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Pain is an experience of unpleasant sensations and emotions associated with actual or potential tissue damage. In the global context, billions of people are affected by pain disorders. There are particular challenges in the measurement and assessment of pain, and the commonly used pain measuring tools include traditional subjective scoring methods and biomarker-based measures. The main tools for biomarker-based analysis are electroencephalography (EEG), electrocardiography and functional magnetic resonance. The EEG-based quantitative pain measurements are of immense value in clinical pain management and can provide objective assessments of pain intensity. The assessment of pain is now primarily limited to the identification of the presence or absence of pain, with less research on multilevel pain. High power laser stimulation pain experimental paradigm and five pain level classification methods based on EEG data augmentation are presented. First, the EEG features are extracted using modified S-transform, and the time-frequency information of the features is retained. Based on the pain recognition effect, the 20–40 Hz frequency band features are optimized. Afterwards the Wasserstein generative adversarial network with gradient penalty is used for feature data augmentation. It can be inferred from the good classification performance of features in the parietal region of the brain that the sensory function of the parietal lobe region is effectively activated during the occurrence of pain. By comparing the latest data augmentation methods and classification algorithms, the proposed method has significant advantages for the five-level pain dataset. This research provides new ways of thinking and research methods related to pain recognition, which is essential for the study of neural mechanisms and regulatory mechanisms of pain. [ABSTRACT FROM AUTHOR]

Lead halide perovskites (LHPs) are emerging as promising candidates for use in various high-performance optoelectronic applications, yet their photophysics remains a topic of debate. Here, we theoretically investigated how the ultrafast optical properties of a few prototype LHPs are affected by many-body interactions, including the bandgap renormalization (BGR) effect, the band-filling (BF) effect, the free-carrier absorption effect, and the exciton effect, at carrier densities ranging from 1016 to 1019 cm−3. The results show that the exciton absorption becomes more obvious near the bandgap with increasing exciton energy (as the halogen component of the LHP is varied from I to Cl). Transient reflectivity results indicate that the signal has one peak below the bandgap as a result of the BGR effect at low carrier densities and one valley above the bandgap originating from the BF effect at high carrier densities. In addition, the absorbance decreases with increasing the carrier density as a result of the BF effect because the filled energy levels are observed at 2 meV above the bottom of the conduction band. The results of the present work are expected to promote the application of LHPs in solar cells, light-emitting diodes, and other photoelectric devices. [ABSTRACT FROM AUTHOR]

MAPbBr3 quantum dots in SiO2 mesopores (∼ 4. 4 nm) were prepared by the spin-coating method, and their luminescence and nonlinear optical properties were studied by time-resolved photoluminescence (TRPL) and Z-scan techniques. The results showed that the absorption and photoluminescence peaks are at 464 nm and 476 nm, respectively. The TRPL spectroscopy showed two relaxation processes, a short lifetime (1.04 ns) and a long lifetime (4.49 ns), attributed to the trap–capture recombination and the electron–hole radiative recombination, respectively. Two-photon absorption (TPA) coefficient was 529 cm/GW at 800 nm. The nonlinear signal changed from TPA to saturable absorption with increase in light intensity. [ABSTRACT FROM AUTHOR]

The development of fluorescent probe for hydrazine (N2H4) detection has attracted much attention due to the important role of N2H4 plays in the fields of medicine, agriculture, biology and environments. In this paper, the optical properties and water solubility of two novel two-photon fluorescent molecular probes (Probe1 and Probe2) before and after the reaction with N2H4 are studied by using the density function theory. The results show that electronic distribution and transition dipole moment of the probes are obviously changed after the reaction with N2H4, thus the optical properties of the molecules are influenced and the detection of N2H4 are realized. In addition, photoinduced electron transfer processes for Probe1 and Probe2 in the presence of N2H4 are theoretically characterized, which explains the experimental observations from the microscopic mechanism. Special attention has been paid on the analysis of the two-photon absorption for the probes with the absence and presence of N2H4 by the response theory method. Both probes with good water solubility show large variation on the two-photon absorption cross section when reacts with N2H4. In particular, the two-photon absorption response of Probe2 is more obvious, so it possesses preferable two-photon fluorescence microscopic imaging ability. More importantly, the receptor effect on the sensing performances of the probes are demonstrated, providing a theoretical reference for the design and synthesis on more efficient two-photon fluorescence N2H4 probes. Our study provides necessary information on the response mechanism of the studied chemosensors and helps to establish the relationship between the structure and optical properties of two-photon fluorescence N2H4 probes. [ABSTRACT FROM AUTHOR]