Self-Templating Engineering of Hollow N-Doped Carbon Microspheres Anchored with Ternary FeCoNi Alloys for Low-Frequency Microwave Absorption.

Rational design and precision fabrication of magnetic-dielectric composites have significant application potential for microwave absorption in the low-frequency range of 2-8 GHz. However, the composition and structure engineering of these composites in regulating their magnetic-dielectric balance to achieve high-performance low-frequency microwave absorption remains challenging. Herein, a self-templating engineering strategy is proposed to fabricate hollow N-doped carbon microspheres anchored with ternary FeCoNi alloys. The high-temperature pyrolysis of FeCoNi alloy precursors creates core-shell FeCoNi alloy-graphitic carbon nano-units that are confined in carbon shells. Moreover, the anchored FeCoNi alloys play a critical role in maintaining hollow structural stability. In conjunction with the additional contribution of multiple heterogeneous interfaces, graphitization, and N doping to the regulation of electromagnetic parameters, hollow FeCoNi@NCMs exhibit a minimum reflection loss (RLmin) of -53.5 dB and an effective absorption bandwidth (EAB) of 2.48 GHz in the low-frequency range of 2-8 GHz. Furthermore, a filler loading of 20 wt% can also be used to achieve a broader EAB of 5.34 GHz with a matching thickness of 1.7 mm. In brief, this work opens up new avenues for the self-templating engineering of magnetic-dielectric composites for low-frequency microwave absorption.

Hierarchical etching-assembly engineering of Fe-based composite microspheres with balanced magnetic-dielectric synergy towards ultrahigh electromagnetic wave absorption.

Hierarchical engineering of magnetic-dielectric composite microspheres has attracted increasing attention owing to its potential to enhance electromagnetic wave absorption (EMA) through magnetic-dielectric synergy. However, optimizing magnetic-dielectric balance in composite microspheres at the nanoscale remains a formidable task due to their limited component optimization and microstructural regulation. Herein, a novel approach is proposed to modify conventional carbonyl iron powder (CIP) microspheres via synergistic etching-assembly strategy. By applying a polydopamine coating, successive tannic acid (TA) etching-assembly, and pyrolysis, hierarchical iron@carbon-1/N-doped carbon (Fe@C-1/NC) composite microspheres are obtained. This overcomes the drawbacks of CIP microspheres, including their high density and poor impedance matching, which hinder EMA performance. Hierarchical carbon layer engineering can introduce abundant dipole centers, heterogeneous interfaces, and conductive networks to induce dielectric loss, while magnetic components contribute to magnetic resonance and eddy current loss, as demonstrated by the results. Accordingly, Fe@C-1/NC composite microspheres demonstrate a minimum reflection loss (RLmin) of -70.7 dB and an effective absorption bandwidth of 3.75 GHz at a matching thickness of 2.3 mm. Generally, this work paves the way towards CIP engineering to provide guidance to the future exploration of hierarchical magnetic-dielectric EMA materials.

Relationship between cardio-ankle vascular index and N-terminal pro-brain natriuretic peptide in hypertension and coronary heart disease subjects.

Arterial stiffness is an independent predictor for vascular diseases. Cardio-ankle vascular index (CAVI) is a new index of arterial stiffness. N-terminal pro-brain natriuretic peptide (NT-proBNP) is a strong prognostic marker in advanced stage of coronary heart disease (CHD). In the present study, we investigated the relationship between CAVI and NT-proBNP in hypertension and CHD subjects. Five hundred one subjects (male/female, 209/292) from Vascular Medicine of Peking University Shougang Hospital were divided into four groups: healthy group (n = 186), hypertension group (n = 159), CHD group (n = 45), and hypertension with CHD group (n = 111). CAVI was measured using VS-1000 apparatus. Our results showed that CAVI was significantly higher in hypertension subjects with CHD than in healthy and hypertension group, respectively (8.42 ± 1.51 vs. 7.77 ± 1.19; 8.42 ± 1.51 vs. 7.92 ± 1.11; both P < .05). NT-proBNP was significantly higher in hypertension subjects with CHD than in healthy, hypertension, and CHD group, respectively (422.48 ± 761.60 vs. 174.29 ± 415.48; 422.48 ± 761.60 vs. 196.14 ± 299.16; 422.48 ± 761.60 vs. 209.66 ± 242.66; all P < .05). And after log transformation of NT-proBNP, this phenomenon also exists (2.32 ± 0.47 vs. 2.03 ± 0.40; 2.32 ± 0.47 vs. 2.09 ± 0.44; 2.32 ± 0.47 vs. 2.12 ± 0.42; all P < .05). There was positive correlation between log NT-proBNP and CAVI in the entire study group, healthy group, and nonhealthy group (r = 0.235, P < .001; r = 0.184, P = .023; r = 0.237, P < .001; respectively). Multivariate analysis showed that NT-proBNP was an independent associating factor of CAVI in all subjects (ß = 0.150, P = .021). Our present study showed that CAVI and NT-proBNP were significantly higher in hypertension subjects with CHD compared with healthy and hypertension groups. There was significant correlation between NT-proBNP and CAVI, which indicates the relationship between arterial stiffness and biomarkers in vascular-related diseases.