1,721,796 research outputs found
Heterogeneity and differential expression of the r- aminobutyric acid A(GABAA)/benzodiazepine receptor in the avian brain during development.
No full textThe DR-tree: A main memory data structure for complex multi-dimensional objects
No full textAn efficient index structure for complex multi-dimensional object, is one of the most challenging requirements in non-traditional applications such as geographic information systems, computer-aided design, and multimedia databases. In this paper we first propose a main memory data structure for complex multi-dimensional objects. Then, we present an extension of the existing multi-dimensional index structure. Among existing multidimensional index structures, the popular R*-tree is selected. The R*-tree is coupled with the main memory data structure to improve the performance of spatial query processing. An analytical model is developed for our index structure. Experimental results show that the analytical model is accurate, the relative error being below 1.5%. The performance of our index structure is compared with that of a state-of-the-art index, structure by experimental measurements. Our index structure outperforms the state-of-the-art index structure due to its ability to reduce a large amount of storage.This research was supported by the basic research program (grant number 99-2-315-001-3)of the Korea Science and Engineering Foundation
Analysis of two-step index structure for complex spatial objects
No full textAn efficient index structure for complex spatial objects is one of the most challenging requirements in non-traditional applications such as geographic information systems (GISs), computer-aided design (CAD), and multimedia databases. In this paper we first propose an extension of an existing index structure called the two-step index structure (TSIS). The TSIS integrates two index structures, one for original objects and the other for their decomposed components. Then, we present a cost model that predicts the performance of the TSIS, In contrast to several earlier investigations on this subject which only considered the filter step, we take into account the performance of the refinement step. Experimental results show that the cost model is accurate, the relative error being below 15%. The performance of our index structure is compared with that of a state-of-the-art index structure by experimental measurements. Our index structure outperforms the state-of-the-art index structure due to its ability to reduce a large amount of storage, (C) 2000 Published by Elsevier Science Inc. All rights reserved
Design of a scalable and programmable sound synthesizer
No full textSound synthesis employed in many multimedia systems is a useful method to generate the sound of musical instruments. Although it has a long history of development, a few researches have been devoted to deriving efficient VLSI architectures. In this paper, we analyze the inherent dataflow of sound synthesis methods and propose a programmable VLSI architecture suitable for a scalable sound synthesizer. The sound quality and the level of polyphony can be enhanced only by increasing the operating speed and enlarging the memory. A fully integrated sound synthesis system is implemented as a prototype to verify the proposed architecture. The prototype chip fabricated in a 0.18-mu m CMOS process occupies 1.5 mm x 1.5 mm, and can synthesize a 64-polyphonic sound in real time. The power consumption ranges from 2.05 to 13.8 m W depending on the level of polyphony and the sound quality.1111sciescopu
An intronless gene encoding a poly(A) polymerase is specifically expressed in testis
No full textPrevious work demonstrated that a single pre-mRNA could generate multiple forms of mammalian poly(A) polymerase mRNAs by alternative splicing or alternative polyadenylation. A cDNA encoding a testis-specific poly(A) polymerase was isolated in this study. The transcription level of Papt in testis of a 2,weeks old mouse was much lower than that of the general poly(A) polymerase gene, Pnp. However, the transcription ratio of Papt to Pap was reversed in testis of a 4 weeks old mouse. Transient expression analysis showed that GFP-Papt fusion protein is present both in the nucleus and cytoplasm of HeLa cells. These results suggest that Papt is involved in polyadenylation of transcripts expressed during spermatogenesis. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved
Atomic-step rearrangement on Si(100) by interaction with antimony
No full textVarious domain structures of Sb:Si(100) surfaces with a miscut of 2 degrees were observed, depending on the Sb coverage and substrate temperature. A single domain of 2 x 1 phase was observed after deposition of 0.5 ML of Sb at a substrate temperature of 375 K, and a single domain of 1 x 2 phase appears after annealing at 600 K the surface on which similar or equal to 2-6 ML of Sb had been deposited at a substrate temperature of 375 K. A double domain of 1 x 2 and 2 x 1 phases appeared after deposition of 0.9 ML of Sb at high substrate temperatures (650-1000 K) or upon annealing the 1 x 2 single domain above 800 K. Also, a c(4 x 4) phase appeared via a 2 x 2 phase after annealing the 1 x 2 surface. Surface mixing, anisotropic stress, and the elimination of the reformed bonding in the S-B step are expected to be the main causes of the observed domain structures and reconstructions.This work was supported in part by the Centre for Molecular Science at KAIST and KOSEF
Spatial query optimization utilizing early separated filter and refinement strategy
No full textDue to the high complexity and large volume of spatial data, a spatial query is usually processed in two steps, called the filter step and the refinement step. However, the two-step processing of the spatial query has been considered locally in one spatial predicate evaluation at the query execution level. This paper presents query optimization strategies which exploit the two-step processing of a spatial query at the query optimization level. The first strategy involves the separation of filter and refinement steps not in the query execution phase but in the query optimization phase. As the second strategy, several refinement operations can be combined in processing a complex query if they were already separated, and as the third strategy several filter operations can also be combined. We call the optimization technique utilizing these strategies the Early Separated Filter And Refinement (ESFAR). This paper also presents an algebra, which is called the Intermediate Spatial Object Algebra (ISOA), and optimization rules for ESFAR. Through experiments using real data, we compare the ESFAR optimization technique with a traditional optimization technique which does not separate filter and refinement steps from the query optimization phase. The experimental results show that the ESFAR optimization technique generates more efficient query execution plans than the traditional one in many cases. (C) 2000 Published by Elsevier Science Ltd. All rights reserved
Reconstructions and step structures on vicinal Si(001) surfaces by interaction with Bi
No full textReconstructions and step structures on vicinal Bi:Si(001) surfaces are studied under various substrate temperatures and Bi coverages. The observed reconstructions are (2x1), (2x2), c(4x4), and (2x7) phases. For step distributions, alternative domain configurations with single layer steps are observed. The population ratios of A terrace to B terrace depend on the substrate temperatures. The observed reconstructions and step distributions are explained by the large size of the Bi atom compared with Si, the anisotropic stress tensor, and the local atomic structure in the S-B step.This work was supported in part by the Center for Molecular Science at KAIST and the
Korea Science and Engineering Foundation (KOSEF) (No. 95-0501-03-01-3)
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