Heterogeneous effects of COVID-19 lockdown measures on air quality in Northern China.

In response to the spread of COVID-19, China implemented a series of control measures. The causal effect of these control measures on air quality is an important consideration for extreme air pollution control in China. Here, we established a difference-in-differences model to quantitatively estimate the lockdown effect on air quality in the Beijing-Tianjin-Hebei (BTH) region. We found that the lockdown measures did have an obvious effect on air quality. The air quality index (AQI) was reduced by 15.2%, the concentration of NO2, PM10, PM2.5, and CO were reduced by 37.8%, 33.6%, 21.5%, and 20.4% respectively. At the same time, we further explored the heterogeneous effects of travel restrictions and the control measure intensity on air quality. We found that the traffic restrictions, especially the restriction of intra-city travel intensity (TI), exhibited a significant heterogeneous effect on NO2 with a decrease of approximately 13.6%, and every one-unit increase in control measures intensity reduced the concentration of air pollutants by approximately 2-4%. This study not only provides a natural, experimental basis for control measures on air quality but also indicates an important direction for future control strategies. Importantly, determining the estimated effect helps formulate accurate and effective intervention measures on the differentiated level of air pollution, especially on extreme air pollution.

On the generation of grooves on crystalline silicon irradiated by femtosecond laser pulses.

Irradiation of crystalline silicon with femtosecond laser pulses produces a variety of quasi-periodic surface structures, among which sub-wavelength ripples creation is largely studied. Here we report an experimental investigation and a theoretical interpretation focusing on the seldom considered issue of quasi-periodic, micron spaced grooves formation. We characterize the morphological evolution of the grooves generation and experimentally single out the variation of the threshold fluence for their formation with the number of pulses N, while typical ripples simultaneously produced in the irradiated area are always considered for comparison. Our experimental findings evidence a power law dependence of the threshold fluence on the number of pulses both for ripples and grooves formation, typical of an incubation behavior. The incubation factor and single pulse threshold are (0.76 ± 0.04) and (0.20 ± 0.04) J/cm2 for ripples and (0.84 ± 0.03) and (0.54 ± 0.08) J/cm2 for grooves, respectively. Surface-scattered wave theory, which allows modeling irradiation with a single pulse on a rough surface, is exploited to interpret the observed structural modification of the surface textures. A simple, empirical scaling approach is proposed associating the surface structures generated in multiple-pulse experiments with the predictions of the surface-scattered wave theory, at laser fluencies around the grooves formation threshold. This, in turn, allows proposing a physical mechanism interpreting the grooves generation as well as the coexistence and relative prominence of grooves and ripples in the irradiated area.

Chromatic annuli formation and sample oxidation on copper thin films by femtosecond laser.

We report an experimental investigation on the irradiation of copper thin films with high repetition rate femtosecond laser pulses (1040 nm, 50 MHz), in ambient air and liquid water. We observe a novel, striking phenomenon of chromatic copper oxides (CuO and Cu2O) annuli generation. The characteristic features of the chromatic copper oxide annuli are studied by exploiting micro-Raman spectroscopy, optical and scanning electron microscopies. In the case of irradiation in water, the seldom investigated effects of the immersion time, tw, after irradiation with a fixed number of pulses are analyzed, and an intriguing dependence of the color of the chromatic annuli on tw is observed. This remarkable behavior is explained by proposing an interpretation scenario addressing the various processes involved in the process. Our experimental findings show that Cu2O nanoparticles (size of ≈20 nm) and Cu2O nanocubes (nanocube edges of ≈30, ≈60 nm) can be effectively generated by exploiting high repetition rate laser-assisted oxidation.

Sclerectomy with nanojoule energy level per pulse by femtosecond fiber laser in vitro.

The use of nanojoule femtosecond pulses (NFP) for highly precise proceeding in anti-glaucoma surgery was evaluated. According to the observation of scanning electron microscopy (SEM), four types of incision patterns, including subsurface, slit-like, spot and cuboid ablations, were accomplished on in vitro sclera by NFP with little collateral damage. In comparison to microjoule femtosecond pulses (MFP), NFP can make extremely precise incisions with smoother inner surface with less peak power density. The present study first illustrates the potential use of NFP in minimally invasive laser sclerectomy for glaucoma therapy.

Why do you choose this program?-A decision-making model of medical students based on grounded theory.

BACKGROUND: This study aims to investigate the reasons behind the decline in the number of applicants and dropouts from N University's reformed program, which includes increased research experience, an optimized curriculum, and other benefits. The ultimate goal is to identify areas for improvement and make the program more appealing to potential students. METHODS: This study utilized the Grounded Theory approach, conducting semi-structured in-depth interviews and applying data collection, coding, and the constant comparative method. As a result, a decision-making model for college students was constructed. RESULTS: Following the initial stages of individual expectation formation, which include inducement and self-efficacy, and the subsequent stage of value assessment, individuals reach a decision. Throughout this process, the individual's circumstances and surroundings continue to influence their decision-making. Additionally, the decision-making procedure follows a Hierarchy Pyramid of Educational Needs. Our findings show that job prospects and continuing education are the primary factors influencing interviewees' decisions. However, it is important to note that individuals may place varying levels of importance on these factors. Additionally, the preferences and priorities of teachers, such as their commitment to research guidance, curriculum development, and maintaining fairness in examinations, can also play a role in shaping these decisions. CONCLUSION: To attract more talented individuals to research-oriented programs, universities should provide more job and higher education opportunities, reform the curriculum thoroughly, and enhance teachers' teaching devotion.

[Ca(2+)-dependent potassium channels play important roles in regulatory volume decrease in human nasopharyngeal carcinoma cells].

It has been shown that cell volume regulation mechanisms play important roles in various cell functions. We demonstrated previously that volume-activated chloride channels were involved in cell volume regulation. The present study aimed to clarify the roles of various types of potassium channels in regulatory volume decrease (RVD) induced by hypotonic challenges in human nasopharyngeal carcinoma cells (CNE-2Z cells). The whole-cell patch clamp technique was used to record hypotonic challenge-induced potassium currents. During current recordings, cells were held at 0 mV and stepped to +/-46 and +/-92 mV, repeatedly. The cell volume was computed from cell diameters. The changes of cell volume were monitored and analyzed by the time-lapse imaging technique. The results showed that the exposure to 160 mOsm/L hypotonic solution caused the cells to swell by (144.5+/-4.2)%, activated a potassium current (59.2 pA/pF+/-13.3 pA/pF at 92 mV), and induced RVD. Cell volume was recovered from hypotonic challenge-induced swelling by (48.9+/-4.6)% after 20 min. The potassium current (at 92 mV) and RVD were inhibited by the calcium-dependent potassium channel blocker, clotrimazole (100 mumol/L), by (98.5+/-2.8)% and (89.3+/-4.9)%, respectively. Depletion of extracellular calcium prevented the activation of the hypotonic challenge-induced potassium current and inhibited the process of RVD. The voltage-gated potassium channel blocker, 4-AP (5 mmol/L), partially inhibited the hypotonic challenge-activated potassium currents by (66.6+/-5.3)% (at 92 mV). These results suggest that the Ca(2+)-dependent potassium channel is the main component of volume-activated potassium channels and plays an important role in volume regulation of CNE-2Z cells. The voltage-gated potassium channels may also contribute in part to the formation of the volume-activated potassium current.

The effects of flipped classrooms on undergraduate pharmaceutical marketing learning: A clustered randomized controlled study.

BACKGROUND: Recently, flipped classrooms (FCs) have gradually been used in Chinese higher education settings. However, few studies have focused on the effects of FCs on interdisciplinary curricula. The purpose of this study was to examine the impact of an FC on the engagement, performance, and perceptions of students and on teacher-student interaction in a pharmaceutical marketing course. DESIGN: A clustered randomized controlled study was conducted, with 137 junior-year pharmacy undergraduates using an FC serving as the intervention group, in contrast to students using lecture-based learning (LBL) as the control group. Flanders' interaction analysis system (FIAS) was used to measure teacher-student interaction, and questionnaires regarding attitudes toward and satisfaction with the teaching model were administered. RESULTS: The students in the FC group scored significantly higher than those in the LBL group (88.21±5.95 vs. 80.05±5.59, t = -8.08, p = 0.000) on pharmaceutical marketing. The multiple linear regression results showed that the FC model had a significant impact on student performance (ß = 8.16, p<0.0001). The percentages of teacher talk in the FC and LBL groups were 21% and 96%, respectively (χ2 = 2170.274, p = 0.000); however, the percentages of student talk in the FC and LBL groups were 75% and 2.6%, respectively (χ2 = 2012.483, p = 0.000). Compared with the LBL group, most students in the FC group held more positive attitudes toward the teaching model; the mean scores for the 8 attitude attributes in the FC group were significantly higher than those in the LBL group (p = 0.000). There were significant differences in the ratings of satisfaction with teacher-student interaction (p = 0.000), the students' learning attitude (p = 0.000), the teacher's preparatory work (p = 0.000), the teaching objective (p = 0.000), and the teaching effect (p = 0.000) between the two groups. CONCLUSION: Compared with LBL methods, implementing the FC model improved student performance, increased teacher-student interaction and generated positive student attitudes toward the experience. As an effective pedagogical model, it can also stimulate pharmacy students' learning interest and improve their self-learning abilities.

Direct Femtosecond Laser Surface Structuring with Optical Vortex Beams Generated by a q-plate.

Creation of patterns and structures on surfaces at the micro- and nano-scale is a field of growing interest. Direct femtosecond laser surface structuring with a Gaussian-like beam intensity profile has already distinguished itself as a versatile method to fabricate surface structures on metals and semiconductors. Here we present an approach for direct femtosecond laser surface structuring based on optical vortex beams with different spatial distributions of the state of polarization, which are easily generated by means of a q-plate. The different states of an optical vortex beam carrying an orbital angular momentum ℓ = ±1 are used to demonstrate the fabrication of various regular surface patterns on silicon. The spatial features of the regular rippled and grooved surface structures are correlated with the state of polarization of the optical vortex beam. Moreover, scattered surface wave theory approach is used to rationalize the dependence of the surface structures on the local state of the laser beam characteristics (polarization and fluence). The present approach can be further extended to fabricate even more complex and unconventional surface structures by exploiting the possibilities offered by femtosecond optical vector fields.

[Construction of cyclin D1 recombinant plasmids and its expression in human nasopharyngeal carcinoma cells].

OBJECTIVE: To construct the eukaryotic expression vectors of human cyclin D1 gene and express them in poorly differentiated nasopharyngeal carcinoma cells (CNE-2Z cells). METHODS: The full-length cyclin D1 was cloned from CNE-2Z cells by RT-PCR. The cDNA fragments were inserted into pIRES2-EGFP plasmids and pEGFP-C2 plasmids and confirmed by restriction enzyme digestion, PCR and sequencing. The recombinant vectors were transfected into CNE-2Z cells via Lipofectamine 2000, and the expression of cyclin D1 in the cells was examined by immunofluorescence and Western blotting. RESULTS: Agarose gel electrophoresis showed a 918 bp band of the RT-PCR products, which matched the expected size. Restriction enzyme digestion, PCR and sequencing demonstrated successful construction of the recombinant vectors. CNE-2Z cells transfected with the recombinant vectors expressed cyclin D1 protein or cyclin D1-GFP protein as were verified by immunofluorescence and Western blotting. CONCLUSION: We have cloned cyclin D1 gene and constructed its eukaryotic expression vectors that can be expressed in nasopharyngeal carcinoma cells, which may facilitate the study of the role of cyclin D1 in the development of nasopharyngeal carcinoma.