IntroductionIn recent decades, there has been a significant increase in childlessness. This paper analysed childlessness in China, specifically examining its socio and regional ...disparities.MethodsWith data from China’s 2020 population census, supplemented with data from China’s 2010 population census and 2015 inter-censual 1% population sample survey, we used a basic indicator of age-specific childlessness proportion, a decomposition method, and probability distribution models to analyse, fit and project childlessness.ResultsWe presented age-specific childlessness proportions for women as a whole and by socioeconomic features, decomposition and projection results. The childlessness proportion increased markedly from 2010 to 2020, reaching 5.16% for women aged 49. The proportion is highest for city women, followed by township women, and is lowest among village women, at 6.29%, 5.50% and 3.72 % for women aged 49, respectively. The proportion for women aged 49 with high college education or above was 7.98%, and only 4.42% for women with junior high school education. The proportion also exhibits marked provincial discrepancies, and the total fertility rate is negatively correlated with childlessness at the province level. The decomposition results distinguished the different contribution of change in educational structure and change in childlessness proportion for subgroups to the total childlessness proportion change. It is projected that city women, women with high education will have higher childlessness proportion, and the proportion will further increase with the rapid increase in education level and urbanisation.ConclusionsChildlessness has risen to a relatively high level, and varies among women with different characteristics. This should be taken into consideration in China’s countermeasures to reduce childlessness and curtail further fertility decline accordingly.
This study introduces the Stiffness-Damping Interventional Rail Vibration Reduction Device (SDIRVRD) as a means to enhance rail vibration suppression. It compares the SDIRVRD with the traditional ...tuned rail damper (TRD) in terms of their vibration suppression mechanisms. The research investigates the influence of the SDIRVRD’s stiffness and damping parameters on the dynamic response of the vehicle and track. It also conducts a comparative analysis of track and vehicle vibration responses before and after the installation of the SDIRVRD, evaluating its effectiveness in reducing both track system and vehicle vibrations. The field test validates the theoretical calculations, and the vibration reduction efficiency is quantified using the insertion loss value. Key findings include the superiority of the SDIRVRD over the TRD in vibration reduction under equivalent damping ratio conditions. The SDIRVRD significantly reduces rail acceleration, displacement, and velocity admittances, with a notable suppression effect on pinned-pinned rail vibration. The stiffness and damping of the SDIRVRD play a crucial role in enhancing its vibration reduction effect, but after the stiffness exceeds 2 kN/mm and further increases the stiffness of the SDIRVRD, the enhancement of its damping effect on the vehicle-track system’s vibration diminishes significantly. The SDIRVRD reduces acceleration vibration levels in the vehicle and track system by approximately 2–3 dB. Insertion Loss measurements show significant vibration reduction in the rail across most frequency domains.
•This paper introduces a novel concept termed the "stiffness-damping interventional rail vibration reduction device" (SDIRVRD), which differs from the previously mentioned vibration and noise reduction methods.•The core idea behind SDIRVRD is to intervene in the existing support system by augmenting both stiffness and damping properties.•Stiffness adjustments are employed to manipulate vibration frequencies, while damping characteristics are harnessed to absorb and dissipate vibration energy. This combined approach aims to effectively reduce vibrations within the track system.•In essence, SDIRVRD represents an innovative strategy that diverges from traditional rail vibration reduction measures, offering the potential to achieve vibration reduction by directly modifying the support system's stiffness and damping characteristics.•This approach opens up new avenues for addressing rail vibration challenges in track structures.
A new type of rail vibration damping device (NTRVDV), which is arranged between the bottom of the rail and track bed, is proposed in this paper. The finite element model of the rail system with the ...NTRVDV and tuned rail damper (TRD) was established, respectively. The impact load was applied to the finite element model, and comparison of the set of existing TRD and NTRVDV on the dynamic response of rail and rail vibration decay rate. The effect of the stiffness change of the elastic layer of the NTRVDV on the rail vibration was studied, and a hammering test verified the theoretical research results. The research results show that compared with the traditional TRD, the NTRVDV has a more obvious suppression effect on rail vibration acceleration. The rail vibration decay rate is significantly improved, especially in the low-frequency stage. With the increase of the stiffness of the elastic layer of the vibration suppression device, the vibration suppression effect of the NTRVDV on the rail is improved. The change of the elastic layer stiffness significantly impacts the rail’s vibration suppression effect in the range of 0–7 kN/mm.
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•CTAB was used to enhance flocculation coal waste slurry combined with bioflocculant.•CTAB could adsorb to the surface of quartz attached to coal waste solid, and neutralize the ...negative charges.•The flocculation of the coal waste slurry was significantly enhanced by the combination of CTAB and bioflocculant.•CTAB could be binding to bioflocculant and form complexes.
A bioflocculant produced by Azotobacter chroococcum, a natural polymer containing sugar and protein, can be used to flocculate coal waste slurry, but electrostatic repulsion impacts the flocculation of quartz attached to the solid coal particles. In this work, cetyltrimethylammonium bromide (CTAB) combined with this bioflocculant were used to flocculate coal waste slurry. The adsorption and zeta potential of CTAB on quartz, kaolinite, and organic matter were investigated in aqueous media. The results show that the data for CTAB adsorption fit the typical Langmuir adsorption model, and that the CTAB adsorption level is higher in an alkaline medium than in an acidic medium. The electrostatic interaction and formation of π-complexes contributed to the adsorption of CTAB on minerals and organic matter. Zeta potential measurements demonstrated that the point of zero charge values shifted to higher pH values after CTAB adsorption on mineral and organic matter surfaces. Furthermore, the behavior of the bioflocculant with the addition of CTAB was investigated to determine the effect of CTAB on the flocculation of coal waste slurry; quartz, kaolinite, and organic matter were used for comparison. Flocculation tests indicated that the optimum CTAB dosage for obtaining higher flocculation rates and clearer suspension of organic matter, quartz, and kaolinite was 50, 100, and 40 mg/L, respectively. A higher flocculation rate and clearer suspension of quartz were obtained in a very acidic medium, while organic matter suspension continued to increase in the pH range of 2.2–6.2 and remained almost constant in an alkaline medium. In addition, there were no significant changes in the flocculation rate or turbidity of kaolinite with an increase in pH. CTAB exhibited significant enhancement in terms of flocculation of coal waste slurry when the bioflocculant was used as a flocculant. Finally, surface tension measurements were taken to confirm the interaction between the bioflocculant and CTAB. The results show that CTAB could bind to the bioflocculant and form complexes.
In this work, we focus on a nonlinear dynamical model proposed by Lavrentovich et al. to compute and simulate spontaneous Ca2+ oscillations evoked by calcium ion efflux in astrocytes. Selected ...parameters are chosen, with observation of periodic and chaotic Ca2+ oscillations in cytosol. The stability analysis of equilibrium is conducted using the center manifold theorem to investigate the dynamics underlying spontaneous Ca2+ oscillations in astrocytes. The results indicate that the Hopf bifurcation represents the dynamical changes in stability of spontaneous Ca2+ oscillations. In addition, numerical simulations are performed to further assess the validity of the aforementioned analysis.
Self-oscillating systems based on thermally responsive polymer materials can realize heat-mechanical transduction in a steady ambient temperature field and have huge application potential in the ...field of micro-active machines, micro-robotics and energy harvesters. Recently, experiments have found that a torus on a hot surface can rotate autonomously and continuously, and its rotating velocity is determined by the competition between the thermally induced driving moment and the sliding friction moment. In this article, we theoretically study the self-sustained rotation of a hollow torus on a hot surface and explore the effect of the radius ratio on its rotational angular velocity and energy efficiency. By establishing a theoretical model of heat-driven self-sustained rotation, its analytical driving moment is derived, and the equilibrium equation for its steady rotation is obtained. Numerical calculation shows that with the increase in the radius ratio, the angular velocity of its rotation monotonously increases, while the energy efficiency of the self-rotating hollow torus motor first increases and then decreases. In addition, the effects of several system parameters on the angular velocity of it are also extensively investigated. The results in this paper have a guiding role in the application of hollow torus motor in the fields of micro-active machines, thermally driven motors and waste heat harvesters.
Abstract
Prior studies have paid much attention to the physical and mental health outcomes of spouse caregivers. However, few have looked at the cognitive trajectory of caregivers and how it was ...associated with the characteristics of caregivers and care recipients. Based on four waves (2011, 2013, 2015, and 2018) of the Chinese Health and Retirement Longitudinal Survey (CHARLS) (N=3137 dyad couples aged 45 and above), cognitive function was measured by Mini-Mental State Examination (MMSE). A parallel process growth model was conducted to explore the association between spouse caregiving and the joint trajectories of caregivers and their recipients’ cognitive decline during the eight years. Preliminary results show that 1) couples’ trajectories are significantly related to each other, although men had a higher initial level of cognitive function than women, their cognitive function declined at a faster rate than women did; 2) The relationship between caregiving and cognitive trajectory varies by gender. Specifically, providing care is positively correlated with slower cognitive decline in men, but not in women. Whereas receiving the care was associated with a faster cognitive decline for both gender. These findings emphasize the need of paying attention to both family caregivers and recipients and the need for more targeted intervention strategies based on the nature of care.
In this study, a new DMF-derived ionic liquid electrolyte EDMFBF4 was prepared, characterized and applied as a high-capacitance electrolyte for electric double-layer capacitors (EDLCs). EDMFBF4 was ...measured to have very high ionic conductivity and low viscosity (24.8 mS cm−1 and 21.6 mPa s at 25 °C), as well as a comparable electrochemical window (4.4 V, on a GC electrode) with EMImBF4, which is one of the most widely studied ionic liquid electrolytes with high performance. Therefore, EDMFBF4 was used as a non-volatile electrolyte for activated carbon-based EDLCs. The EDMFBF4-based EDLCs are capable to operate stably over a voltage of 2.7 V, and the specific capacitance of activated carbon was determined to be 165 F g−1 (100th cycle at 1 mA cm−2 and 30 °C), which is much larger than in the case of EMImBF4 (126 F g−1). Besides, EDMFBF4 showed lower ohmic resistance and double layer resistance than EMImBF4 in EDLCs. The high performance of EDMFBF4 electrolyte should be related to the quasi-linear EDMF cation of moderate size, which is presumably more suitable for enhanced ion mobility and compact electric double layer.
Carbon dioxide sequestration by minerals containing calcium or magnesium is a safe and stable approach to reduce the concentration of CO2 in the atmosphere. In this work, the bioleaching method was ...applied to pretreat the anorthite, aiming to improve the carbonation conversion rate of anorthite with low energy consumption, low cost, and no pollution. A bacteria named Herbaspirillum huttiense W-01 was found and selected as the strain. The effects of the bacterial strain on the Ca2+ leaching behavior of anorthite and the corresponding carbonation conversion rate were investigated. Then, the strengthening mechanism of the bacteria was clarified from the Ca2+ leaching rate and the crystal structure of anorthite. The bioleaching results showed that after 9 days of treatment, the pH value of the fermentation solution decreased to 6.01 from 7.20, and the concentration of Ca2+ was 8.1 mmol/L with a 4.65% leaching rate, which was about twice that of sterile medium. During the pretreatment period of one to 9 days, the carbonation conversion rate of different systems (A1: anorthite and bacteria, B1: anorthite and medium, C1: anorthite and distilled water, D1: anorthite and bacteria, cleaning step to remove the medium components) increased with time. After 9 days, the carbonation conversion rate of system D1 reached 18.74%, which was 3.46% higher than that of system C1, suggesting a better carbon sequestration effect of anorthite after the bioleaching pretreatment. In addition, a bioleaching residue with weakened thermal stability and decreased crystallinity was formed after the microbial pretreatment. Furthermore, it can be seen that the surface of the bioleaching residue was rough and showed obvious corrosion at the edges, and the specific surface area increased from 0.5187 m2/g to 0.9883 m2/g. It is precisely because of the changes in the crystal structure of anorthite caused by bioleaching, especially in mineralogy and morphology, that the carbonation activity of anorthite was enhanced. This research may provide a reference for the enhancement of carbon dioxide mineralization by basic or ultrabasic rocks through microbial methods.
Facile and reliable detection of total bilirubin (Bt, summation of indirect and direct bilirubin) and direct bilirubin (Bd) in human serum is of crucial importance to clinical diagnosis. However, it ...is still a challenge to explore an ideal recognition system for discriminating Bd and indirect bilirubin (Bi). In this work, a dual-functional sensor for Bt and Bd was first built on pH-controlled and mimetic peroxidase-catalyzed fluorescence enhancement. The fluorescence of nitrogen-doped graphene quantum dots (NGQDs) can be effectively quenched by bilirubin through the IFE process. With the catalysis of dopamine-derived magnetic ferrite nanoparticles (CoFe2O4-DOPA), both Bd and Bi were oxidized by H2O2 to colorless and fluorescent oxidates at pH 8.0. Interestingly, only Bd was oxidized at pH 3.5. The discriminating principle of Bd and Bi relied on their pH-controlled oxidation potentials. A sensitive sensor for Bt and Bd was developed on the enhanced fluorescence of the NGQDs/CoFe2O4-DOPA/H2O2 sensing system after bilirubin oxidation, which was originated from a combination of the fluorescence recovery of NGQDs and newly spawned fluorescence of bilirubin oxidates. The designed probe well quantifies Bt and Bd with the detection limits of 10 and 50 nM, respectively. Moreover, a portable diagnostic kit was fabricated and successfully used for the detection of Bt and Bd in 60 unrelated human serum samples, and the obtained results were almost consistent with those measured by biochemistry analyzer. The present kit exhibits the superiorities of high sensitivity and stability, interference-resistant, and green reagents, making it a promising candidate for bilirubin detection in the clinical diagnosis of jaundice.
