Building atomic clock lasers with integrated photonics
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Vernier microcombs for integrated optical atomic clocks
Kerr microcombs have drawn substantial interest as mass-manufacturable, compact alternatives to bulk frequency combs. This could enable the deployment of many comb-reliant applications previously confined to laboratories. Particularly enticing is the prospect of microcombs performing optical frequency division in compact optical atomic clocks. Unfortunately, it is difficult to meet the self-referencing requirement of microcombs in these systems owing to the approximately terahertz repetition rates typically required for octave-spanning comb generation. In addition, it is challenging to spectrally engineer a microcomb system to align a comb mode with an atomic clock transition with a sufficient signal-to-noise ratio. Here we adopt a Vernier dual-microcomb scheme for optical frequency division of a stabilized ultranarrow-linewidth continuous-wave laser at 871 nm to an ~235 MHz output frequency. This scheme enables shifting an ultrahigh-frequency (~100 GHz) carrier-envelope offset beat down to frequencies where detection is possible and simultaneously placing a comb line close to the 871 nm laser—tuned so that, if frequency doubled, it would fall close to the clock transition in 171Yb+. Our dual-comb system can potentially combine with an integrated ion trap towards future chip-scale optical atomic clocks.
The circadian clock in enamel development
Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes. The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli. Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown. Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms. Teeth enamel is formed by enamel-forming cells known as ameloblasts, which are regulated and orchestrated by the circadian clock during amelogenesis. This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis. Several physiological processes are involved, including gene expression, cell morphology, metabolic changes, matrix deposition, ion transportation, and mineralization. Next, the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed. Circadian rhythm disruption can directly lead to Enamel Hypoplasia, which might also be a potential causative mechanism of amelogenesis imperfecta. Finally, future research trajectory in this field is extrapolated. It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.
Transcriptional dynamics in type 2 diabetes progression is linked with circadian, thermogenic, and cellular stress in human adipose tissue
The prevalence of type 2 diabetes (T2D) has increased significantly over the past three decades, with an estimated 30–40% of cases remaining undiagnosed. Brown and beige adipose tissues are known for their remarkable catabolic capacity, and their ability to diminish blood glucose plasma concentration. Beige adipose tissue can be differentiated from adipose-derived stem cells or through transdifferentiation from white adipocytes. However, the impact of T2D progression on beige adipocytes’ functional capacity remains unclear. Transcriptomic profiling of subcutaneous adipose tissue biopsies from healthy normal-weight, obese, prediabetic obese, and obese subjects diagnosed with T2D, reveals a progressive alteration in cellular processes associated with catabolic metabolism, circadian rhythms, thermogenesis-related signaling pathways, cellular stress, and inflammation. MAX is a potential transcription factor that links inflammation with the circadian clock and thermogenesis during the progression of T2D. This study unveils an unrecognized transcriptional circuit that increasingly disrupts subcutaneous adipose tissue oxidative capacity during the progression of T2D. These findings could open new research venues for developing chrono-pharmaceutical strategies to treat and prevent T2D.
Signaling pathway mechanisms of circadian clock gene Bmal1 regulating bone and cartilage metabolism: a review
Circadian rhythm is ubiquitous in nature. Circadian clock genes such as Bmal1 and Clock form a multi-level transcription-translation feedback network, and regulate a variety of physiological and pathological processes, including bone and cartilage metabolism. Deletion of the core clock gene Bmal1 leads to pathological bone alterations, while the phenotypes are not consistent. Studies have shown that multiple signaling pathways are involved in the process of Bmal1 regulating bone and cartilage metabolism, but the exact regulatory mechanisms remain unclear. This paper reviews the signaling pathways by which Bmal1 regulates bone/cartilage metabolism, the upstream regulatory factors that control Bmal1, and the current Bmal1 knockout mouse models for research. We hope to provide new insights for the prevention and treatment of bone/cartilage diseases related to circadian rhythms.
Advancements in ultrafast photonics: confluence of nonlinear optics and intelligent strategies
Automatic mode-locking techniques, the integration of intelligent technologies with nonlinear optics offers the promise of on-demand intelligent control, potentially overcoming the inherent limitations of traditional ultrafast pulse generation that have predominantly suffered from the instability and suboptimality of open-loop manual tuning. The advancements in intelligent algorithm-driven automatic mode-locking techniques primarily are explored in this review, which also revisits the fundamental principles of nonlinear optical absorption, and examines the evolution and categorization of conventional mode-locking techniques. The convergence of ultrafast pulse nonlinear interactions with intelligent technologies has intricately expanded the scope of ultrafast photonics, unveiling considerable potential for innovation and catalyzing new waves of research breakthroughs in ultrafast photonics and nonlinear optics characters.
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