Photonic chip-based low-noise microwave oscillator.

Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb1-3. Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division4,5. Narrow-linewidth self-injection-locked integrated lasers6,7 are stabilized to a miniature Fabry-Pérot cavity8, and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb9. The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of -96 dBc Hz-1 at 100 Hz offset frequency that decreases to -135 dBc Hz-1 at 10 kHz offset-values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems.

Fiber-coupled 2 mL vacuum-gap Fabry-Perot reference cavity for portable laser stabilization.

Vacuum-gap Fabry-Perot cavities are indispensable for the realization of frequency-stable lasers, with applications across a diverse range of scientific and industrial pursuits. However, making these cavity-based laser stabilization systems compact, portable, and rugged enough for use outside of controlled laboratory conditions has proven difficult. Here, we present a fiber-coupled 1396 nm laser stabilization system requiring no free-space optics or alignment, built for a portable strontium optical lattice clock. Based on a 2 mL vacuum-gap Fabry-Perot cavity, this system demonstrates thermal noise-limited performance and 1 × 10-14 fractional frequency instability. Fiber-integrated optical components have been instrumental in both advancing the field of optics and leveraging those advances across disciplines to facilitate other fields of study. This portable system represents a major step toward making the frequency stability of cavity-based systems broadly accessible.

Compact, portable, thermal-noise-limited optical cavity with low acceleration sensitivity.

We develop and demonstrate a compact (less than 6 mL) portable Fabry-Pérot optical reference cavity. A laser locked to the cavity is thermal noise limited at 2 × 10-14 fractional frequency stability. Broadband feedback control with an electro-optic modulator enables near thermal-noise-limited phase noise performance from 1 Hz to 10 kHz offset frequencies. The additional low vibration, temperature, and holding force sensitivity of our design makes it well suited for out-of-the-lab applications such as optically derived low noise microwave generation, compact and mobile optical atomic clocks, and environmental sensing through deployed fiber networks.

Substance P ameliorates TNF-α-mediated impairment of human aortic vascular cells in vitro.

Vascular diseases are caused by endothelial dysfunction due to inflammation. On endothelial injury, the expression of extracellular matrix (ECM) is enhanced and nitric oxide (NO) bioavailability becomes deficient. This condition affects endothelial metabolism and leads to vascular destruction. The aim of this investigation was to determine whether substance P (SP) is able to protect the endothelium against inflammatory stress. To this end, aortic endothelial cells were pre-treated with SP, followed by tumour necrosis factor α (TNF-α), and cellular responses were evaluated using a combination of cell biology and quantification assays, as well as western blot analyses. Our results show that TNF-α enhanced ECM expression and reduced NO production within 4 hours, promoting immune cell adhesion to the endothelium and monocyte chemoattractant protein-1 (MCP-1) secretion from aortic smooth muscle cells. However, SP treatment ameliorated TNF-α-induced endothelial impairment by maintaining low ECM levels. Our data suggest that this protective effect is mediated by Akt activation and NO-enriched conditions. The inhibition of aortic endothelial cell injury by SP also reduced MCP-1 production in aortic smooth muscle cells. Together, our data indicate that SP can protect aortic endothelial and smooth muscle cells from inflammatory injury, which suggests that SP may prevent cardiovascular disease.

Substance P Alleviates Retinal Pigment Epithelium Dysfunction Caused by High Glucose-Induced Stress.

When the retina is constantly affected by high glucose (HG) due to diabetes, the barrier function of the retinal pigment epithelium (RPE) is impaired, accompanied by unnecessary vascularization. This eventually leads to the development of diabetic retinopathy (DR). This study investigated the recovery effect of substance P (SP) on RPE injured by HG. RPE was treated with HG for 24 h, and HG-induced cellular injuries were confirmed. SP was added to the dysfunctional RPE. Compared to RPE in low glucose (LG) conditions, HG-damaged RPE had large, fibrotic cell shapes, and its cellular viability decreased. HG treatment reduced tight junction protein expression levels and caused oxidative stress by interrupting the antioxidant system; this was followed by inflammatory factor intracellular adhesion molecule-1 (ICAM-1), Monocyte chemotactic protein-1 (MCP-1), and angiogenesis factor vascular endothelial growth factor (VEGF) expression. SP treatment contributed to RPE recovery by enhancing cell viability, tight junction protein expression, and RPE function under HG conditions, possibly by activating the Akt signaling pathway. Importantly, SP treatment reduced ICAM-1, MCP-1, and VEGF expression. Collectively, SP activated survival signals to suppress oxidative stress and improve retinal barrier function in RPE, accompanied by immune suppression. This suggests the possible application of SP to diabetic retinal injuries.

Changes in Sleep Satisfaction of Korean Adolescents in the Pre- and Post-COVID-19 Eras and Its Effects on Health Behaviors.

Adolescence is a crucial period for cognitive and psychological development and physical maturation. During this period, hormonally influenced circadian rhythms lead to reduced hours of sleep, and it is important to determine whether sleep quality is sufficient for fatigue relief. Non-face-to-face classes during coronavirus disease-2019 (COVID-19) potentially affected adolescents' sleep quality, psychological state, amount of physical activity, smoking, alcohol consumption, and internet (smartphone) use. We investigated the effects of the COVID-19 situation on adolescents' sleep satisfaction and its relation to the aforementioned factors. Data of 109,281 adolescents collected via an online survey, conducted from 3 June 2019 to 12 July 2019 and from 3 August 2020 to 13 November 2020, were analyzed. Health status comparison between the satisfactory and unsatisfactory sleep groups yielded significant results (odds ratio [OR] = 1.10, confidence interval [CI] = 1.04-1.17) for 2020. In both groups, perceived health was worse in 2019 than in 2020 (OR = 2.72, CI = 2.53-2.92). During COVID-19, non-face-to-face classes increased adolescents' sleep satisfaction. Their psychological state improved, while amount of physical activity (muscle-strengthening exercises), average weight, and internet (smartphone) use increased. Smoking and alcohol consumption decreased.

Substance P Hinders Bile Acid-Induced Hepatocellular Injury by Modulating Oxidative Stress and Inflammation.

Liver failure is an outcome of chronic liver disease caused by steatohepatitis and cholestatic injury. This study examined substance P (SP) effect on liver injury due to cholestatic stress caused by excessive bile acid (BA) accumulation. Chenodeoxycholic acid (CDCA) was added to HepG2 cells to induce hepatic injury, and cellular alterations were observed within 8 h. After confirming BA-mediated cellular injury, SP was added, and its restorative effect was evaluated through cell viability, reactive oxygen species (ROS)/inflammatory cytokines/endothelial cell media expression, and adjacent liver sinusoidal endothelial cell (LSEC) function. CDCA treatment provoked ROS production, followed by IL-8 and ICAM-1 expression in hepatocytes within 8 h, which accelerated 24 h post-treatment. Caspase-3 signaling was activated, reducing cell viability and promoting alanine aminotransferase release. Interestingly, hepatocyte alteration by CDCA stress could affect LSEC activity by decreasing cell viability and disturbing tube-forming ability. In contrast, SP treatment reduced ROS production and blocked IL-8/ICAM-1 in CDCA-injured hepatocytes. SP treatment ameliorated the effect of CDCA on LSECs, preserving cell viability and function. Collectively, SP could protect hepatocytes and LSECs from BA-induced cellular stress, possibly by modulating oxidative stress and inflammation. These results suggest that SP can be used to treat BA-induced liver injury.

Effect of Job Stress on Burnout among Nurses Responding to COVID-19: The Mediating Effect of Resilience.

Background: This study was conducted to evaluate the relationship of job stress, burnout, and resilience of 271 nurses who worked alternately at a university hospital in South Korea Province and a state-designated inpatient ward for COVID-19 in Korea. Methods: The study sample included nurses who worked at a university hospital in South Korea, during the period between February 2020 and May 2021. The participants (n = 271) responded to an online survey between April 2021 and 12 May 2021. The questionnaire included information related to job stress, burn out, and resilience. Results: In phase 1 of regression, job stress had a significant negative effect on resilience of recovery (ß = −0.397, p < 0.001). In phase 2, job stress had a significant positive effect on burnout (ß = 0.513, p < 0.001). In phase 3, resilience had a significant negative effect on burnout (ß = −0.459, p < 0.001). Seventy-five percent of burnout was directly associated with job stress, while 25% of burnout was indirectly associated through mediated effects, through resilience. Conclusions: The promotion of resilience would not only serve as the basis for active coping in situations where burnout and stress are severe, but also serve as a basic driving force for actively overcoming them. Further study to cope with stress and reduce burnout at the organizational level should be conducted.

Awareness and Needs of Smoking Cessation Services for Female Emotional Laborers, Parcel Delivery Workers, Transportation Workers, and Construction Workers in South Korea.

Although South Korea has implemented various smoking cessation services, women who are emotional laborers, as well as parcel delivery, transportation, and construction workers, have poor access to these services. This study evaluated the smoking-related characteristics of workers in these four occupations as well as the awareness of and need for smoking cessation services. In total 808 workers in these four occupations aged 19 years and above were recruited nationwide and had their data analyzed. The participants' age, marital status, number of work hours per week, job-related stress, age when they started smoking, average number of cigarettes a day, types of tobacco products, close relationships to others who smoke, number of attempts to quit smoking, plans to quit smoking, awareness of cessation services, prior utilization of cessation services, and need for cessation services were surveyed. Compared with parcel delivery workers, female emotional laborers and transportation and construction workers had more attempts to quit smoking, plans to quit smoking, and prior utilization of smoking cessation services, moreover, construction workers had a significantly lower awareness of smoking cessation services. Parcel delivery workers need smoking cessation programs, mobile applications to help them quit smoking, and improvements in their work environments. Cessation services and education should be promoted at workplaces and among managers.

Chip-based laser with 1-hertz integrated linewidth.

Lasers with hertz linewidths at time scales of seconds are critical for metrology, timekeeping, and manipulation of quantum systems. Such frequency stability relies on bulk-optic lasers and reference cavities, where increased size is leveraged to reduce noise but with the trade-off of cost, hand assembly, and limited applications. Alternatively, planar waveguide-based lasers enjoy complementary metal-oxide semiconductor scalability yet are fundamentally limited from achieving hertz linewidths by stochastic noise and thermal sensitivity. In this work, we demonstrate a laser system with a 1-s linewidth of 1.1 Hz and fractional frequency instability below 10-14 to 1 s. This low-noise performance leverages integrated lasers together with an 8-ml vacuum-gap cavity using microfabricated mirrors. All critical components are lithographically defined on planar substrates, holding potential for high-volume manufacturing. Consequently, this work provides an important advance toward compact lasers with hertz linewidths for portable optical clocks, radio frequency photonic oscillators, and related communication and navigation systems.

The Utilization of National Tobacco Cessation Services among Female Smokers and the Need for a Gender-Responsive Approach.

Despite the steadily increasing prevalence of female smoking, gender-responsive tobacco cessation services have not been widely provided worldwide. The purpose of this study is to identify factors associated with the use of tobacco cessation services among female tobacco product users in Korea from a national perspective. We performed a logistic regression analysis using data from 663 female smokers; 11.0% of female smokers had used government-supported smoking cessation services. A logistic regression model showed a statistically significant association between the utilization of smoking cessation services and a history of pregnancy and childbirth, depression, current use of heated tobacco products and multiple tobacco products, parental smoking status and receiving advice to quit. With regard to the motivation ruler, those in their 50s reported a higher importance than those in their 20s. Weight gain concerns when quitting smoking were the lowest among the participants aged 19-29. The need to develop gender-specific smoking cessation programs is the highest among the participants aged 39-49 and the lowest among those aged 19-29. This study suggests several factors related to the utilization of national health services among female smokers. Further studies considering gender-specific needs for the development of gender-responsive tobacco cessation support are needed.

Successful Smoking Cessation among Women Smokers Based on Utilizing National Smoking Cessation Service Type in Korea.

BACKGROUND: This study aimed to evaluate the successful smoking cessation across different national smoking cessation services. METHODS: This study included data that had been previously entered into the integrated information system for smoking cessation services and comprised 144,688 participants after excluding missing data. These clinics provide face-to-face counseling, phone calls, text messages, and e-mail services for six months and nine sessions. RESULTS: The women-only program had the lowest success rate (11.3%). Compared with the women-only program, the six-month success rate of smoking cessation clinic at public health centers (OR = 3.72, CI = [3.52, 3.92]), visiting-type smoking cessation clinics (OR = 2.97, CI = [2.79, 3.16]), the residential 4 -night 5-day program (OR = 7.79, CI = [6.49, 9.35]), and a program for inpatients (OR = 2.36, CI = [1.89, 2.94]) showed a significant increase. CONCLUSIONS: Emotional labor workers who participated in the women-only program had low smoking cessation success rates, while those who participated in the residential 4-night 5-day program had high success rates.