Formation of 2-alkyl-(2H)-thiapyrans and 2-alkylthiophenes in cooked beef and lamb

2-Alkyl-(2H)-thiapyrans and 2-alkylthiophenes have been identified in the volatiles of cooked beef and lamb. The quantities of both groups of compounds were higher in the meat of animals fed lipid supplements high in n-3 polyunsaturated fatty acids. 2-Alkyl-(2H)-thiapyrans were formed when (E,E)-2,4-dienals (C(6)-C(11)) and hydrogen sulfide were heated at 140 degrees C for 30 min. This confirmed their proposed route of formation in cooked meat from lipid-derived aldehydes and hydrogen sulfide; the latter was produced from the degradation of cysteine, via the Maillard reaction. The mass spectra and NMR spectra of these thiapyrans are reported for the first time. Although 2-alkyl-(2H)-thiapyrans were found to have only low odor potency, the reactions by which they are formed may have important implications for meat flavor. These reactions may remove potent aroma compounds and their intermediates from meat, thus modifying the overall aroma profile.     

Antioxidative activity of green tea treated with radical initiator 2, 2'-azobis(2-amidinopropane) dihydrochloride

This study investigated the antioxidative activity of green tea extract, and a green tea tannin mixture and its components, under conditions of radical generation using the hydrophilic azo compound, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate peroxyl radicals at a constant and measurable rate in the cultured renal epithelial cell line, LLC-PK(1), which is susceptible to oxidative damage. Treatment with AAPH decreased cell viability and increased the formation of thiobarbituric acid-reactive substances. However, green tea extract, and the tannin mixture and its components, comprising (-)-epigallocatechin 3-O-gallate (EGCg), (-)-gallocatechin 3-O-gallate (GCg), (-)-epicatechin 3-O-gallate (ECg), (-)-epigallocatechin (EGC), (+)-gallocatechin (GC), (-)-epicatechin (EC), and (+)-catechin (C), showed protective activity against AAPH-induced cellular damage. The tannin mixture and its components exhibited higher antioxidative activity than the green tea extract. Furthermore, EGCg and GCg had higher activity than EGC and GC, respectively. In particular, EGCg exerted the most significant cellular protective activity against AAPH. These results indicate that green tea tannin may inhibit cellular loss and lipid peroxidation resulting from the peroxyl radical generated by AAPH, and that the chemical structure of tannin is also involved in the activity, suggesting that the O-dihydroxy structure in the B ring and the galloyl groups are important determinants for radical scavenging and antioxidative potential.     

2BLZ-2型垄上镇压式精密播种机的研制与试验

2BLZ-2型垄上镇压式精密播种机，设计安装了组合式仿形传动轮，集仿形传动作用为一体。采用了组合内窝孔式玉米排种器，实现精密播种。设置了两组弹簧，以保证播深一致及实现镇压力可调。通过田间作业试验和技术性能分析，证明该机具有良好的工作质量和可靠的技术性能。     

植物C_2H_2型锌指蛋白的研究进展

锌指蛋白是转录因子的一种,对真核生物的生长发育及逆境胁迫的耐受能力都有着重要关系,而植物C2H2型锌指蛋白是研究较多、较为明确的一种锌指蛋白,该蛋白大部分锌指结构具有一段高度保守的氨基酸序列QALGGH,这是植物中独有的特征,且据报道该C2H2型锌指蛋白与逆境胁迫是相关的。本文主要综述了植物C2H2型锌指蛋白的分类、结构和功能,植物C2H2型锌指蛋白与DNA、RNA和蛋白质的相互作用,以及概述了与盐胁迫、低温胁迫、干旱胁迫、氧胁迫和光胁迫等逆境胁迫相关的植物C2H2型锌指蛋白,最后还对其进一步的深入研究进行了展望,这就为日后利用基因工程技术改良作物品质、提高作物的抗逆性提供了有利条件。     

Antifungal activity of 4-methyl-6-alkyl-2H-pyran-2-ones

A number of 4-methyl-6-alkyl-alpha-pyrones were synthesized and characterized on the basis of 1H NMR and mass spectroscopy. These compounds were tested in vitro against pathogenic fungi, namely, Sclerotium rolfsii Saccardo, Rhizoctonia bataticola (Taub.) Butler, Pythium aphanidermatum (Edson) Fitz., Macrophomina phaseolina (Tassi), Pythium debaryanum (Hesse), and Rhizoctonia solani Nees. Lower homologues were less effective, whereas compounds such as 4-methyl-6-butyl-alpha-pyrone, 4-methyl-6-pentyl-alpha-pyrone, 4-methyl-6-hexyl-alpha-pyrone, and 4-methyl-6-heptyl-alpha-pyrone were found effective against all of the test fungi. They inhibited mycelial growth by approximately 50% (ED50) at 15-50 microg/mL. 4-Methyl-6-hexyl-alpha-pyrone, which was found most effective, was tested against S. rolfsii in a greenhouse at 1, 5, and 10% concentrations. The 10% aqueous emulsion of 4-methyl-6-hexyl-alpha-pyrone suppressed disease development in tomato by 90-93% as compared with the untreated infested soil in the greenhouse after 35 days of treatment.     

Anaerobic reoxidation of Mn2+, Fe2+, S0 and S2– in submerged paddy soils

Anaerobic reoxidation of reduced products in paddy soils was investigated. Ferrous iron (Fe²⁺) and monosulfide ion (S^2–) added to the soil chemically reduced MnO₂ to Mn²⁺, and MnO₂ and Fe(OH)₃ to Mn²⁺ and Fe²⁺, respectively, where Fe²⁺ and S^2– were considered to be oxidized to Fe³⁺ and S⁰. Elemental sulfur was oxidized to sulfate by anaerobic incubation with NO₃ ^– MnO₂ and Fe(OH)₃. A new conceptual model for the reduction processes in submerged paddy soil including the reoxidation processes of reduced products, in which soil heterogeneity in paddy fields was taken into consideration, was proposed based on the results. Received: 20 October 1996     

NO和H2O2依赖Ca2+/CaM信号调控马铃薯花青素积累

以不同块茎颜色马铃薯品种陇薯8号、陇薯7号、LC310-2和山东彩肉为材料,研究外源NO、H2O2、NO+ H2O2处理对马铃薯块茎花青素合成及其信号物质Ca2+-ATPase和CaM的影响.结果表明:外源NO和H2O2处理后,4个基因型马铃薯薯皮和薯肉花青素积累,Ca2+-ATPase活性升高,CaM含量增加,其效果为NO+ H2O2＞H2O2＞NO＞水(CK),并且花青素的积累量与Ca2+-ATPase活性和CaM含量均呈正相关,其平均决定系数达0.9194和0.8859.说明NO和H2O2对马铃薯花青素合成具有一定的促进作用,而细胞Ca2 +/CaM信号发挥了NO和H2O2对马铃薯花青素合成诱导的信号调节.     

Simulated warming and low O2 promote N2O and N2 emissions in subtropical montane forest soil

Journal of Soils and Sediments - The montane subtropical forest soils contain huge nitrogen stocks, and climate warming might drive its volatilization due to the promotion of gaseous losses of...     

Synthesis and sensorial properties of 2-alkylalk-2-enals and 3-(acetylthio)-2-alkyl alkanals

Parallel synthesis was applied to prepare a series of 3-(acetylthio)-2-alkyl alkanals by Michael addition of thioacetic acid under alkaline conditions to alpha,beta-unsaturated 2-alkyl-substituted aldehydes, which were obtained by aldol condensation of the corresponding primary aldehydes as starting materials. The target compounds were characterized in terms of GC, MS, and NMR data. The sensory properties of the odorants, such as odor quality and odor detection threshold value, were determined with a trained panel. Structure-activity relationships are discussed, suggesting that the 1,3-oxygen-sulfur functionality, required for the "olfactophore" of tropical/vegetable notes, can further be extended to the acetylthio derivatives.     

分子氢对红萍固氮活性的支持作用(英文)

本工作研究了分子氢对不同生长条件下三种红萍:细绿萍(Azollsa filiculoides),卡洲萍(Azolla caroniana)和小叶萍(Azolla microphylla)的固氮活性的支持作用,结果表明,在5000—20000lx不同光照强度下,分子氢对红萍固氮活性均有支持作用,当光照强度为10000lx时,10％的分子H_2可使红萍的固氮活性增加30—80％,在5000lx弱光条件下,相同浓度分子氢使红萍固氮活性增加的幅度比10000lx光照时大。在相同的光照条件下,大叶萍的固氮活性较高,分子氢对其固氮活性的支持作用也较强,说明了在萍藻共生体系中,光能利用、固氮效率与分子氢利用效率呈正相关。同时,分子氢对于红萍固氮活性受尿素毒害所致的抑制也有减慢作用。在培养液中尿素浓度超过5ppm时,红萍的固氮活性受到抑制,当尿素浓度达到50ppm时,其固氮活性抑制率达50—60％,但20％的分子氢可使其固氮活性恢复到正常培养下的70％以上。在一定的尿素浓度范围内,红萍固氮活性受抑程度愈大,分子氢对其减慢的作用也愈强。     

Lipase-assisted generation of 2-methyl-3-furanthiol and 2-furfurylthiol from thioacetates

Enzymatic hydrolysis of S-3-(2-methylfuryl) thioacetate and S-2-furfuryl thioacetate using lipase from Candida rugosa produced 2-methyl-3-furanthiol and 2-furfurylthiol, respectively. When reactions were carried out at room temperature and pH 5.8, 2-methyl-3-furanthiol was produced in a optimal yield of 88% after 15 min of reaction, whereas 2-furfurylthiol was obtained in a yield of 80% after 1 h of reaction time. Enzymatic hydrolysis was also performed in n-hexane, n-pentane, and water/propylene glycol mixture. The reaction rates in these media were slower as compared to those in aqueous medium; however, the reaction yields were quite similar. As expected, the stability of the generated 2-methyl-3-furanthiol and 2-furfurylthiol was better in n-hexane, n-pentane, and the water/propylene glycol mixture as compared to that in water or phosphate buffer.     

Evaluation of antiradical capacity by H2O2-hemin-induced luminol chemiluminescence

This paper describes a screening method for antioxidant potential determination based on luminol/hemin/hydrogen peroxide chemiluminescence. The emission depletion, caused by an antiradical compound added during the chemiluminescence decay, is proportional to the number of reactive species trapped. Therefore, the difference between the areas of the emission decay curves, obtained in the absence and in the presence of the potential antioxidant, is a measure for the antiradical capacity of the sample. The technique has been applied to measure the antiradical capacity of pure compounds and complex mixtures from natural origin, providing reliable results that indicate the method's feasibility.     

乌拉草纤维的超声波辅助碱氧-浴法提取工艺优化

为了提取一种新型植物纤维-乌拉草纤维并研究其性能,采用超声波-碱氧-浴法从乌拉草秸秆中提取乌拉草纤维,用多指标正交试验方法对超声波时间,碱煮时间,碱用量和双氧水用量进行优化设计,并通过对直径,断裂强度,回潮率3个指标的综合分析评价确定最佳提取工艺,对处理后的乌拉草纤维进行基本性能测试及保暖、抗菌效果测试.结果表明:最佳工艺参数为:超声波时间为70 min;碱氧-浴时间为100 min;0.75 L溶液中碱质量浓度为8 g/L;双氧水质量浓度为12 g/L.采用最优工艺所提取的乌拉草纤维平均直径、长度、断裂强度及回潮率分别为47.19μm、152.59 mm、2.03×10?4MPa和15.33%,与苎麻纤维性能相似,可满足可纺性要求.并有一定的保暖性和优良的抑菌效果.     

土壤CO2与喀斯特洞穴CO2季节变化响应分析

为了揭示土壤CO_2对洞穴内环境的意义,对大风洞和响水洞2016年洞内环境指标和上覆土壤的相关数据进行统计与回归分析。结果表明,洞内CO_2浓度、土壤CO_2浓度具有显著的季节性特征,土壤2#对应的洞内空气CO_2在夏冬两季差值达793~884mg/kg。土壤水PCO_2和滴水PCO_2在夏冬两季的差值最高可分别达1.12和0.41,因此洞内滴水PCO_2、土壤水PCO_2也表现出明显的季节性特征。土壤CO_2、洞内空气CO_2、洞内滴水PCO_2和土壤水PCO_2间均表现出一定的滞后现象,如4#土壤水PCO_2与滴水PCO_2的相关系数,由非滞后条件下的0.123上升至滞后条件下的0.596。同时在滞后条件下,土壤CO_2对洞内CO_2的贡献率的总和最高可达84.6%,高于非滞后条件下的值。     

Effects of combined and sequential addition of dual oxidants (H2O2/S2O8(2-)) on the aqueous carbofuran photodegradation

Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) (CBF) is a widely used insecticide. Traditional methods like hydrolysis and direct photolysis cannot remove CBF effectively. In this study, the photodecay of 0.1 mM CBF in UV/H2O2, UV/S2O8(2-), and UV/H2O2/S2O8(2-) and sequential addition of a second oxidant were studied under UV light at 254 nm. The degradations of CBF follow pseudo-first-order decay kinetics. Direct photolysis was slow, but the corresponding degradation rate was increased with the addition of hydrogen peroxide (H2O2) or potassium peroxydisulfate (K2S2O8). In the UV/H2O2 reaction, the optimum reaction rate was 0.9841 min-1 at 10 mM H2O2 (pH 7); however, retardation is observed if H2O2 is overdosed. Such retardation is not observed in the UV/S2O8(2-) system, but a nonlinear increment of removal efficiency is identified. The UV/H2O2/S2O8(2-) process on the other hand shows the best performance in CBF degradation, but it has a less effective mineralization than that of the sole UV/S2O8(2-) reaction.     

A Research Note on the Adsorption of CO2 and N2

Experiments were made for the adsorption of CO2 and N2 on typical adsorbents to investigate the effects of porous structure and surface affinity of adsorbents as well as those of adsorption temperature...     

复合纳米TiO2-CeO2的制备及其紫外屏蔽性能

采用直接沉淀法制备了TiO2-CeO2纳米复合氧化物,分析了不同铈钛摩尔比、pH和不同反应温度对合成复合氧化物及其紫外屏蔽效果的影响。研究结果表明,采用直接沉淀法制得了面心立方结构CeO2和锐钛矿型的TiO2混合物,铈钛摩尔比为0.4时复合氧化物在250～450nm波段之间有良好的紫外屏蔽性能。     

Photodegradation of metolachlor applying UV and UV/H2O2

Metolachlor is one of the most widely used herbicides in the world for controlling weeds. It has been detected in both ground and surface waters in the United States, and there are rising concerns in regard to its health risks and in developing effective treatment processes for its removal from water. Degradation of metolachlor via ultraviolet (UV) photolysis and an UV/hydrogen peroxide advanced oxidation process (AOP) was studied. The quantum yield of metolachlor at 254 nm was found to be 0.302 +/- 0.001 mol E-1 through direct UV photolysis in the range of pH 6-8. The second-order rate constant of the reaction between metolachlor and hydroxyl radical was determined to be 9.07 (+/-0.21) x 10(9) M-1 s-1 by using a competition kinetics model that utilized nitrobenzene as a reference compound. In addition, these parameters were successfully applied in modeling the kinetics of elimination of metolachlor using an UV/H2O2 process in both laboratory and natural waters. The formation of several photolysis byproducts was identified using gas chromatography/mass spectrometry, and a scheme for the metolachlor photodegradation pathway is proposed.     

Sol-Gel SiO2 Powders Sequestrants of Be2+ in Diluted Solutions

Silica powders of varying morphology were prepared by the sol-gel technique. Typical sol-gel parameters, such as pH of the hydrolysing water solution,H₂O/≡Si-OCH₂CH₃ molar ratio,thermostatting temperature, and rate of addition of hydrolysingwater, were varied in order to prepare different tailoredsamples, which were then exhaustively hydrolyzed in boilingwater. Samples were characterized by several analyticaltechniques, including surface area and porosity determinations,FT-IR spectroscopy, and thermogravimetric-mass spectrometriccoupled analyses. Samples were used as sequestrants to fixBe²⁺ from diluted water solutions, starting from 5 Beμg L^-1. Their adsorption capabilities werecompared; results were analyzed and discussed taking intoaccount the morphological features of used samples and possible preferential Be²⁺ adsorption by active sites present on the sol-gel SiO₂ surface.