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Log Scale (log + scale)
Selected AbstractsTesting whether samples of blue-green algae have the same cell densityENVIRONMETRICS, Issue 3 2001Geoff M. Laslett Abstract The toxicity of a blue-green algae sample is a function of its cell density, so it is important to know if related samples in a set have different cell densities. Several plausible tests of the null hypothesis of no difference are proposed. Our study assumes that cells are counted in the laboratory using inverse Poisson sampling of blue-green algae colonies, a common Australian technique. In the case of two samples, four standardized difference tests and two likelihood ratio tests are compared on a suite of simulated samples. One of the likelihood ratio tests assumes that colony size has a gamma distribution, but the other makes no explicit assumption. All tests are found to have virtually the same power, but the standardized difference test on the log scale and the likelihood ratio tests have nearly invariant standard null distributions and hence are more convenient to use. The semi-parametric likelihood ratio test generalizes to the multi-sample case very easily. Its performance on three samples is investigated, and found to be satisfactory. Copyright © 2001 John Wiley & Sons, Ltd. [source] Comparison of sample size formulae for 2 × 2 cross-over designs applied to bioequivalence studiesPHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 4 2005Arminda Lucia Siqueira Abstract We consider the comparison of two formulations in terms of average bioequivalence using the 2 × 2 cross-over design. In a bioequivalence study, the primary outcome is a pharmacokinetic measure, such as the area under the plasma concentration by time curve, which is usually assumed to have a lognormal distribution. The criterion typically used for claiming bioequivalence is that the 90% confidence interval for the ratio of the means should lie within the interval (0.80, 1.25), or equivalently the 90% confidence interval for the differences in the means on the natural log scale should be within the interval (,0.2231, 0.2231). We compare the gold standard method for calculation of the sample size based on the non-central t distribution with those based on the central t and normal distributions. In practice, the differences between the various approaches are likely to be small. Further approximations to the power function are sometimes used to simplify the calculations. These approximations should be used with caution, because the sample size required for a desirable level of power might be under- or overestimated compared to the gold standard method. However, in some situations the approximate methods produce very similar sample sizes to the gold standard method. Copyright © 2005 John Wiley & Sons, Ltd. [source] Lattice energy of zinc blende (AIIIBV and AIIBVI) solidsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2008A. S. Verma Abstract In this paper we present an expression relating the lattice energy (U in kcal/mol) for the AIIIBV and AIIBVI semiconductors with the product of ionic charges (Z1Z2) and nearest-neighbor distance d (Å). The lattice energy of these compounds exhibit a linear relationship when plotted on a log,log scale against the nearest-neighbor distance d (Å), but fall on different straight lines according to the ionic charge product of the compounds. A fairly good agreement has been found between the observed and calculated values of the lattice energy for AIIIBV and AIIBVI semiconductors. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A new method for estimating age-at-death from the first rib,AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Elizabeth A. DiGangi Abstract A new method for estimating adult age-at-death from the first rib was developed as a modification of the Kunos et al. (Am J Phys Anthropol 110 (1999) 303,323) method. Data were collected on three aspects of the first rib (costal face, rib head, and tubercle facet) for 470 known-age males of Balkan ancestry collected as evidence during investigations conducted by the International Criminal Tribunal for the former Yugoslavia (ICTY). Ages-at-death range from 12 to 90 years (mean of 47.7 years). Several variables were extracted from the original study utilizing all three skeletal aspects of the first rib. This list was modified to 11 variables as preliminary tests on seriations of the samples were undertaken. A cumulative probit model with age measured on a log scale was used to calculate the mean and standard deviation of the ages-of-transition for each component. Multivariate analysis of the three components was also performed. The lowest correlation (r = 0.079, controlling for age) was between the geometric shape of the costal face and the surface texture of the tubercle facet. Assuming a correlation of zero, these two traits were used to calculate the highest posterior density regions for estimating individual ages-at-death. Age-at-death estimates generated from 50 and 95% posterior density regions indicate that this method captures age-related change reaching the ninth decade. The Bayesian statistical approach used here produced a valuable and promising new method for estimating age-at-death. Additional research is necessary to determine if these highest posterior density regions produce results highly correlated with age in other samples and its applicability to females. Am J Phys Anthropol 2009. © 2008 Wiley-Liss, Inc. [source] Pharmacokinetics and allometric scaling of levormeloxifene, a selective oestrogen receptor modulatorBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2003O. Østerberg Abstract The pharmacokinetics of a new selective oestrogen receptor modulator levormeloxifene was investigated in mice, rats, cynomolgus monkeys and humans by compartmental pharmacokinetics. Levormeloxifene was administered as an oral solution in all studies. Allometric scaling was used to predict human pharmacokinetic parameters and the performance of the approach was evaluated. Mean values of clearance confounded by F(CL/F) were 0.073, 0.29, 3.18 and 2.4 l/h in mice, rats, monkeys and humans, respectively. Values of distribution volume at steady state confounded by F(Vss/F) were 0.073 and 7.5 l in mice and rats. In monkeys, values of the central volume F(Vc/F) and volume at steady state F(Vss/F) were 28.9 and 57.9 l, respectively. In humans, values of Vc/F and Vss/F were 106 and 587 l, respectively. Predicted CL/F and Vss/F showed a linear relationship when plotted vs BW on a log,log scale; for CL/F, r was 0.95,0.98 and for Vss/F, r was 0.99. Using allometric scaling the predicted human Vss/F deviated 3-fold from the experimentally determined values. Observed values of CL/F deviated 21,25 fold from the predicted, the latter depending on the scaling method. Confidence intervals for the predicted parameters showed major lack of precision for all the allometric scaling methods. Copyright © 2003 John Wiley & Sons, Ltd. [source] 2436: A critical look at meibometry as a means to monitor Meibomian gland functionACTA OPHTHALMOLOGICA, Issue 2010P VERSURA Purpose To evaluate the diagnostic performance of meibometry in classifying and quantifying Meibomian gland dysfunction(MGD) Methods Ninety-six patients with MGD (138 eyes, 62 women, 34 men) and 30 normal control subjects(55 eyes)were enrolled. Eighty six eyes were classified as high delivery (HD)-MGD (meibomian seborrhea/hypersecretory MGD), 52 as low delivery (LD)-MGD on the basis of expression quality scores and morphological signs. Direct Meibometry (DM) measurements were made with an MB550 Meibometer (Courage-Khazaka GmbH). Standard curves were constructed relating arbitrary Meibometer optical density units (AU). Integrated Meibometry (IM) was performed on scanned images of the lipid blots. Symptoms were scored by OSDI,Schirmer test I, Break Up Time (BUT), tear osmolarity (Tearlab, Ocusense), conjunctival scraping cytology were performed. Statistical analysis used SPSS 14.0 and MedCalc 5.0 Results AU values plotted on a log scale correlated highly with the lipid equivalent values (R2= 0.913). Significant differences were found between control subjects vs all MGD patients and between HD vs LD-MGD patients for all the parameters evaluated. In particular: controls: 300+/-121 AU (0.04+/-0.015 microliter), LD-MGD: 218+/-122 AU (0.03+/-0.015) and HD-MGD: 564+/-115 AU (0.07+0.015) (median+/-SD). Significant correlation was found DM vs IM (r=0.691,p<0.0001) and DM was shown to be correlated with BUT, OSDI score, scraping score and tear osmolarity, especially in LD-MGD patients. The selected DM diagnostic cut off for LD-MGD was <275 AU (sens 73, spec 60, PPV 63) and for HD-MGD was >450 AU; (sens 86, spec 87, PPV 91) Conclusion Meibometry is confirmed to be a reliable method to distinguish normal subjects from MGD subgroups with a good degree of accuracy [source] | |||||||||||||