一种简易的γ光子剂量学用组织模拟材料

研制了一种由石腊、碳、硫及软木粉组成的γ组织模拟材料,其有效原子序数Z_e=7.51;电子密度为ρ_e=3.34×10~(23)e/g:质量密度ρ=1.003g/cm~3,能同时满足与肌肉组织基本一致的条件,该材料可适用于制成模体,在一些辐射实验研究中也是一种水的较好替代物。     

Type of bacterial starter culture,aging and fermentation effects on some characteristics of inoculated beef sausages

Beef sausage mixes were inoculated with either Pediococcus acidilactici with Staphylococcus xylosus or P. acidilactici with S. carnosus, subdivided and then held for 0, 24, 48 or 72 h at 8–10 °C prior to fermentation. After aging (pre-fermentation holding), the mixes were fermented for 16 h ending at 41 °C. Moisture, protein and fat contents of all sausage mixes did not differ due to holding effects over all starter cultures. The pH of mixes followed the same pattern for all mixes, declining (p < 0.05) from approximately 5.8 to pH 5.2–5.3 at 72 h aging and to 4.4–4.5 after fermentation. Total acidity of the mixes followed an inverse pattern to pH, increasing (p < 0.05) after fermentation although there was no effect due to type of starter culture. Aging had no effect on nonprotein nitrogen (NPN) content as ΔNPN among all cultures. After fermentation, however, sausages held 72 h and inoculated with S. carnosus had higher NPN contents compared to P. acidilactici alone (p < 0.05) and with S. xylosus (p < 0.10). The same effects of starter cultures on changes in total amino acid concentration were observed. Concentrations of individual amino acids showed increases depending on pre-fermentation aging period (0 h versus 72 h) followed by fermentation.     

电离辐射的生物效应——ICRP 60号出版物附件B内容简介及讨论

本文简要介绍了国际放射防护委员会(ICRP)1990年建议书(ICRP 60号出版物)附件 B 的主要内容,并对危险系数、组织权重因子及新的放射性核素年摄入量限值等有关问题进行了初步讨论。     

药用植物白芍愈伤组织中产芍药双苷的研究(英文)

In order to facilitate the preparation of paeoniflorin (PF) and albiflorin (AF), two chief bioactive constituents in Paeonia lactiflora Pal (PL), induction and culture of callus from PL were studied. With a modified woody plant medium supplemented with 0.5 mg·L?1 6-benzylaminopurine, 1.0 mg·L?1 naphthylacetic acid, 0.1 mg·L?1 thidiazuron and 30 g·L?1 sucrose, callus was induced from four kinds of explants:leaf, stems, petiole, and root. The potency to form callus varies between different explants and leaf explants exhibits the highest capacity (100%). On the other hand, root-derived cal us (R-callus) produces the highest level of total amount of PF and AF, 31.8 mg·g?1 dry mass, which is higher than the corresponding level in the root of field cultivated PL. Further-more, the time needed is only 40 days, remarkably shorter than the cultivation time of PL, about 4–5 years. Higher accumulation levels of PF and AF with shorter production time indicate that cal us culture of PL is a promising powerful tool for production of PF and AF in the future.     

Nitrous oxide production kinetics during nitrate reduction in river sediments

A significant amount of nitrogen entering river basins is denitrified in riparian zones. The aim of this study was to evaluate the influence of nitrate and carbon concentrations on the kinetic parameters of nitrate reduction as well as nitrous oxide emissions in river sediments in a tributary of the Marne (the Seine basin, France). In order to determine these rates, we used flow-through reactors (FTRs) and slurry incubations; flow-through reactors allow determination of rates on intact sediment slices under controlled conditions compared to sediment homogenization in the often used slurry technique. Maximum nitrate reduction rates (R_m) ranged between 3.0 and 7.1 μg N g⁻¹ h⁻¹, and affinity constant (K_m) ranged from 7.4 to 30.7 mg N-NO₃⁻ L⁻¹. These values were higher in slurry incubations with an R_m of 37.9 μg N g⁻¹ h⁻¹ and a K_m of 104 mg N-NO₃⁻ L⁻¹. Nitrous oxide production rates did not follow Michaelis-Menten kinetics, and we deduced a rate constant with an average of 0.7 and 5.4 ng N g⁻¹ h⁻¹ for FTR and slurry experiments respectively. The addition of carbon (as acetate) showed that carbon was not limiting nitrate reduction rates in these sediments. Similar rates were obtained for FTR and slurries with carbon addition, confirming the hypothesis that homogenization increases rates due to release of and increasing access to carbon in slurries. Nitrous oxide production rates in FTR with carbon additions were low and represented less than 0.01% of the nitrate reduction rates and were even negligible in slurries. Maximum nitrate reduction rates revealed seasonality with high potential rates in fall and winter and low rates in late spring and summer. Under optimal conditions (anoxia, non-limiting nitrate and carbon), nitrous oxide emission rates were low, but significant (0.01% of the nitrate reduction rates).     

In situ grown fibrous composites of poly(dl-lactide) and hydroxyapatite as potential tissue engineering scaffolds

In situ grown hydroxyapatite (HA) within electrospun poly(dl-lactide) (PDLLA) fibers were initially investigated as potential tissue engineering scaffolds with respect to the mechanical performances, biomineralization capability, degradation behaviors, cell growth and differentiation profiles. The tensile strength and Young’s moduli of in situ grown composites (IGC) were 8.2 ± 1.1 and 63.5 ± 5.6 MPa, respectively, which were significantly higher than those of blend electrospun composites (BEC) with 25.2% of HA inoculation. The interactions between HA and matrix polymers were approved by the red-shifts of CO stretching and OH- stretching modes and the increases in glass transition temperatures of fibrous composites. The localization of apatite phase on the fiber surface improved the biomineralization capability and enhanced the morphological stability of the fibers and fibrous mats even when the degradation of matrix polymers was detected. The cell viability and alkaline phosphatase levels were significantly higher for composites IGC, indicating favorable scaffolds for cell proliferation and osteogenic differentiation.     

软组织内热治疗针体外温度变化的特点分析

目的研究软组织内热治疗针在体外的温度分布特点,为进一步研究其在体内温度分布打下基础。方法使用数字测温仪测量软组织内热治疗针在设定42％、50％、60％、80％下加热5min、10min、15min、20min时从针尖至针体末端每隔2cm处的温度。结果内热针针身温度分布分3段：针尖温度中等,距针尖2—6cm段温度较高,距针尖10cm到针体末端段温度较低。针尖到针身8cm段温度差别较小,与设定加热温度接近。针尖温度比设定加热温度低1-2℃。针身温度随加热时间的变化波动不明显。结论软组织内热治疗针在体外加热过程中,针身温度容易控制,稳定性好,针尖温度与设定温度接近。     

Effect of Lactobacillus cultures on microbiological,chemical and odour changes during storage of rainbow trout fillets

The purpose of this study was to investigate the effect of applying two Lactobacillus protective cultures on microbiological, chemical and odour changes during storage of refrigerated vacuum‐packed rainbow trout (Oncorrynchus mykiss) fillets. Lactobacillus sakei CECT 4808 and Lb. curvatus CECT 904^T were inoculated individually or in combination into rainbow trout fillets. The samples were vacuum‐packed and stored at 4 ± 0.5 °C and were assessed during a 20‐day storage period for microbiological (Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria (LAB), H₂S‐producing bacteria, yeasts and moulds) and chemical (pH, total volatile basic nitrogen, lipid oxidation) parameters and off‐odour. Samples inoculated with Lb. sakei and with both strains had significantly (P≤0.05) lower counts of all microbiological spoilage indicator organisms (Enterobacteriaceae, Pseudomonas spp., H₂S‐producing bacteria, yeasts and moulds) than those inoculated with Lb. curvatus or the controls. All chemical parameters examined and off‐odour scores were also significantly (P≤0.05) improved in the samples inoculated with Lb. sakei or with both strains compared with those inoculated with Lb. curvatus or the controls. Lb. sakei generally showed a better preservative effect (P≤0.05) than the combination of strains. Inoculation with Lb. sakei CECT 4808 could provide an additional hurdle to improve shelf‐life of refrigerated vacuum‐packaged trout fillets, as inoculation with this strain resulted in extension of shelf‐life by 5 days. Furthermore, this strain showed some antioxidative ability, which could retard lipid oxidation in fish. Copyright © 2006 Society of Chemical Industry     

混合发酵剂的筛选及对发酵猪肉香肠加工特性及安全性能的影响

通过比较不同比例植物乳杆菌与木糖葡萄球菌的复合发酵剂的生长活性、产酸能力、耐盐及耐亚硝酸盐特性,筛选最佳复配比例的混合发酵剂并制作发酵香肠。旨在探究复合发酵剂对发酵香肠理化品质及生物胺的影响。结果表明:植物乳杆菌与木糖葡萄球菌复合比为1:1时,具有较好的生长、产酸、耐盐及耐亚硝酸盐能力。接种1:1的植物乳杆菌与木糖葡萄球菌混合发酵剂制备的香肠pH值下降速率快于单一乳酸菌组和空白对照组;发酵结束混合组pH值降为4.95,显著低于对照组和单一组(P<0.05);pH值下降改变了蛋白质与水分结合能力、促使香肠Aw随之降低,使得混合组Aw低于单一组和对照组;相比香肠色泽,3组差异不显著(P>0.05)。成熟后期混合组尸胺和组胺检出量均低于单一组和对照组。由研究结果可知添加复合发酵剂有助于提高香肠安全性、缩短发酵成熟周期。