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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK and Boston, USA : Blackwell Publishers Ltd
    British journal of educational technology 32 (2001), S. 0 
    ISSN: 1467-8535
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Education
    Notes: In this paper, the application of Bayesian networks to student modeling is discussed. A review of related work is made, and then the structural model is defined. Two of the most commonly cited reasons for not using Bayesian networks in student modeling are the computational complexity of the algorithms and the difficulty of the knowledge acquisition process. We propose an approach to simplify knowledge acquisition. Our approach applies causal independence to factor the conditional probabilities and decrease the parameters required for each question to a number linear in the number of concepts. This also provides the new parameters with an intuitive meaning that makes their specification easier. Finally, we present an example to illustrate the use of our approach.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Surface Science Letters 209 (1989), S. A40 
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    International Journal of Biochemistry 22 (1990), S. 729-735 
    ISSN: 0020-711X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Surface Science 209 (1989), S. 215-228 
    ISSN: 0039-6028
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
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    Madrid : Periodicals Archive Online (PAO)
    Archivo español de arqueología. 58:151/152 (1985) 3 
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 142 (2000), S. 373-381 
    ISSN: 0942-0940
    Keywords: Keywords: Age; prognosis; severe head injury; logistic regression.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary ¶ The authors analyzed the relationship between patient age and the final outcome in a series of 810 patients aged 14 years or older who were consecutively admitted between 1987 and 1996 after suffering a severe closed head injury.  The most relevant clinico-radiological variables were prospectively collected in a Data Bank. Stratified and logistic regression analyses were performed in order to assess the influence of age on adverse outcome and the interaction between patient age and other prognostic indicators.  Our results reaffirm that the adverse outcome rate increases steadily with age in severe head injured patients and that age effect on outcome is independent of other prognostic variables. The odds of having an adverse outcome increases significantly over 35 years of age being 10 times higher in patients older than 65 years as compared to those aged 15–25 years (reference age group). The adverse influence of an advanced age on the final outcome has not yet been satisfactorily explained but an older brain may have an impaired ability to recover after a pathological insult as compared to a younger one.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0942-0940
    Keywords: Keywords: Meningioma; recurrence; radiotherapy; computed tomography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  The authors undertook a follow-up study of 286 patients who underwent surgical treatment for intracranial meningioma between 1973 and 1994, in order to analyse clinical, radiological, topographic, histopathological and therapeutic factors significantly influencing tumour recurrence.  All patients were followed by using either computed tomography (CT) or magnetic resonance from 3 months to 17 years since first surgery (mean follow-up: 4.1 years). Forty-four (15.4%) recurrences were detected during this time period. Overall recurrence rates were 14%, 37% and 61% at 5, 10 and 15 years, respectively.  Factors significantly associated with tumour relapse in bivariate analysis were: tumour location at petroclival and parasagittal (middle third) regions, incomplete surgical resection (assessed by Simpson's classification), atypical and malignant histological types (WHO classification), presence of nucleolar prominence, presence of more than 2 mitosis per 10 high-power fields, and heterogeneous tumour contrast enhancement on the CT scan.  The multivariate analysis using the Cox's proportional hazards model identified the following risk factors for recurrence: incomplete surgical resection (Relative risk: 2.2; 95% Confidence interval: 1.33–3.64), non conventional histological type (RR: 2.13; 95%CI: 1–4.53), heterogeneous contrast enhancement on the CT scan (RR: 2.25; 95%CI: 1.1–4.72) and presence of more than 2 mitosis per 10 high-power fields (RR: 2.28; 95%CI: 0.99–5.27). Patients without any of these features showed low recurrence rates (4% and 18% at 5 and 10 years), and thus, they need less clinical and radiological controls through the follow-up than patients with some of these risk factors.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0016-7835
    Keywords: Key words Guatemala ; K/T boundary ; Biostratigraphy ; Limestone breccias ; Chicxulub impact?
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Limestone breccia deposits in southern Mexico, Guatemala and Belize have recently been interpreted as proximal to distal ballistic fallout deposits, generated by a bolide impact that struck Yucatan at K/T boundary time. We review the age, lithology and the depositional environment of five K/T boundary sections in the South Petén area of Guatemala (Caribe, Aserradero, Chisec, Actela, Chemal) in order to evaluate the nature and origin of K/T limestone breccia deposition. The sections are located 500 km south of the proposed impact site at Chicxulub and trend in an east–west direction from the Guatemala/Mexico border to southern Belize. In four of the five sections examined, a breccia unit up to 50 m thick overlies reef-bearing shallow-water limestones of late Cretaceous (Campanian-Maastrichtian) age. Rhythmically bedded limestones, marls and siltstones of early Danian age overlie the breccia and were deposited under middle-to outer-neritic conditions. The breccia consists of differently coloured layers of shallow-water limestones. Clast size generally decreases upsection to thin layers of predominantly rounded clasts, and these fine-grained rudstones grade into grainstones at the top. In at least one section (EI Caribe) diagenetically altered glass spherules are present in the uppermost layers of the grainstone. These glass spherules are of stratigraphic position and chemical composition similar to black and yellow glass from Beloc, Haiti and Mimbral, Mexico, which some workers have chemically linked to melt glass within the breccia of the Chicxulub cores. We suggest that breccia deposition in Guatemala may have been multi-event, over an extended time period, and related to the collision of the Yucatan and Chortis plates as well as related to a major impact or volcanic event at the end of the Cretaceous.
    Type of Medium: Electronic Resource
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