pH and Salt-Assisted Macroscopic Chirality Inversion of Gadolinium Coordination Polymer

The precise adjustment of handedness of helical architectures is important to regulate their functions. Macroscopic chirality inversion has been achieved in organic supramolecular systems by pH, metal ions, solvents, chiral and non-chiral additives, temperature, and light, but rarely in coordination polymers (CPs). In particular, salt-assisted macroscopic chirality inversion has not been reported. In this work, we carried out a systematic investigation on the role of pH and salt in regulating the morphology of CPs based on Gd(NO₃)₃ and R-(1-phenylethylamino)methylphosphonic acid (R-pempH₂). Without extra NO₃⁻, the chirality inversion from the left-handed superhelix R-M to the right-handed superhelix R-P can be achieved by pH modulation from 3.2 to 3.8. The addition of NaNO₃ (2.0 eq) at pH 3.8 results in an inversion of chiral sense from R-P to R-M as a pure phase. To our knowledge, this is the first example of salt-assisted macroscopic helical inversion in artificial systems.     

3-Hydroxymethylglutaryl flavonol glycosides from a Mongolian and Tibetan medicine, Oxytropis racemosa

Three new flavonol 3-O-glycosides, rhamnetin 3-O-[(S)-3-hydroxy-3-methyl-glutaroyl(1→6)]-β-D-glucopyranoside (1), rhamnocitrin 3-O-[(S)-3-hydroxy-3-methylglutaroyl(1→6)]-β-D-glucopyranoside (2), and isorhamnetin 3-O-[(S)-3-hydroxy-3-methylglutaroyl(1→6)]-α-L-rhamnopyranosyl(1→2)-β-D-glucopyranoside (3), along with 13 known compounds, were isolated from Oxytropis racemosa TURCZ. Their structures were deduced by means of spectroscopic methods and chemical evidence. 2 and 6 showed cytotoxic activities against HCT-8 (IC?? 6.38 μM) and A549 (IC?? 5.20 μM), respectively.     

含氟聚合物分子链的构象和柔顺性

通过对含氟聚合物分子链内旋转构象的分析,发现含氟聚合物与其它结构类型的聚合物一样,其玻璃化转变温度Tg与分子链横截面积A和分子链内旋转让阻因子σ之间的关系遵循同样的规律^[1,2]。建议用Tg=973(σ-1.44)来计算含氟聚合物的分子链内旋转位阻因子。内旋转位阻因子相同时,含氟聚合物的玻璃化转变温度较其它结构类型的聚合物为高(图2),可归结为含氟聚合物分子链的紧密堆积。     

General solutions of coupled thermoelastic problem

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变量核奇异积分和分数次微分加权范不等式

用T和D^γ（0 ≤ γ ≤ 1）分别表示变量核奇异积分和分数次微分算子.T^*和T^#分别为T的共轭算子及拟共轭算子.利用球调和多项式展式,本文得到了TD^γ-D^γT和（T^*-T^#）D^γ在?^q,λ_ω（Rⁿ）上的有界性.同时也得到了变量核奇异积分的积T₁T₂和拟积T₁°T₂的加权范不等式.     

基于N-十二酰基-l-脯氨酸为载体的对映异构PVC膜选择性电极的研制

合成了手性物质N-十二酰基-l-脯氨酸(N-DDO-l-Pro)(脯氨酸, Pro), 作为PVC膜电极的载体, 在PVC膜表面与被测试液中Cu(II)与脯氨酸形成的配合物[Cu(II)(l-Pro)₂]或[Cu(II)(d-Pro)₂]进行配体交换, 形成[(l-Pro)Cu(II) (N-DDO-l-Pro)]或[(d-Pro)Cu(II)(N-DDO-l-Pro)]配合物. 由于生成的配合物热力学稳定性不同, 电极能优先响应l-Pro, 线性范围10^－4～10^―1 mol•L^－1, 斜率57 mV•dec^－1, 检测限3.89×10^－5 mol•L^－1. 电极能够对脯氨酸进行手性检测, 其对映选择性系数lg为－3.19.     

高效固体酸SBA-15-Zr(OTf)3催化胺或醇开环环氧化合物

通过简单的一锅两步法制备了三氟金属(铝,钛,锆)接枝介孔SBA-15 (AlTf/S,TiTf/S,ZrTf/S)固体酸材料,并通过XRD,N2吸附,TGA,FTIR,原位吡啶FTIR和元素分析对这些材料进行了详细的表征.其中,ZrTf/S能够高效催化环氧化物温和条件下被胺或醇开环生成对应β-氨基醇或β-烷氧基醇,并且催化剂能循环利用.ZrTf/S相较于AlTf/S和TiTf/S酸性最强,因而催化活性也最高.     

酸水解-气相色谱法测定奶粉中的二十二碳六烯酸

建立了盐酸水解,索氏提取总脂肪酸,氢氧化钾甲醇溶液甲酯化,硫酸氢钠处理,气相色谱测定奶粉中二十二碳六烯酸(DHA)含量的方法。采用三因素三水平正交试验对氢氧化钾甲醇溶液甲酯化条件进行了优化,得到最优反应条件为:1 mol/L氢氧化钾在25 ℃反应5 min。甲酯化衍生液经硫酸氢钠处理,在SP-2560气相色谱柱(100 m×0.25 mm×0.20 μ m)上进行55 min程序升温测定DHA含量。DHA在5.0~300 mg/L范围内呈良好线性,相关系数为0.9999。DHA质量浓度为10、50、100 mg/L时目标峰峰面积的相对标准偏差(RSD)分别为3.4%、1.2%和1.1%。方法检出限为2 mg/kg,回收率为90.4%~93.5%。该法用于实际样品的检测,结果令人满意。     

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include ³H, ¹⁴C, ³⁶Cl, ⁴¹Ca, ^59,63Ni, ^89,90Sr, ⁹⁹Tc, ¹²⁹I, ^135,137Cs, ²¹⁰Pb, ^226,228Ra, ²³⁷Np, ²⁴¹Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.     

A density-functional theory investigation on desorption of O2 on Sn（111） and its comparison with initial oxidation on the X（111） （X=Si,Ge, Sn,Pb） surfaces

<正>The first-principles calculations are performed to investigate the adsorption of O₂ molecules on an Sn（111） 2×2 surface.The chemisorbed adsorption precursor states for O₂ are identified to be along the parallel and vertical channels, and the surface reconstructions of Sn（lll） induced by oxygen adsorption are studied.Based on this,the adsorption behaviours of O₂ on X（111）（X=Si,Ge,Sn,Pb） surfaces are analysed,and the most stable adsorption channels of O₂ on X（111）（X=Si,Ge,Sn,Pb） are identified.The surface reconstructions and electron distributions along the most stable adsorption channels are discussed and compared.The results show that the O₂ adsorption ability declines gradually and the amount of charge transferred decreases with the enhancement of metallicity.