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1.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor at a 68% confidence level. 相似文献
2.
铂纳米颗粒在汽车行业中被广泛用作汽车尾气催化剂。随着铂纳米颗粒在工业生产中的广泛应用,它在环境中广泛分布并可能从植物累积进入食物链中。因此,建立一种在农产品中的定量分析方法是至关重要的。以酶消解的前处理方法结合单颗粒-电感耦合等离子体质谱法(Single particle ICP-MS,SP-ICP-MS)测定农产品中纳米铂颗粒(PtNPs)粒径分布及颗粒数量浓度。通过优化前处理提取条件,当Macerozyme R-10酶为10 mg、柠檬酸缓冲溶液浓度为5 mmol/L、提取时间36 h时,农产品中PtNPs提取效果较高。PtNPs粒径检出限为20 nm,颗粒浓度检出限为5×105 particle/L,铂颗粒浓度回收率在(81±3)%~(91±4)%,加标后平均粒径(41±3)~(47±2)nm,与50 nm PtNPs标准溶液粒径接近。方法操作简单、检出限低、准确度高,适用于农产品中PtNPs定量分析,为客观评价农产品铂纳米毒性效应提供可靠的分析技术。 相似文献
3.
为研究并解决测试生物质样品中碱金属和碱土金属含量的干扰,采用微波消解-电感耦合等离子体发射光谱(ICP-OES)法对生物质中的碱金属和碱土金属钾、钙、钠、镁元素进行测定,考察了样品消解后不同的酸体系,共存元素干扰对钾、钠、钙、镁含量测定的干扰研究。经过研究表明,接近分析标准曲线酸浓度的样品干扰小,铅、铟、钛、锰元素对钠元素测定造成干扰,砷、铜、镉对钙元素测定干扰,铝对钾元素测定有干扰,镁测定不受共存元素干扰影响,运用干扰系数法可以减少共存元素对测定元素的误差。各待测元素标准曲线相关系数大于0.9996,检出限为0.0014~0.023 mg/L,玉米芯各元素的相对标准偏差为0.98%~1.9%,加标回收率为80.2%~106%;西瓜皮的各元素相对标准偏差为0.91%~2.3%,加标回收率为85.3%~106%。方法用于测定国家标准物质GBW07603,各元素结果均在标准值参考范围内。方法用于测定生物质中碱金属和碱土金属的结果,用t检验法与离子色谱测定值进行比对,结果无显著性差异。 相似文献
4.
Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method 下载免费PDF全文
As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results. 相似文献
5.
微波是一种能量传递方式。与传统电加热相比,微波加热具有加热速度快、热惯性小、选择性加热等特点,因而被视为一种优质的能量来源。微波催化是一种使用微波对反应系统供能,从而推动催化反应进行的化学过程。近年来,许多研究者致力于探索和发展微波催化技术,包括利用微波技术提升化学反应速率、开发具有出色微波吸收能力的催化剂、建立节能环保的微波催化系统等。本文首先介绍了微波的相关理论,讲述了材料对微波的吸收原理;然后从微波催化降解挥发性有机物(Volatile Organic Compounds, VOCs)、微波催化污水处理、微波催化生物质热解和微波催化碳氢化合物转化等方面综述了微波催化在能源环境中的应用;最后对微波催化过程的机理展开了讨论。 相似文献
6.
为了实现充分且高效的消解目的,以石墨消解为样品前处理方法,用电感耦合等离子体质谱法测定出指甲样本中铬、锰、钴、镍、锌、砷、硒、钼、镉、锡、锑、铊、铅、汞等14种元素的浓度。将人体指甲样本以浓硝酸和双氧水为消解液经过石墨炉于110 ℃高温充分消解后稀释50倍,在相应的标准系列下,根据不同元素的原子质量选择相近的内标元素,计算相应元素的浓度,对此方法进行标准曲线线性、精密度、加标回收实验、质控物质的参照等方法学特性评估。人体指甲样本中14种元素的标准曲线线性良好(R2=0.999),总变异系数在0.58%~6.7%的范围内,加标回收率在80.8%~113%。使用此法检测与指甲构成成分相似的头发有证质控样品,检测结果全部在证书标准值范围内。采用的方法样本消解充分,安全性高,标准曲线相关性良好,线性范围广,检测金属元素多元,具有良好的精密度和准确度等优点。 相似文献
7.
《Mendeleev Communications》2022,32(1):1-8
Lignin and mixed lignocellulosic natural polymer wastes have been accumulated in landfills over the past hundred years. These wastes should be processed to produce added- value chemicals and materials. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of lignocellulosic polymer wastes, including production of hydrogen, synthesis gas, phenols, and monomers. The focus is made on microwave and plasma technologies used for lignocellulosic wastes processing. 相似文献
8.
Tong Liu Bao-Qing Guo Yan-Hui Zhou Jun-Long Zhao Yu-Liang Fang Qi-Cheng Wu Chui-Ping Yang 《Frontiers of Physics》2022,17(6):61502
Transferring entangled states between matter qubits and microwave-field (or optical-field) qubits is of fundamental interest in quantum mechanics and necessary in hybrid quantum information processing and quantum communication. We here propose a way for transferring entangled states between superconducting qubits (matter qubits) and microwave-field qubits. This proposal is realized by a system consisting of multiple superconducting qutrits and microwave cavities. Here, „qutrit” refers to a three-level quantum system with the two lowest levels encoding a qubit while the third level acting as an auxiliary state. In contrast, the microwave-field qubits are encoded with coherent states of microwave cavities. Because the third energy level of each qutrit is not populated during the operation, decoherence from the higher energy levels is greatly suppressed. The entangled states can be deterministically transferred because measurement on the states is not needed. The operation time is independent of the number of superconducting qubits or microwave-field qubits. In addition, the architecture of the circuit system is quite simple because only a coupler qutrit and an auxiliary cavity are required. As an example, our numerical simulations show that high-fidelity transfer of entangled states from two superconducting qubits to two microwave-field qubits is feasible with present circuit QED technology. This proposal is quite general and can be extended to transfer entangled states between other matter qubits (e.g., atoms, quantum dots, and NV centers) and microwave- or optical-field qubits encoded with coherent states. 相似文献
9.
为提高土壤检测的重金属得率,采用了微波消解/电热板组合预处理-电感耦合等离子体质谱法(ICP-MS)测定土壤重金属含量。分析了硝酸(HNO3)、氢氟酸(HF)、高氯酸(HClO4)和盐酸(HCl)组合消解液及赶酸温度对土壤预处理影响。结果显示:在硝酸和盐酸混合消解液中,硝酸占比越高,铬(Cr)、钴(Co)、铜(Cu)、镉(Cd)得率更高;消解液体系中加入氢氟酸可使消解更加彻底,提高铬与铜的得率。最优预处理消解条件为硝酸 6ml+ 氢氟酸 2ml消解液组合进行微波消解,1ml 高氯酸于155℃电热板上赶酸。经土壤标准样品GBW07401(GSS-1)和GBW07452(GSS-23)实际应用,预处理条件优化后测试准确度和稳定性均显著提高。此外使用元素铑(Rh)作为内标物时,其方法稳定性和准确性高于内标物钪(Sc)和锗(Ge)。可为相关国家土壤重金属测定标准的修制订提供方法学参考。 相似文献
10.
A design of resonant cavity with an improved coupling-adjusting mechanism for the W-band EPR spectrometer 下载免费PDF全文
We report a new design of resonant cavity for a W-band electron paramagnetic resonance (EPR) spectrometer. An improved coupling-adjusting mechanism, which is robust, compact, and suits with both solenoid-type and split-pair magnets, is utilized on the cavity, and thus enables both continuous-wave (CW) and pulsed EPR experiments. It is achieved by a tiny metal cylinder in the iris. The coupling coefficient can be varied from 0.2 to 17.9. Furthermore, two pistons at each end of the cavity allow for adjustment of the resonant frequency. A horizontal TE011 geometry also makes the cavity compatible with the two frequently used types of magnets. The coupling-varying ability has been demonstrated by reflection coefficient (S11) measurement. CW and pulsed EPR experiments have been conducted. The performance data indicates a prospect of wide applications of the cavity in fields of physics, chemistry and biology. 相似文献