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排序方式: 共有295条查询结果,搜索用时 15 毫秒
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Maryam Koohi Monireh Ghavami Bibi Narjes Haerizade Hasan Zandi Mohammad Zaman Kassaee 《Journal of Physical Organic Chemistry》2014,27(9):735-746
[6]n Cyclacenes and short zigzag [6]n carbon nanotubes (n = 5–10) have unstable singlet open‐shell (Sos) ground states. We have boosted their stability by implementing altering Ge―C bonds that acquire Scs ground states with larger band gap (ΔELUMO–HOMO) at B3LYP and BPW91 levels of theory. Fascinatingly, homodesmic calculations indicated release of almost two folds of strain energy upon substitution of germanium for carbon. This may turn the green lights for synthesis of germanium–carbon cyclacenes and short zigzag nanotubes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
285.
Suyu Shi Yamin Pan Bo Lu Changyu Shen Chuntai Liu 《Journal of Macromolecular Science: Physics》2014,53(8):1431-1441
A bipolar membrane (BPM) of carboxymethyl cellulose (CMC) and chitosan (CS) with superior performance was prepared based on the macromolecules containing metal elements. A carboxymethyl cellulose cation layer was modified by copper phthalocyanine 16-carboxylic acid (CuPc(COOH)16) to improve its ion exchange capacity as well as cation transfer rate and promote water splitting at the intermediate layer. Chitosan was crosslinked with acetyl ferrocene to prepare the anion layer. A casting method was used to prepare the BPM which showed excellent physical and chemical properties after modification. To improve the compatibility of the anion-exchange layer and cation-exchange layer, polyethylene glycol (PEG) was blended with both the CMC and CS. Scanning electron microscopy (SEM) images illustrated a structure that consisted of an anion layer and a cation layer that were closely combined with each other. The swelling results implied a proper hydrophilic performance and good shape stability in an alkali solution ([OH?]≤10 mol·L?1) of the BPM. After modification, the BPM with the metal elements exhibited good thermal stability, as shown by the thermogravimetry (TG) results. Compared with the BPM that was unmodified, both the AC impedance and the working voltage were decreased sharply. Furthermore, the modified BPM exhibited higher ion penetrability which is beneficial for its wide application. 相似文献
286.
高层建筑物荷载与地下水开采叠加作用下的地面沉降特征 总被引:1,自引:0,他引:1
在地下水开采和高层建筑荷载叠加作用下,城市地面沉降分布愈加复杂。以天津塘沽地区为例,考虑到土体在固结沉降中的平衡条件、弹性本构条件、变形协调条件和水流连续条件,以比奥固结理论为基础,建立了高层建筑荷载和地下水开采叠加作用下三维地面沉降模型,采用有限元方法进行了数值计算。结果表明,高层建筑物的附加荷载作用在其建成后的3~4a内将产生可观的地面沉降量; 抽水和高层建筑荷载叠加作用下的地面沉降存在耦合效应,叠加作用下的地面沉降值小于可比条件下单独抽水和单独荷载作用下地面沉降值之和。 相似文献
287.
Mabkhot YN Al-Majid AM Barakat A Alshahrani S Siddiqui Y 《Molecules (Basel, Switzerland)》2011,16(8):6502-6511
A series of new bis(heterocycles) featuring thieno[2,3-b]thiophene rings was synthesized in a combinatorial manner. Intramolecular cyclization of enaminone derivatives with appropriate N-nucleophiles afforded the target compounds. All compounds were characterized by 1H-, 13C-NMR, GCMS, IR, and UV-Vis spectrometry. These compounds represent a new class of sulfur- and nitrogen-containing heterocycles that should also be of interest as new materials. 相似文献
288.
Bibi?Adohi Bassel?Haidar Luis?Costa Vincent?Laur Christian?BrosseauEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2015,88(10):280
We report experimental results from frequency-domain spectroscopy on graphene (GE) filled polyvinylidene difluoride trifluoroethylene P(VDF-TrFE). The dielectric properties of these polymer nanocomposites (GPN) were investigated over a broad range of frequency (from 102 Hz to a few GHz) and a broad range of temperature (from 150 K to 370 K) by using two measurement techniques: impedance spectroscopy and asymmetrical stripline. Care is needed in relating the GE content to the dielectric properties of GPN since the addition of GE to P(VDF-TrFE) can result in a nonmonotonic permittivity change. At low frequency (<1 MHz) the relaxation spectra is not Debye like but is characterized with a broad relaxation time distribution especially at low temperatures. This effect originates from the freezing process of dipoles and Maxwell-Wagner-Sillars (MWS) interfacial polarization. Additionally, a fit of the effective permittivity versus GE content suggests that our data are in accord with the two-exponent phenomenological percolation equation (TEPPE). These experimental results draw attention to the importance of the large surface area of the GE nanoparticles in controlling the interface between the GE flakes and the polymer phase. 相似文献
289.
石墨炉原子吸收法测定生物样品中的铊 总被引:1,自引:0,他引:1
为建立测定生物样品中铊的石墨炉原子吸收法,通过微波消解,采用基本改进剂,改变石墨炉灰化温度等操作条件,提高了该法的准确度和精密度.结果表明,方法的线性范围为0~100 μg/L;检出限:血为0.10 mg/L;尿为0.02 mg/L;头发为0.20 mg/kg;回收率:血为83.1%~108%;尿为89.6%~105%... 相似文献
290.
Youzhi Hu Xia Li Xinyang He Rui He Yamin Li Xiaojuan Liu Houcheng Liu 《Molecules (Basel, Switzerland)》2022,27(22)
The effects of supplemental UV-A (385 nm) period and UV-A intensity for 5 days before harvest (DBH) on growth, antioxidants, antioxidant capacity, and glucosinolates contents in Chinese kale (Brassica oleracea var. alboglabra Bailey) were studied in plant factory. In the experiment of the UV-A period, three treatments were designed with 10 W·m−2 UV-A supplement, T1(5 DBH), T2 (10 DBH), and no supplemental UV-A as control. In the experiment of UV-A intensity, four treatments were designed with 5 DBH, control (0 W·m−2), 5 w (5 W·m−2), 10 w (10 W·m−2), and 15 w (15 W·m−2). The growth light is as follows: 250 μmol·m−2·s−1; red light: white light = 2:3; photoperiod: 12/12. The growth and quality of Chinese kale were improved by supplemental UV-A LED. The plant height, stem diameter, and biomass of Chinese kale were the highest in the 5 W·m−2 treatment for 5 DBH. The contents of chlorophyll a, chlorophyll b, and total chlorophyll were only highly increased by 5 W·m−2 UV-A for 5 DBH, while there was no significant difference in the content of carotenoid among all treatments. The contents of soluble sugar and free amino acid were higher only under 10 DBH treatments than in control. The contents of total phenolic and total antioxidant capacity were the highest in 5 W·m−2 treatment for 5 DBH. There was a significant positive correlation between total phenolic content and DPPH and FRAP value. After 5 DBH treatments, the percentages and contents of total aliphatic glucosinolates, sinigrin (SIN), gluconapin (GNA), and glucobrassicanapin (GBN) were highly increased, while the percentages and contents of glucobrassicin (GBS), 4-methoxyglucobrassicin (4-MGBS), and Progoitrin (PRO) were significantly decreased, especially under 10 W·m−2 treatment. Our results show that UV-A LED supplements could improve the growth and quality of Chinese kale, and 5 W·m−2 UV-A LED with 5 DBH might be feasible for Chinese kale growth, and 10 W·m−2 UV-A LED with 5 DBH was better for aliphatic glucosinolates accumulation in Chinese kale. 相似文献