The acceptance of virtual environment (VE) technology requires scrupulous optimization of the most basic interactions in order to maximize user performance and provide efficient and enjoyable virtual interfaces. Motivated by insufficient understanding of the human factors design implications of interaction techniques and tools for virtual interfaces, this paper presents results of a formal study that compared two basic interaction metaphors for egocentric direct manipulation in VEs, virtual hand and virtual pointer, in object selection and positioning experiments. The goals of the study were to explore immersive direct manipulation interfaces, compare performance characteristics of interaction techniques based on the metaphors of interest, understand their relative strengths and weaknesses, and derive design guidelines for practical development of VE applications.
Abstract-Conventional database systems are designed for managing textual and numerical data, and retrieving such data is often based on simple comparisons of text/numerical values. However, this simple method of retrieval is no longer adequate for the multimedia data, since the digitized representation of images, video, or data itself does not convey the reality of these media items. In addition, composite data consisting of heterogeneous types of data also associates with the semantic content acquired by a user's recognition. Therefore, content-based retrieval for multimedia data is realized taking such intrinsic features of multimedia data into account. Implementation of the content-based retrieval facility is not based on a single fundamental, but is closely related to an underlying data model, a priori knowledge of the area of interest, and the scheme for representing queries. This paper surveys recent studies on content-based retrieval for multimedia databases from the point of view of three fundamental issues. Throughout the discussion, we assume databases that manage only nontextual/numerical data, such as image or video, are also in the category of multimedia databases.
We investigated the therapeutic effect of antilnphocyte serum (ALS) on clinically overt diabetes by using a nonobese diabetic (NOD) Immunotherapy with ALS. ALS was obtained by immunizing rabbits with a pool of lymph node cells prepared from NOD, C3H/He, DBA/2, and (C57BL/6 x A)F1 mice (11). A 0.4-ml injection of ALS was given intraperitoneally to diabetic NOD mice on days 0 (the first day of treatment regardless of the duration of diabetes) and +2. Control mice were given 0.4 ml ofnormal rabbit serum (NRS) on days 0 and +2. Blood glucose levels were monitored every 2-3 days initially and once a week thereafter. Achievement of euglycemia (<11 mM) and independence from exogenous insulin treatment after immunotherapy was defined as clinical remission.Immunotherapy with Monoclonal Antibodis (mAbs). Hybridoma cells producing anti-CD4 (anti-L3T4, clone GK 1.5) mAb were kindly provided by Kevin J. Lafferty (Barbara Davis Center for Juvenile Diabetes, Denver). Hybridomas producing anti-CD8 (anti-Lyt 2.1, clone 116-13.1, and antiLyt 2.2, clone 41-3.48) mAb were obtained from American Type Culture Collection. Ascites fluid that contained mAbs at -5 mg/ml was used. Diabetic NOD mice were treated with anti-CD4 mAb at 0.2 ml on days 0, 7, 14, and 21 and/or 0.1 ml of anti-CD8 (anti-Lyt 2.1) mAb on days 0 and 14. This treatment protocol has been shown (12) to achieve long-term removal of CD4' and/or CD8+ T lymphocytes from peripheral lymphoid organs in other inbred mouse strains. Control diabetic NOD mice were treated with 0.2 ml of anti-Lyt 2.2 mAb on days 0, 7, 14, and 21.Flow Cytometric Analysis. Peripheral lymph node cells were stained with fluorescein isothiocyanate conjugates of mAb 53-6.7 (anti-CD8) and phycoerythrin-conjugates of mAb GK1.5 (anti-CD4), both of which were obtained from Becton Dickinson. Two-color analysis was performed with a singlebeam flow cytometer, FACScan (Becton Dickinson) and the FACSCAN Research Software (Becton Dickinson).Islet Isolation and Transplantation. Because insulitis generally starts at 4 weeks of age (1), NOD islet donors were Abbreviations: NOD, nonobese diabetic; ALS, anti-lymphocyte serum; NRS, normal rabbit serum; mAb, monoclonal antibody.tTo whom reprint requests should be addressed at: CRI, New
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