1,721,125 research outputs found
Partial rollback in object-oriented/object-relational database management systems with dual buffer
No full textPartial rollback mechanism has been widely supported by many database management systems (DBMSs). It allows a transaction to be rolled back partially, that is, only back to a certain savepoint set by the user. A partial rollback, however, makes the DBMS buffer management complicated because it requires the DBMS to restore the state of not only the database but also the buffers. There are several literatures addressing such a partial rollback in a relational DBMS (RDBMS), which has page buffer only. However, to our knowledge, there exists no literature addressing it in an object-oriented/relational DBMS (OO/ORDBMS). The RDBMS partial rollback scheme cannot be applied to OO/ORDBMSs directly. The reason is that, unlike RDBMSs, many OO/ORDBMSs use dual buffer which consists of object buffer and page buffer. In this paper, we thoroughly study the partial rollback schemes for OO/ORDBMSs with dual buffer. For this, we propose four different partial rollback schemes which are based on (single) page buffer, (single) object buffer, dual buffer using a soft log, and dual buffer using shadows, respectively. The schemes proposed are practical enough to be implemented in a real OO/ORDBMS. The results of performance evaluations show that the dual buffer-based scheme using shadows achieves the best performance. (c) 2005 Elsevier B.V. All rights reserved
Catalytic CO2 hydrogenation to formic acid over carbon nanotube-graphene supported PdNi alloy catalysts
No full textPure formic acid was successfully produced via CO2 hydrogenation for the first time over a heterogeneous catalyst of PdNi alloy on a carbon nanotube-graphene (CNT-GR) support in water as an eco-friendly solvent without a base additive. The highest formic acid yield obtained was 1.92 mmol with a turnover number of 6.4 and a turnover frequency of 1.2 x 10(-4) s(-1) under mild reaction conditions of 40 degrees C and 50 bar. Alloying Pd with Ni brought a significant enhancement in catalytic activity compared to the monometallic Pd catalyst. In addition, the CNT-GR composite as a catalytic support improved the dispersion of Pd-Ni alloy particles, which exhibited good stability under the reaction conditions.1126sciescopu
Coke tolerance of Ni/Al2O3 nanosheet catalyst for dry reforming of methane
No full textIn the dry reforming of methane with CO2, coke formation in the catalyst during the reaction is the most serious problem. As a coke resistant reforming catalyst, Ni/Al2O3 nanosheets were synthesized by a solvothermal method. The synthesized nanosheet catalysts demonstrated highly stable methane conversion, although the amount of deposited carbon was similar to that in Ni/Al2O3 with a random morphology that deactivated rapidly. The critical effect of nanosheet morphology has been demonstrated on the coke tolerance of the nickel-based dry reforming catalyst.clos
THE FUZZY SET MODEL-BASED ON N-ARY POSITIVELY COMPENSATORY OPERATORS
No full textWe have enhanced the fuzzy set model by replacing MIN and MAX operators with binary positively compensatory operators. Though the binary operators provide higher retrieval effectiveness, they can give different document values for logically equivalent queries, e.g. t1 AND (t2 AND t3) and (t1 AND t2) AND t3. This is because they do not satisfy the basic boolean processing laws such as distributive. In this paper we propose n-ary positively compensatory operators by extending the binary forms, which alleviate the aforementioned problem. We show through performance evaluation that the n-ary operators provide better retrieval effectiveness than the binary
A conflict detection mechanism for authorization using intention types in object-oriented database systems
No full textMany object-oriented database systems have used the notion of implicit authorization to avoid the overhead caused by explicitly storing all authorizations for each object. In implicit authorization, it is very important to detect efficiently conflicts between existing authorizations and new authorizations to be added. In this article we propose a conflict detection mechanism in the OODBMSs using implicit authorization with the notion of intention type authorization. When Lye grant an authorization on a node n in the database granularity hierarchy, the existing method is inefficient in determining the conflicts since it needs to examine all authorizations on the descendants of the node n. In contrast, our mechanism has the advantage of detecting the conflicts at the node n where an explicit authorization is to be granted without examining any authorizations below the node n. Thus, the proposed mechanism can detect a conflict with the average time complexity of O(d), which is smaller than O(m(d)) of existing methods, where m is the number of children nodes at an arbitrary level and d is the difference of levels between the node with an existing explicit authorization and the higher node where an explicit authorization is to be granted. We also show that the additional storage overhead of storing all authorizations is negligible when compared with the total number of all explicit authorizations
Vasopressin-Sensitive Aqp2 Regulation Mediated by the TAZ-NR4A1 Axis in Renal Collecting Duct Cells
No full textRegulation of aquaporin-2 (Aqp2) gene is essential for body water homeostasis. This study investigated how TAZ (a transcriptional coactivator with PDZ-binding motif, Wwtr1) controls vasopressin-driven AQP2 expression. AQP2 expression was studied using collecting duct-specific TAZ-knockout (TAZ(f/f); HoxB7Cre) mice and siRNA-mediated knockdown of TAZ in vasopressin-responsive mpkCCDc11 cells. Downstream factors of TAZ were identified using transcriptomics and bioinformatics. The TAZ(f/f); HoxB7Cre mice demonstrated polyuria and a significant decrease in AQP2 abundance in the kidney cortex and the outer medulla. dDAVP treatment (10(-9) M, 24 h) on mpkCCDc11 cells significantly increased AQP2 mRNA and protein levels. However, siRNA-mediated TAZ knockdown (TAZ-KD) markedly attenuated these effects without affecting cAMP levels. Immunocytochemical analysis revealed a substantial decrease in AQP2 immunolabeling intensity in TAZ-KD cells following dDAVP stimulation. RNA sequencing analysis identified 1370 and 1985 differentially expressed genes in TAZ-KD cells under basal conditions and after dDAVP treatment, respectively. Among 17 previously identified transcription factor (TF) candidates, seven (Nr4a1, Cebpb, Mef2d, Elf3, Klf5, Junb, Stat3) were significantly upregulated by dDAVP in either control or TAZ-KD conditions. Among them, RT-qPCR analysis identified Nr4a1 as a TAZ-dependent TF, and immunoblotting revealed reduced NR4A1 protein levels in TAZ-KD cells upon dDAVP stimulation. This finding suggests its role as a TAZ-regulated target in dDAVP response pathway. Accordingly, Nr4a1-KD reduced the dDAVP-induced upregulation of Aqp2 mRNA and protein. KEGG pathway enrichment analysis revealed that HIF-1 signaling and glycolysis as central pathways affected by TAZ. TAZ-NR4A1 axis acts as a novel transcriptional regulatory mechanism in controlling vasopressin-mediated AQP2 expression
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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