Anticounterfeiting is a highly required technique to protect the product and the consumer rights in the modern society. The conventional luminescent anticounterfeiting is based on downconversion ...luminescence excited by an ultraviolet light, which is easy to be faked. In this work, we realized six luminescent modes in a niobate-based structure (LiNbO3:RE3+, RE3+ = Pr3+, Tm3+, Er3+, Yb3+), in which photostimulated luminescence of LiNbO3:Pr3+, and upconversion luminescence color evolution of LiNbO3:Er3+ were first presented. Based on the above luminescent modes of LiNbO3:RE3+, multilevel anticounterfeiting devices were developed. By employing mechanoluminescence and persistent luminescence, we achieved dual-mode anticounterfeiting that could display the luminescent patterns without any direct irradiation. In addition, another dual-mode anticounterfeiting based on photostimulated luminescence and upconversion luminescence excited by a near-infrared light was realized, which could display the anticounterfeiting patterns in both static and dynamic states. To obtain an even higher anticounterfeiting level, downconversion luminescence, thermoluminescence, photostimulated luminescence, and upconversion luminescence were simultaneously applied in a food trademark. This four-mode anticounterfeiting trademark could not only show a static–dynamic luminescence that is hard to be faked but also allow consumers to distinguish the food freshness. The presented multilevel anticounterfeiting strategies could be employed to resolve the counterfeit issues in various fields.
This review summarizes the recent advancements in the mechanical properties of fiber-reinforced polymer (FRP) composites reinforced with graphene and carbon nanotubes (CNTs). Different synthesis ...methods for incorporating graphene and CNTs into the FRP structure are reviewed and discussed. The enhancement of graphene and CNTs on the improvement of the interfacial shear strength (IFSS), interlaminar shear strength (ILSS), interlaminar fracture toughness (ILFT), tensile strength, tensile modulus, flexural strength, flexural modulus, impact resistance and fatigue characteristics of FRP composites is emphatically reviewed, especially the discussion of various performance related reinforcement mechanisms. These enhancement mechanisms are a complex project, in which the key is the interface problem between fiber and matrix caused by graphene and CNTs. This review provides an in-depth review of the improvement of each mechanical property due to the modification of interfacial properties between fibers and a nanofiller-reinforced matrix. In the selected representative papers, the addition process and strengthening mechanism of CNTs and graphene are reviewed in detail, and four enhancement mechanisms and synergistic effects are analyzed, including wettability, mechanical interlocking, chemical bonding and transition layer. Aiming at the improvement of ILFT of composite laminates, various nano strengthening strategies caused by graphene and CNTs and the toughening principle to prevent delamination failure are discussed in detail. The modeling and analysis tools for mechanical properties of graphene and carbon nanotube reinforced composites, including molecular dynamics method, finite element method and multi-scale modeling method, are reviewed. Finally, some problems in the enhancement mechanism of graphene and carbon nanotubes are discussed.
Abstract
Centrosymmetric-oxide/polydimethylsiloxane elastomers emit ultra-strong non-pre-irradiation mechanoluminescence under stress and are considered one of the most ideal mechanoluminescence ...materials. However, previous centrosymmetric-oxide/polydimethylsiloxane elastomers show severe mechanoluminescence degradation under stretching, which limits their use in applications. Here we show an elastomer based on centrosymmetric fluoride CaF
2
:Tb
3+
and polydimethylsiloxane, with mechanoluminescence that can self-recover after each stretching. Experimentation indicates that the self-recoverable mechanoluminescence of the CaF
2
:Tb
3+
/polydimethylsiloxane elastomer occurs essentially due to contact electrification arising from contact-separation interactions between the centrosymmetric phosphors and the polydimethylsiloxane. Accordingly, a contact-separation cycle model of the phosphor–polydimethylsiloxane couple is established, and first-principles calculations are performed to model state energies in the contact-separation cycle. The results reveal that the fluoride–polydimethylsiloxane couple helps to induce contact electrification and maintain the contact-separation cycle at the interface, resulting in the self-recoverable mechanoluminescence of the CaF
2
:Tb
3+
/polydimethylsiloxane elastomer. Therefore, it would be a good strategy to develop self-recoverable mechanoluminescence elastomers based on centrosymmetric fluoride phosphors and polydimethylsiloxane.
Data regarding different metabolic phenotypes and bone markers including bone mineral content (BMC) and osteocalcin (OCN) among children and adolescents are very limited. Hence, the purpose of this ...investigation was to explore the relationship between different metabolic phenotypes and BMC or OCN among Chinese children and adolescents. This cross-sectional study included 1,328 children and adolescents aged between 12 and 18 years who were selected from four schools in Yinchuan city from 2018 to 2020 by stratified cluster random sampling. Subjects were divided into four groups according to BMI and metabolic status, as follows: metabolically healthy obesity (MHO), metabolically unhealthy obesity (MUO), metabolically unhealthy normal weight (MUNW), and metabolically healthy normal weight (MHNW). The MHNW, MUNW, MHO, and MUO phenotypes in boys were 48.4%, 30.5%, 6.7%, and 14.4%, respectively, and were 47.8%, 33.6%, 6.6%, and 12.1% in girls, respectively. The MHO and MUO phenotypes had higher BMC than the MHNW or MUNW phenotype (all p < 0.05), and the MUO phenotype with BMC was significantly higher than MHO group in boys (p < 0.05). We discovered a significant positive correlation between BMC and the MHO (OR = 8.82, 95% CI = 2.04–38.16), MUO phenotypes (OR = 13.53, 95% CI = 4.10–44.70), while no association was found between OCN and metabolic phenotypes in neither boys nor girls. Overweight/obese children and adolescents had higher BMC, and there existed sex differences in the effect of metabolic status on BMC among them. OCN was not supposed to be an index of bone health in this study.
In this work, ultra-strong yellow and green mechanoluminescence was presented for Y
3
Al
5
O
12
:Ce
3+
and Ba
0.5
Sr
0.5
Si
2
O
2
N
2
:Eu
2+
, respectively. In addition to the emitting color, the ...above materials showed distinct trap dependence/independence and spontaneous radiation behaviors, leading to instantaneous mechanoluminescence without any afterglow for Y
3
Al
5
O
12
:Ce
3+
and persistent mechanoluminescence for Ba
0.5
Sr
0.5
Si
2
O
2
N
2
:Eu
2+
. By ingeniously combining the above unique mechanoluminescence behaviors, two types of intriguing and unprecedented devices were achieved. The devices are a mechanics-induced triple-mode anticounterfeiting device capable of displaying embedded information in varied emitting colors and dynamic patterns and a comprehensive tactile sensor that can simultaneously sense/record the contact load, motion trail, and contact position for objects moving on the surface. This work is the first to present application designs by simultaneously utilizing transient and persistent mechanoluminescence. The as-fabricated devices showed unique superiority and advancement in their own fields. Particularly, the mechanoluminescence-based tactile sensor realized comprehensive sensing functionalities within a single unit and required no extra circuit designs.
An intriguing mechanics-induced triple-mode anticounterfeiting device and a moving tactile sensor were developed by simultaneously utilizing transient and persistent mechanoluminescence.
Stiffened structure-induced gain-phase errors degrade the performance of the high-resolution two-dimensional multiple signal classification (2D-MUSIC) algorithm, which makes it impossible to ensure ...the high accuracy of impact localization results. To eliminate the localization bias caused by these errors, a calibrated 2D-MUSIC-based impact localization method is first introduced. Firstly, time-frequency characteristics of the non-stationary impact signals are evaluated by experiment to obtain a clear first wave packet or a wave packet that purely corresponds to a single mode through continuous wavelet transform (CWT). Then, the uniform linear array covariance matrix with gain-phase errors is calibrated to be constructed as a Toeplitz structural matrix. By reconstructing covariance matrix R, 2D-MUSIC-based impact localization is calibrated for stiffened curved composite structures. Experimental research on the stiffened curved composite panel is carried out, and these impact localization results demonstrate the validity and effectiveness of the calibrated 2D-MUSIC-based method.
Persistent luminescence (PersL) phosphor is a glow‐in‐the‐dark material that has been widely applied. Here, we report a multicolor PersL phosphor Sr2Ga2GeO7:Pr3+. The PersL color can be tuned from ...deep red to blue. It reveals that the luminescent color modulation of the Sr2Ga2GeO7:Pr3+ phosphor is essentially associated with the cross‐relaxation effect of Pr3+ in the host with low‐phonon assistance energy. The PersL lifetime of the multicolor phosphors can be also tuned. Based on the unique features of Sr2Ga2GeO7:Pr3+ phosphor, some simple PersL images are fabricated to emit dynamic multicolor information, and it shows that the PersL image even depicts dynamic multicolor anticounterfeiting.
Here, we report a multicolor PersL phosphor Sr Ga GeO :Pr .The PersL color can be tuned from deep red to blue. It reveals that the multicolor luminescence of the phosphor is essentially associated with the crossrelaxation effect of Pr . What's more,the PersL lifetime of the multicolor phosphor can be also tuned. Based on the unique features of Sr Ga GeO :Pr phosphor, some luminescent images are fabricated for dynamic multicolor anticounterfeiting.
The aim of this study was to assess the associations of body fat distribution and lean body mass (LBM) with blood pressure (BP) in normal-weight Chinese children and adolescents.
A total of 898 ...normal-weight Chinese children and adolescents, aged 10-18 years, were included this cross-sectional study via a cluster sampling method. The bioelectrical impedance analysis (BIA) was used to measure body composition. The participants were measured for blood pressure (BP) using a calibrated electronic sphygmomanometer according to the standard method by the "American Hypertension Education Project Working Group".
Body composition was related to abnormal BP in normal-weight children and adolescents. After the model adjusted for age, smoking, and drinking, regression analysis showed that fat mass percentage (FMP) was negatively associated with abnormal BP, while LBM was positively associated with abnormal BP in boys(P < 0.05). Whereas FMP and visceral fat level (VFL) were positively associated with abnormal BP in girls (P < 0.05).
There are sex differences in the relationships between total body fat, visceral fat and lean body mass with abnormal BP in normal-weight youths. Therefore, it is of great significance to pay attention to the relative influence of the body composition of the boys and girls in the prevention and treatment of hypertension in youths.
The relationship between visceral adiposity index (VAI) and unhealthy metabolic phenotype remained unclear in children and adolescents. This study aimed to investigate their association and compared ...the ability of VAI and traditional adiposity indicators (body mass index, waist circumference and waist-to-height ratio) to predict metabolically unhealthy phenotype among normal-weight, overweight and obese children and adolescents. In this cross-sectional study, 1722 children and adolescents aged 12-18 years were selected by cluster random sampling, underwent a questionnaire survey, physical examination and biochemical tests. Participants were divided into four phenotypes according to the combination of the weight status determined by body mass index (BMI) and metabolic syndrome components. Receiver operating characteristic (ROC) analysis and multivariate logistic regression were used to compare the predictive capacity between VAI and traditional adiposity indicators and their relationship with metabolically unhealthy phenotype. We found that VAI had better performance in predicting metabolically unhealthy phenotype than traditional adiposity indicators, the area under the receiver-operating characteristic curve (AUC) were 0.808 and 0.763 for boys and girls with normal-weight, 0.829 and 0.816 for boys and girls with overweight and obese (all P < 0.001). VAI was most strongly related to metabolically unhealthy phenotype whether or not to adjust the age, the adjusted OR and 95%CI was 6.15 (4.13-9.14) in boys with normal weight, and 5.90 (3.06-11.36), 4.95 (2.35-10.41) in boys and girls with overweight and obese, respectively (all P < 0.001). Our findings suggested VAI could be used as a comprehensive predictor to identify unhealthy metabolic phenotype in children and adolescents.
Abstract
There is no study exploring the association between triglyceride-glucose (TyG) index and skeletal muscle mass in Chinese adolescents. Therefore, the objective of this study is to explore the ...association between TyG index and appendicular lean mass (ALM) in Chinese adolescents. In this study, 1336 adolescents (805 boys, 60.25%) aged 12–18 years in China were randomly selected through a stratified cluster sampling. According to the tertiles of TyG index, we separated all participants into three groups, and LM was measured by Bioelectrical Impedance Analysis. The TyG index was negatively related to ALM/weight in Chinese adolescents whether stratified by gender (boys:
β
= − 0.293; girls:
β
= − 0.195; all
P
< 0.001). After adjusting for age and BMI, a significant correlation between the TyG index and ALM/weight was observed only in boys (
β
= − 0.169,
P
= 0.001). The highest TyG index tertile was significantly associated with low ALM/weight after adjusting for all covariates in the full sample (OR = 3.04, 95% CI 1.12–8.26,
P
= 0.029) and boys (OR = 4.68, 95% CI 1.22–17.95,
P
= 0.025) only in overweight/obese group. Our findings suggested elevated levels of TyG index may be a risk factor of low ALM/weight in Chinese adolescents, especially in boys.
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