Synthesis,photoluminescence properties and energy transfer behavior of color-tunable fluorapatite phosphor Sr9Gd(PO4)5(SiO4)F2:Tb3+/Sm3+

Tb³⁺-Sm³⁺ co-doped Sr₉Gd(PO₄)₅(SiO₄)F₂ (SGPSF) phosphors were prepared through a solid-state reaction, and their luminescence properties as well as energy transfer mechanism have been investigated in detail. The SGPSF:Tb³⁺, Sm³⁺ phosphors system could be efficiently excited at wavelengths ranging from 200 to 500 nm, which is well matched with the spectra of near ultraviolet chips. The emission of SGPSF:Tb³⁺, Sm³⁺ phosphor covers the entire visible region with sharp peaks in the blue, green, and red regions. The emission color of SGPSF:Tb³⁺, Sm³⁺ could be adjusted from green (0.275, 0.378) to red (0.519, 0.295) by controlling the doping content of Sm³⁺/Tb³⁺.     

Isolation and characterization of Listeria monocytogenes in Chinese food obtained from the central area of China

The objective of this study was to investigate the prevalence and characteristics of Listeria monocytogenes isolated from Chinese food, including frozen dumplings, flavored raw meat, roasted meat, braised meat, and a cold vegetable dish with sauce. A total of 900 food samples were collected from supermarkets, open-air markets, and delicatessens in three large cities in the central area of China to examine the presence of L. monocytogenes; 21 (2.3%) of the samples were positive for this pathogen. Among the different samples, braised meat showed the highest L. monocytogenes detection rate (4.4%). Samples obtained from delicatessens showed a much higher L. monocytogenes contamination rate (8.3%) than those from open-air markets (6.7%) or supermarkets (0%). Multilocus sequence typing (MLST) analysis indicated that the 21 bacterial isolates belonged to 12 ST subgroups. ST5 was the largest and contained 7 isolates (33.3%); it was followed by ST474, ST121 and ST9 (each containing 2 isolates [10.5%]). Antibiotic susceptibility analysis showed that the 21 L. monocytogenes isolates were thoroughly resistant to cefoxitin but highly susceptible to doxycycline and ciprofloxacin. The presence of 10 virulence genes was evaluated by PCR, which showed that inlA, inlC, inlJ, prfA, hlyA, and plcB were present in all isolates and that inlB, actA, plcA and iap were present in 71.4–90.5% of the isolates. This study provides a useful reference for risk assessment and control of L. monocytogenes contamination in Chinese food and for the treatment of clinical listeriosis.     

Synthesis and photoluminescent properties of high-efficient color-tunable Ba3Y2B6O15: Ce3+, Tb3+ phosphors

High-efficient Ce³⁺/Tb³⁺ co-doped Ba₃Y₂B₆O₁₅ phosphors with multi color-emitting were firstly prepared, and their structural and luminescent properties were studied by XRD Rietveld refinement, emission/excitation spectra, fluorescence lifetimes as well as temperature-variable emission spectra. Upon 365?nm excitation, the characteristic blue Ce³⁺ band along with green Tb³⁺ peaks were simultaneously found in the emission spectra. Moreover, by increasing concentration of Tb³⁺, a blue-to-green tunable emitting color could be realized by effective Ce³⁺→Tb³⁺ energy transfer. Furthermore, all Ba₃Y₂B₆O₁₅: Ce³⁺, Tb³⁺ phosphors exhibit high internal quantum efficiency of ~?90%, while the temperature-variable emission spectra reveal that the phosphors possess impressive color stability as well as good thermal stability (T₅₀ =?~?120?°C). The results indicate that these efficient color-tuning Ba₃Y₂B₆O₁₅: Ce³⁺, Tb³⁺ might be candidate as converted phosphor for UV-excited light-emitting diodes.     

广东省沿海常见海水鱼中多不饱和脂肪酸及其与甲基汞共摄入对神经发育的风险-获益评估

目的分析广东省沿海常见海水鱼的脂肪酸含量和甲基汞(MeHg)污染水平,定量评估摄入海水鱼对神经发育的风险-获益,为广东省海水鱼的膳食指导提供科学依据。方法在广东省沿海地区采集20种常见海水鱼样品(共174尾),检测各种脂肪酸和MeHg的含量,并采用联合国粮食与农业组织/世界卫生组织(FAO/WHO)提出的以智力商数(IQ)值为健康终点的风险-获益定量评估模型,评估海水鱼对神经发育的净健康效应。结果 20种海水鱼总脂肪酸含量均值为0.73～19.95 g/100 g,多不饱和脂肪酸(PUFA)为0.18～5.82 g/100 g,总n-3 PUFA为135.69～2 232.74 mg/100 g,二十二碳六烯酸(DHA)为73.61～1 334.00 mg/100 g,二十碳五烯酸(EPA)为43.76～945.67 mg/100 g,所有海水鱼样品的MeHg含量均未超过GB 2762—2017《食品安全国家标准食品中污染物限量》。基于广东省居民海水鱼消费量均值(100 g/周)、P97.5消费量(830 g/周)、推荐消费量(280 g/周)三种消费模式食用不同鱼种的IQ值净效应为0.5～5.7、3.8～5.6和1.3～5.7,仅在830 g/周的极端消费水平下摄入海鳗带来的MeHg暴露量超过了暂定每周耐受摄入量(PTWI,1.6μg/kg BW)。结论按中国居民膳食指南的推荐量消费广东省沿海常见海水鱼,均能对新生儿和婴幼儿带来一定的IQ值净增长效应,但对MeHg含量相对较高的鱼种(如海鳗)需注意食用频率不宜过大。     

Generation Adequacy: Who Decides?

While market-based methods for generation expansion are the preferred long-term approach, there is currently too much uncertainty regarding how consumers and suppliers will respond to spot price signals. Therefore, policymakers should encourage demand-side experiments and investments to ensure that, when prices rise, customers will be able to respond.     

Automatic devices' resolution in nuclear emulsion observation

Some results on the precision obtainable using automatic devices in nuclear emulsion measurements and simplified methods for their application in standard work are presented.     

2015—2020年我国食用植物油质量安全风险因素分析

保障食用油质量安全一直是我国食品安全监管工作的重点和难点。基于2015—2020年2 701 份我国食用植物油抽检不合格数据，运用内容分析法对不合格植物油的品种、包装规格、产地和产业链主体特征进行了初步分析，对植物油不合格的原因进行了探讨。结果表明：过氧化值和酸值超标、苯并(a)芘超标、黄曲霉毒素B1超标、溶剂残留量超标、非法添加乙基麦芽酚和脂肪酸组成不合格是导致我国食用植物油质量安全问题的主要风险因素。运用交叉分析法和方差分析法分别识别了食用植物油质量安全风险因素在不同植物油品种、包装规格、产地和产业链主体中检出频率和检测值的差异，旨在为采取更具针对性的监管措施应对食用植物油质量安全风险，进而提高食用植物油质量安全水平提供借鉴。     

Structural aspects of lithium insertion in transition metal oxide electrodes

There is a considerable lack of detailed information on the structure of lithiated phases of popular-consensus positive electrode materials for lithium/polymer and lithium-ion/polymer batteries. Having illustrated this phenomenon for the specific cases of LiMn₂O₄ and V₆O₁₃, some suggestions are made to present the problem in a more general context. The need for single-crystal diffraction studies is indicated.