具有沉积结构环氧树脂电磁屏蔽材料的制备及表征

文中首先构筑具有三维结构的四针状氧化锌负载银(Ag@T-ZnO)和二维石墨烯纳米片(GNS)的混杂导电网络,随后灌注环氧树脂固化得到具有沉积结构的Ag@T-ZnO/GNS/EP复合材料,系统研究了Ag@T-ZnO和GNS的配比对复合材料屏蔽效能和力学性能的影响。当Ag@T-ZnO和GNS总质量分数为复合材料的20%且二者质量比为9:1时,二者之间的协同作用及独特的沉积导电网络结构赋予了复合材料优异的屏蔽效能和力学性能,在X波段的平均屏蔽效能可以达到83.8 dB,拉伸性能可达到51.6 MPa。为设计制备兼具优异力学性能和屏蔽性能的复合材料提供了新的思路。

Chromosome-scale assembly of the Dendrobium chrysotoxum genome enhances the understanding of orchid evolution

As one of the largest families of angiosperms,the Orchidaceae family is diverse.Dendrobium represents the second largest genus of the Orchidaceae.However,an assembled high-quality genome of species in this genus is lacking.Here,we report a chromosome-scale reference genome of Dendrobium chrysotoxum,an important ornamental and medicinal orchid species.The assembled genome size of D.chrysotoxum was 1.37 Gb,with a contig N50 value of 1.54 Mb.Of the sequences,95.75%were anchored to 19 pseudochromosomes.There were 30,044 genes predicted in the D.chrysotoxum genome.Two whole-genome polyploidization events occurred in D.chrysotoxum.In terms of the second event,whole-genome duplication(WGD)was also found to have occurred in other Orchidaceae members,which diverged mainly via gene loss immediately after the WGD event occurred;the first duplication was found to have occurred in most monocots(tau event).We identified sugar transporter(SWEET)gene family expansion,which might be related to the abundant medicinal compounds and fleshy stems of D.chrysotoxum.MADS-box genes were identified in D.chrysotoxum,as well as members of TPS and Hsp90 gene families,which are associated with resistance,which may contribute to the adaptive evolution of orchids.We also investigated the interplay among carotenoid,ABA,and ethylene biosynthesis in D.chrysotoxum to elucidate the regulatory mechanisms of the short flowering period of orchids with yellow flowers.The reference D.chrysotoxum genome will provide important insights for further research on medicinal active ingredients and breeding and enhances the understanding of orchid evolution.

Adsorption of trichlorphon on phyllosilicate minerals:Effect of low-molecular-weight organic acids

The use of trichlorphon in large quantities causes a large number of organic pollutants to enter water, sediments, and soils. Phyllosilicate minerals are considered effective adsorbents for organic pollutants. However, the adsorption behavior of organic pollutants on soil minerals affected by low-molecular-weight organic acids(LMWOAs) is not fully understood. In this study, the effect of LMWOAs on the adsorption behavior of trichlorphon on phyllosilicate minerals was investigated using a combination of adsorption measurements and molecular spectroscopic techniques(attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR) and X-ray photoelectron spectroscopy(XPS)). The adsorption of trichlorphon onto kaolinite(KAO) and montmorillonite(MON) was suppressed by increasing pH, indicating that electrostatic interaction played a key role in adsorption, especially at low pH. In the presence of citric acid(CA), there was an obvious promotion of trichlorphon adsorption on KAO and MON. In the presence of oxalic acid(OA), the adsorption of trichlorphon on KAO was promoted, whereas the adsorption on MON was inhibited, especially at pH 4.0. The presence of CA and OA increased the adsorption by increasing the exposure of hydrophobic sites of KAO and MON. The results from ATR-FTIR and XPS also indicated that the hydrophobic Si–O sites of phyllosilicate minerals were the preferred adsorption sites for trichlorphon in the presence of CA and OA, probably driven by the hydrophobic effect. However, the weak effect of OA on MON caused an increase in the electrostatic repulsion between MON and trichlorphon molecules, thus inhibiting adsorption. This study is significant for a deeper understanding of self-purification of soil and sediment systems in the presence of organic pollutants.

Effects of rhamnolipids on bacterial communities in a dioxin-contaminated soil and the gut of earthworms added to the soil

The biosurfactants rhamnolipids and the “soil ecosystem engineers” earthworms are often used to remediate contaminated soils. However, the effects of rhamnolipids on earthworm intestinal flora and microbial community in soil containing earthworms are not clearly understood. In our study, a 21-d microcosm experiment was carried out to reveal the effects of rhamnolipids on microbial abundance, composition, and metabolism, as well as contaminant degradation capacity. Both rhamnolipids and earthworms had positive effects on soil bacteria. Rhamnolipid-amended soil(RT) showed higher bacterial abundance and metabolic activity than earthworm-amended soil(ET), while the improvement in bacterial composition and contaminant degradation capacity by rhamnolipids was lower than that by earthworms. Notably, these effects were further amplified by the combined treatment of rhamnolipids and earthworms(RET). Specifically, the bacterial abundance(log-transferred) increased from 9.5 copies g-1in the control with no addition to 10.3, 10.6, and 11.1 copies g-1in ET, RT, and RET, respectively. Compared to ET, the relative abundance of the dominant phylum, Proteobacteria, increased from 41.66% to 51.67% in RET,and more pollutant-degrading bacteria were also enriched in RET. Therefore, the increases in bacterial abundance and contaminant-degrading bacteria led to the following ranking of soil dioxin removal rate: RET(77.28%) > ET(59.83%) > RT(24.65%) > control(4.71%). Moreover, the addition of rhamnolipids enhanced the abundance of bacterial functional genes involved in metabolism and environmental information processing. In addition, the composition and diversity of bacteria in the gut of earthworms were conspicuously affected by rhamnolipids, and the relative abundance of Microbacterium and Shewanella increased significantly(P < 0.05). Therefore, this study revealed that rhamnolipids remarkably influenced the abundance, composition, and metabolism of the microbial community in earthworm gut, further promoting the degradation rate of dioxin, providing theoretical support for optimizing the combined application of rhamnolipids and earthworms in soil bioremediation engineering and for the assessment of the ecological impact of rhamnolipids.

Management of Intraductal Papilloma of the Breast Diagnosed on Core Needle Biopsy:Latest Controversies

Intraductal papillomas(IDPs),including central papilloma and peripheral papilloma,are common in the female population.Due to the lack of specific clinical manifestations of IDPs,it is easy to misdiagnose or miss diagnose.The difficulty of dif-ferential diagnosis using imaging techniques also contributes to these conditions.Histopathology is the gold standard for the diagnosis of IDPs while the possibility of under sample exists in the percutaneous biopsy.There have been some debates about how to treat asymptomatic IDPs without atypia diagnosed on core needle biopsy(CNB),especially when the upgrade rate to carcinoma is considered.This article concludes that further surgery is recommended for IDPs without atypia diagnosed on CNB who have high-risk factors,while appropriate imaging follow-up may be suitable for those without risk factors.

Structures and catalytic performances of Me/SAPO-34(Me=Mn,Ni,Co)catalysts for low-tem perature SCR of NO_x by ammonia

Me/SAPO-34(Me=Mn,Ni,Co)series of catalysts were prepared by a wetness impregnation method and investigated for the selective catalytic reduction of nitrogen oxides with ammonia(NH 3-SCR).Among them,Mn/SAPO-34 catalyst was found as the most promising candidate based on its superior low-temperature activity.The catalysts were characterized by X-ray diffraction(XRD),transmission electron microscopy images(TEM),nuclear magnetic resonance(NMR),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction and desorption(TPR and TPD),and diffuse reflectance infrared Fourier transformed spectroscopy(DRIFTS)of NH_(3)/NO_(x)adsorption.Mn/SAPO-34 is obviously different from Ni/SAPO-34 and Co/SAPO-34 in the active species state and distribution.Surface MnO_(x)species which play an essential role in NO oxidation and NO_(2)adsorption,act as better active sites than nickel and cobalt mostly in the form of the aluminates and silicates.

Comparable charge transport property based on S…S interactions with that of π-π stacking in a bis-fused tetrathiafulvalene compound

Compact molecular packing with short π-π stacking and large π-overlap in organic semiconductors is desirable for efficient charge transport and high carrier mobility.Thus charge transport anisotropy along different directions is commonly observed in organic semiconductors.Interestingly,in this article,we found that comparable charge transport property were achieved based on the single crystals of a bis-fused tetrathiafulvalene derivative(EM-TTP) compound along two interaction directions,that is,the multiple strong S…S intermolecular interactions and the π-π stacking direction,with the measured electrical conductivity and hole mobility of 0.4 S cm^(-1),0.94 cm^2 V^(-1) s^(-1) and 0.2 S cm^(-1),0.65 cm2 V^(-1) s^(-1),respectively.This finding provides us a new molecular design concept for developing novel organic semiconductors with isotropic charge transport property through the synergistic effect of multiple intermolecular interactions(such as S…S interactions) and π-π stacking.