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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The VLDB journal 2 (1993), S. 361-406 
    ISSN: 0949-877X
    Keywords: Performance ; simulation models ; B+-tree structures ; resource conditions ; workload parameters ; lock modes ; data contention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A number of algorithms have been proposed to access B+-trees concurrently, but they are not well understood. In this article, we study the performance of various B+-tree concurrency control algorithms using a detailed simulation model of B+-tree operations in a centralized DBMS. Our study covers a wide range of data contention situations and resource conditions. In addition, based on the performance of the set of B+-tree concurrency control algorithms, which includes one new algorithm, we make projections regarding the performance of other algorithms in the literature. Our results indicate that algorithms with updaters that lock-couple using exclusive locks perform poorly as compared to those that permit more optimistic index descents. In particular, the B-link algorithms are seen to provide the most concurrency and the best overall performance. Finally, we demonstrate the need for a highly concurrent long-term lock holding strategy to obtain the full benefits of a highly concurrent algorithm for index operations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The VLDB journal 6 (1997), S. 241-256 
    ISSN: 0949-877X
    Keywords: Key words: Optimization – Cost models – Join methods – Buffer allocation – Performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. In this paper, we re-examine the results of prior work on methods for computing ad hoc joins. We develop a detailed cost model for predicting join algorithm performance, and we use the model to develop cost formulas for the major ad hoc join methods found in the relational database literature. We show that various pieces of “common wisdom” about join algorithm performance fail to hold up when analyzed carefully, and we use our detailed cost model to derive op timal buffer allocation schemes for each of the join methods examined here. We show that optimizing their buffer allocations can lead to large performance improvements, e.g., as much as a 400% improvement in some cases. We also validate our cost model's predictions by measuring an actual implementation of each join algorithm considered. The results of this work should be directly useful to implementors of relational query optimizers and query processing systems.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The VLDB journal 2 (1993), S. vii 
    ISSN: 0949-877X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical psychology 6 (1999), S. 0 
    ISSN: 1468-2850
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Psychology
    Notes: This literature review summarizes the psychometric properties of 12 measures used to assess readiness to change substance abuse. Assessment methods vary, and include algorithms, self-administered questionnaires, and clinical ratings. We describe each and summarize reliability and validity information. Some measures have poor psychometric properties, whereas limited psychometric data are available for others. No single measure emerges as best for use in clinical settings, and promising candidates differ regarding target population and assessment method. Although the Transtheoretical Model inspired much of the empirical work on readiness to change, the psychometric literature provides inconsistent support for the stages of change. Readiness to change may best be conceptualized as a multidimensional and continuous construct with complex relationships to behavior, cognition, and environmental context.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical psychology 3 (1996), S. 0 
    ISSN: 1468-2850
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Psychology
    Notes: Seriously mentally ill adults are at high risk for human immunodeficiency virus (HIV) infection. We review the empirical literature that documents this elevated risk in psychiatric patients and identify factors that have been associated with enhanced risk. Our review indicates five characteristics related to HIV risk in psychiatric populations: psychopathology severity and symptomatology, substance abuse proximal to sexual behavior, misinformation about HIV transmission, perceptions of invulnerability, and sttuational, lifestyle factors. Understanding these characteristics can lead to improved HIV preventive intervention models. However, we also note that studies have been limited by unreliable psychiatric diagnoses and sampling constraints. We conclude with suggestions for research, practice, and prevention based on findings in the empirical literature and theories of HIV risk reduction.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 100 (1993), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of obstetric, gynecologic and neonatal nursing 32 (2003), S. 0 
    ISSN: 1552-6909
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective: To present the preintervention data collected for a pilot HIV-prevention randomized controlled trial specifically developed for single, sexually active adolescent girls. Design: Comparative, descriptive design using confidential self-administered questionnaires. Setting: An urban family planning clinic that provided gynecologic services to adolescents. Participants: One hundred twenty-nine single, sexually active adolescent girls 15 to 19 years of age (44% minority, 34% economically disadvantaged). Main Outcome Measures: In addition to demographics and risk behaviors, the following were assessed: HIV-related information (i.e., knowledge) and motivation to reduce risk (i.e., perceived vulnerability, readiness to change HIV risk behaviors, behavioral intentions, pros and cons of condom use, and confidence in condom use). Results: Assessments revealed limited HIV-related knowledge, ambivalence regarding risk reduction, and considerable risk behaviors. Compared with girls at lower risk for HIV infection (i.e., consistent condom users), those at higher risk (i.e., inconsistent or non-condom-users) were more likely to be White and older and to have better HIV-related knowledge but less motivation to reduce risk (i.e., behavioral intentions to use condoms, condom-use confidence) than girls at lower risk. Conclusion: These data document (a) the need for HIV prevention interventions targeted to all sexually active adolescent girls and (b) the importance of including a motivational component in the intervention.
    Type of Medium: Electronic Resource
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  • 8
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    Unknown
    Washington, etc. : Periodicals Archive Online (PAO)
    Explicator. 52:2 (1994:Winter) 119 
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 159 (1947), S. 643-644 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE formation of diazonium complexes from unsaturated amines is not a unique property of the aromatic series. Many, but not all, unsaturated heterocyclic amines respond similarly1. With aliphatic amino-compounds, nitrous acid, under certain conditions, may give a diazo-grouping ...
    Type of Medium: Electronic Resource
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  • 10
    facet.materialart.
    Unknown
    Provincetown, Mass., etc. : Periodicals Archive Online (PAO)
    Journal of Psychology. 124:4 (1990:July) 391 
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