Bulk quantities of hexagonal boron nitride (h-BN) nanosheets have been synthesized via a simple template- and catalyst-free chemical vapor deposition process at 1100−1300 °C. Adjusting the synthesis and chemical reaction parameters, the thickness of the BN nanosheets can be tuned in a range of 25−50 nm. Fourier transform infrared spectra and electron energy loss spectra reveal the typical nature of sp2-hybridization for the BN nanosheets. It shows an onset oxidation temperature of 850 °C for BN nanosheets compared with only about 400 °C for that of carbon nanotubes under the same conditions. It reveals a strong and narrow cathodoluminescence emission in the ultraviolet range from the h-BN nanosheets, displaying strong ultraviolet lasing behavior. The fact that this luminescence response would be rather insensitive to size makes the BN nanosheets ideal candidates for lasing optical devices in the UV regime. The h-BN nanosheets are also better candidates for composite materials in high-temperature and hazardous environments.

No abstract

No abstract

Single-phase perovskite-type manganese oxides La0.8 −xNa0.2□xMnO3+δ with x = 0.01–0.04 have been prepared by the modified sol–gel method and the influence of the vacancy concentration in the A site on their structures and magnetocaloric properties has systematically been investigated. The experimental results revealed that the samples calcinated at 1573 K remained single phase and were constituted by submicrometre homogeneous particles without deviation from the nominal stoichiometry upon heating. For all the compositions explored in this work, the average manganese oxidation state is practically constant, at 3.37 ± 0.02. Magnetic measurement results show that an appropriate amount of vacancy concentration in the A site is favourable to both the Curie temperature and magnetic entropy change for polycrystalline La0.8−xNa0.2□xMnO3+δ compounds. An approximately linear relation between Curie temperature and magnetic entropy change was observed. For La0.771Na0.198Mn1.000□ 0.029O2.94, the largest value of magnetic entropy change of 3.86 J kg−1 K−1 under a field of 10 kOe and the Curie temperature of 364 K were obtained.

The inter-grain exchange-coupling interactions, effective anisotropy, and coercivity in nanocomposite Nd2Fe14B/α−Fe magnets were investigated. The effective anisotropy of nanocomposite magnets has been calculated starting from the statistics of boundaries between magnetically hard-hard, hard-soft, and soft-soft grains. The result shows that the effective anisotropy decreases with reduction in grain size and/or increase in soft phase components. When grain sizes reduce to 4–5 nm, Keff decreases to 1/3−1/4 of the ordinary value of K. The coercivity in nanocomposite magnets demonstrates a similar behavior. The decrement of coercivity is mainly due to the reduction of effective anisotropy. Considering the opposite varying trend the remanence demonstrates with respect to the effective anisotropy and the coercivity, we conclude that the mean grain size should be in the range of 10–15 nm and the volume fraction of soft phase should be less than 50% in order to achieve high energy product magnets.

The involvement of gut microbiota in T-cell trafficking into tumor tissue of colorectal cancer (CRC) remains to be further elucidated. The current study aimed to evaluate the expression of major cytotoxic T-cell trafficking chemokines (CTTCs) and chemokine-associated microbiota profiles in both tumor and adjacent normal tissues during CRC progression. We analyzed the expression of chemokine C-X-C motif ligands 9, 10, and 11 (CXCL9, CXCL10, and CXCL11), and C-C motif ligand 5 (CCL5), characterized gut mucosa-associated microbiota (MAM), and investigated their correlations in CRC patients. Our results showed that the expression of CXCL9, CXCL10, and CXCL11 was significantly higher in tumor than in adjacent normal tissues in 136 CRC patients. Notably, the high expression of CXCL9 in tumor tissues was associated with enhanced CD8+ T-cell infiltration and improved survival. Moreover, the MAM in tumor tissues showed reduction of microbial diversity and increase of oral bacteria. Microbial network analysis identified differences in microbial composition and structure between tumor and adjacent normal tissues. In addition, stronger associations between oral bacteria and other gut microbes were observed. Furthermore, the correlation analysis between the defined MAM and individual CTTCs showed that the CTTCs’ correlated operational taxonomic units (OTUs) in tumor and adjacent normal tissues rarely overlap with each other. Notably, all the enriched OTUs were positively correlated with the CTTCs in either tumor or adjacent normal tissues. Our findings demonstrated stronger interactions between oral bacteria and gut microbes, and a shifted correlation pattern between MAM and major CTTCs in tumor tissues, underlining possible mechanisms of gut microbiota–host interaction in CRC.

No abstract

No abstract