Carboxymethyl cellulose/poly(vinyl alcohol) blended films reinforced by buckypapers of carbon nanotubes and 2D material (MoS2): Enhancing mechanical strength, toughness, and barrier properties

Plastic waste is one cause of climate change. To solve this problem, packaging films are increasingly produced from biodegradable polymers. Eco-friendly carboxymethyl cellulose and its blends have been developed for such a solution. Herein, a unique strategy is demonstrated to improve the mechanical and barrier properties of carboxymethyl cellulose/poly(vinyl alcohol) (CMC/PVA) blended films for the packaging of nonfood dried products. The blended films were impregnated with buckypapers containing different combinations of multiwalled carbon nanotubes, two-dimensional molybdenum disulfide (2D MoS₂) nanoplatelets, and helical carbon nanotubes (HCNTs). Compared to the blend, the polymer composite films exhibit significant increases in tensile strength (~105 %, from 25.53 to 52.41 MPa), Young's modulus (~297 %, from 155.48 to 617.48 MPa), and toughness (~46 %, from 6.69 to 9.75 MJ m^-3). Polymer composite films containing HCNTs in buckypapers offer the highest toughness. For barrier properties, the polymer composite films are opaque. The water vapor transmission rate of the blended films decreases (~52 %, from 13.09 to 6.25 g h^-1 m^-2). Moreover, the maximum thermal-degradation temperature of the blend rises from 296 to 301 °C, especially for the polymer composite films with buckypapers containing MoS₂ nanosheets that contribute to the barrier effect for both water vapor and thermal-decomposition gas molecules.

[Naringenin promotes osteogenic differentiation of BMSCs via SDF-1α/CXCR4 signaling axis]

PURPOSE

To explore the influence of naringenin on osteogenic differentiation of bone mesenchymal stem cells(BMSCs), and the role of SDF-1α/CXCR4 signaling axis in the osteogenic differentiation by naringenin.

METHODS

BMSCs of the rats were isolated,cultured and tested. CCK-8 assay was used to explore the proliferation ability of BMSCs in different concentrations of naringenin, and alkaline phosphatase(ALP) activity was detected. RT-qPCR was used to detect the mRNA expression of ALP, OCN, CXCR4 and SDF-1α in different groups. The expressions of CXCR4 and SDF-1α protein in BMSCs during osteogenic differentiation in different experimental groups were detected by ELISA. SPSS 21.0 software package was used for statistical analysis of the data.

RESULTS

The results of cell identification showed that the cultured cells were BMSCs. At 1 d and 3 d, all concentrations of naringenin had no significant effect on the proliferation of BMSCs; and at 5 d, 50 μg/mL of naringenin promoted proliferation of BMSCs；furthermore, at 7 d, all concentrations of naringenin promoted proliferation of BMSCs(P＜0.05). ALP activity value gradually increased in each concentration over time. From the RT-qPCR experiment, the mRNA expression of ALP, OCN, CXCR4 and SDF-1α in the naringenin group and the osteogenic induction group was significantly increased compared with the medium group(P＜0.05). ELISA assay showed that the protein expressions of CXCR4 and SDF-1α increased gradually in the four groups as time went on and the expression of two proteins was the highest in 100 μg/mL naringenin group.

CONCLUSIONS

Naringenin can promote the proliferation and osteogenic differentiation of BMSCs. SDF-1α/CXCR4 signaling axis is involved in the osteogenic differentiation of BMSCs by naringenin,particularly in the early stage of BMSCs osteogenic differentiation.

Graphite films/carbon fiber fabric/ polyurethane composites with ultrahigh in-plane thermal conductivity and enhanced mechanical properties

Thermally conductive composites have attracted great attention in virtue of their crucial role in thermal management. In this work, laminated composites were prepared by laying graphite films (GF) and carbon fiber fabrics (CF) in a certain order, then penetrating thermoplastic polyurethane (TPU), finally hot-pressing. In order to enhance the inter-layer strength, the graphite films were perforated with arrays of 1 mm holes in diameter which have intervals of 4 mm and permit the seeping of liquid TPU through them. The in-plane thermal conductivity (TC) of composite reaches 242 W m^-1 K^-1 with the loading of 25 vol% GF and 60 vol% CF, which is 1210 times that of pure TPU. The great improvement of TC is ascribed to the thermal conductive pathways formed by continuous GF with ultrahigh TC. The addition of CF enhances markedly the mechanical properties of composites. Bending strength and modulus of composites are 5.56 and 17.09 times that of pure TPU, respectively. The proposed design and manufacture method are facile and effective to obtain polymeric composites simultaneously with high TC and good mechanical properties.

[Analysis of the first cluster of cases in a family of COVID-19 in Gansu Province]

The epidemiological history and clinical characteristics of 7 cases of COVID-19 and 1 case of close contact in the first family aggregation epidemic of COVID-19 in Gansu Province were analyzed. The first patient A developed on January 22, 2020, with a history of residence in Wuhan, and confirmed severe cases of NCP on January 24, 2020; patient B, on January 23, 2020, diagnosed on January 31, severe cases; patient C, asymptomatic, diagnosed on January 27; patient D, asymptomatic, diagnosed on January 27; patient E, on January 24, diagnosed on January 28; patient F, asymptomatic, diagnosed on January 31; Patient G was asymptomatic and was diagnosed on January 31. In close contact, H was asymptomatic, PCR test was negative and asymptomatic, and he was discharged early. Among the 7 patients, 1 case died of (B) aggravation, and the other patients' condition was effectively controlled after active treatment. Except for the discharged cases, 5 cases were positive for COVID-19 specific IgM antibody and 1 case was negative. In this clustering outbreak, 4 patients remained asymptomatic, but PCR and IgM antibodies were positive, indicating that asymptomatic patients may be the key point to control the epidemic. Specific IgM antibody screening for patients whose pharyngeal swab nucleic acid test is negative but with ground glass-like lung lesions is very important for early detection and early isolation.

[Analysis of the first cluster of cases in a family of novel coronavirus pneumonia in Gansu Province]

The epidemiological history and clinical characteristics of 7 cases of COVID-19 and 1 case of close contact in the first family aggregation epidemic of COVID-19 in Gansu Province were analyzed. The first patient A developed on January 22, 2020, with a history of residence in Wuhan, and confirmed severe cases of NCP on January 24, 2020; patient B, on January 23, 2020, diagnosed on January 31, severe cases; patient C, asymptomatic, diagnosed on January 27; patient D, asymptomatic, diagnosed on January 27; patient E, on January 24, diagnosed on January 28; patient F, asymptomatic, diagnosed on January 31; Patient G was asymptomatic and was diagnosed on January 31. In close contact, H was asymptomatic, PCR test was negative and asymptomatic, and he was discharged early. Among the 7 patients, 1 case died of (B) aggravation, and the other patients' condition was effectively controlled after active treatment. Except for the discharged cases, 5 cases were positive for COVID-19 specific IgM antibody and 1 case was negative. In this clustering outbreak, 4 patients remained asymptomatic, but PCR and IgM antibodies were positive, indicating that asymptomatic patients may be the key point to control the epidemic. Specific IgM antibody screening for patients whose pharyngeal swab nucleic acid test is negative but with ground glass-like lung lesions is very important for early detection and early isolation.

A study on the local corrosion behavior and mechanism of electroless Ni-P coatings under flow by using a wire beam electrode

The local corrosion behavior and mechanism of Ni–P coatings in a 3.5 wt% sodium chloride solution with different flow speeds (0 m s⁻¹, 0.5 m s⁻¹, 1 m s⁻¹) were investigated through a wire beam electrode (WBE) with morphological, elemental and electrochemical analyses as well as numerical simulations. It was found that the microstructure of the Ni–P coating was in the shape of broccoli and possessed satisfactory compactness and uniformity. The numerical simulations showed that the speed increased and the static pressure decreased at the local area. Combined with WBE, it was found that the average corrosion potential decreased at that area. The results indicated that the corrosion tendency and corrosion rate of the Ni–P coating were larger at higher speeds, and the corrosion resistance could be improved by the electroless Ni–P coating. WBE was helpful in revealing the local electrochemical information of the Ni–P coating.

The local corrosion behavior and mechanism of Ni–P coatings in an NaCl solution with different flow speeds were investigated through a wire beam electrode with morphological, elemental and electrochemical analyses as well as numerical simulations.

Three-Dimensional Graphene Foam-Filled Elastomer Composites with High Thermal and Mechanical Properties

To meet the increasing demands for effective heat management of electronic devices, a graphene-based polymeric composite is considered to be one of the candidate materials owing to the ultrahigh thermal conductivity (TC) of graphene. However, poor graphene dispersion, low quality of exfoliated graphene, and strong phonon scattering at the graphene/matrix interface restrict the heat dissipation ability of graphene-filled composites. Here, a facile and versatile approach to bond graphene foam (GF) with polydimethylsiloxane (PDMS) is proposed, and the corresponding composite with considerable improvement in TC and insulativity is fabricated. First, three-dimensional GF was coated with polydopamine (PDA) via π-π stack and functional groups from PDA reacted with 3-aminopropyltriethoxysilane (APTS). Then, the modified GF was compressed (c-GF) to enhance density and infiltrated with PDMS to get the c-GF/PDA/APTS/PDMS composite. As a result, these processes endow the composite with high TC of in-plane 28.77 W m^-1 K^-1 and out-of-plane 1.62 W m^-1 K^-1 at 11.62 wt % GF loading. Besides, the composite manifests obvious improvement in mechanical properties, thermal stability, and insulativity compared to neat PDMS and GF/PDMS composite. An attempt to use the composite for cooling a ceramic heater is found to be successful. Above results open a way for such composites to be applied for the heat management of electronic devices.

High shielding effectiveness of multilayer graphene oxide aerogel film/polymer composites

In this work, an efficient and simple method is proposed to fabricate lightweight and flexible composites composed of a reduced graphene oxide aerogel film (rGO-AF) and a polydimethylsiloxane (PDMS) matrix.

Capacitance enhancement by electrochemically active benzene derivatives for graphene-based supercapacitors

Various aromatic molecules have been reported to improve the performance of reduced graphene oxide (rGO)-based supercapacitors.

Vertically and compactly rolled-up reduced graphene oxide film/epoxy composites: a two-stage reduction method for graphene-based thermal interfacial materials

Schematic of the fabrication procedure of thermal-reduced vertically aligned reduced graphene oxide (TR-VArGO)/epoxy composite. This efficient and simple method includes two reduction stages to fabricate a thermal-reduced VArGO (TR-VArGO)/epoxy composite.

Comparative studies on species identification of Noctuoidea moths in two nature reserve conservation zones (Beijing, China) using DNA barcodes and thin-film biosensor chips

Rapid and accurate identification of species is required for the biological control of pest Noctuoidea moths. DNA barcodes and thin-film biosensor chips are two molecular approaches that have gained wide attention. Here, we compare these two methods for the identification of a limited number of Noctuoidea moth species. Based on the commonly used mitochondrial gene cytochrome c oxidase I (the standard DNA barcode for animal species), 14 probes were designed and synthesized for 14 species shared by two national nature reserves in Beijing and Hebei, China. Probes ranged in length from 18 to 27 bp and were designed as mismatch probes to guarantee that there were at least three base differences between the probe and nontarget sequences. The results on the chip could be detected by the naked eye without needing special equipment. No cross-hybridizations were detected although we tested all probes on the 14 target and 24 nontarget Noctuoidea species. The neighbour-joining tree of the 38 species based on COI sequences gave 38 highly supported independent groups. Both DNA barcoding and thin-film biosensor chips, based on the COI gene, are able to accurately identify and discriminate the 14 targeted moth species in this study. Because of its speed, high accuracy and low cost, the thin-film biosensor chip is a very practical means of species identification. Now, a more comprehensive chip will be developed for the identification of additional Noctuoidea moths for pest control and ecological protection.

Influence of age, growth, and sex on cardiac myocyte size and number in rats

The effects of altered neonatal nutrition on cardiac myocyte size and number was examined in 21-day-old and 3-month-old rats. Nutritional differences in growth rate were produced in newborns by adjusting litter size to four (fast-growing), eight (normally growing), or 16 (slow-growing) pups per litter. Isolated myocytes were prepared from animals in each group to evaluate changes in cell size and number. Heart weight (mg +/- S.D.), at 21 days of age, was 398 +/- 51 for "fast-growing" rats, 329 +/- 43 for "normally growing" rats, and 228 +/- 24 for "slow-growing" rats. Body weights showed a comparable decline with reduced nutrition. In adults, treatment-related differences in body and heart weight were present in males but not females. "Slow-growing" rats had 21% fewer myocytes than "fast-growing" rats at 21 days of age, a change that persisted in adults. Values for myocyte number from "normally growing" rats were intermediate between those of "fast and slow-growing" rats at both 21 days and 3 months of age. In each heart region of weanling rats, myocyte length and volume were smallest in 16 per litter rats. Cellular dimensions increased progressively with better nutrition.(ABSTRACT TRUNCATED AT 250 WORDS)