then discussing the potential directions for future research.</p

Secondary bending effects in progressively damaged single-lap, single-bolt composite joints

Static tensile experiments and progressive failure simulations of single-bolt, single- and double-lap joints were carried out to comparatively investigate secondary bending effects, which present significant eccentric-loading phenomena in single-lap joints but are almost non-existent in symmetric double-lap joints. Progressive damage models of single-lap and double-lap joints were established, from which the numerical predictions were found to be in good agreement with the experimental outcomes. Experimental macro-scope failure patterns and seven numerical micro-scope failure modes obtained from the progressive damage analyses were presented for the two types of joints. The effects of secondary bending on the mechanical degradation and failure mechanism of single-lap joints were revealed. Some characterizations of secondary bending in the joints, such as a characterized parameter on the AGARD points, joint deformations and contact states, were quantitatively traced during the total progressive damage process. All these characterizations increased the understanding of the effects of secondary bending on the failure process of a single-bolt, single-lap joint. Keywords: Composite, Bolted joint, Secondary bending, Progressive damage analysi

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and human studies to investigate the cortical processing of nociceptive information. These laser-evoked brain potentials (LEPs) consist of several transient responses that are time-locked to the onset of laser stimuli. However, the functional properties of the LEP responses are still largely unknown, due to the lack of a sampling technique that can simultaneously record neural activities at the surface of the cortex (i.e., electrocorticogram [ECoG] and scalp electroencephalogram [scalp EEG]) and inside the brain (i.e., local field potential [LFP]). To address this issue, we present here an animal protocol using freely moving rats. This protocol is composed of three main procedures: (1) animal preparation and surgical procedures, (2) a simultaneous recording of ECoG and LFP in response to nociceptive laser stimuli, and (3) data analysis and feature extraction. Specifically, with the help of a 3D-printed protective shell, both ECoG and LFP electrodes implanted on the rat&#39;s skull were securely held together. During data collection, laser pulses were delivered on the rat&#39;s forepaws through gaps in the bottom of the chamber when the animal was in spontaneous stillness. Ongoing white noise was played to avoid the activation of the auditory system by the laser-generated ultrasounds. As a consequence, only nociceptive responses were selectively recorded. Using the standard analytical procedures (e.g., band-pass filtering, epoch extraction, and baseline correction) to extract stimulus-related brain responses, we obtained results showing that LEPs with a high signal-to-noise ratio were simultaneously recorded from ECoG and LFP electrodes. This methodology makes the simultaneous recording of ECoG and LFP activities possible, which provides a bridge of electrocortical signals at the mesoscopic and macroscopic levels, thereby facilitating the investigation of nociceptive information processing in the brain.</p

Deciphering Authentic Nociceptive Thalamic in Rats

The thalamus and its cortical connections play a pivotal role in pain information processing, yet the exploration of its electrophysiological responses to nociceptive stimuli has been limited. Here, in 2 experiments we recorded neural responses to nociceptive laser stimuli in the thalamic (ventral posterior lateral nucleus and medial dorsal nucleus) and cortical regions (primary somatosensory cortex [S1] and anterior cingulate cortex) within the lateral and medial pain pathways. We found remarkable similarities in laser-evoked brain responses that encoded pain intensity within thalamic and cortical regions. Contrary to the expected temporal sequence of ascending information flow, the recorded thalamic response (N1) was temporally later than its cortical counterparts, suggesting that it may not be a genuine thalamusgenerated response. Importantly, we also identified a distinctive component in the thalamus, i.e., the early negativity (EN) occurring around 100 ms after the onset of nociceptive stimuli. This EN component represents an authentic nociceptive thalamic response and closely synchronizes with the directional information flow from the thalamus to the cortex. These findings underscore the importance of isolating genuine thalamic neural responses, thereby contributing to a more comprehensive understanding of the thalamic function in pain processing. Additionally, these findings hold potential clinical implications, particularly in the advancement of closed-loop neuromodulation treatments for neurological diseases targeting this vital brain region

Cross-Species Investigation on Resting State Electroencephalogram

Resting state electroencephalography (EEG) during eyes-closed and eyes-open conditions is widely used to evaluate brain states of healthy populations and brain dysfunctions in clinical conditions. Although several results have been obtained by measuring these brain activities in humans, it remains unclear whether the same results can be replicated in animals, i.e., whether the physiological properties revealed by these findings are phylogenetically conserved across species. In the present study, we describe a paradigm for recording resting state EEG activities during eyes-closed and eyes-open conditions from rats, and investigated the differences between eyes-closed and eyes-open conditions for humans and rats. We found that compared to the eyes-open condition, human EEG spectral amplitude in the eyes-closed condition was significantly higher at 8-12 Hz and 18-22 Hz in the occipital region, but significantly lower at 18-22 Hz and 30-100 Hz in the frontal region. In contrast, rat EEG spectral amplitude was significantly higher in the eyes-closed condition than in the eyes-open condition at 1-4 Hz, 8-12 Hz, and 13-17 Hz in the frontal-central region. In both species, the 1/f-like power spectrum scaling of resting state EEG activities was significantly higher in the eyes-closed condition than in the eyes-open condition at parietal-occipital and frontal regions. These results provided a neurophysiological basis for future translational studies from experimental animal findings to human psychophysiology, since the validity of such translation critically relies on a well-established experimental paradigm and a carefully-examined signal characteristic to bridge the gaps across different species.</p

Genome-Wide Identification and Expression Analysis of <i>BrATG</i>s and Their Different Roles in Response to Abiotic Stresses in Chinese Cabbage

Autophagy is an important degradation pathway that maintains cellular homeostasis in living organisms and plays a key role in plant fitness and immunity. To date, more than 30 autophagy-related genes (ATGs) have been identified in model plants such as Arabidopsis. However, autophagy in Chinese cabbage, the largest cultivated vegetable crop in China, has scarcely been studied. We identified 64 Chinese cabbage autophagy-associated genes, named BrATGs, at the genome-wide level. The majority of the BrATGs were highly conserved over a long evolutionary period, and the expression patterns indicated that BrATGs were most highly expressed in the healing tissues and flowers. Furthermore, BrATGs responded to the stresses of the heavy metal Cd, drought, salt, and low and high temperatures to varying degrees. Among them, BrATG8c/8j was specifically induced in response to drastic temperature changes; BrATG4c was upregulated only in response to drought and salt stress; and BrATG8f/10/VTI12C was highly expressed only in response to Cd stress. This work will advance the understanding of the molecular mechanisms underlying the abiotic stress response in Chinese cabbage