Preparation and characterization of diphenyl silicone rubber/microfiber glass wool composite thermal control films

Innovative research on the development of thermal control films for spacecraft surfaces is presented. A hydroxy-terminated random copolymer of dimethylsiloxane-diphenylsiloxane (PPDMS) was prepared from hydroxy silicone oil and diphenylsilylene glycol by a condensation reaction, and then liquid diphenyl silicone rubber base material (denoted as PSR) was obtained by adding hydrophobic silica. Microfiber glass wool (MGW) with a fiber diameter of ∼3 μm was added to the liquid PSR base material, which upon solidifying at room temperature, formed a 100 μm thick PSR/MGW composite film. The infrared radiation properties, solar absorption, thermal conductivity, and thermal dimensional stability of the film were evaluated. Moreover, the dispersion of the MGW in the rubber matrix was confirmed by optical microscopy and field-emission scanning electron microscopy. The PSR/MGW films exhibited a glass transition temperature of -106 °C, thermal decomposition temperature exceeding 410 °C, and low α/ε values. The homogeneous distribution of MGW in the PSR thin film resulted in a notable reduction in its linear expansion coefficient, as well as its thermal diffusion coefficient. Consequently, it exhibited a significant capacity for thermal insulation and retention. For the sample with 5 wt% of MGW, the linear expansion coefficient and thermal diffusion coefficient at 200 °C were reduced to 0.53% and 2.703 mm s^-2, respectively. Thus, the PSR/MGW composite film has good heat-resistance stability and low-temperature endurance, along with low α/ε values and excellent dimensional stability. Additionally, it facilitates effective thermal insulation and temperature control, and can be an ideal material for thermal control coatings on spacecraft surfaces.

In situ liquid cell SEM observation of dynamic processes of Au nanoparticles

In situ liquid cell electron microscopy (LC-EM) is a powerful platform for real time nanoscale imaging of liquid systems. In situ liquid cell scanning electron microscopy (LC-SEM) as a relatively low cost and potentially more convenient characterization method, has not been as widely used as compared to in situ liquid cell transmission electron microscopy (LC-TEM). This paper reports a real time high resolution and comprehensive characterization of Au nanoparticles (NPs) and nanoparticle clusters (NPCs), which are surface-decorated with cetyltrimethylammonium bromide (CTAB), in an oleic acid (OA) emulsion system with LC-SEM. Single NP resolution images are routinely collected with both secondary electron (SE) and backscattered electron (BSE) imaging modes, with different SEM systems. Energy dispersive spectroscopy (EDS) mapping data clearly demonstrates the single particle level chemical element distributions, particle stacking structure, as well as the preferred distribution of OA molecules on the Au particle surfaces. Moreover, both liquid droplet growth and particle motions are observed with LC-SEM, among which, ways for faster tracking the single particle level dynamic motion behavior of Au NPs and NPCs are explored. We expect that our work will bring new insight of high resolution and fast analysis in a broad range of materials in liquid with LC-SEM.

Improving the thermal stability of poly[methyl(trifluoropropyl)siloxane] by introducing diphenylsiloxane units

A series of poly(methyl(trifluoropropyl)-diphenyl siloxane) (P(MTFPS-co-DPS)) was synthesized by polycondensation of diphenylsilanediol and methyltrifluoropropylsiloxanediol. Their chemical structures were investigated by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimeter (DSC). The effect of diphenylsiloxane (DPS) units on the thermal stability of poly[methyl(trifluoropropyl)siloxane] (PMTFPS) was studied by thermogravimetric analysis (TGA), isothermal degradation tests, and pyrolysis-gas chromatography-mass spectrometry (Py-GCMS). The results showed that the thermal stability of PMTFPS improved with the introduction of DPS units into the chain. In particular, the temperature for 5% mass loss in PMTFPS increased by 72 °C under a nitrogen atmosphere. In addition, the mechanism by which the DPS units improve the thermal stability of PMTFPS was also investigated.

Is there a correlation between sensory impairments and social isolation in middle-aged and older Chinese population? Cross-sectional and longitudinal evidence from a nationally representative survey

Purpose

The aim of this study is to investigate the cross-sectional and longitudinal associations between sensory impairments (SIs) including single vision impairment (SVI), single hearing impairment (SHI), and dual sensory impairments (DSI) with social isolation in the middle-aged and older Chinese population.

Methods

Data were obtained from the China Health and Retirement Longitudinal Survey (CHARLS). In total, 11,674 Chinese older adults aged over 45 were included at baseline 2011, and 6,859 participants who accomplished all four interviews from 2011 to 2018 were adapted for longitudinal analyses. Sensory status and social isolation measurements including social disconnectedness and self-perceived loneliness were collected. Assessment of social disconnectedness included the number of types of social activities in which they participated and the frequency of such participation. Loneliness referred to the subjective perception of loneliness. Other covariates included socio-demographic characteristics, medical conditions, and lifestyle-related factors. The impacts of baseline sensory status on social disconnectedness and loneliness were assessed using univariate and multivariate generalized linear models. A generalized linear model with generalized estimation equations (GEE) was used to assess the association between time-varying sensory statuses with social disconnectedness or loneliness over 8 years after being adjusted with multi-confounding factors.

Results

Participants with SIs had significantly higher levels of social disconnectedness and self-perceived loneliness, compared to those who were free of SI. All kinds of SIs were significantly associated with loneliness according to both cross-sectional and longitudinal data. The correlations between DSI and social disconnectedness or loneliness at baseline and over 8 years were also noticed. SHI was found to be significantly associated with both frequency and types of social activities according to cross-sectional data and with the frequency of social activity participation in longitudinal analysis. SVI was only associated with the types of social activities at baseline (all p-values < 0.05).

Conclusion

Sensory impairments, especially dual sensory impairments, have explicitly detrimental effects on social isolation among the older Chinese population. Over time, single hearing impairment specifically jeopardizes their frequency rather than types of social activities participation.

Sensory impairments and subjective well-being status in middle-aged and older Chinese population: Cross-sectional and longitudinal analyses of a nationally representative survey

Purpose

To investigate the impacts of sensory impairments (SIs) including single vision impairment (SVI), single hearing impairment (SHI) and dual sensory impairment (DSI) on subjective wellbeing measurements including life expectancy (LE), life satisfaction (LS) and self-rated health (SRH) in middle-aged and older Chinese population.

Methods

We obtained data from the China Health and Retirement Longitudinal Survey (CHARLS). In total, 9,293 Chinese middle-aged and older adults aging over 45 were included at baseline 2011 in this study, and 3,932 participants who accomplished all 4 interviews from 2011 to 2018 were adapted for longitudinal analyses. Sensory status and subjective wellbeing measurements were collected. Other covariates included socio-demographic characteristics, medical condition and lifestyle-related factors. The impacts of baseline sensory status on LE, LS and SRH were assessed using univariate and multivariate logistic regression analyses. A linear regression analysis with generalized estimating equations (GEE) was used to assess the association between time-varying sensory statuses with LE, LS and SRH over 8 years after being adjusted with multi-confounding factors.

Results

Participants with SIs had significantly lower level of LE, LS, and SRH, compared to those who were free of SI. All kinds of SIs were significantly associated with LE, LS, and SRH according to cross-sectional data. The correlations between SIs and LE or SRH over 8 years were also noticed. However, only SHI and DSI were found to be significantly associated with LS according to longitudinal data (all p values < 0.05).

Conclusion

Sensory impairments had explicitly detrimental effects on subjective wellbeing status over time among middle-aged and older Chinese population.

Impact of COVID-19 Related Knowledge and Precautions on Emotional and Behavioral Problems Among Children During the Post-pandemic in China: The Explanatory Value of Emotional Problems Among Caregivers

To investigate the prevalence of emotional and behavioral problems (EBPs) among children during the COVID-19 post-pandemic in China; examine associations between COVID-19-related knowledge and precautions and problems in children, and explore the potential explanatory value of the mental health status of caregivers on any associations observed. Based on a cross-sectional design, caregivers of 6,017 children from 12 primary schools in Shanghai and Taizhou, China, were invited to complete an online survey from June 26 to July 6, 2020. EBPs of the children were assessed using the Strengths and Difficulties Questionnaire (SDQ), while the emotional problems of caregivers were assessed using the Depression Anxiety Stress Scales-21 (DASS-21). Structural equation modeling was employed to estimate the direct and indirect associations (explained by the emotional problems of caregivers) between COVID-19-related knowledge and precautions and the EBPs among children. The overall prevalence of EBPs in the sample was 12.5%, and 5.3% of them had a high or very high SDQ total difficulties score during the COVID-19 post-pandemic. After adjustment for covariates, higher COVID-19-related knowledge (β = -0.83; P < 0.001) and precautions (β = -0.80; P < 0.001) were significantly associated with lower SDQ total difficulties score among children. There was an explanatory effect of emotional problems of caregivers on the aforementioned associations, which explained 31% and 41% of the total effect, respectively. Higher levels of knowledge and precautions of COVID-19 were associated with lower EBPs among children, and the relationship was partially explained by the emotional problems in caregivers. It may be beneficial to improve pandemic-related prevention education and adopt psychological interventions toward the emotional status of caregivers for the psychological health of children.

In situ embedding dual-Fe nanoparticles in synchronously generated carbon for the synergistic integration of magnetic resonance imaging and drug delivery

In situ incorporating versatile magnetic iron nanoparticles into ordered mesoporous carbon (OMC) by means of synthetic methodology for functional integration is a great challenge. Inspired by the phenomenon of uniovular twins in nature, a homometallic [Fe₉(μ₃-O)₄(O₃PPh)₃(O₂CCMe₃)₁₃] ({Fe₉P₃}) cluster was synthesized and used as the ovulum to in situ produce dual-Fe nanoparticle (γ-Fe₂O₃ and Fe(PO₃)₃)-functionalized OMC (dual-Fe/OMC). In vitro magnetic resonance imaging (MRI) studies showed a longitudinal relaxation (r ₁) and transverse relaxation (r ₂) of 9.74 and 26.59 mM^-1 s^-1 with a r ₂/r ₁ ratio of 2.73 at 0.5 T. The MRI performances were further examined by mouse model with a subcutaneous HeLa tumor. In addition, the low cytotoxicity, considerable loading capacity and delivery of doxorubicin hydrochloride (DOX) were also studied in vitro. These results demonstrate the feasibility of the concept of uniovular twins in the one-pot preparation of dual-Fe/OMC for functional integration.

Corrosion of dental alloys in artificial saliva with Streptococcus mutans

A comparative study of the corrosion resistance of CoCr and NiCr alloys in artificial saliva (AS) containing tryptic soy broth (Solution 1) and Streptococcus mutans (S. mutans) species (Solution 2) was performed by electrochemical methods, including open circuit potential measurements, impedance spectroscopy, and potentiodynamic polarization. The adherence of S. mutans to the NiCr and CoCr alloy surfaces immersed in Solution 2 for 24 h was verified by scanning electron microscopy, while the results of electrochemical impedance spectroscopy confirmed the importance of biofilm formation for the corrosion process. The R(QR) equivalent circuit was successfully used to fit the data obtained for the AS mixture without S. mutans, while the R(Q(R(QR))) circuit was found to be more suitable for describing the biofilm properties after treatment with the AS containing S. mutans species. In addition, a negative shift of the open circuit potential with immersion time was observed for all samples regardless of the solution type. Both alloys exhibited higher charge transfer resistance after treatment with Solution 2, and lower corrosion current densities were detected for all samples in the presence of S. mutans. The obtained results suggest that the biofilm formation observed after 24 h of exposure to S. mutans bacteria might enhance the corrosion resistance of the studied samples by creating physical barriers that prevented oxygen interactions with the metal surfaces.

Caspase-8 and Caspase-9 Functioned Differently at Different Stages of the Cyclic Stretch-Induced Apoptosis in Human Periodontal Ligament Cells

Background

Human periodontal ligament (PDL) cells underwent apoptosis after mechanical stretch loading. However, the exact signalling pathway remains unknown. This study aimed to elucidate how the apoptotic caspases functioned in the cyclic stretch-induced apoptosis in human PDL cells.

Materials and Methods

In the present study, 20% cyclic stretch was selected to load the cells for 6 or 24 h. The following parameters were analyzed: apoptotic rates, the protein levels of caspase-3, -7, -8 and -9 and the activities of caspase-8 and -9. Subsequently, the influences of caspase-8 and caspase-9 inhibitors on the apoptotic rate and the protein level of the activated caspase-3 were assessed as well.

Results

The apoptotic rates increased in response to cyclic stretch, but the cells entered different apoptotic stages after 6 and 24 h stretches. Caspase-3, -7, -8 and -9 were all activated after stretch loading. The stretch-induced apoptosis and the protein level of the activated caspase-3 were inhibited after inhibiting both caspase-8 and caspase-9 in both 6 and 24 h stretched cells and after inhibiting caspase-9 in 24 h stretched cells.

Conclusion

Caspase-8 and -9 functioned differently at different apoptotic stages in human PDL cells after cyclic stretch.

G4-Tetra DNA Duplex Induce Lung Cancer Cell Apoptosis in A549 Cells

The specific DNA is typically impermeable to the plasma membrane due to its natural characters, but DNA tetra structures (DTNs) can be readily uptake by cells in the absence of transfection agents, providing a new strategy to deliver DNA drugs. In this research, the delivery efficiency of tetrahedral DNA nanostructures was measured on adenocarcinomic human alveolar basal epithelial (A549) cells via delivering AS1411 (G4). The DNA tetra-AS1411 complex was rapidly and abundantly uptake by A549 cells, and the induced apoptosis was enhanced. Furthermore, biodistribution in mouse proved the rapid clearance from non-targeted organs in vivo. This study improved the understanding of potential function in DNA-based drug delivery and proved that DTNs-AS1411 could be potentially useful for the treatment of lung cancer.