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Separate Tests (separate + test)

Distribution by Scientific Domains
Life Sciences40%

Terms modified by Separate Tests

  • separate test set
    		•

    Selected Abstracts

    Use of multiplex real-time PCR (TaqMan) for the detection of potato viruses,

    EPPO BULLETIN, Issue 3-4 2000
    N. Boonham
    Certain viruses affect the quality of potato tubers for either table use or processing. Visual discrimination of these viruses is problematic because of variable symptoms, but is important if proper controls are to be implemented. Work at the Central Science Laboratory has concentrated on the detection of Potato mop-top pomovirus (PMTV), Tobacco rattle tobravirus (TRV) (both associated with the disease spraing) and the tuber necrotic strain of Potato Y potyvirus (PVYNTN), the symptoms of which can often be confused with spraing. A nucleic acid-based approach has been adopted as TRV is often found as naked RNA with no associated coat protein, and accurate discrimination of PVY strains is impossible by serology. The multiplex TaqMan assay developed in this work streamlines the testing, replacing two separate tests currently used (a TRV RT-PCR and a PMTV enzyme-linked immunosorbent assay) with a single-tube assay, which has no post-PCR manipulations. The assay has been shown to be more sensitive than either of the tests which it replaces, allowing 100- and 10000-fold increases in sensitivity for TRV and PMTV detection respectively. The test reliably detected over 40 different isolates of TRV and PMTV obtained from a wide range of cultivars and locations, including samples where existing tests failed. A PCR-based method capable of discriminating strains of PVY was also developed. [source]

    Experimental and computational investigation of three-dimensional mixed-mode fatigue

    FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2002
    S. C. Forth
    Experimental and computational methods were developed to model three-dimensional (3-D) mixed-mode crack growth under fatigue loading with the objective of evaluating proposed 3-D fracture criteria. The experiments utilized 7075-T73 aluminium forgings cut into modified ASTM E740 surface crack specimens with pre-cracks orientated at angles of 30, 45 and 60° in separate tests. The progress of the evolving fatigue crack was monitored in real time using an automated visualization system. In addition, the amplitude of the loading was increased at prescribed intervals to mark the location of the 3-D crack front for post-test inspection. In order to evaluate proposed crack growth equations, computer simulations of the experiments were conducted using a 3-D fracture model based on the surface integral method. An automatic mesher advanced the crack front by adding a ring of elements consistent with local application of fracture criteria governing rate and direction of growth. Comparisons of the computational and experimental results showed that the best correlation was obtained when KII and KIII were incorporated in the growth rate equations. [source]

    Delayed neuropsychologic dysfunction after liver transplantation for acute liver failure: A matched, case-controlled study

    LIVER TRANSPLANTATION, Issue 10 2002
    Elizabeth W. Jackson
    Although several studies have identified posttransplant neurologic sequelae in patients with acute liver failure (ALF), the effects of these sequelae on neuropsychologic functioning after transplant is unknown. This study compared neuropsychologic functioning of ALF patients with chronic liver disease patients after liver transplantation. After liver transplantation, seven ALF patients were compared with a matched control group of patients who had been transplanted for chronic liver disease. The patients were matched by gender, age (within 5 years), and time since transplantation (within 2 years). Patients completed a 2-hour battery of tests, which included measures of attention, memory, motor performance, abstract conceptualization, and visuospatial perception. There were no significant differences between the groups on measures of socioeconomic status or education. Significant differences were found on three separate tests: WAIS-III Vocabulary, WAIS-III Similarities, and WMS-III Paired Associate Learning II. Although these tests measure distinct functions (vocabulary knowledge, abstract conceptualization, and delayed verbal recall), they may be influenced by broader verbal functions, such as verbal fluency, conceptualization, and the ability to articulate ideas. When patients were asked what functions had noticeably deteriorated since transplantation, nearly all complained of memory difficulties, and there was no difference between groups. However, more ALF than chronic liver disease (CLD) patients complained of concentration difficulties. The results of this study suggest that ALF patients may experience more neuropsychologic dysfunction after transplant. Further studies are required to expand on these initial observations with the potential to improve patient care and referral to appropriate rehabilitative services. [source]

    Statistical power when testing for genetic differentiation

    MOLECULAR ECOLOGY, Issue 10 2001
    N. Ryman
    Abstract A variety of statistical procedures are commonly employed when testing for genetic differentiation. In a typical situation two or more samples of individuals have been genotyped at several gene loci by molecular or biochemical means, and in a first step a statistical test for allele frequency homogeneity is performed at each locus separately, using, e.g. the contingency chi-square test, Fisher's exact test, or some modification thereof. In a second step the results from the separate tests are combined for evaluation of the joint null hypothesis that there is no allele frequency difference at any locus, corresponding to the important case where the samples would be regarded as drawn from the same statistical and, hence, biological population. Presently, there are two conceptually different strategies in use for testing the joint null hypothesis of no difference at any locus. One approach is based on the summation of chi-square statistics over loci. Another method is employed by investigators applying the Bonferroni technique (adjusting the P -value required for rejection to account for the elevated alpha errors when performing multiple tests simultaneously) to test if the heterogeneity observed at any particular locus can be regarded significant when considered separately. Under this approach the joint null hypothesis is rejected if one or more of the component single locus tests is considered significant under the Bonferroni criterion. We used computer simulations to evaluate the statistical power and realized alpha errors of these strategies when evaluating the joint hypothesis after scoring multiple loci. We find that the ,extended' Bonferroni approach generally is associated with low statistical power and should not be applied in the current setting. Further, and contrary to what might be expected, we find that ,exact' tests typically behave poorly when combined in existing procedures for joint hypothesis testing. Thus, while exact tests are generally to be preferred over approximate ones when testing each particular locus, approximate tests such as the traditional chi-square seem preferable when addressing the joint hypothesis. [source]

    A Comparison of Eight Methods for the Dual-Endpoint Evaluation of Efficacy in a Proof-of-Concept HIV Vaccine Trial

    BIOMETRICS, Issue 3 2006
    Devan V. Mehrotra
    Summary To support the design of the world's first proof-of-concept (POC) efficacy trial of a cell-mediated immunity-based HIV vaccine, we evaluate eight methods for testing the composite null hypothesis of no-vaccine effect on either the incidence of HIV infection or the viral load set point among those infected, relative to placebo. The first two methods use a single test applied to the actual values or ranks of a burden-of-illness (BOI) outcome that combines the infection and viral load endpoints. The other six methods combine separate tests for the two endpoints using unweighted or weighted versions of the two-part z, Simes', and Fisher's methods. Based on extensive simulations that were used to design the landmark POC trial, the BOI methods are shown to have generally low power for rejecting the composite null hypothesis (and hence advancing the vaccine to a subsequent large-scale efficacy trial). The unweighted Simes' and Fisher's combination methods perform best overall. Importantly, this conclusion holds even after the test for the viral load component is adjusted for bias that can be introduced by conditioning on a postrandomization event (HIV infection). The adjustment is derived using a selection bias model based on the principal stratification framework of causal inference. [source]