Size Dependent Phase Transformation of Liquid Gallium.

As the most popular liquid metal (LM), gallium (Ga) and its alloys are emerging as functional materials due to their unique combination of fluidic and metallic properties near room temperature. As an important branch of utilizing LMs, micro- and submicron-particles of Ga-based LM are widely employed in wearable electronics, catalysis, energy, and biomedicine. Meanwhile, the phase transition is crucial not only for the applications based on this reversible transformation process, but also for the solidification temperature at which fluid properties are lost. While Ga has several solid phases and exhibits unusual size-dependent phase behavior. This complex process makes the phase transition and undercooling of Ga uncontrollable, which considerably affects the application performance. In this work, extensive (nano-)calorimetry experiments are performed to investigate the polymorph selection mechanism during liquid Ga crystallization. It is surprisingly found that the crystallization temperature and crystallization pathway to either α -Ga or ß -Ga can be effectively engineered by thermal treatment and droplet size. The polymorph selection process is suggested to be highly relevant to the capability of forming covalent bonds in the equilibrium supercooled liquid. The observation of two different crystallization pathways depending on the annealing temperature may indicate that there exist two different liquid phases in Ga.

Impact of closed-off management due to COVID-19 rebound on maternal depression during pregnancy.

BACKGROUND: This study aimed to assess the impacts of closed-off measures with different strictness levels (lockdown, partial lockdown and non-lockdown) and geographic proximity to patients with coronavirus disease 2019 (COVID-19) on prenatal depression during an epidemic rebound of COVID-19. METHODS: This was a cross-sectional web-based survey including 880 pregnant women. Depressive symptoms were measured by Self-Rating Depression Scale (SDS) and geographic proximity was calculated using Geographic Information Systems. Linear and logistic regression were used to assess the associations of closed-off measures and geographic proximity with SDS scores and depressive symptoms. Restricted cubic splines were used to model non-linear associations between geographic proximity and depression symptoms. RESULTS: Compared with those living in non-lockdown areas, women in lockdown areas had higher SDS scores (adjusted ß: 3.51, 95% CI: 1.80, 5.21) and greater risk of depressive symptoms (adjusted OR: 4.00, 95% CI: 2.18, 7.35), but evidence for partial lockdown was not obvious. A progressive increase in the risk of depressive symptoms was found with decreasing distance to COVID-19 patients when geographic proximity was <8 kilometers. Compared to those in the 5th quintile of geographic proximity, women in the first, second and third quintiles had at least 6 times higher risk of depressive symptoms. CONCLUSIONS: Pregnant women under strict closed-off management during COVID-19 epidemic have high risk of depression. A specific range around the residences of reported COVID-19 patients should be underlined as potential clustering of high prenatal depression levels. Our findings highlight the importance of enhancing mental health management during the COVID-19 epidemic for pregnant women.

Factors influencing treatment status of syphilis among pregnant women: a retrospective cohort study in Guangzhou, China.

BACKGROUND: Many syphilis infected pregnant women do not receive treatment, representing a major missed opportunity to reduce the risk of syphilis-related adverse pregnancy outcomes. This study explored correlates of treatment among pregnant women with syphilis in Guangzhou, China. METHODS: Pregnant women with a diagnosis of syphilis in Guangzhou between January 2014 and December 2016 were included. Information of syphilis treatment and correlates were extracted from a comprehensive national case-reporting system. Multivariate logistic regression was used to identify the correlations between information on the demographic characteristics, previous history, clinical characteristics about current syphilis, information of diagnosing hospital, and receiving no treatment or inadequate treatment among syphilis-seropositive pregnant women. A causal mediation analysis was used to explore the potential mediating role of the timing of syphilis diagnosis in the correlates. RESULTS: Among 1248 syphilis-seropositive pregnant women, 379 (30.4%) women received no treatment or inadequate treatment. Migrant pregnant women (adjusted OR = 1.83, 95% CI: 1.25-2.73), multiparous participants (adjusted OR = 3.68, 95% CI: 2.51-5.50), unmarried participants (adjusted OR = 3.21, 95% CI: 1.97-5.28) and unemployed participants (adjusted OR = 2.43, 95% CI: 1.41-4.39) were more likely to receive no treatment or inadequate treatment. Participants who with history of syphilis infection (adjusted OR = 0.59, 95% CI: 0.42-0.82) and with high school and higher education participants (adjusted OR = 0.69, 95% CI: 0.49-0.97) were less likely to receive untreated or inadequately treatment. And that the impact of all these factors (except for the migrants) on treatment status are fully mediated through the syphilis diagnosis time, with the direct effect of migrants that would have resulted in a higher rate of no or inadequate treatment (OR = 2.34, 95% CI: 1.08-5.32) was partially cancelled out by the syphilis diagnosis time. CONCLUSIONS: Pregnant women who were migrant without local residence and women with syphilis diagnosed at a later gestational age were more likely to slip through the cracks of the existing antenatal care system. More programs should focus on eliminating these gaps of residence-related health inequalities. This research highlights actionable elements for health services interventions that could increase syphilis treatment rates among pregnant women.

Terahertz spectroscopic detection of antifatigue illegal additives in health care product matrices.

Tadalafil is an illegal additive in antifatigue supplements. It is often misused in various plant dietary supplements (BDS), resulting in serious health risks. In this paper, terahertz spectroscopy combined with chemometrics is used to quantitatively analyze the content of tadalafil in nutritional and health products. The absorption coefficient spectrum of tadalafil in the range of 0.1-2.5 THz was obtained, and an obvious characteristic absorption peak appeared at 1.7 THz. To verify the accuracy of this characteristic absorption peak theoretically, tadalafil was simulated by density functional theory, and the calculated terahertz vibration spectrum matched well with the experimental spectrum. Then, the pure fatigue-based nutraceutical matrix and pure tadalafil were mixed in different proportions, and the terahertz absorption coefficient spectra of the mixtures were obtained. Finally, a quantitative analysis model of the tadalafil mixture was developed based on the support vector regression (SVR) algorithm, and the SVR model was optimized using particle swarm optimization (PSO) and genetic algorithm (GA), respectively. Compared with the SVR model, both PSO-SVR and GA-SVR enabled some improvement in their prediction accuracy, but the PSO-SVR model ran faster at 4.85 s, whereas the GA-SVR model had a higher prediction accuracy with a prediction set correlation coefficient (R P) of 0.9996 and a root mean square error (RMSEP) of 0.011. In summary, this study used terahertz time-domain spectroscopy for the identification and quantification of tadalafil in health product matrices. This study provides a new solution for the nondestructive detection of illegally added tadalafil in antifatigue health products, which is pivotal to the quality control of the health product industry.

Design of a terahertz dual-channel modulator based on metamaterials.

In this paper, we propose a terahertz dual-channel modulator by combining a high electron mobility transistor (HEMT) with a metamaterials structure, in which the HEMT is embedded in the opening of the structure metamaterial. The modulator consists of a metamaterial structure, silicon carbide (SiC), HEMT active device, and feeder. The concentration of the two-dimensional electron gas (2DEG) in the HEMT can be controlled by gate voltages, and the change of the concentration can realize the modulation of the intensity and phase of the terahertz wave. The simulation results indicate that when a single channel works, the modulation depth is 90.7% at 0.22 THz and 94.0% at 0.34 THz. When both channels work, the modulation depth is 88.9% at 0.22 THz and 93.3% at 0.34 THz. The terahertz modulator designed in this paper can work in two frequency bands and can be controlled independently, which efficiently uses the spectrum resources and has broad application prospects in the field of terahertz communication.

Syphilis-attributable adverse pregnancy outcomes in China: a retrospective cohort analysis of 1187 pregnant women with different syphilis treatment.

BACKGROUND: Syphilis is responsible for a substantial burden of preventable adverse outcomes in pregnancy. The purpose of this study was to compare the frequency of adverse pregnancy outcomes among syphilis-seropositive women who received different treatment regimens at different times in Guangzhou, China. METHODS: Pregnant women with syphilis infection who received prenatal and delivery services in Guangzhou between January 2014 and December 2016 were included. Association between treatment status and the composite adverse outcomes (preterm birth, infant smaller than gestational age, stillbirth, and spontaneous abortion) was estimated. RESULTS: Of 1187 syphilis-seropositive pregnant women included in the analysis, 900 (75.8%) syphilis-seropositive pregnant women received treatment, and 287(24.2%) did not receive treatment. Adverse pregnancy outcomes were observed among 16.3% (147/900) of women with treatment and 33.8% (97/287) of women without treatment. Syphilis-seropositive pregnant women treated with one or two courses of penicillin had a similar risk of adverse pregnancy outcomes (adjusted RR = 1.36, 95% CI: 0.94-1.96). Adverse outcomes were more common among women whose non-treponemal serum test titer was >1:8 and received treatment after 28 weeks compared to before 28 weeks (adjusted RR = 2.34, 95% CI: 1.22-4.48). CONCLUSIONS: Women who received one course of penicillin and women who received two courses of penicillin had a similar risk of adverse pregnancy outcomes. Syphilis treatment before 28 weeks of pregnancy is critical. Strategies to promote high-quality prenatal services are needed.

Design and 3D Printing of Stretchable Conductor with High Dynamic Stability.

As an indispensable part of wearable devices and mechanical arms, stretchable conductors have received extensive attention in recent years. The design of a high-dynamic-stability, stretchable conductor is the key technology to ensure the normal transmission of electrical signals and electrical energy of wearable devices under large mechanical deformation, which has always been an important research topic domestically and abroad. In this paper, a stretchable conductor with a linear bunch structure is designed and prepared by combining numerical modeling and simulation with 3D printing technology. The stretchable conductor consists of a 3D-printed bunch-structured equiwall elastic insulating resin tube and internally filled free-deformable liquid metal. This conductor has a very high conductivity exceeding 104 S cm-1, good stretchability with an elongation at break exceeding 50%, and great tensile stability, with a relative change in resistance of only about 1% at 50% tensile strain. Finally, this paper demonstrates it as a headphone cable (transmitting electrical signals) and a mobile phone charging wire (transmitting electrical energy), which proves its good mechanical and electrical properties and shows good application potential.

Validity and Reproducibility of a Dietary Questionnaire for Consumption Frequencies of Foods during Pregnancy in the Born in Guangzhou Cohort Study (BIGCS).

This study aimed to examine the reproducibility and validity of a new food frequency questionnaire (FFQ) used in a birth cohort study to estimate the usual consumption frequencies of foods during pregnancy. The reference measure was the average of three inconsecutive 24 h diet recalls (24 HR) administrated between two FFQs, and the reproducibility was measured by repeating the first FFQ (FFQ1) approximately eight weeks later (FFQ2). A total of 210 pregnant women from the Born in Guangzhou Cohort Study (BIGCS) with full data were included in the analysis. The Spearman's correlation coefficients of FFQ1 and FFQ2 ranged from 0.33 to 0.71. The intraclass correlation coefficients of the two FFQs ranged from 0.22 to 0.71. The Spearman's correlation coefficients of the 24 HR and FFQ2 ranged from 0.23 to 0.62. Cross-classification analysis showed 65.1% of participants were classified into same and contiguous quintiles, while only 3.2% were misclassified into the distant quintiles. Bland-Altman methods showed good agreement for most food groups across the range of frequencies between FFQ1 and FFQ2. Our findings indicated that the reproducibility and validity of the FFQ used in BIGCS for assessing the usual consumption frequencies of foods during pregnancy were acceptable.