Robust and Flame-Retardant Zylon Aerogel Fibers for Wearable Thermal Insulation and Sensing in Harsh Environment.

The exceptional lightweight, highly porous, and insulating properties of aerogel fibers make them ideal for thermal insulation. However, current aerogel fibers face limitations due to their low resistance to harsh environments and a lack of intelligent responses. Herein, a universal strategy for creating polymer aerogel fibers using crosslinked nanofiber building blocks is proposed. This approach combines controlled proton absorption gelation spinning with a heat-induced crosslinking process. As a proof-of-concept, Zylon aerogel fibers that exhibited robust thermal stability (up to 650 °C), high flame retardancy (limiting oxygen index of 54.2%), and extreme chemical resistance are designed and synthesized. These fibers possess high porosity (98.6%), high breaking strength (8.6 MPa), and low thermal conductivity (0.036 W m-1 K-1 ). These aerogel fibers can be knotted or woven into textiles, utilized in harsh environments (-196-400 °C), and demonstrate sensitive self-powered sensing capabilities. This method of developing aerogel fibers expands the applications of high-performance polymer fibers and holds great potential for future applications in wearable smart protective fabrics.

Multifunctional MXene/C Aerogels for Enhanced Microwave Absorption and Thermal Insulation.

Two-dimensional transition metal carbides and nitrides (MXene) have emerged as promising candidates for microwave absorption (MA) materials. However, they also have some drawbacks, such as poor impedance matching, high self-stacking tendency, and high density. To tackle these challenges, MXene nanosheets were incorporated into polyacrylonitrile (PAN) nanofibers and subsequently assembled into a three-dimensional (3D) network structure through PAN carbonization, yielding MXene/C aerogels. The 3D network effectively extends the path of microcurrent transmission, leading to enhanced conductive loss of electromagnetic (EM) waves. Moreover, the aerogel's rich pore structure significantly improves the impedance matching while effectively reducing the density of the MXene-based absorbers. EM parameter analysis shows that the MXene/C aerogels exhibit a minimum reflection loss (RLmin) value of - 53.02 dB (f = 4.44 GHz, t = 3.8 mm), and an effective absorption bandwidth (EAB) of 5.3 GHz (t = 2.4 mm, 7.44-12.72 GHz). Radar cross-sectional (RCS) simulations were employed to assess the radar stealth effect of the aerogels, revealing that the maximum RCS reduction value of the perfect electric conductor covered by the MXene/C aerogel reaches 12.02 dB m2. In addition to the MA performance, the MXene/C aerogel also demonstrates good thermal insulation performance, and a 5-mm-thick aerogel can generate a temperature gradient of over 30 °C at 82 °C. This study provides a feasible design approach for creating lightweight, efficient, and multifunctional MXene-based MA materials.

Age-dependent Changes in Skeletal Muscle Mass and Visceral Fat Area in a Chinese Population.

OBJECTIVE: The present study was conducted to demonstrate the age-dependent changes in skeletal muscle mass and visceral fat area in a population of Chinese adults aged 30-92 years old. METHODS: A total of 6669 healthy Chinese men and 4494 healthy Chinese women aged 30-92 years old were assessed for their skeletal muscle mass and visceral fat area. RESULTS: The results showed age-dependent decreases in the total skeletal muscle mass indexes in both men and women aged 40-92 years old as well as age-dependent increases in the visceral fat area in men aged 30-92 years old and in women aged 30-80 years old. Multivariate regression models showed that the total skeletal muscle mass index was positively associated with the body mass index and negatively associated with the age and visceral fat area in both sexes. CONCLUSION: The loss of skeletal muscle mass becomes obvious at approximately 50 years of age, and the visceral fat area commences to increase at approximately 40 years of age in this Chinese population.

Passive Daytime Radiative Cooling of Silica Aerogels.

Silica aerogels are one of the most widely used aerogels, exhibiting excellent thermal insulation performance and ultralow density. However, owing to their plenitude of Si-O-Si bonds, they possess high infrared emissivity in the range of 8-13 µm and are potentially robust passive radiative cooling (PRC) materials. In this study, the PRC behavior of traditional silica aerogels prepared from methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) in outdoor environments was investigated. The silica aerogels possessed low thermal conductivity of 0.035 W/m·K and showed excellent thermal insulation performance in room environments. However, sub-ambient cooling of 12 °C was observed on a clear night and sub-ambient cooling of up to 7.5 °C was achieved in the daytime, which indicated that in these cases the silica aerogel became a robust cooling material rather than a thermal insulator owing to its high IR emissivity of 0.932 and high solar reflectance of 0.924. In summary, this study shows the PRC performance of silica aerogels, and the findings guide the utilization of silica aerogels by considering their application environments for achieving optimal thermal management behavior.

Super-Stretchable Hybrid Aerogels by Self-Templating Strategy for Cross-Media Thermal Management.

Personal thermal management (PTM) materials have attracted increasing attention owing to their application for personal comfort in an energy-saving mode. However, they normally work in the same media such as in the air, and little is known about what will happen in other media like water. In this study, a system for cross-media thermal management (CMTM): passive cooling in air and thermal insulation underwater is proposed. Hybrid aerogels comprising thermoplastic polyurethane (TPU) matrix and superhydrophobic silica aerogel particle (SSAP) for CMTM are designed and synthesized using a thermally induced phase separation and self-templating strategy. The TPU matrix endows the aerogels with super stretchability (500%), shape memory, and outstanding healing recovery rate (89.9%), which are ideal characteristics for potential wearable usage. Additionally, the TPU and SSAP endow the aerogel with high solar reflectivity and infrared emissivity, thus achieving a sub-ambient cooling of 10.6 °C in air. Moreover, the SSAP endows the aerogels with low thermal conductivity (0.052 W m-1 ·K-1 ) and high hydrophobicity (143°), enabling the aerogels for underwater thermal insulation. The CMTM performance of the aerogels makes them for potential uses in cross-media environments such as reefs and islands where cooling in air and thermal insulation in water are required.

Hyperelastic Kevlar Nanofiber Aerogels as Robust Thermal Switches for Smart Thermal Management.

Aerogels, the lightest artificial solid materials characterized by low density and thermal conductivity, high porosity, and large specific surface area, have attracted increasing interest. Aerogels exhibit single-mode thermal insulation properties regardless of the surrounding temperature. In this study, hyperelastic Kevlar nanofiber aerogels (HEKAs) are designed and fabricated by a slow-proton-release-modulating gelation and thermoinduced crosslinking strategy. The method does not use crosslinking agents and endows the ultralow-density (4.7 mg cm-3 ) HEKAs with low thermal conductivity (0.029 W m-1 K-1 ), high porosity (99.75%), high thermal stability (550 °C), and increased compression resilience (80%) and fatigue resistance. Proofs of the concept of the HEKAs acting as on-off thermal switches are demonstrated through experiments and simulations. The thermal switches exhibit a rapid thermal response speed of 0.73 °C s-1 , high heat flux of 2044 J m-2 s-1 , and switching ratio of 7.5. Heat dissipation can be reversibly switched on/off more than fifty times owing to the hyperelasticity and fatigue resistance of the HEKAs. This study suggests a route to fulfill the hyperelasticity of highly porous aerogels and to tailor heat flux on-demand.

Lightweight and flexible PAN@PPy/MXene films with outstanding electromagnetic interference shielding and Joule heating performance.

Lightweight and flexible multifunctional materials with excellent electromagnetic interference (EMI) shielding and Joule heating performances are highly demanded for smart and wearable electronics. In this work, polyacrylonitrile (PAN) nanofiber films are prepared by electrospinning and then coated with polypyrrole (PPy) via vapor deposition, yielding a continuous three-dimensional (3D) conductive network of PAN@PPy. Ti3C2Tx MXene nanosheets with high electrical conductivity are sprayed on the PAN@PPy film to enhance its EMI shielding performance. The as-prepared PAN@PPy/MXene films (55 µm thick) exhibit a high EMI shielding effectiveness (SE) of 32 dB, achieving an extraordinarily high normalized surface-specific SE (SSE/t) of up to 17 534.5 dB cm2 g-1 from 8.2 to 12.4 GHz; simultaneously, the temperatures of PAN@PPy/MXene films can be driven up to 170.5 °C at an input voltage of 4 V, and exhibit fast-response, stable, and long-term Joule heating performance. The high SSE/t and efficient Joule heating ability of the films bode potential applications in smart and wearable devices.

Bioinspired Multilayer Structures for Energy-Free Passive Heating and Thermal Regulation in Cold Environments.

Passive thermal regulation has attracted increasing interest owing to its zero-energy consumption capacity, which is expected to alleviate current crises in fossil energy and global warming. In this study, a biomimetic multilayer structure (BMS) comprising a silica aerogel, a photothermal conversion material (PTCM), and a phase change material (PCM) layer is designed inspired by the physiological skin structure of polar bears for passive heating with desirable temperature and endurance. The transparent silica aerogel functions as transparent hairs and allows solar entry and prevents heat dissipation; the PTCM, a glass plate coated with black paint, acts as the black skin to convert the incident sunlight into heat; and the PCM composed of n-octadecane microcapsules stores the heat, regulating temperature and increasing endurance. Impressively, outdoor and simulated experiments indicate efficient passive heating (increment of 60 °C) of the BMS in cold environments, and endurance of 157 and 92 min is achieved compared to a single aerogel and PTCM layer, respectively. The uses of the BMS for passive heating of model houses in winter show an increase of 12.1 °C. COMSOL simulation of the BMSs in high latitudes indicates robust heating and endurance performance in a -20 °C weather. The BMS developed in this study exhibits a smart thermal regulation behavior and paves the way for passive heating in remote areas where electricity and fossil energy are unavailable in cold seasons.

Metabolic syndrome and the incidence of lung cancer: a meta-analysis of cohort studies.

BACKGROUND: Metabolic syndrome (MetS) has been related to the pathogenesis of variety categories of cancers. This meta-analysis aimed to determine the association between MetS and the incidence of lung cancer. METHODS: Relevant cohort studies were identified by search of PubMed, Embase, and Cochrane's Library databases. Cochrane's Q test and I2 statistic were used to analyze the heterogeneity. Random-effect model which incorporates the potential heterogeneity was used for the meta-analysis. RESULTS: Five cohort studies with 188,970 participants were included. A total of 1,295 lung cancer cases occurred during follow-up. Meta-analyses showed that neither MetS defined by the revised NCEP-ATP III criteria (hazard ratio [HR]: 0.94, 95% confidence interval [CI]: 0.84 to 1.05, p = 0.25; I2 = 0) nor the IDF criteria (HR: 0.82, 95% CI: 0.61 to 1.11, p = 0.20; I2 = 0) was associated with an affected risk of lung cancer. Subgroup analyses showed consistent results in women and in men, in studies performed in Asian and non-Asian countries, and in prospective and retrospective cohorts (p all > 0.05). Meta-analysis limited to studies with the adjustment of smoking status also showed similar results (HR: 0.91, 95% CI: 0.80 to 1.05, p = 0.21; I2 = 0). No publication bias was detected based on the Egger regression test (p = 0.32). CONCLUSIONS: Current evidence from cohort studies does not support that MetS is an independent risk factor for the incidence of lung cancer.

Association Between Statin Use and Prognosis of Breast Cancer: A Meta-Analysis of Cohort Studies.

Background: Statin, a lipid-lowering drug, has been suggested to confer anticancer efficacy. However, previous studies evaluating the association between statin use and prognosis in breast cancer showed inconsistent results. A meta-analysis was performed to evaluate the association between statin use and clinical outcome in women with breast cancer. Methods: Cohort studies comparing recurrence or disease-specific mortality in women with breast cancer with and without using of statins were identified by search of PubMed, Embase, and Cochrane's Library databases. A random-effect model, incorporating the inter-study heterogeneity, was used to combine the results. Subgroup analyses were performed to evaluate the influences of study characteristics on the outcomes Results: Seventeen cohort studies with 168,700 women with breast cancer were included. Pooled results showed that statin use was significantly associated with a lower risk of breast cancer recurrence (adjusted hazard ratio [HR] = 0.72, p < 0.001) and breast cancer mortality (HR = 0.80, p < 0.001). Subgroup analysis showed that timing of statin use, statin type, study design, sample size, or quality score did not significantly affect the outcomes. However, statin use was associated with more remarkably reduced breast cancer recurrence in studies with mean follow-up duration ≤ 5 years (HR = 0.55, p < 0.001) than that in studies of >5 years (HR = 0.83, p = 0.01). Conclusions: Statin use is associated with reduced recurrence and disease-specific mortality in women with breast cancer. These results should be validated in randomized controlled trials.

Multifunctional Aramid Nanofiber/Carbon Nanotube Hybrid Aerogel Films.

Lightweight, robust, and thin aerogel films with multifunctionality are highly desirable to meet the technological demands of current society. However, fabrication and application of these multifunctional aerogel films are still significantly underdeveloped. Herein, we demonstrate a multifunctional aerogel film composed of strong aramid nanofibers (ANFs), conductive carbon nanotubes (CNTs), and hydrophobic fluorocarbon (FC) resin. The obtained hybrid aerogel film exhibits large specific surface area (232.8 m2·g-1), high electrical conductivity (230 S·m-1), and excellent hydrophobicity (contact angle of up to 137.0°) with exceptional Joule heating performance and supreme electromagnetic interference (EMI) shielding efficiency. The FC coating renders the hydrophilic ANF/CNT aerogel films hydrophobic, resulting in an excellent self-cleaning performance. The high electrical conductivity enables a low-voltage-driven Joule heating property and an EMI shielding effectiveness (SE) of 54.4 dB in the X-band at a thickness of 568 µm. The specific EMI SE is up to 33528.3 dB·cm2·g-1, which is among the highest values of typical metal-, conducting-polymer-, or carbon-based composites. This multifunctional aerogel film holds great promise for smart garments, electromagnetic wave shielding, and personal thermal management systems.

The association between time-mean serum uric acid levels and the incidence of chronic kidney disease in the general population: a retrospective study.

BACKGROUND: Investigations on the role of the time-mean serum uric acid (SUA) value in determining the risk of chronic kidney disease (CKD) are limited. We investigated whether the time-mean SUA value indicates the risk of CKD, and explored associations of the baseline and time-mean SUA levels with kidney function decline and incident CKD in a healthy population. METHODS: We initiated an inhabitant-based cohort study between January 2011 and December 2016. All participants completed a yearly medical check-up at the Zhejiang Province People's Hospital and had baseline estimated glomerular filtration rates (eGFR) > 60 ml/min/1.73m2. The SUA level and eGFR were assessed every year in the follow-up period. A multivariate adjusted binary logistic regression analysis and Cox proportional hazards models were used to evaluate the risk of newly-developed CKD among different stratified groups. RESULTS: During the 6-year follow-up period, 227 (4.4%) participants developed CKD. In multivariable-adjusted analyses, the odds ratio (OR) for new-onset CKD increased, with higher time-mean SUA levels than at baseline (OR: 1.00 [reference], 2.709 [95% confidence interval: 1.836-5.293], 3.754 [1.898-7.428], and 7.462 [3.694-15.073]). After adjustment for potential cofounders, a multivariate Cox proportional hazard model showed that a higher SUA increased the risk of developing CKD (the adjusted hazard ratios of the highest and lowest quartiles for the baseline and time-mean SUA levels were 1.689 [1.058-2.696] and 6.320 [3.285-12.159], respectively). CONCLUSION: An increased time-mean and single SUA value were independently associated with an increased likelihood of eGFR decline and development of new-onset CKD in the general population.

Hyperbaric oxygen treatment at various stages following chronic constriction injury produces different antinociceptive effects via regulation of P2X4R expression and apoptosis.

PURPOSE: The aims of this study were to investigate the effect of hyperbaric oxygen (HBO) treatment at various stages following chronic constriction injury (CCI) and to explore the underlying mechanisms of HBO treatment. METHODS: Forty adult male Sprague-Dawley rats were randomly assigned to five groups (n = 8 for each group): the sham group, CCI group, HBO1 group, HBO2 group, and HBO3 group. Neuropathic pain was induced by CCI of the sciatic nerve. HBO treatment began on postoperative days 1, 6, and 11 and continued for 5 days. The mechanical withdrawal threshold and thermal withdrawal latency were tested on preoperative day 3 and postoperative days 1, 3, 5, 7, 10, 14, and 21. The expression of P2X4R was determined by immunohistochemistry and western blot analysis. Cell apoptosis was measured using TUNEL staining. The expression of caspase 3 was measured using reverse transcription polymerase chain reaction (RT-PCR). Electron microscopy was used to determine the ultrastructural changes. RESULTS: Early HBO treatment beginning on postoperative day 1 produced a persistent antinociceptive effect and inhibited the CCI-induced increase in the expression of P2X4R without changing CCI-induced apoptosis. In contrast, late HBO treatment beginning on postoperative day 11 produced a persistent antinociceptive effect and inhibited CCI-induced apoptosis and upregulation of caspase-3 without changing the expression of P2X4R. In addition, late HBO treatment reduced CCI-induced ultrastructural damage. However, HBO treatment beginning on postoperative day 6 produced a transient antinociceptive effect without changing the expression of P2X4R or CCI-induced apoptosis. CONCLUSION: HBO treatment at various stages following CCI can produce antinociceptive effects via different mechanisms. Early HBO treatment is associated with inhibition of P2X4R expression, and late HBO treatment is associated with inhibition of cell apoptosis.