Synthesis and isolation of <Emphasis Type="Italic">trans</Emphasis>-7, <Emphasis Type="Italic">cis</Emphasis>-9 octadecadienoic acid and other CLA isomers by base conjugation of partially hydrogenated γ-linolenic acid

CLA is of considerable interest because of reported potentially beneficial effects in animal studies. CLA, while not yet unambiguously defined, is a mixture of octadecadienoic acids with conjugated double bonds. The major isomer in natural products is generally considered to be cis-9,trans-11-octadecadienoic acid (c9, t11), which represents >75% of the total CLA in most cases. Other isomers are drawing increased attention. The t7,c9 isomer, which is often the second-most prevalent CLA in natural products, has been reported to represent as much as 40% of total CLA in milk from cows fed a high-fat diet. The need for a reference material became apparent in a recent study directed specifically at measuring t7,c9-CLA in milk, plasma, and rumen. A suitable standard mixture was produced by stirring 0.5 g of γ-linolenic acid (all cis-6,9, 12-C_18∶3) with 100 mL of 10% hydrazine hydrate in methanol for 2.5 h at 45°C. The solution was diluted with H₂O and acidified with HCl. The resulting partially hydrogenated FA were extracted with ether/petroleum ether, dried with Na₂SO₄, and conjugated by adding of 6.6% KOH in ethlylene glycol and heating for 1.5 h at 150–160°C. Approximately 20 mg each of cis-6, trans-8; trans-7, cis-9; cis-9, trans-11; and rans-10, cis-12 were obtained along with other FA. Methyl esters (FAME) of these four cis/trans isomers were resolved by Ag⁺HPLC (UV 233) and partially resolved by GC/(MS or FID) (CP-Sil 88). Treatment of these FAME with I₂ yielded all possible cis/trans (geometric) isomers for the four positions 6,8; 7,9; 9,11; and 10,12.     

平衡施肥理论与肥料高效利用

结合施肥实践阐述了平衡施肥原理中静态的横向平衡和动态的纵向平衡概念,并提出具有纵向平衡特点的速度复合型控释肥,其养分释放速度能与作物的养分需求基本一致,可显著提高肥料利用率和作物产量。     

榆济天然气管道内腐蚀原因

为了明确榆济天然气管道内腐蚀原因,首先对榆济天然气管道输送天然气成分、清管记录等服役状况进行调研。其次针对管道内壁不同时钟位置的腐蚀状况进行宏观腐蚀形貌观察,使用扫描电镜(SEM)对腐蚀产物进行微观观察,使用X射线衍射(XRD)对腐蚀产物进行成分分析。结果表明,管道内部存在局部腐蚀,腐蚀产物以Fe2O3和FeCO3为主。因此CO2腐蚀是造成榆济天然气管道内腐蚀的主要原因。     

双相不锈钢在H2SO4＋NaCI介质中的腐蚀磨损

测定了α γ双相不锈钢在H2SO4及H2SO4＋NaCI介质中的腐蚀率、磨损率、腐蚀磨损率和钝化膜破坏后的修复时间，研究了磨损表面的硬度变化以及摩擦系数的变化规律，观察了磨痕及磨屑形貌等，实验表明氯离子对双相不锈钢腐蚀磨损的影响与磨损表面的脆性剥落有关。     

低压下[C6mim][PF6]用于二氧化碳吸收及解吸性能研究

研究了接近1 atm、293～333 K条件下[C6mim][ PF6]静态吸收二氧化碳的动力学特性,结果表明,温度和真空度对解吸效率有显著影响.363 K时该离子液体对吸收二氧化碳后解吸率达到66.67％,而真空条件下,室温时的解吸率就能达到95％.探讨了吸收-解吸循环使用次数及保存时间对该离子液体吸收-解吸二氧化碳性能的影响,发现吸收-解吸过程中[ C6mim][ PF6]的质量损失率低于0.05％,经过58次循环及约240天保存后,其吸收二氧化碳的容量和速率未发生明显改变.同时对其吸收过程的活化能及溶解焓等参数进行了拟合计算:Ea为5 836.93 J/mol,△H为10 957.66 J/mol.     

Incidence of adenoviruses in raw and treated water

Adenoviruses are of major public health importance and are associated with a variety of clinical manifestations, i.e. gastroenteritis, eye infections and respiratory infections. The importance of water in the epidemiology of adenoviruses and the potential health risks constituted by adenoviruses in water sources and supplies are widely recognised. This study was conducted to assess the incidence of human adenoviruses in raw and treated water systems. Various raw and treated water were routinely monitored for the presence of adenoviruses, over a 1-year period (July 2000-June 2001). The supplies were derived from acceptable quality surface water sources using treatment processes, which conform to international standards for the production of safe drinking water. Adenoviruses were detected by firstly amplifying the viruses in cell cultures and then amplifying the extracted nucleic acids of these viruses using molecular techniques (nested PCR). The results indicated human adenoviruses present in 13 (12.75%) of the raw and 9 (4.41%) of the treated water samples tested. The combination of cell culture and nested PCR has proved to be a quick and reliable method for the detection of adenoviruses in water environments.     

改革开放以来我国城市化进程中的土地制度研究

土地制度是影响城市化进程的关键性因素.我国现行的土地制度加大了农民向城市迁移的意愿与在城市定居能力之间的差距,这也是导致我国城市化失衡的根源.只有进一步改革土地制度,以土地配置市场化和产权明晰化为目标,实现土地资源的优化配置,才能打破土地制度的约束并进一步推动我国城市化的健康发展.     

钢筋混凝土桁架式转换层施工技术

长沙东方·新世界工程采用钢筋混凝土桁架式转换层,桁架总高4．8m、跨度12m,施工难度大。分析钢筋混凝土桁架式转换层施工重点及难点,介绍钢筋混凝土桁架式转换层钢筋、混凝土工程,模板及支撑系统施工技术。     

论铜的化合物对金在含氰溶液中溶解速度的影响

含氰工作溶液中存在铜的络合阴离子,使金的溶解速度显著下降。其原因在文献中归结两点:一是氰化物离子合成铜的最高氰化络合物;其二反应表面上形成一层被吸附的络合氰化铜或单一氰化铜CuCN薄膜。于是,考虑溶解过程的变化因素并以均等表面(这在表面上形成薄膜时是特别必要的)进行的铜的影响     

Inactivation of Enterobacter sakazakii in infant milk formula by gamma irradiation: determination of D10-value

ABSTRACT:  Enterobacter sakazakii is an emerging foodborne pathogen that has caused several cases of meningitis and necrotizing entercolitis in infants and has been associated with infant formulas. Five strains of E. sakazakii were inoculated individually into brain heart infusion broth and rehydrated or dehydrated infant milk formula and exposed to ionizing radiation. E. sakazakii strains in brain heart infusion broth and rehydrated infant milk formula (RIMF) were exposed to irradiation dose of up to 1 kGy while strains in dehydrated infant milk formula (DIMF) were exposed to irradiation dose of up to 9 kGy. The D₁₀-values were determined by using a linear regression model. Average calculated D₁₀-values ranged from 0.21 to 0.29 kGy, 0.24 to 0.37 kGy, and 1.06 to 1.71 kGy in brain heart infusion broth, RIMF, and DIMF, respectively. The results obtained from this study will be useful for powdered infant milk formula industries to reduce the risk associated with E. sakazakii .