An Innovative model of magnetically intercalated expanded graphite for calculating radar attenuation performance at 2–18 GHz

With the emergence of various filtering technologies, the radar jamming efficiency of the technology based on radar cross section is ever lower, therefore cannot meet military requirements. In this context, the jamming technology based on attenuation mechanism has been developed and plays an increasingly important role in disturbing radar detecting. Magnetically expanded graphite (MEG) has excellent attenuation efficiency because it can cause dielectric loss as well as magnetic loss. Moreover, MEG features good impedance matching, which makes more incidence of electromagnetic waves into the material; and its multi-layer structure is conducive for electromagnetic wave reflection and absorption. In this work, the structure model of MEG was established by analyzing the layered structure of expanded graphite (EG) and the dispersion of intercalated magnetic particles. The electromagnetic parameters of thus-modeled MEG were calculated based on the equivalent medium theory; and effects of EG size, magnetic particle type and volume fraction on the attenuation performance were studied by the variational method. It is indicated that MEG with 500-μm diameter has the best attenuation effect and the highest increment of absorption cross section appears at 50% volume fraction of the magnetic particles at 2 GHz. The imaginary part of complex permeability of the magnetic material has the most significant influence on the attenuation effect of MEG. This study provides guidance for the design and application of MEG materials in disturbing radar detecting field

Tailoring Transition Metals and Biuret into Laser-Ignitable Energetic Coordination Polymers with Improved Oxygen Balance and Multidentate Coordination Structures

Eight kinds of energetic coordination polymers (ECPs) with multi-coordination were designed and synthesized by combining the carbonyl group with coordination potential in biuret with transition metal nitrates and perchlorates (Co2+, Ni2+, Cu2+, and Ag+). The structures of these complexes are confirmed by infrared spectroscopy, elemental analysis, and X-ray single-crystal diffraction. The physical and chemical performance test results show that the solvent-free ECPs 7 (Cu(BIU)2(ClO4)2) has the best performance (Tdec = 328 °C, D = 7600 km·s–1, P = 27.8 Gpa, IS = 25 J, FS = 240 N). Among them, ECPs 7 and 8 (Ag(BIU)ClO4) have good detonation performance during hot plate and laser ignition tests (ECPs 7: P = 15 W, τ = 6 ms, E = 80 mJ; ECPs 8: P = 20 W, τ = 5 ms, E = 100 mJ). The result shows that improving the oxygen balance of ligands and constructing multidentate coordination structures may be a new effective strategy for improving the performance of laser-sensitive ECPs

Heptaketides from an Endolichenic Fungus <i>Biatriospora</i> sp. and Their Antifungal Activity

Twelve new heptaketides, biatriosporins A–L (<b>1</b>–<b>12</b>), biatriosporin M (<b>13</b>) (a ramulosin derivative), and 19 known compounds (<b>14</b>–<b>32</b>) were isolated from the endolichenic fungus <i>Biatriospora</i> sp. (8331C). The structures of these compounds were determined by analyzing MS and NMR data. The absolute configurations of compounds <b>1</b>, <b>2</b>, <b>7</b>, and <b>9</b> were determined by single-crystal X-ray diffraction analysis, whereas compound <b>10</b> was deduced with Mosher’s method. Four of the compounds were active in an antifungal assay. The most potent compound, compound <b>4</b>, also sensitized clinically derived azole-resistant <i>Candida albicans</i> strains to fluconazole (FLC). A mechanistic investigation revealed that <b>4</b> inhibited the function of efflux pumps and reduced the transcriptional expression of the efflux-pump-related genes <i>CDR1</i> and <i>CDR2</i>