Evaluating two stages of silicone-containing arylene resin oxidation via experiment and molecular simulation

Silicon-containing aryl acetylene resin(PSA)is a new type of high-temperature resistant resin with excellent oxidation resistance,whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still remains unclear.Herein,the oxidation behavior and mechanisms of PSA resin are systematically investigated combining kinetic analysis and Reax FF molecular dynamics(MD)simulations.Thermogravimetric analysis indicates that the oxidation process of PSA resin undergoes two main steps:oxidative mass gain and oxidative degradation.The distributed activation energy model(DAEM)is employed for describing oxidation processes and the best-fit one is obtained using genetic algorithms and differential evolution.DAEM model demonstrates that the oxidative weight gain stage is dominated by two virtual reactants and the oxidative degradation stage consists of three virtual reactants.Correspondingly,the observation of MD reaction pathways indicates that oxygen oxidation of unsaturated structures occurs in the initial stage,which results in the formation of PSA resin oxides.Furthermore,cracked pieces react with O_(2)to generate CO and other chemicals in the second step.The resin matrix's great antioxidation resilience is illustrated by the formation of SiO_(2).The analysis based on MD simulations exhibits an efficient computational proof with the experiments and DAEM methods.Based on the results,a two-stage reaction mechanism is proposed,which provides important theoretical support for the subsequent study of the oxidation behavior of silica-based resins.

134例老年急性髓系白血病的临床特点及预后分析

目的:分析老年急性髓系白血病(acute myeloid leukemia,AML)(非早幼粒细胞白血病)的临床特点,治疗方式以及疗效和预后特点。方法:收集2015年1月至2023年2月北京大学国际医院收治的134例老年AML患者资料,回顾性分析患者初诊时的白细胞计数、骨髓原始细胞计数、细胞遗传学及分子学特点、ELN危险分层,根据不同治疗方案将患者分为高强度化疗组和低剂量治疗组,观察在治疗过程中强化疗是否能给患者带来生存获益以及影响老年患者生存的因素。结果:高强度化疗患者36例,22例完全缓解(complete response,CR)(61.1%),低剂量治疗90例中46例获得CR(51.1%),其中19例阿扎胞苷(AZA)联合维奈克拉(VEN)治疗换着中14例获得CR(73.7%);高强度化疗与低剂量治疗的总生存期(overall survival,OS)分别为15个月和14.5个月(P=0.226)。欧洲白血病网(ELN)危险分层低、中、高危组患者OS分别为18、14、9个月(P=0.009),低危组高强度化疗和低剂量治疗的OS分别为22个月和15个月(P=0.745),中危组分别为9个月和15个月(P=0.783),高危组分别为9个月和8个月(P=0.739)。强化疗(36例)与阿扎胞苷+维奈克拉治疗(19例)相比OS分别为15个月和17个月(P=0.689)。TP53基因突变者6例,预后明显差于无突变者,中位生存期分别为2个月和14个月(P=0.004)。低、中、高危患者的1年生存率为79%、53%和44%,3年生存率分别为41%、20%和3%。多因素分析显示外周血高白细胞计数(P=0.034)、ELN危险分层(P=0.002)、合并症(P=0.017)与OS相关,而治疗强度、年龄、性别、骨髓原始细胞计数与OS无明显相关性。高强度化疗在老年AML中没有显示明显的生存获益,但这一结果在低危患者中有待于进一步观察。TP53突变者预后较差。多因素分析预测老年AML的生存期时,基线的分子学特征、白细胞计数、合并症比治疗强度更重要。

Ultrafine Vacancy-Rich Nb_(2)O_(5)Semiconductors Confined in Carbon Nanosheets Boost Dielectric Polarization for High-Attenuation Microwave Absorption

The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss;achieving high-attenuation microwave absorption and realizing in-depth comprehension of dielectric loss mechanisms remain challenges.Herein,ultrafine oxygen vacancy-rich Nb_(2)O_(5)semiconductors are confined in carbon nanosheets(ov-Nb_(2)O_(5)/CNS)to boost dielectric polarization and achieve high attenuation.The polarization relaxation,electromagnetic response,and impedance matching of the ov-Nb_(2)O_(5)/CNS are significantly facilitated by the Nb_(2)O_(5)semiconductors with rich oxygen vacancies,which consequently realizes an extremely high attenuation performance of-80.8 dB(>99.999999%wave absorption)at 2.76 mm.As a dielectric polarization center,abundant Nb_(2)O_(5)–carbon heterointerfaces can intensify interfacial polarization loss to strengthen dielectric polarization,and the presence of oxygen vacancies endows Nb_(2)O_(5)semiconductors with abundant charge separation sites to reinforce electric dipole polarization.Moreover,the three-dimensional reconstruction of the absorber using microcomputer tomography technology provides insight into the intensification of the unique lamellar morphology regarding multiple reflection and scattering dissipation characteristics.Additionally,ov-Nb_(2)O_(5)/CNS demonstrates excellent application potential by curing into a microwave-absorbing,machinable,and heat-dissipating plate.This work provides insight into the dielectric polarization loss mechanisms of nano-semiconductor/carbon composites and inspires the design of high-performance microwave absorption materials.

An ion-released MgI_(2)-doped separator inducing a LiI-containing solid electrolyte interphase for dendrite-free Li metal anodes

Lithium metal batteries are among the strong contenders to satisfy the ever-increasing needs of energy storage systems,which however suffer from poor composition of the solid electrolyte interphase(SEI)layer and uncontrolled Li dendrites formation.In this regard,we report on the design of an ionreleased MgI_(2)-doped polyacrylonitrile(PAN)based nanofiber(MPANF)separator,which can lead to conducive SEI layer and dendrite-free Li anode.The combination of the lithophilic MgI_(2)nanoparticles with polarized PAN matrix comprehensively functions as a high-compatible interpenetrating network to homogenize ionic transportation and confront dendrite growth.The released I ions introduce the highion-conductivity LiI into SEI layer,which could induce the formation of favorable and protective interface layer in the early stage,as embodied in the enrichment of advantageous components such as LiN_(x)O_(y),Li_(2)O,LiF,and Li_(3)N.Profited from the high-affinity MPANF separator,the Li||Li symmetric cell achieves an ultralow voltage hysteresis of 46 mV with an extended lifespan of 580 h.And a prolonged lifetime of 590cycles with an enhanced specific capacity of 140.1 m Ah g^(-1)and the Coulombic efficiency of 96.2%at 1C can be obtained in full cells.This work may offer a facile and high-affinity alternative to traditional polymeric separators for high-performance and dendrite-free Li metal batteries.

Urchin-like Nb_(2)O_(5)hollow microspheres enabling efficient and selective photocatalytic C–C bond cleavage in lignin models under ambient conditions

Selective cleavage of robust C−C bonds to harvest value-added aromatic oxygenates is an intriguing but challenging task in lignin depolymerization.Photocatalysis is a promising technology with the advantages of mild reaction conditions and strong sustainability.Herein,we show a novel urchin-like Nb_(2)O_(5)hollow microsphere(U-Nb_(2)O_(5)HM),prepared by one-pot hydrothermal method,are highly active and selective for C_(α)−C_(β)bond cleavage of ligninβ-O-4 model compounds under mild conditions,achieving 94%substrate conversion and 96%C−C bond cleavage selectivity.Systematic experimental studies and density functional theory(DFT)calculations revealed that the superior performance of U-Nb_(2)O_(5)HMs arises from more exposed active sites,more efficient free charge separation and the active(001)facet,which facilitates the activation of Cβ−H bond of lignin models and generate key Cβradical intermediates by photogenerated holes,further inducing the C_(α)−C_(β)bond cleavage to produce aromatic oxygenates.This work could provide some suggestions for the fabrication of hierarchical photocatalysts in the lignin depolymerization system.