Ce3+浓度对Er3+/Yb3+共掺K2YF5发光性质的影响

利用溶剂热法合成Er~(3+)/Yb~(3+)/Ce~(3+)共掺杂的K_2YF_5微晶.在980 nm红外激光激发下,微晶产生有效的可见上转换辐射及1.5μm近红外辐射.随着Ce~(3+)掺杂量的增加,上转换荧光逐渐减弱,而1.5μm红外光随Ce~(3+)掺杂浓度的增加先增加而后减弱,当Ce~(3+)掺杂浓度为4%时,1.5μm近红外辐射最强,约为不掺杂Ce~(3+)样品辐射强度的4倍.微晶发光性能的变化被归因于Er~(3+)、Ce~(3+)之间的能量交叉弛豫.结合掺杂离子的能级结构,对微晶的发光机理进行详细的讨论.     

Children's perseverative appearance-reality errors are related to emerging language skills

Two experiments explored the communicative bases of preschoolers' object appearance-reality (AR) errors. In Experiment 1, 3-, 4-, and 5-year-olds (N = 36) completed the AR test (with high- and low-deceptive objects), a control test with the same discourse structure but nondeceptive stimuli, and stimulus naming and memory tests. AR performance correlated positively with control (discourse) and naming test performance. Object deceptiveness had little effect. In Experiment 2, 3- and 4-year-olds (N = 64) completed AR tests that experimentally varied question phrasing and use of exemplar objects. Children also completed memory, vocabulary, and control tests (of verbal perseveration). AR performance variance was predicted by a composite perseveration score from three non-AR tasks, vocabulary, and exemplars. The results indicate that the discourse structure of the AR test elicits a perseverative tendency that is mediated by children's verbal knowledge.     

The "how" and "why" of the ancient Greek long jump with weights: a five-fold symmetric jump in a row?

A plausible explanation for the ancient long jump records from Greek antiquity is sought on the basis of pictorial and written sources, and corroborated with practical tests. Ancient sources report that athletes jumped more than 15 m with weights in their hands, which enabled them to jump further than without these weights. It is proposed that the ancient Greek long jump was a continuous succession of five standing broad jumps, in which the landing phase of one jump was also the countermovement for the next jump. Four trained athletes jumped further with (14.64 +/- 0.76 m, range 13.64-15.63 m) than without weights (13.88 +/- 0.70 m, range 12.60-14.75 m; P = 0.001). These results show that this technique is executable, fits with ancient written and pictorial sources, and allows trained modern athletes to jump distances well over 15 m. The extra distance jumped when using weights may be due to changes in the position of the jumper's centre of mass at take-off and at landing, and an increase in take-off velocity stemming from several biomechanical mechanisms.     

Evidence for the interchangeability of an avoidance behavior and a negative occasion setter

Recent research on avoidance behavior provided evidence that such behavior can function as a negative occasion setter. We tested this hypothesis further by investigating whether the modulatory function of a stimulus occasion setter transfers selectively to a relation previously modulated by an avoidance behavior, and whether the modulatory function of an avoidance behavior transfers selectively to a relation previously modulated by a stimulus occasion setter. The three experiments reported in this article provided evidence to support this hypothesis. Furthermore, the results of Experiment 1 suggested that the presence of counterconditioning trials is not a necessary condition for an avoidance behavior to function as a negative occasion setter. All three reported experiments support the occasionsetting account of avoidance behavior.     

安徒生:世界儿童文学的太阳

1 Hans Christian Andersen was born on April 2,1805,in 1)Odense,Denmark.He was an author and poet particularly known for his children's fairy tale stories.Andersen was the first Danish author to 2)emerge from 3)poverty and be recognized during his lifetime.He was 4)acclairned for having delighted children worldwide,receiving honors from royalty.Many of his stories,including "The Ugly Duckling" and "The Princess and the Pea," remain classics of the genre.He died in 5)Copenhagen on August 4,1875.     

2．荷兰莱顿大学2020年未来发展宣言书

教师和学生为了研究和教学目的需要大量的、高质量的数字化资料，包括历史资料，最好是完整的人类记录。这些数字资源应该是可信赖的、可检索到的、并以有意义的方式组织起来。此外，教师和学生希望对这些资料进行注释、汇集、拆分、关联、插入内部链接，作为其学术研究或学习活动的一部分。而那些水平更高的研究专家们希望使用更先进的技术，如数据和文本挖掘技术、能够验证假说或提高他们研究水平的工具。     

Deafness and attention in deaf children

The study shows the differences between hearing parents and deaf instructors interacting with deaf children and directing their attention. Data were collected at home and at a service for special needs in Bristol, England. The mother or instructor was asked to play naturally with the child with the toys provided. When the child's attention was focused during their play, the mother or instructor had to try to direct the child's attention to each of the toys. The results suggest that both groups (mothers and instructors) were effective in directing attention to objects not in the immediate area of play; however, hearing mothers were more successful than deaf instructors.     

A pilot project of a cancer patient library in Italy: results of a customer-satisfaction survey and its products

AIMS: The purpose of this study is to determine the degree of satisfaction of users of the Cancer Information Point section of the Library for Patients (CIP-LP), active since 1998 at the National Cancer Institute of Aviano, Italy. The CIP-LP is based on a skilled intermediary, adequate informative material and a specific location, within the Scientific Library of the Institute. PATIENTS AND METHODS: A survey was developed to assess service functionality and quality from the users' viewpoint. During a 6-month period, a questionnaire was mailed to 194 patients and relatives who previously used the CIP-LP; 113 (58%) were returned and processed. RESULTS: Of the respondents, 91% were pleased with the CIP-LP and 95% would recommend the service to other people. The information obtained contributed to a clearer understanding of the illness and treatment (45% as first answer) and a better control of the situation (33%). Fifty-one per cent evaluated the information received as 'good', 42%'excellent' and 4%'of sufficient quality'. CONCLUSION: This survey shows the appreciation and usefulness in the users' perception of a specific hospital library for cancer patients and their relatives, providing an information service supplementary to doctor-patient communication.     

Birth in an ordinary instant

Our daily lives are a series of ordinary moments and unnoticed thresholds-times that define us in ways we often do not give much attention. While we consider childbirth to be one of life's extra-ordinary events, the hours of labor and birth need not be dramatic (or traumatic) ones. I describe a quiet, well-supported birth in the Netherlands that is cause for celebration of the beauty of an ordinary instant that can define and enrich the human experience.