Mobile phone-based smoking-cessation intervention in patients with chronic diseases in China: a Sequential Multiple Assignment Randomized Trial (SMART).

INTRODUCTION: Mobile phone-based interventions show promise for smoking cessation but often face low engagement. This study assessed the feasibility and preliminary effectiveness of a 2-phase, multi-component mobile phone-based smoking cessation intervention for patients with chronic diseases. METHODS: This Sequential Multiple Assignment Randomized Trial (SMART) recruited smokers with chronic diseases from hospitals in Zhuhai, China. Participants received brief cessation advice and were randomized to personalized chat support (PCS, n=64) or group chat support (GCS, n=64) for 1 month. At 1-month, PCS non-responders (continuing smokers) were re-randomized to receive either multi-component optional support (MOS) or continued PCS for 2 months. GCS non-responders were re-randomized to receive PCS or continued GCS. Responders continued with their initial intervention for 2 months. Feasibility outcomes included eligibility, participation, retention, intervention engagement, and satisfaction. Preliminary effectiveness was assessed by abstinence rates among non-responders. RESULTS: Of 160 screened, 128 (all male, 46.1% aged≤39 years) participated. At 1-month, 51 and 53 non-responded to PCS and GCS, respectively. Of them, 26 were re-randomized to receive PCS-MOS and 26 to receive GCS-PCS. At 6-month, PCS-MOS showed a non-significant higher validated abstinence rate compared to PCS alone (11.5% vs. 4.2%, odds ratio [OR] 3.13, 95%CI 0.30-32.31, P=0.34), GCS-PCS showed a non-significant lower validated abstinence rate compared to GCS (0% vs. 11.1%, OR 0.50, 95%CI 0.15-1.67, P=0.26). CONCLUSIONS: This trial showed the feasibility of leveraging hospital visits as teachable opportunities and integrating mobile phone-based smoking cessation support into chronic disease management in China. Optional treatments alongside mobile support showed preliminary effectiveness.

Sub-Nanosecond Single Mode-Locking Pulse Generation in an Idler-Resonant Intracavity KTA Optical Parametric Oscillator Driven by a Dual-Loss-Modulated Q-Switched and Mode-Locked Laser with an Acousto-Optic Modulator and MoWS2.

The synthesis of 2D MoWS2 nanosheets involved the liquid-phase exfoliation technique was explored in this paper. The nonlinear optical response of MoWS2 was characterized in the 1 µm wavelength range, and its suitability as a saturable absorber (SA) was confirmed. Experimental demonstrations were conducted by using MoWS2 as an SA in an idler-resonant intracavity KTA optical parametric oscillator (OPO) driven by a dual-loss-modulated Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM). By appropriately tuning the pump power and the AOM repetition rate, the Q-switched envelope pulse widths for the signal and idler waves could be significantly reduced to be shorter than the cavity round-trip transit time, i.e., the interval between two neighboring mode-locking pulses. Consequently, this enabled the generation of sub-nanosecond single mode-locking pulses with a low repetition rate, high pulse energy, and remarkable stability. With a repetition rate of 1 kHz and maximal pulse energies of 318 µJ and 169 µJ, respectively, sub-nanosecond single mode-locking pulses of the signal and idler waves were generated. The theoretical model was established using coupled rate equations with a Gaussian spatial distribution approximation. The numerical simulation results for generating sub-nanosecond single mode-locking pulses for the signal and idler waves within their respective Q-switched envelopes aligned fundamentally with the experimental results, proving that MoWS2 can be a potential nanomaterial for further optoelectronic applications.

One-Step Fabrication of 0D Cs4PbBr6 Perovskite with Nonlinear Optical Properties for Ultrafast Pulse Generation.

Low-dimensional lead halide perovskites demonstrate remarkable nonlinear optical characteristics attributed to their distinctive physical structures and electronic properties. Nevertheless, the investigation into their nonlinear optical properties remains in its incipient stages. This study addresses this gap by precisely controlling solvent volumes to synthesize both 0D Cs4PbBr6 and Cs4PbBr6/CsPbBr3 perovskites. Remarkably, as saturable absorbers, both pure Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites exhibit favorable nonlinear optical properties within the C-band, showcasing modulation depths of 9.22% and 16.83%, respectively. Moreover, for the first time, Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites have been successfully integrated into erbium-doped fiber lasers to realize the mode-locking operations. The utilization of the Cs4PbBr6/CsPbBr3 composites as a saturable absorber that enables the generation of conventional soliton mode-locked laser pulses with a pulse duration of 688 fs, and a repetition frequency of 10.947 MHz at a central wavelength of 1557 nm. Cs4PbBr6 is instrumental in generating laser pulses at a frequency of 10.899 MHz, producing pulse widths of 642 fs at the central wavelength of 1531.2 nm and 1.02 ps at the central wavelength of 1565.3 nm, respectively. The findings of this investigation underscore the potential utility of 0D Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites as promising materials for optical modulation within fiber laser applications.

Engagement With a Mobile Chat-Based Intervention for Smoking Cessation: A Secondary Analysis of a Randomized Clinical Trial.

Importance: Determining how individuals engage with digital health interventions over time is crucial to understand and optimize intervention outcomes. Objective: To identify the engagement trajectories with a mobile chat-based smoking cessation intervention and examine its association with biochemically validated abstinence. Design, Setting, and Participants: A secondary analysis of a pragmatic, cluster randomized clinical trial conducted in Hong Kong with 6-month follow-up. From June 18 to September 30, 2017, 624 adult daily smokers were recruited from 34 community sites randomized to the intervention group. Data were analyzed from March 6 to October 30, 2023. Intervention: Chat-based cessation support delivered by a live counselor via a mobile instant messaging app for 3 months from baseline. Main Outcomes and Measures: Group-based trajectory modeling was used to identify engagement trajectories using the participants' weekly responses to the messages from the counselor over the 3-month intervention period. The outcome measures were biochemically validated tobacco abstinence at 3-month (end of treatment) and 6-month follow-ups. Covariates included sex, age, educational level, nicotine dependence, past quit attempt, and intention to quit at baseline. Results: Of 624 participants included in the analysis, 479 were male (76.8%), and the mean (SD) age was 42.1 (16.2) years. Four distinct engagement trajectories were identified: low engagement group (447 [71.6%]), where participants maintained very low engagement throughout; rapid-declining group (86 [13.8%]), where participants began with moderate engagement and rapidly decreased to a low level; gradual-declining group (58 [9.3%]), where participants had high initial engagement and gradually decreased to a moderate level; and high engagement group (58 [5.3%]), where participants maintained high engagement throughout. Compared with the low engagement group, the 6-month validated abstinence rates were significantly higher in the rapid-declining group (adjusted relative risk [ARR], 3.30; 95% CI, 1.39-7.81), gradual-declining group (ARR, 5.17; 95% CI, 2.21-12.11), and high engagement group (ARR, 4.98; 95% CI, 1.82-13.60). The corresponding ARRs (95% CI) of 3-month validated abstinence were 4.03 (95% CI, 1.53-10.59), 5.25 (95% CI, 1.98-13.88), and 9.23 (95% CI, 3.29-25.86). Conclusions and Relevance: The findings of this study suggest that higher levels of engagement with the chat-based smoking cessation intervention were associated with greater biochemically validated tobacco abstinence. Improving engagement with digital interventions may increase intervention benefits. Trial Registration: ClinicalTrials.gov Identifier: NCT03182790.

Ultrafast nonlinear optical response of layered violet phosphorus for femtosecond noise-like pulse generation.

As a new member of two-dimensional (2D) phosphorene, 2D layered violet phosphorus (VP) has unique optoelectronic properties and good environmental stability, showing its huge advantages in optoelectronic applications. In this paper, the ultrafast nonlinear optical (NLO) properties of layered VP nanosheets at 1 µm band were explored, which exhibit an obvious saturable absorption response with a modulation depth of ∼1.97%. Meanwhile, the fast and slow carrier lifetimes of VP nanosheets at 1µm band were also determined as 295.9 fs and 2.36 ps, respectively, which are much shorter than that of most reported 2D materials. The excellent saturable absorption response combined with ultrashort carrier lifetimes indicate the prospect of layered VP nanosheets as a fast saturable absorber (SA) for ultrafast laser modulation. Then we demonstrated a Yb-doped fiber laser based on the VP-deposited taper-shaped fiber (TSF) SA, which delivers stable Q-switched mode-locked (QSML) pulses, dual-wavelength mode-locked pulses and 404-fs noise-like pulses. This work fully demonstrates the great potential of 2D VP materials for 1 µm ultrashort laser pulse generation.

Six-watt diode-pumped Tm:GdVO4 laser at 2.29†µm.

A compact Tm:GdVO4 laser pumped by a 794 nm laser diode generated 6.09 W at 2.29 µm (3H4 → 3H5 Tm3+ transition) with a high slope efficiency of 30.8% and linear laser polarization (π). The polarized spectroscopic properties of Tm3+ in GdVO4 were also revised. The peak stimulated-emission cross section of Tm3+ is 2.97 × 10-20 cm2 at 2280 nm, corresponding to an emission bandwidth of 42 nm for π-polarized light.

Diode-pumped efficient high-power cascade Tm:GdVO4 laser simultaneously operating at ∼2†µm and ∼2.3 µm.

The laser diode (LD)-pumped efficient high-power cascade Tm:GdVO4 laser simultaneously operating on the 3F4 → 3H6 (at ∼2 µm) and 3H4 → 3H5 (at ∼2.3 µm) Tm3+ transition was first reported in this paper. The cascade Tm:GdVO4 laser generated a maximum total continuous-wave (CW) laser output power of 8.42 W with a slope efficiency of 40%, out of which the maximum ∼2.3 µm CW laser output power was 2.88 W with a slope efficiency of 14%. To our knowledge, 2.88 W is the highest CW laser output power amongst the LD-CW-pumped ∼2.3 µm Tm3+-doped lasers reported so far.

Optical absorption of bismuthene with a single vacancy: first-principle calculations.

The exceptional mechanical, electronic, topological, and optical properties, make bismuthene an ideal candidate for various applications in ultrafast saturation absorption and spintronics. Despite the extensive research efforts devoted to synthesizing this material, the introduction of defects, which can significantly affect its properties, remains a substantial obstacle. In this study, we investigate the transition dipole moment and joint density of states of bismuthene with/without single vacancy defect via energy band theory and interband transition theory. It is demonstrated that the existence of the single defect enhances the dipole transition and joint density of states at lower photon energies, ultimately resulting in an additional absorption peak in the absorption spectrum. Our results suggest that the manipulation of defects in bismuthene has enormous potential for improving the optoelectronic properties of this material.

Third-order optical nonlinearity and passively Q-switching operation with BiOCl nanosheets at 1.3†µm.

In this contribution, we measured the third-order nonlinear optical response of bismuth oxychloride (BiOCl) nanosheets with the open-aperture (OA) and the closed-aperture (CA) Z-scan techniques with a variable excitation intensity at 1.34 µm. The effective nonlinear absorption coefficient ßeff and the nonlinear refractive index n2 of the prepared BiOCl nanosheets with abundant oxygen vacancies were obtained under the excitation intensity. The third-order nonlinear optical susceptibility |χ(3)| was 1.64 × 10-9 esu. The nonlinear optical features of BiOCl enabled it as a superb saturable absorber for pulse laser generation. As a consequence, we demonstrated the first passively Q-switched Nd:GdVO4 laser with the BiOCl saturable absorber, producing a shortest pulse duration of 543 ns and a highest repetition rate of 227 kHz, leading to a maximum pulse energy of 74 nJ. Our findings show that BiOCl nanosheets with oxygen vacancies have large nonlinear optical sensitivities and can be exploited to generate optical pulses.

2-µm nonlinear post-compression for generating ∼100-MHz few-cycle laser pulses with watt-level average power.

We firstly report a high pulse repetition rate (101.4 MHz) nonlinear post-compression based on the normal dispersion fiber (NDF) operating in 2-µm wavelength region. With only one-stage NDF-based nonlinear pulse compressor, the 2-µm ultrafast laser pulses are compressed from ∼460 fs down to 70 fs, corresponding to ∼10.4 optical oscillation cycle. With two-stage nonlinear pulse compressor, the input ultrafast laser pulses are further compressed to 28.3 fs (∼4.3 optical oscillation cycle). In each case, the average power of the compressed 2-µm laser pulses exceeds 1 W, which is believed to be the highest average power never achieved at ∼100-MHz pulse repetition rate. The efficiencies of the one-stage and two-stage nonlinear pulse compressors are 64% and 47% respectively.

Large-scale few-layered MoS2 as a saturable absorber for Q-switching operation at 2.3†µm.

In this Letter, the fabrication of large-scale (50.8 mm in diameter) few-layered MoS2 with physical vapor deposition on sapphire is described. Open-aperture Z-scan technology with a home-made excitation source at 2275 nm was applied to explore its nonlinear saturable absorption properties. The as-grown few-layered MoS2 membrane possessed a modulation depth of 17% and a saturable intensity of 1.185 MW cm-2. As a consequence, the deposited MoS2 membrane was exploited as a saturable absorber to realize a passively Q-switched Tm:YAP laser for the first time, to the best of our knowledge. Pulses as short as 316 ns were generated with a repetition rate of 228 kHz, corresponding to a peak power of 5.53 W. Results confirmed that the two-dimensional layered MoS2 could be beneficial for mid-infrared photonic applications.

Diode-pumped Tm3+,Ho3+ co-doped GAGG mode-locking laser near the 2.1µm wavelength region.

In this paper, a laser diode (LD) pumped passive mode-locking Tm,Ho:GAGG laser based on a semiconductor saturable absorber mirror (SESAM) is reported. By adjusting the group delay dispersions inside the laser cavity and transmissions of the output couplers (OCs), a shortest pulse duration of 10.84 ps at 2089.9 nm is achieved, the average output power is 33.17 mW and the laser runs at a 83.01 MHz repetition rate. A maximum average output power of 66.43 mW is also obtained at 2089.9 nm with a pulse duration of 16.56 ps by using an OC of 3%. To the best of our knowledge, this is the first report on the mode-locking Tm,Ho:GAGG laser.

Changes in tobacco use at the early stage of the COVID-19 pandemic: Results of four cross-sectional surveys in Hong Kong.

INTRODUCTION: Changes in tobacco use since the COVID-19 outbreak differed by countries and little is known about changes in the use of specific tobacco products. METHODS: We analyzed data from four cross-sectional telephone/online surveys from April to June 2020 to investigate such changes since the 1st and 2nd wave outbreaks (February to April 2020) in Hong Kong. The respondents were 1595 adults (83.2% male) who used tobacco before the COVID-19 outbreak from our previous intervention study and surveys. We investigated the changes in tobacco use, intention to quit and quit attempts during the outbreak. RESULTS: About two-thirds (65.3%) of respondents reported no change in overall tobacco use, while 23.1% used less (including cessation) and 11.6% used more, resulting in a net decrease of 11.5 percentage points. A greater net decrease was observed for cigarettes (14.3% points) than heated tobacco products (HTPs, 3.3% points) and electronic cigarettes (e-cigarettes, 2.5% points). Decreased use was mainly due to the more extended stay at home (63.2%), health considerations (52.6%) and mask-wearing (47.4%), while increased use was for passing time (75.0%) and releasing stress (46.4%). Eight percent of cigarette, HTP and e-cigarette users reported a higher intention to quit since the pandemic outbreak. Nineteen percent of tobacco users (176/948) attempted to quit during the pandemic. Only 2.9% (46/1569) were abstinent at the time of the survey. CONCLUSIONS: Overall tobacco use decreased after the first two waves of the COVID-19 outbreak in Hong Kong. A greater proportion of cigarette users decreased use than HTP and e-cigarette users. Given the different methods used in the four surveys, future studies should aim for a large and representative sample.

Compact diode-pumped continuous wave and passively Q switched Tm:YAG laser at 2.33†µm.

Compact diode-pumped continuous wave (CW) and passively Q switched Tm:YAG lasers operating on the 3H4 → 3H5 transition are demonstrated. Using a 3.5-at.% Tm:YAG crystal, a maximum CW output power of 1.49 W is achieved at 2330 nm with a slope efficiency of 10.1%. The first Q switched operation of the mid-infrared Tm:YAG laser around 2.3 µm is realized with a few-atomic-layer MoS2 saturable absorber. Pulses as short as 150 ns are generated at a repetition rate of 190 kHz, corresponding to a pulse energy of 1.07 µJ. Tm:YAG is an attractive material for diode-pumped CW and pulsed mid-infrared lasers emitting around 2.3 µm.

Watt-level diode-pumped Tm:YVO4 laser at 2.3 µm.

In this Letter, a watt-level laser diode (LD)-pumped ∼2.3-µm (on the 3H4→3H5 quasi-four-level transition) laser is reported based on a 1.5 at.% a-cut Tm:YVO4 crystal. The maximum continuous wave (CW) output power obtained is 1.89 W and 1.11 W with the maximum slope efficiency of 13.6% and 7.3% (versus the absorbed pump power) for the 1% and 0.5% transmittance of the output coupler, respectively. To the best of our knowledge, the CW output power of 1.89 W we obtained is the highest CW output power amongst the LD-pumped ∼2.3-µm Tm3+-doped lasers.

Experimental and Theoretical Study of an Actively Q-Switched Tm:YLF Laser with an Acousto-Optic Modulator.

We report the characteristics of a diode-end-pumped, high-repetition-rate, acoustic-optic (AO) Q-switched Tm:YLF laser operating from 5 kHz to 10 kHz. In the continuous-wave (CW) regime, a maximum average output power of 8.5 W was obtained with a slope efficiency of 30.7%. Under the AO Q-switching regime, a maximum output power of 7.32 W was obtained at a repetition frequency of 5 kHz with a pulse width of 68 ns and a pulse energy of 1.4 mJ, corresponding to a peak power of 21.5 kW. A time-dependent rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the cross-relaxation phenomenon, upconversion losses and ground-state depletion are taken into account. Additionally, the evolution processes of population inversion density and intracavity photon number density with time are also presented. The theoretical results well predict the dependence of laser output characteristics of Tm:YLF crystal on the incident pump powers.

Vacancy-Induced Magnetism in Fluorographene: The Effect of Midgap State.

Based on density functional theory, we have systematically investigated the geometric, magnetic, and electronic properties of fluorographene with three types of vacancy defects. With uneven sublattice, the partial defect structures are significantly spin-polarized and present midgap electronic states. The magnetic moment is mainly contributed by the adjacent C atoms of vacancy defects. Furthermore, the strain dependence of the bandgap is analyzed and shows a linear trend with applied strain. This defect-induced tunable narrow bandgap material has great potential in electronic devices and spintronics applications.

Theoretical and experimental investigations on doubly Q-switched Tm:YAP laser with EOM and Sb2Te3 nanosheets.

In this paper, two-dimensional material Sb2Te3 nanosheets are fabricated and the optical nonlinear response is investigated. A laser diode (LD) end-pumped doubly Q-switched Tm:YAP laser with electro-optic modulator (EOM) and Sb2Te3 nanosheets based saturable absorber (SA) is presented. The shortest pulse duration of 38 ns is achieved at the pulse repetition frequency of 100 Hz, corresponding to the highest peak power of 111.8 kW. The double Q-switching technique shows the advantages of pulse duration compression and peak power improvement. The coupled rate equations for the doubly Q-switched laser are developed and the corresponding numerical simulation agrees with the experimental results. We believe that the Sb2Te3 is a potential nanomaterial for the application in optoelectronic field.

Layered Metallic Vanadium Disulfide for Doubly Q-Switched Tm:YAP Laser with EOM: Experimental and Theoretical Investigations.

In the current study, layered metallic vanadium disulfide (VS2) is fabricated by a liquid-phase exfoliation method, and its microstructures as well as optical characteristics are investigated. Based on first-principles calculations, the band structure and density of the states of both bulk T-VS2 and monolayer H-VS2 are illustrated, showing the metallic behavior with a zero band gap. By using VS2 as the saturable absorber in a doubly Q-switched Tm:YAP laser with an EOM, the Q-switching laser pulses at 2 µm with 22 ns and 200 Hz are generated, corresponding to the single pulse energy of 755 µJ and the peak power of 34.3 kW. The coupled rate equations of the doubly Q-switched laser are given, and the numerical simulations agree with the experimental results. The results indicate that VS2 is a promising nanomaterial due to its nonlinear optical property. The doubly Q-switched laser demonstrates a high level of performance in reducing pulse width and enhancing pulse peak power.

Family E-Chat Group Use Was Associated with Family Wellbeing and Personal Happiness in Hong Kong Adults amidst the COVID-19 Pandemic.

Instant messaging (IM) is increasingly used for family communication amidst the COVID-19 pandemic. However, evidence remains scarce on how family e-chat groups were used and their associations with family and individual wellbeing amidst the pandemic. The numbers of family e-chat groups, functions used, and messages sent and received daily in groups were reported by 4890 adults in May 2020, and their associations with family wellbeing and personal happiness and the mediation effect of family communication quality were examined. Results showed that sending/receiving text messages was most commonly used, followed by receiving/sending photos/pictures, making voice calls, receiving/sending short videos and voice messages, and making video calls. Women and older people used more non-text functions. Higher levels of family wellbeing and personal happiness were associated with having more groups, receiving/sending photos/pictures, video calls, more IM functions used, and more IM messages received/sent daily. Forty-six point two to seventy-five point five percent of their associations with more groups and more functions used were mediated by family communication quality. People having more family e-chat groups and using more IM functions may be more resilient amidst the pandemic, while those without or with low use of family e-chat groups amidst the pandemic would need more attention and assistance in the presence of social distancing.