国产十种乌头的染色体研究   总被引：1，自引：0，他引：1  

商效民  李正理 《中国科学院研究生院学报》1984,22(5):378-385

本文描述了我国产毛茛科乌头属的10个种的染色体数目和形态。  根据该属染色体基 数为8(x＝8)，可将这些种归为二倍体、四倍体、六倍体和八倍体种。  10种乌头的染色体在数目、大小、结构上表现出相关性。其中具根状茎而多年生的种多为二倍体，染色体形态较大，第3-7号多为近端着丝点(st)染色体, 具块茎而二年生的种多为多倍体，染色体形态较小，第3-7号多为近中着丝点(sm)染色体。染色体演化方向可能是二倍体→多倍体、大→ 小、st→sm。这进一步证明根状茎种较块茎种原始。根据染色体数目和形态，又可将这些种的染色体分为两类。这进一步支持了目前分类学上的牛扁亚属和乌头亚属的划分。本文还讨论了这些种的有关分类问题。  相似文献   

Unsupervised word sense disambiguation for Korean through the acyclic weighted digraph using corpus and dictionary     

Yeohoon Yoon  Choong-Nyoung Seon  Songwook Lee  Jungyun Seo 《Information processing & management》2006

Word sense disambiguation (WSD) is meant to assign the most appropriate sense to a polysemous word according to its context. We present a method for automatic WSD using only two resources: a raw text corpus and a machine-readable dictionary (MRD). The system learns the similarity matrix between word pairs from the unlabeled corpus, and it uses the vector representations of sense definitions from MRD, which are derived based on the similarity matrix. In order to disambiguate all occurrences of polysemous words in a sentence, the system separately constructs the acyclic weighted digraph (AWD) for every occurrence of polysemous words in a sentence. The AWD is structured based on consideration of the senses of context words which occur with a target word in a sentence. After building the AWD per each polysemous word, we can search the optimal path of the AWD using the Viterbi algorithm. We assign the most appropriate sense to the target word in sentences with the sense on the optimal path in the AWD. By experiments, our system shows 76.4% accuracy for the semantically ambiguous Korean words.  相似文献   

Optimization of some factors affecting the performance of query expansion     

Young Mee Chung  Jae Yun Lee 《Information processing & management》2004,40(6):29

This paper examines the factors affecting the performance of global query expansion based on term co-occurrence data and suggests a way to maximize the retrieval effectiveness. Major parameters to be optimized through experiments are term similarity measure and the weighting scheme of additional terms. The evaluation of four similarity measures tested in query expansion reveal that mutual information and Yule's Y, which emphasize low frequency terms, achieve better performance than cosine and Jaccard coefficients that have the reverse tendency. In the evaluation of three weighting schemes, similarity weight performs well only with short queries, whereas fixed weights of approximately 0.5 and similarity rank weights were effective with queries of any length. Furthermore, the optimal similarity rank weight achieving the best overall performance seems to be the least affected by test collections and the number of additional terms. For the efficiency of retrieval, the number of additional terms needs not exceed 70 in our test collections, but the optimal number may vary according to the characteristics of the similarity measure employed.  相似文献   

Parsimonious translation models for information retrieval     

Seung-Hoon Na  In-Su KangJong-Hyeok Lee 《Information processing & management》2007

In the KL divergence framework, the extended language modeling approach has a critical problem of estimating a query model, which is the probabilistic model that encodes the user’s information need. For query expansion in initial retrieval, the translation model had been proposed to involve term co-occurrence statistics. However, the translation model was difficult to apply, because the term co-occurrence statistics must be constructed in the offline time. Especially in a large collection, constructing such a large matrix of term co-occurrences statistics prohibitively increases time and space complexity. In addition, reliable retrieval performance cannot be guaranteed because the translation model may comprise noisy non-topical terms in documents. To resolve these problems, this paper investigates an effective method to construct co-occurrence statistics and eliminate noisy terms by employing a parsimonious translation model. The parsimonious translation model is a compact version of a translation model that can reduce the number of terms containing non-zero probabilities by eliminating non-topical terms in documents. Through experimentation on seven different test collections, we show that the query model estimated from the parsimonious translation model significantly outperforms not only the baseline language modeling, but also the non-parsimonious models.  相似文献   

An empirical study of query expansion and cluster-based retrieval in language modeling approach     

Seung-Hoon Na  In-Su Kang  Ji-Eun Roh  Jong-Hyeok Lee 《Information processing & management》2007

The term mismatch problem in information retrieval is a critical problem, and several techniques have been developed, such as query expansion, cluster-based retrieval and dimensionality reduction to resolve this issue. Of these techniques, this paper performs an empirical study on query expansion and cluster-based retrieval. We examine the effect of using parsimony in query expansion and the effect of clustering algorithms in cluster-based retrieval. In addition, query expansion and cluster-based retrieval are compared, and their combinations are evaluated in terms of retrieval performance by performing experimentations on seven test collections of NTCIR and TREC.  相似文献   

Library Jargon Creates Barriers for Potential Users of Health Library and Information Services     

Helen Kiely 《Health information and libraries journal》2020,37(3):228-232

This paper is based on Helen Kiely’s Masters dissertation on MA in Library and Information Service Management, successfully completed at the University of Sheffield in 2018. The aim of the study was to explore the extent to which users of a health care library service understood common terminology used by clinical librarians/information professionals. A survey was developed based on the terminology used for common services and was distributed to staff and students at an acute NHS Foundation Trust. One hundred and eight people participated over a four week period and were asked to provide definitions to the terms. Analysis of the responses for accuracy and common themes indicates that jargon can be a barrier to user access and recommendations are made with respect to the need for outreach to users and the language used in this practice for creating better accessibility. F.J.  相似文献   

In search of a new, linguistically and culturally sensitive paradigm in deaf education     

Simms L  Thumann H 《American annals of the deaf》2007,152(3):302-311

For more than a century, educators have recognized the low academic achievement of deaf children in America. Teacher training programs in deaf education historically have emphasized medical-pathological views of deaf people and deaf education rather than appropriate pedagogies that draw upon and build on deaf students' linguistic and cultural knowledge. A recent and growing interest in educating deaf children bilingually acknowledges the value of American Sign Language and English in the classroom. The authors address the dire need for prospective teachers and teacher educators to rethink their views of deaf people and, in doing so, rethink the teaching methodologies in deaf education.  相似文献   

Children with autism illuminate the role of social intention in word learning   总被引：2，自引：0，他引：2  

Parish-Morris J  Hennon EA  Hirsh-Pasek K  Golinkoff RM  Tager-Flusberg H 《Child development》2007,78(4):1265-1287

To what extent do children with autism (AD) versus typically developing children (TD) rely on attentional and intentional cues to learn words? Four experiments compared 17 AD children (M age=5.08 years) with 17 language- and 17 mental-age-matched TD children (M ages=2.57 and 3.12 years, respectively) on nonverbal enactment and word-learning tasks. Results revealed variability in all groups, but particularly within the AD group. Performance on intention tasks was the most powerful predictor of vocabulary in the AD group but not in the TD groups. These findings suggest that word learning cannot be explained exclusively by either attentional or intentional processes, and they provide evidence of a special role for intentional understanding in the vocabulary development of AD children.  相似文献   

Investigation of potential gender bias in the peer review system at Reproduction     

Marie Biolková  Tom Moore  Karen Schindler  Karl Swann  Andy Vail  Lindsay Flook  Helen Dick  Greg Fitzharris  Christopher A. Price  Norah Spears 《Learned Publishing》2023,36(1):25-30

  相似文献   

Religious Development in African American Adolescents: Growth Patterns That Offer Protection     

Daniel B. Lee  Enrique W. Neblett 《Child development》2019,90(1):245-259

Although religiosity promotes resilient outcomes in African American (AA) adolescents, there is a lack of research that examines the protective role of religious development in the context of stressful life events (SLEs). In 1,595 AA adolescents, a cohort-sequential design was used from ages 12 to 18 to examine subtypes of religiosity, as well as distinct developmental patterns within subtypes. The protective role of religious development was also examined in the context of SLEs. The study findings indicated two subtypes of religiosity—extrinsic and intrinsic religiosity—as well as low and high developmental patterns in the identified subtypes. Furthermore, the protective influence of extrinsic and intrinsic religiosity gradually diminished from age 12 to 18 in the context of SLEs.  相似文献