Formation of toxic aldehydes in cod liver oil after ultraviolet irradiation

Formaldehyde, acrolein, malonaldehyde (MA), acetaldehyde and propanal produced from cod liver oil upon ultraviolet irradiation (λ_max=300 nm) were derivatized into nitrogenor sulfur-containing compounds and then analyzed by capillary gas chromatography with a nitrogen-phosphorus detector or a flame photometric detector. Acrolein and MA were formed at levels of 10.9±3.06 and 190.2±38.4 nmol/mg of fish oil, respectively. Maximum levels of formaldehyde, acetaldehyde and propanal formed were 7.0±0.90, 49.1±4.5 and 35.8±4.0 nmol/mg of oil, respectively. Formation of propanal in large quantities corresponded to the high content of ɛ-3 fatty acids in cod liver oil.     

Hybrid photocatalytic membranes embedding decatungstate for heterogeneous photooxygenation

The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity behavior has been evidenced by comparison with homogeneous oxidations.     

受阻哌啶和有机硫醚对顺—1,4—聚丁二烯光稳定机理研究

就２，２‘－二（４－甲基－６－叔丁基酚基）硫醚、二－（４－羟苯基）硫醚、二「－（３，５）－二叔丁基－４－羟苄基」－羧乙基甲酯基硫醚、二（丙酸二月桂酯基）硫醚等有机硫醚化合物和癸二酸二（２，２，６，６－四甲基－４－哌啶基酯）、２，２，６，６－甲四基哌啶等受阻类化合物对顺－１，４－聚丁二烯的光稳定作用，用ＩＲ，ＥＳＲ和ＴＬＣ等方法作了研究。发现这两类稳定剂之间具有反协同效应，并对此种反协同效应的机理作     

N,N-二甲基对甲基苯胺的自动氧化

N,N-二甲基对甲基苯胺(DMT)是一个典型的电子给体,可以和多种电子受体形成称之为CCT(Contact Charge Transfer)的络合物。在光照条件下,这种络合物可以生成离子自由基,从而引起一系列反应。同时,DMT又是一个还原剂,很容易发生氧     

Photooxidation of Some Mono-, Di-, and Tri-chlorophenols in Aqueous Solution by Hydrogen Peroxide/UV Combinations

A number of chlorophenols, namely 2-, 3-, and 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, have been decomposed in aqueous solution by using hydrogen peroxide as the oxidizing agent under UV radiation emitted by a 400 W high-pressure mercury lamp in a thermostatted Pyrex-glass column photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For H₂O₂/chlorophenol mole ratios between 1: 1 and 16: 1, the photooxidation reaction approached pseudo-first order kinetics, and the rate constants increased with increasing ratio of the oxidant. A theoretical model for the degradation pathway is proposed. The fact that the reaction order was not simply unity could be attributed to the complex reaction sequence processing via a radical mechanism through colored intermediates possibly comprising hydroquinone, catechol and resorcinol.     

Pheomelanin Effect on UVB Radiation-Induced Oxidation/Nitration of l-Tyrosine

Pheomelanin is a natural yellow-reddish sulfur-containing pigment derived from tyrosinase-catalyzed oxidation of tyrosine in presence of cysteine. Generally, the formation of melanin pigments is a protective response against the damaging effects of UV radiation in skin. However, pheomelanin, like other photosensitizing substances, can trigger, following exposure to UV radiation, photochemical reactions capable of modifying and damaging cellular components. The photoproperties of this natural pigment have been studied by analyzing pheomelanin effect on oxidation/nitration of tyrosine induced by UVB radiation at different pH values and in presence of iron ions. Photoproperties of pheomelanin can be modulated by various experimental conditions, ranging from the photoprotection to the triggering of potentially damaging photochemical reactions. The study of the photomodification of l-Tyrosine in the presence of the natural pigment pheomelanin has a special relevance, since this tyrosine oxidation/nitration pathway can potentially occur in vivo in tissues exposed to sunlight and play a role in the mechanisms of tissue damage induced by UV radiation.     

基于红外光谱法的SBS沥青光氧老化机理

通过AH-70基质沥青及PG76-22改性沥青的短期热氧老化(RTFO)和模拟光氧老化试验,运用红外光谱分析法研究真实环境中太阳光中紫外光对沥青胶结料的影响。探讨了沥青胶结料在紫外光和氧的双重因素的作用下,化学组分中各官能团的变化规律;从化学结构方面阐述了沥青胶结料的老化机理。     

光氧老化的Parylene C膜结构研究

计算了8类不同Parylene C膜光氧老化产物的几何构型、电子结构以及键离解能,并通过热重(TG)和热裂解气相色谱/质谱(PGC/MS)等手段研究了老化样品的热解过程和热解产物.计算结果和实验数据显示,主链上的CH2-CH2链节为整个体系中的薄弱环节,氧化后该链节变得更不稳定,而且氧化后Parylene C膜主链上生成了-OH等含氧基团.     

Effect of addition of Agaricus blazei mushroom residue to milk enriched with Omega‐3 on the prevention of lipid oxidation and bioavailability of bioactive compounds after in vitro gastrointestinal digestion

The residue from a hydroalcoholic extract of the mushroom Agaricus blazei (MAR) was evaluated for phenolic compounds, flavonoids and antioxidant activity. The ability of MAR to slow the oxidation of Omega‐3 resulting from light exposure in milk matrix, and its bioavailability after in vitro digestion was investigated. MAR presented phenolic compounds and flavonoids and showed antioxidant activity. At each concentration, addition of MAR to Omega‐3‐supplemented milk inhibited the production of conjugated dienes and malonaldehyde compared with samples without MAR. The bioavailability assay showed that polyphenols were still present after in vitro digestion and had antioxidant activity.     

神府煤不同密度级组分光氧化残留物的研究

在固定床光氧化反应器中，对神府煤不同密度级组分进行了紫外光光氧化研究．利用元素分析、溶胀度测定及红外光谱分析等方法研究了煤光氧化固体残留物的结构和性质．结果表明：光氧化对神府煤不同密度级组分的脱氮有明显效果；光氧化后固体残留物交联点间的平均分子量减小，交联度增加．各煤组分的腐殖酸产率随着光氧化时间的增加而增大，腐殖酸产率依次为D2〉D3〉D4．