Objective
To assess the current prevalence of and risk factors for infertility among couples of reproductive age in China.
Design
Population‐based cross‐sectional study.
Setting
We approached 25 270 ...couples in eight provinces/municipalities, of whom 18 571 (response rate 74%) were interviewed.
Population
Couples living together and married for more than 1 year, of whom the female spouse was 20–49 years old.
Methods
Women were approached via telephone and face‐to‐face conversation to complete the standardised and structured questionnaire by trained interviewers.
Main outcome measures
Prevalence of and risk factors for infertility.
Results
Among women ‘at risk’ of pregnancy, the prevalence of infertility was 15.5% (2680/17 275). Among 10 742 women attempting to become pregnant, the prevalence of infertility was 25.0% (2680/10 742), which increased with age in the second population. Among women who failed to achieve pregnancy in the last 12 months, 3470 finished our questionnaire about fertility care, and 55.2% (1915/3470) of them had sought medical help. Sociodemographic risk factors for infertility included lower educational level adjusted odds ratio (aOR) 3.4, 95% CI 2.0–5.5 and employment (aOR 2.3, 95% CI 1.9–2.9). Clinical risk factors were irregular menstrual cycle (aOR 1.8, 95% CI 1.2–2.5), light menstrual blood volume (aOR 1.6, 95% CI 1.2–2.0), history of cervicitis (aOR 1.5, 95% CI 1.2–2.0) and endometriosis (aOR 3.1, 95% CI 1.1–9.3), previous stillbirth (aOR 2.1, 95% CI 1.3–3.3) and miscarriage (aOR 2.7, 95% CI 2.1–3.5). In addition, history of operation was a significant risk factor of infertility.
Conclusions
Among couples of reproductive age in China, the prevalence of infertility was 25%, and almost half of the couples experiencing infertility had not sought medical help.
Tweetable
In China, 25% of couples actively attempting to become pregnant suffered infertility.
Tweetable
In China, 25% of couples actively attempting to become pregnant suffered infertility.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract Objectives Many studies have shown that insomnia is a common problem among university students, but there are wide variations in the prevalence of insomnia. In this systematic review, we ...aimed to explore the prevalence of insomnia among university students using scientific and conclusive methods. Study design A systematic review is designed to analyze the studies reporting on prevalence of insomnia among university students. Methods Systemic searches were conducted in PubMed, BioMed Central, EBSCO, ScienceDirect, Ovid LWW and Medline databases between January 2000 and July 2014, The Meta analyst software was used to calculate the prevalence rate of each study, the pooled means of prevalence rates and 95% CIs across studies were then calculated and presented. Results Seven articles that met the inclusion and exclusion criteria were selected. The overall sample size in the current review was 16,478, with a minimum of 219 and a maximum of 10,322. The prevalence rates of the seven studies ranged between 9.4% (95%CI 8.8–10.0%) and 38.2% (95% CI 35.4–41.1%). Overall, the total students studied with a weighted mean prevalence of 18.5% (95% CI 11.2–28.8%), considerably higher than rates of 7.4% (95% CI 5.8–9.0%) reported in general population. Conclusions This review emphasized that insomnia prevalence in university students is considerably higher than that in general population, suggested that more attention should be paid to insomnia in university students.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Weyl points are often believed to appear in pairs with opposite chirality. In this work, we show by first-principles calculations and symmetry analysis that single Weyl phonons with linear dispersion ...and double Weyl phonons with quadratic dispersion are simultaneously present between two specific phonon branches in realistic materials with trigonal or hexagonal lattices. These phonon Weyl points are guaranteed to locate at high-symmetry points due to the screw rotational symmetry, forming a unique triangular Weyl complex. In sharp contrast to conventional Weyl systems with surface arcs terminated at the projections of a pair of Weyl points with opposite chirality, the phonon surface arcs of the unconventional triangular Weyl complex connect the projections of one double Weyl point and two single Weyl points. Importantly, the phonon surface arcs originating from the triangular Weyl complex are extremely long and span the entire surface Brillouin zone. Furthermore, there are only nontrivial phonon surface states across the isofrequency surface, which facilitates their detection in experiments and further applications. Our work not only offers the promising triangular phonon Weyl complex but also provides guidance for exploring triangular Weyl bosons in both phononic and photonic systems.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Dirac semimetals associated with bulk Dirac fermions are well known in topological electronic systems. In sharp contrast, three-dimensional (3D) Dirac phonons in crystalline solids are still ...unavailable. Here we perform symmetry arguments and first-principles calculations to systematically investigate 3D Dirac phonons in all space groups with inversion symmetry. The results show that there are two categories of 3D Dirac phonons depending on their protection mechanisms and positions in momentum space. The first category originates from the four-dimensional irreducible representations at the high symmetry points. The second category arises from the phonon branch inversion, and the symmetry guarantees Dirac points to be located along the high symmetry lines. Furthermore, we reveal that nonsymmorphic symmetries and the combination of inversion and time-reversal symmetries play essential roles in the emergence of 3D Dirac phonons. Our work not only offers a comprehensive understanding of 3D Dirac phonons but also provides significant guidance for exploring Dirac bosons in both phononic and photonic systems.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The ferromagnetic Weyl semimetals with inversion symmetry usually possess odd pairs of Weyl fermions. Here, we present an inversion eigenvalue argument to dictate the existence of even pairs of ...ferromagnetic Weyl fermions. We show, by a combination of first-principles calculations and symmetry analyses, that this exotic topological feature can be verified in ferromagnetic oxides in different space groups. In particular, a realistic candidate, i.e., hollandite RbCr_{4}O_{8} with a high Curie temperature (∼295 K), hosts intriguing twin pairs of Weyl fermions, which are robustly stable against perturbations. Moreover, our effective model and symmetry analysis show that the twin pairs of Weyl fermions originate from a mirrored nodal ring pair. The nontrivial surface states and Fermi arcs of RbCr_{4}O_{8} are clearly visible, further revealing the topological features. This work strengthens the understanding of the parity analysis in exploring ferromagnetic topological materials with unconventional fermionic excitations.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Abstract Objective In China, elderly make up a large proportion of the society, but their mental health is often overlooked. The aim of this study is to compare mental health and related influencing ...factors among the empty-nest and the non-empty-nest elderly, and attain the purpose of improving their quality of life. Study design Cross-sectional survey. Methods A cross-sectional survey was conducted among 488 elderly people aged 60–92 years in six districts of Taiyuan, China. A demographic questionnaire and SCL-90-R were employed to collect demographic variables and evaluate mental health, respectively. Multiple regression analysis was performed to estimate factors related to mental health of the elderly. Results The empty-nest elderly were mostly male, married, higher education level, higher income and living in urban areas. The scores of SCL-90-R among the empty-nest elderly were lower than those of the non-empty-nest elderly except for psychoticism. Comparing with scores of national norms, some dimension of SCL-90-R had statistically significant differences. Multiple regression analysis showed that the main risk factors of the empty-nest elderly were gender and income, whereas the main risk factor of the non-empty-nest elderly was chronic diseases. Conclusion The mental health status of the empty-nest elderly was better than that of the non-empty-nest elderly. Overall mental health of the study population was at a high level compared with national norms. The elderly who were male, with younger age, having higher income, and without chronic diseases had better mental health status.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban ...atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NOx and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ng m-3, higher than those reported in other summertime studies (0.14–6.44 ng m-3). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low- to high-NOx regimes coincided with a shift from organic- to inorganic-dominated oxidation products. The transition thresholds were NO2∼20 ppb for daytime andNO2∼25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO3- concentrations and (NO3-)/NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while theNO3- concentrations and (NO3-)/NACs ratios showed increasing trends, signaling a shift from organic- to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NC+4M5NC) / 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH > 30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as important factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols.
The manufacture of high-performance electronic devices with micrometre or even submicrometre dimensions by solution processing and direct printing, requires the ability to control accurately the flow ...and spread of functional liquid inks on surfaces. This can be achieved with the help of surface-energy patterns causing inks to be repelled and dewetted from pre-defined regions of the substrate. To exploit this principle for the fabrication of submicrometre device structures, a detailed understanding of the factors causing ink droplets to dewet on patterned surfaces is required. Here, we use hydrophobic surface-energy barriers of different geometries to study the influence of solution viscosity, ink volume, and contact angle on the process of dewetting of inkjet-printed droplets of a water-based conducting polymer. We demonstrate polymer field-effect transistor devices with channel length of 500 nm fabricated by surface-energy-assisted inkjet printing.
► We use ECAP to synthesise nanocrystalline 304 SS (80–120
nm). ► We prove that nanocrystallisation of SS increases its corrosion resistance. ► Thickness and composition of passive film on ...nanocrystalline SS show no difference from as-received one. ► The improved corrosion resistance of ECAPed SS was caused by compactness and stability improvement of the passive film.
Effect of microstructure change on the corrosion behaviour of equal channel angular pressed (ECAPed) 304 stainless steel (SS) was investigated. Nanostructure (80–120
nm) was obtained after 4 and 8 passes ECAP and exhibited a higher corrosion resistance than as-received SS. However, thickness and composition of the passive film formed in air at room temperature on both as-received and 8-pass samples show little difference, indicating that Cr diffusion is not enhanced by the formation of nanostructure. The improved corrosion resistance of ECAPed SS is not caused by thickness or composition change, but by compactness and stability improving of the passive film.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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