Composite Foams of the Graphitic Carbon Nitride@Carbon Nanofibrils Conferred a Superamphiphilic Property and Reinforced Thermal Stability.

Herein, we demonstrated the preparation of novel three-dimensional (3D) superamphiphilic g-C3N4@carbon nanofibers foam (g-C3N4@CNFs) via a two-step approach: liquid nitrogen treatment-freeze-drying; the foams possessed good thermal stability. In this approach, melamine acted as a nitrogen source, and nanofibrillated cellulose (NFCs) functioned as a 3D skeleton. The thermal stability of the as-prepared g-C3N4@CNFs-3 foam was much higher than that of g-C3N4@CNFs-1, as indicated by thermogravimetric data, including an increase of the onset weight loss point (Tonset) by 238.6 °C and an improvement of the maximal weight loss rate (Tmax) by 258.8 °C. The combination of g-C3N4 with CNFs conferred a reduction in the heat release rate (ca. -86%) and the total heat release (ca. -75%). Furthermore, the composition of the hydrophilically oxygenated functional groups and hydrophobic triazine domains in g-C3N4@CNFs rendered it a unique amphiphilic property (contact angle close to 0° within 1.0 s for water and 0° within 12 ms for hexane). A high storage capacity for water and various organic solvents of the superamphiphilic g-C3N4@CNFs foam was found, up to 40-50 times its original weight. The discovery of these superamphiphilic foams is of great significance for the development of superwetting materials and may find their applications in oil emulsion purification and catalyst support fields.

Screen time among school-aged children of aged 6-14: a systematic review.

BACKGROUND: Screen time refers to the time an individual spends using electronic or digital media devices such as televisions, smart phones, tablets or computers. The purpose of this study was to conduct systematic review to analyze the relevant studies on the length and use of screen time of school-aged children, in order to provide scientific basis for designing screen time interventions and perfecting the screen use guidelines for school-aged children. METHODS: Screen time related studies were searched on PubMed, EMBASE, Clinical Trials, Controlled Trials, The WHO International Clinical Trials Registry Platform, the Cochrane Central Register of Controlled Trials, CNKI, and Whipple Journal databases from January 1, 2016 to October 31, 2021. Two researchers independently screened the literature and extracted the data, and adopted a qualitative analysis method to evaluate the research status of the length and usage of screen time of school-aged students. RESULTS: Fifty-three articles were included. Sixteen articles studied screen time length in the form of continuous variables. Thirty-seven articles studied screen time in the form of grouped variables. The average screen time of schoolchildren aged 6 to 14 was 2.77 h per day, and 46.4% of them had an average screen time ≥ 2 h per day. A growth trend could be roughly seen by comparing studies in the same countries and regions before and after the COVID-19 outbreak. The average rates of school-aged children who had screen time within the range of ≥ 2 h per day, were 41.3% and 59.4% respectively before and after January 2020. The main types of screen time before January 2020 were watching TV (20 literatures), using computers (16 literature), using mobile phones/tablets (4 literatures). The mainly uses of screens before January 2020 were entertainment (15 literatures), learning (5 literatures) and socializing (3 literatures). The types and mainly uses of screen time after January 2020 remained the same as the results before January 2020. CONCLUSIONS: Excessive screen time has become a common behavior among children and adolescents around the world. Intervention measures to control children's screen use should be explored in combination with different uses to reduce the proportion of non-essential uses.

Giant photon momentum locked THz emission in a centrosymmetric Dirac semimetal.

Strong second-order optical nonlinearities often require broken material centrosymmetry, thereby limiting the type and quality of materials used for nonlinear optical devices. Here, we report a giant and highly tunable terahertz (THz) emission from thin polycrystalline films of the centrosymmetric Dirac semimetal PtSe2. Our PtSe2 THz emission is turned on at oblique incidence and locked to the photon momentum of the incident pump beam. Notably, we find an emitted THz efficiency that is giant: It is two orders of magnitude larger than the standard THz-generating nonlinear crystal ZnTe and has values approaching that of the noncentrosymmetric topological material TaAs. Further, PtSe2 THz emission displays THz sign and amplitude that is controlled by the incident pump polarization and helicity state even as optical absorption is only weakly polarization dependent and helicity independent. Our work demonstrates how photon drag can activate pronounced optical nonlinearities that are available even in centrosymmetric Dirac materials.

Magnetically tunable dual-band terahertz absorption based on guided-mode resonance.

We propose a magnetically tunable dual-band terahertz (THz) absorber by using an InAs substrate with a subwavelength zero-contrast germanium grating. The results demonstrate that the absorption peaks in this absorber can be dynamically tuned by changing the intensity and the rotation angle of the applied transverse magnetic field, which is achievable at a moderate order of magnitude of 0.1 Tesla. In addition, we investigate the distribution of magnetic field intensity and find that the magnetically tunable absorption originates from the combination of the magneto-optical effect and the guided-mode resonance effect, where the absorption peaks shift in different directions at normal incidence and oblique incidence. Furthermore, the absorption intensity of the proposed structure could reach 99% with an ultra-high Q-factor of 258. This work paves the way for actively adjustable high-resolution THz absorption or a nonreciprocal thermal emitter.

Terahertz wave emission from the trigonal layered PtBi2.

In this work, broadband terahertz (THz) wave emissions have been detected from the trigonal layered PtBi2 on the excitation of the femtosecond laser pulses. Such THz generation is found to arise from the dominated linear photogalvanic effect, which is further discovered to strongly depend on the unique electronic structures of PtBi2. Furthermore, an effective nonlinear susceptibility of PtBi2 is also obtained and is nearly two orders of magnitude larger than that of the traditional nonlinear crystal for THz generation.

Tuning of Optical Behavior in Monolayer and Bilayer Molybdenum Disulfide Using Hydrostatic Pressure.

Researchers have shown great interest in two-dimensional crystals recently, because of their thickness-dependent electronic and optical properties. We have investigated the Raman and photoluminescence spectra of free-standing monolayer and bilayer MoS2, as a function of pressure. As the enforcement of layer interaction, an electronic and a crystal phase transition were revealed at ∼6 GPa and ∼16 GPa, respectively, in bilayer MoS2, while no phase transition in the monolayer is observed. The electronic phase transition at ∼6 GPa is supposed to be a direct interband changing to an indirect Λ-K interband transition, and the new structure shown at ∼16 GPa is not metallized and supposed to be a transformation from stacking faults due to layer sliding like 2Hc to 2Ha. The different pressure-induced features of monolayer MoS2, compared with bilayer MoS2, can help to get a better understanding about the importance of interlayer interaction on modifying the optical properties of MoS2 and other fundamental understanding of 2D materials.

The loss of ZnO as the support for metal catalysts by H2 reduction.

The reduction of ZnO in a ZnO-supported catalyst to metallic zinc, the alloying of metallic zinc with a second metal and the evaporation of zinc species in a reductive atmosphere of hydrogen was investigated in this study. The results show that the reduction temperature was the determining factor for the transformation of zinc species. The complete removal of ZnO in a ZnO-supported catalyst can be achieved at 700 °C. The effects of different metals supported on ZnO on the transformation of ZnO were also investigated. Cu, Co and Ni species can slow the ZnO loss due to the priority for the reduction of these metal oxides and the formation of metal-Zn intermetallics. Fe based catalysts noticeably accelerated the loss of ZnO, which can be ascribed to the high oxophilicity of Fe and the strong interactions between the metal and support.

Comprehensively Analyzed Macrophage-Regulated Genes Indicate That PSMA2 Promotes Colorectal Cancer Progression.

Colorectal cancer (CRC) is the third most common cancer worldwide. Here, we identified tumor-associated macrophages (TAMs) as regulators of genes in CRC. In total, the expressions of 457 genes were dysregulated after TAM coculture; specifically, 344 genes were up-regulated, and 113 genes were down-regulated. Bioinformatic analysis implied that these TAM-related genes were associated with regulation of the processes of macromolecule metabolism, apoptosis, cell death, programmed cell death, and the response to stress. To further uncover the interplay among these proteins, we constructed a PPI network; 15 key regulators were identified in CRC, including VEGFA, FN1, JUN, CDH1, MAPK8, and FOS. Among the identified genes, we focused on PSMA2 and conducted loss-of-function experiments to validate the functions of PSMA2 in CRC. To further determine the mechanism by which PSMA2 affected CRC, we conducted multiple assays in CRC cell lines and tissues. PSMA2 enhanced the proliferation, migration and invasion of CRC cells. Moreover, our data indicated that PSMA2 expression was dramatically increased in stage 1, stage 2, stage 3, and stage 4 CRC samples. Our data indicated that PSMA2 was one target of miR-132. A miR-132 mimic greatly hindered CRC cell proliferation. In addition, the luciferase assay results revealed that miR-132 directly regulated PSMA2. Moreover, our data indicated that miR-132 expression was greatly decreased in CRC samples, which was associated with longer survival times of CRC patients, implying that miR-132 was a probable biomarker for CRC. Collectively, these data indicate that PSMA2 is a promising target for the therapy of CRC.

Poly(vinylidene chloride)-based carbon with ultrahigh microporosity and outstanding performance for CH4 and H2 storage and CO2 capture.

Poly(vinylidene chloride)-based carbon (PC) with ultrahigh microporisity was prepared by simple carbonization and KOH activation, exhibiting great potential to be superior CO2, CH4, and H2 adsorbent at high pressures. The CO2 uptake for pristine PC is highly up to 3.97 mmol/g at 25 °C and 1 bar while the activated PC exhibits a slightly lower uptake at 1 bar. However, the activated PC has an outstanding CO2 uptake of up to 18.27 mmol/g at 25 °C and 20 bar. Gas uptakes at high pressures are proportional to the surface areas of carbons. The CH4 uptake for the activated PC is up to 10.25 mmol/g (16.4 wt % or 147 v/v) at 25 °C and 20 bar which is in a top-ranked uptake for large surface area carbons. Furthermore, H2 uptake on the activated PC reaches 4.85 wt % at -196 °C and 20 bar. Significantly, an exceptionally large H2 storage capacity of up to 2.43 wt % at 1 bar was obtained, which is among the largest value reported to date for any porous adsorbents, to the best of our knowledge. The ease of preparation and large capture capacities endow this kind of carbon attractive as promising adsorbent for CH4, H2, and CO2 storage.