排序方式: 共有67条查询结果,搜索用时 144 毫秒
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建立婴幼儿营养米粉中黄曲霉毒素B1的高效液相色谱荧光检测器测定方法。样品以甲醇–水(体积比70∶30)溶液匀质提取,过黄曲霉毒素B1免疫层析亲和柱净化,经CNW Athena C18色谱柱分离和光化学柱后衍生反应器衍生后,用带有荧光检测器的高效液相色谱仪测定。采用峰面积外标法定量黄曲霉毒素B1含量。黄曲霉毒素B1在0~10μg/L的浓度范围内线性关系良好,相关系数为0.999 8,检出限为0.25μg/kg。在3个添加水平下加标回收率为97.7%~106.9%,测定结果的相对标准偏差为1.7%(n=6)。该方法的灵敏度、准确度、精密度均符合黄曲霉毒素B1的检测技术要求,适用于婴幼儿营养米粉中黄曲霉毒素B1的日常检测。 相似文献
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文章简要叙述了有关大质量恒星形成的理论以及相关观测证据。目前大质量恒星形成的理论主要有两种,即吸积说和并合说.吸积说认为,大质量星可能与小质量星形成于相似的过程;并合说主张大质量星可能是由小质量年轻星碰撞合并而成.解决这两种理论争论的关键在于在大质量星附近能否观测到吸积盘的存在,最新的观测表明大质量星更有可能是通过吸积增加自身的质量,但最终解决这一问题可能还需要更多的观测证据。文章还提出了一些本领域尚未解决的问题,为感兴趣的研究者提供参考。 相似文献
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Ilektra Sperdouli Julietta Moustaka Georgia Ouzounidou Michael Moustakas 《Molecules (Basel, Switzerland)》2021,26(14)
We investigated flavonoid accumulation and lipid peroxidation in young leaves (YL) and mature leaves (ML) of Arabidopsis thaliana plants, whose watering stopped 24 h before sampling, characterized as onset of drought stress (OnDS), six days before sampling, characterized as mild drought stress (MiDS), and ten days before sampling, characterized as moderate drought stress (MoDS). The response to drought stress (DS) of photosystem II (PSII) photochemistry, in both leaf types, was evaluated by estimating the allocation of absorbed light to photochemistry (ΦPSII), to heat dissipation by regulated non-photochemical energy loss (ΦNPQ) and to non-regulated energy dissipated in PSII (ΦNO). Young leaves were better protected at MoDS than ML leaves, by having higher concentration of flavonoids that promote acclimation of YL PSII photochemistry to MoDS, showing lower lipid peroxidation and excitation pressure (1 − qp). Young leaves at MoDS possessed lower 1 − qp values and lower excess excitation energy (EXC), not only compared to MoDS ML, but even to MiDS YL. They also possessed a higher capacity to maintain low ΦNO, suggesting a lower singlet oxygen (1O2) generation. Our results highlight that leaves of different developmental stage may display different responses to DS, due to differential accumulation of metabolites, and imply that PSII photochemistry in Arabidopsis thaliana may not show a dose dependent DS response. 相似文献
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弗兰德斯互动分析系统可以量化课堂教学中的语言行为。以初中化学一节常态课为研究课例,基于弗兰德斯互动分析系统,结合教师他评和自评,从教学目标、教学内容、教学过程和教学效果等4方面进行了全面的分析与评价,并根据评价结果,针对教学目标制订、有效提问、科学的课堂语言结构的营造以及实验探究的实施等提出了可行性的有效策略,从而为青年教师通过教学实践来促进个人专业发展提供依据。 相似文献
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Xingran Cui Leirong Tian Zhengwen Li Zikai Ren Keyang Zha Xinruo Wei Chung-Kang Peng 《Entropy (Basel, Switzerland)》2020,22(11)
Heart rate variability (HRV) has been widely used as indices for autonomic regulation, including linear analyses, entropy and multi-scale entropy based nonlinear analyses, and however, it is strongly influenced by the conditions under which the signal is being recorded. To investigate the variability of healthy HRV under different settings, we recorded electrocardiograph (ECG) signals from 56 healthy young college students (20 h for each participant) at campus using wearable single-lead ECG device. Accurate R peak to R peak (RR) intervals were extracted by combing the advantages of five commonly used R-peak detection algorithms to eliminate data quality influence. Thorough and detailed linear and nonlinear HRV analyses were performed. Variability of HRV metrics were evaluated from five categories: (1) different states of daily activities; (2) different recording time period in the same day during free-running daily activities; (3) body postures of sitting and lying; (4) lying on the left, right and back; and (5) gender influence. For most of the analyzed HRV metrics, significant differences (p < 0.05) were found among different recording conditions within the five categories except lying on different positions. Results suggested that the standardization of ECG data collection and HRV analysis should be implemented in HRV related studies, especially for entropy and multi-scale entropy based analyses. Furthermore, this preliminary study provides reference values of HRV indices under various recording conditions of healthy young subjects that could be useful information for different applications (e.g., health monitoring and management). 相似文献
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婴幼儿谷类辅助食品是婴幼儿营养的重要能量来源,其主要原料为大米,而水稻极易从其生长的土壤和水中吸收重金属Cd积累到谷粒中,导致大米中Cd的残留浓度相对较高,从而对婴幼儿谷类辅助食品构成潜在威胁。提出了电感耦合等离子体串联质谱(ICP-MS/MS)测定婴幼儿谷类辅助食品中重金属Cd的新策略。样品经微波消解处理后,采用ICP-MS/MS进行测定。婴幼儿谷类辅助食品中Cd的测定所面临的质谱干扰主要来源于高浓度Mo所形成的Mo基多原子干扰离子(MoO+,MoN+,MoC+)以及Sn所形成的同量异位素(112Sn+,114Sn+,116Sn+)。针对这些干扰,在MS/MS模式下,分别采用H2,NH3/He和O2为反应气,考察不同Cd同位素的质谱干扰消除效果和分析灵敏度。结果表明,在H2和NH3/He反应模式下,H2和NH3均能与Mo基干扰离子发生质量转移反应,而不与Sn+反应,可选择110Cd+,111Cd+和113Cd+进行测定,但H2与Mo基干扰离子反应速度较慢,难以彻底消除高浓度Mo基质中对Cd的质谱干扰;在O2反应模式下,所有干扰离子均能与O2发生质量转移反应,虽然获得的分析灵敏度略低于NH3/He反应模式,但背景等效浓度(BEC)明显比NH3/He反应模式低。确定了以O2为反应气消除干扰测定Cd的最优分析方案。利用标准参考物质评价了方法的准确性,采用国标法(GB5009.268—2016)进行对比分析验证了方法的可靠性。结果表明,Cd的LOD为2.03~13.4 ng·L-1,标准参考物质的测定值与认定值基本一致,在95%的置信水平,对比分析结果之间无显著性差异。方法的灵敏度高,结果准确可靠,适用于大批量婴幼儿谷类辅助食品中重金属Cd的高通量测定。 相似文献
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AbstractThe effectiveness of dairy treated wastewater (TWW) was evaluated, in comparison with tap water (TW), on a Tunisian olive orchard (Olea europea, cv Chemlali), irrigated manually (MI) and by surface dripping (SDI). To this purpose, tree growth, biomass and fruiting were monthly tested for a one-year period. Similar trunk diameters, nodes/tree, root lengths were obtained, independently of source and system of irrigation. Also, comparable tree length and leaf area, shoots/tree and biomass, were observed between TWW and TW plants. However, such parameters improved under SDI rather than MI. Fruiting occurred only in TWW and TW trees treated by MI. Concerning growth, biomass and fruiting, TWW represented a valid alternative source for the irrigation of olive orchard, especially in Tunisia, already facing the freshwater scarcity. Monitoring of soil, TWW, fruits and oil will be required to validate the use of such effluent for olive orchard irrigation. 相似文献