以短链季铵盐/脂肪酸盐为模板合成超微孔二氧化硅

超微孔材料具有1~2 nm的孔径,在分离、催化应用中有望展现出择形催化的能力。 寻找经济、简便的合成超微孔材料的表面活性剂体系是一项有意义的工作。 本研究以短链季铵盐(十烷基三甲基溴化铵,记为C₁₀TAB)和不同链长脂肪酸酸盐混合胶束为模板剂,硅酸钠为硅源,成功制备出高度有序超微孔SiO₂。 通过小角X射线衍射、N₂吸附-脱附、傅里叶变换红外光谱、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对产品的结构和性能进行了表征。 结果表明,合成体系中脂肪酸盐碳链长、加入量、晶化温度等对产物孔道有序性有很大影响。 当选择正辛酸钠(SO)为助表面活性剂,当n(C₁₀TAB):n(Na₂SiO₃):n(SO):n(H₂O)=1:1.5:0.3:800,晶化温度为80 ℃时,可以得到高度有序超微孔SiO₂。 煅烧后样品比表面积为1300 m²/g,孔体积0.49 cm³/g,孔径分布在1.90 nm。     

Raman spectroscopic study of the hydration of short-chain poly(oxyethylene)s C <Subscript>1</Subscript>E<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>C <Subscript>1</Subscript> (<Emphasis Type="Italic">n</Emphasis>=1−4)

The hypothesis that the degree of hydration of poly(oxyethylene) (POE) in aqueous solution depends on the mole ratio of water molecules to ether oxygen atoms in the molecule has been verified by studying the isotropic Raman spectra in the O−H stretching region for four short-chain POEs (C ₁E _n C ₁ withn=1−4). Excellent coincidence of the O−H stretching Raman band for all four POEs studied in the range of mole ratio H₂O/O _ether from 25 to 0.6 was observed, thus confirming the assumption stated above. A conclusion that all ether oxygen atoms in the POE molecule participate in hydrogen bonding with water molecules has been made.     

The Development of Stable 3-Nitro-2-pyridinesulfenyl Reagents and Their Application to Peptide Chemistry

Development of 3-Nitro-2-pyridinesulfenyl (Npys) halide reagents and their application to peptide chemistry are discussed     

Monitoring the Reaction of the Body State to Antibiotic Treatment against Helicobacter pylori via Infrared Spectroscopy: A Case Study

The current understanding of deviations of human microbiota caused by antibiotic treatment is poor. In an attempt to improve it, a proof-of-principle spectroscopic study of the breath of one volunteer affected by a course of antibiotics for Helicobacter pylori eradication was performed. Fourier transform spectroscopy enabled searching for the absorption spectral structures sensitive to the treatment in the entire mid-infrared region. Two spectral ranges were found where the corresponding structures strongly correlated with the beginning and end of the treatment. The structures were identified as methyl ester of butyric acid and ethyl ester of pyruvic acid. Both acids generated by bacteria in the gut are involved in fundamental processes of human metabolism. Being confirmed by other studies, measurement of the methyl butyrate deviation could be a promising way for monitoring acute gastritis and anti-Helicobacter pylori antibiotic treatment.     

Structures and properties of different low density polyethylenes

Low density polyethylenes (LDPE) made by the known high pressure processes show significantly different molecular structures. When the reaction conditions are variable, e.g. in a tubular reactor (resinT) or in a system of two autoclaves with a lower temperature in the first reactor (resinA ₂ ^* ), the polymer shows a narrower molecular weight distribution, but wider distributions of long-chain and short-chain branching compared with a polymer produced at constant temperature and under practically ideal mixing in a stirred autoclave reactor (resinA). The polymerT displays a decrease in long-chain and short-chain branching with growing molecular weight and differs from sampleA in the type of long-chain branching and in the molecular shape.A-type molecules show tree-like branching and nearly globular shapes whereas theT-type molecules are characterized by comb-like branching and consequently have more extended (rod-like but flexible) conformations. These structures may be interpreted in terms of reaction kinetics. The differences in molecular structure lead to changes in the morphology. For example, the bulk density distributions of the polymersT andA ₂ ^* are narrower than that of polymerA although the latter has a much narrower short-chain branching distribution. The morphology (e.g. crystallinity and crystal size) is dominated by the tendency of short sidechains to accumulate in the amorphous phase and by the limited mobility of the molecules in the melt during crystallization. The proportion of short side-chains incorporated in the crystalline phase ranges from about 20% at high molecular weights to about 7% at low molecular weights for the resinsA andT. The physical and technological properties are closely related to molecular structure and morphology. They may be optimized by selecting suitable polymerization conditions, e.g. by use of a new two-autoclave process.In memoriam Prof. Dr. Dr. h. c. mult. Otto Bayer.Vorgetragen auf der Frühjahrstagung des Fachausschusses Polymerphysik der Deutschen Physikalischen Gesellschaft, Regensburg, 15.–17. März 1982.     

Bioactivity Profiles of Cytoprotective Short-Chain Quinones

Short-chain quinones (SCQs) have been investigated as potential therapeutic candidates against mitochondrial dysfunction, which was largely thought to be associated with the reversible redox characteristics of their active quinone core. We recently reported a library of SCQs, some of which showed potent cytoprotective activity against the mitochondrial complex I inhibitor rotenone in the human hepatocarcinoma cell line HepG2. To better characterize the cytoprotection of SCQs at a molecular level, a bioactivity profile for 103 SCQs with different compound chemistries was generated that included metabolism related markers, redox activity, expression of cytoprotective proteins and oxidative damage. Of all the tested endpoints, a positive correlation with cytoprotection by SCQs in the presence of rotenone was only observed for the NAD(P)H:quinone oxidoreductase 1 (NQO1)-dependent reduction of SCQs, which also correlated with an acute rescue of ATP levels. The results of this study suggest an unexpected mode of action for SCQs that appears to involve a modification of NQO1-dependent signaling rather than a protective effect by the reduced quinone itself. This finding presents a new selection strategy to identify and develop the most promising compounds towards their clinical use.     

气相色谱–质谱法测定食用植物油中短链脂肪酸的测量不确定度评定

采用气相色谱–质谱法(GC–MS)测定食用植物油中短链脂肪酸含量,对测量结果的不确定度进行评定,探讨提高测量准确度的方法。依据方法建立数学模型,分析得出不确定度主要来源于样品制备过程、计量器具的使用、标准溶液配制、测量设备、人员读数误差、方法回收率,计算各不确定度分量,得到相对标准不确定度和扩展不确定度。结果表明,当食用植物油中短链脂肪酸测定结果为13.1 mg/kg时,其扩展不确定度为1.8 mg/kg(k=2)。测量设备、标准溶液配制过程引入的不确定度较大,应在实验过程中予以控制和关注。     

大体积采样结合高分辨气相色谱-电子捕获负化学源-低分辨质谱法测定空气中的短链氯化石蜡

建立了大体积采样结合高分辨气相色谱-电子捕获负化学源-低分辨质谱(HRGC-ECNI-LRMS)测定空气中短链氯化石蜡(SCCPs)的定量分析方法。联合使用酸化硅胶复合层析柱和碱性氧化铝层析柱净化处理空气样品中的SCCPs,并对净化条件进行优化。使用该方法计算得到氯含量为58.1%~63.3%的SCCPs系列标准储备溶液的总响应因子与氯含量线性相关,相关系数(R²)大于0.99。该方法的仪器检出限(S/N≥3)为4.2 pg,定量限(S/N≥10)为12 pg。SCCPs的方法检出限(MDL)为0.34 ng/m³(n=7),实际样品加标回收率均达80%以上。该方法灵敏度高、选择性好,能满足空气样品中SCCPs的监测和分析需求。     

固相萃取-气相色谱-负化学离子源质谱法测定运动场所合成材料面层和稀释剂中的短链氯化石蜡

建立了用于运动场所合成材料面层和稀释剂中短链氯化石蜡（SCCPs）总含量测定的固相萃取-气相色谱-负化学离子源质谱法（SPE-GC-NCI-MS）。对气相色谱和质谱的分析条件进行了优化;试样经超声提取、弗罗里硅土固相萃取小柱净化后,选择性离子监测模式（SIM）扫描,外标法定量。方法在0.0501~100.17 mg/L的宽广范围内有良好的线性关系,线性相关系数R²为0.9995,方法检出限低至0.50 μg/g（即0.000050%）,平均回收率为83.2%~96.3%,相对标准偏差为1.56%~6.02%。对10批次实际样品进行检测,含量在0.016%~0.55%范围内,检测结果满足欧盟对此类物质的限量要求。方法可用于运动场所合成材料面层和稀释剂中短链氯化石蜡的实际检测。     

An experimental investigation of the shear behaviour of polyethylenes with different structures

Rheological properties in shear flow are presented for four different polyethylene samples: a high density, a linear low density and two low density polyethylenes manufactured using different techniques. Tests have been performed with the aid of capillary types of instrument equipped with capillaries of various lengths at three different temperatures. End correction factors have been determined and true flow curves obtained. Swelling ratios for both unannealed and annealed samples have been determined as well as the shear rate and shear stress at which irregularities begin. In some cases generalized plots have been prepared and in all cases the rheological response is discussed in terms of molecular characteristics, in particular the average molecular weight, molecular weight distribution and degree of branching.