Nonlinear dynamics of an interband cascade laser with optical injection.

This work reports the nonlinear dynamics of a mid-infrared interband cascade laser (ICL) subject to optical injection. It is shown that the stable locking regime is asymmetric and broadens with increasing injection strength. Outside the locking regime, the ICL mostly produces period-one oscillations. However, three categories of periodic pulse oscillations are observed in the vicinity of the Hopf bifurcation and the saddle-node bifurcation. In particular, it is found that the ICL generates broadband chaos at a near-threshold pump current, and the chaos bandwidth is over 300 MHz.

Broadband chaos of an interband cascade laser with a 6-GHz bandwidth.

Near-infrared semiconductor lasers subject to optical feedback usually produce chaos with a broad bandwidth of a few GHz. However, the reported mid-infrared interband cascade lasers (ICLs) only show chaos with a limited bandwidth below 1 GHz. Here we show that an ICL with optical feedback is able to generate broadband chaos as well. The mid-infrared chaos exhibits a remarkable bandwidth of about 6 GHz, which is comparable to that of the near-infrared counterpart. In addition, the spectral coverage in the electrical domain reaches as high as 17.7 GHz. It is found that the chaos bandwidth generally broadens with increasing feedback ratio and/or increasing pump current of the laser, while it is insensitive to the feedback length.

Green Synthesis of Dracocephalum kotschyi-Coated Silver Nanoparticles: Antimicrobial, Antioxidant, and Anticancer Potentials.

BACKGROUND The environmentally friendly production of silver nanoparticles (AgNPs) has gained significant attention as a sustainable alternative to traditional chemical methods. This study focused on synthesizing AgNPs using extract of Dracocephalum kotschyi (D. kotschyi), a medicinal plant. MATERIAL AND METHODS The biosynthesis of AgNPs was monitored using UV-visible spectrophotometry. The role of phytoconstituents from D. kotschyi in stabilizing AgNPs was analyzed using Fourier-transform infrared (FTIR) spectroscopy. Dynamic light scattering (DLS) spectroscopy was used to determine the size, charge, and polydispersity of the nanoparticles, while scanning electron microscopy (SEM) was employed to assess their morphology. We evaluated the antimicrobial efficacy of the synthesized AgNPs against various bacteria, their antioxidant properties via a 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, and their cytotoxic activity against the HeLa cervical cancer cell line. RESULTS The formation of AgNPs was indicated by a color change and the emergence of a surface plasmon resonance peak at 418 nm. The nanoparticles demonstrated significant antimicrobial, antioxidant, cytotoxic, and anticancer activities. Morphology, size, and shape analysis revealed nearly spherical particles with an average size of 43 nm. FTIR confirmed the presence of phenolic compounds in the extract, serving as reducing and capping agents. X-ray diffraction (XRD) analysis confirmed the crystalline structure of the nanoparticles. Antimicrobial assessments showed effectiveness against Escherichia coli and Staphylococcus aureus. The DPPH scavenging assay demonstrated efficient antioxidant activity, and potent apoptotic anticancer effects were observed on cervical cancer cells. CONCLUSIONS The extract of D. kotschyi was effective as a reducing agent in the environmentally friendly synthesis of AgNPs, which exhibited noteworthy antimicrobial, antioxidant, and anticancer properties. These findings suggest potential biomedical applications for the synthesized AgNPs.

Uniform spike trains in optically injected quantum cascade oscillators.

It has been experimentally and theoretically analyzed that noise-induced excitability in quantum well and quantum dot semiconductor laser systems usually produces sharp spike patterns of non-uniform amplitude. In this paper, we experimentally record that a quantum cascade oscillator injected externally with a monochromatic laser beam exhibits a series of highly uniform spike trains, which occur in the proximity of the saddle-node bifurcation. Theoretical analysis based on a properly designed single-mode rate equation model endowed with quantum noise reveals that this high uniformity has its primary origin in the ultrashort carrier lifetime of the quantum cascade laser gain medium that is typically close to 1 ps.

Nonlinear dynamics of a quantum cascade laser with optical injection.

This work presents the nonlinear dynamics of a quantum cascade laser subject to optical injection. Within the stable locking regime, the optical power shows a hysteresis behavior as a function of the detuning frequency. Outside the stable locking regime, the laser mostly produces periodic oscillations. However, the laser pumped at a high pump current also generates spiking pulsations with uniform amplitude, which occur in the vicinity of the negative locking boundary.

Copper ion detection using novel silver nanoclusters stabilized with amido black 10B.

Novel fluorescent silver nanoclusters (AgNCs) were synthesized using amido black 10B (AB) as a stabilizing agent and then employed for the detection of copper ions (Cu(2+)). The AB-stabilized AgNCs (AB-AgNCs) were well dispersed in aqueous solution with an average diameter of around 1.3 nm and exhibited illustrious blue fluorescence emission. Moreover, the fluorescence of AB-AgNCs could be quenched efficiently by Cu(2+), which might be a result of the coordination between Cu(2+) and the free recognition group of AB on surfaces of AB-AgNCs, inducing the aggregation of AB-AgNCs. Based on the linear decrease of fluorescence intensity, the Cu(2+) concentration was determined in the range of 0.01-1.1 µmol L(-1) and the limit of detection (LOD) was 4.0 nΜ. In addition, the detection of Cu(2+) could be performed with AB-AgNCs in the presence of other ions, including 13 kinds of conventional metal ions and 11 kinds of anions. Based on the above experiment, the developed AB-AgNC probe was successfully further applied to detect Cu(2+) in three electroplating effluents, which showed high accuracy.

Enhancing emotional expression in cat-like robots: strategies for utilizing tail movements with human-like gazes.

In recent years, there has been a significant growth in research on emotion expression in the field of human-robot interaction. In the process of human-robot interaction, the effect of the robot's emotional expression determines the user's experience and acceptance. Gaze is widely accepted as an important media to express emotions in human-human interaction. But it has been found that users have difficulty in effectively recognizing emotions such as happiness and anger expressed by animaloid robots that use eye contact individually. In addition, in real interaction, effective nonverbal expression includes not only eye contact but also physical expression. However, current animaloid social robots consider human-like eyes as the main emotion expression pathway, which results in a dysfunctional robot appearance and behavioral approach, affecting the quality of emotional expression. Based on retaining the effectiveness of eyes for emotional communication, we added a mechanical tail as a physical expression to enhance the robot's emotional expression in concert with the eyes. The results show that the collaboration between the mechanical tail and the bionic eye enhances emotional expression in all four emotions. Further more, we found that the mechanical tail can enhance the expression of specific emotions with different parameters. The above study is conducive to enhancing the robot's emotional expression ability in human-robot interaction and improving the user's interaction experience.

Good Deeds Could Come From Frustrated Individuals.

Frustration is often seen as negative, but as to whether it may have a positive impact on the individual is still undecided. This research was conducted to explore the influence of frustration on altruistic tendency and altruistic level in college students (17-21 years old). By presenting a highly difficult task combined with negative feedback, we effectively induced frustration in Experiment 1 (n = 70). By assessing the donation behavior of participants (n = 54) in a real-life scenario following the experimental manipulation of frustration, we examined the relationship between frustration and altruism in Experiment 2. Results showed that frustrating situations could, on some level, improve altruistic behavior [t (8.834) = 3.013, p = 0.015]. More specifically, among participants who donated, the amount donated was higher in the frustration group compared to the control (fulfillment) group; the proportion of people who donated did not differ by group.

Sevoflurane inhibits progression of glioma via regulating the HMMR antisense RNA 1/microRNA-7/cyclin dependent kinase 4 axis.

Sevoflurane (Sev) is a volatile anesthetic that can inhibit tumor malignancy. Glioma is a main brain problem, but the mechanism of Sev in glioma progression is largely unclear. This study aims to explore a potential regulatory network of long noncoding RNA (lncRNA)/microRNA (miRNA)/mRNA associated with the function of Sev in glioma progression. LncRNA HMMR antisense RNA 1 (HMMR-AS1), miR-7 and cyclin-dependent kinase 4 (CDK4) abundances were examined via quantitative reverse transcription polymerase chain reaction and western blot. Cell viability, invasion, and colony formation ability were analyzed via cell counting kit-8, transwell analysis, and colony formation. The target association was analyzed via dual-luciferase reporter analysis and RNA pull-down. The in vivo function of Sev was investigated by xenograft model. HMMR-AS1 abundance was increased in glioma tissues and cells, and reduced via Sev. Sev constrained cell viability, invasion, and colony formation ability via decreasing HMMR-AS1 in glioma cells. miR-7 expression was decreased in glioma, and was targeted via HMMR-AS1. HMMR-AS1 silence restrained cell viability, invasion, and colony formation ability by up-regulating miR-7 in glioma cells. Sev increases miR-7 abundance via decreasing HMMR-AS1. CDK4 was targeted via miR-7, and highly expressed in glioma. miR-7 overexpression inhibited cell viability, invasion, and colony formation ability via reducing CDK4 in glioma cells. CDK4 expression was reduced by Sev via HMMR-AS1/miR-7 axis. Sev suppressed cell growth in glioma by regulating HMMR-AS1. Sev represses glioma cell progression by regulating HMMR-AS1/miR-7/CDK4 axis.