107,087 research outputs found
A population genetics model of marker-assisted selection
No full textA deterministic two-loci model was developed to predict genetic response to marker-assisted selection (MAS) in one generation and in multiple generations. Formulas were derived to relate linkage disequilibrium in a population to the proportion of additive genetic variance used by MAS, and in turn to an extra improvement in genetic response over phenotypic selection. Predictions of the response were compared to those predicted by using an infinite-loci model and the factors affecting efficiency of MAS were examined. Theoretical analyses of the present study revealed the nonlinearity between the selection intensity and genetic response in MAS. In addition to the heritability of the trait and the proportion of the marker-associated genetic variance, the frequencies of the selectively favorable alleles at the two loci, one marker and one quantitative trait locus, were found to play an important role in determining both the short- and long-term efficiencies of MAS. The evolution of linkage disequilibrium and thus the genetic response over several generations were predicted theoretically and examined by simulation. MAS dissipated the disequilibrium more quickly than drift alone. In some cases studied, the rate of dissipation was as large as that to be expected in the circumstance where the true recombination fraction was increased by three times and selection was absent
Costatoria (Costatoria?) subrotunda (BITTNER, 1901) a Smithian (Lower Triassic) marker from Tethys
No full textThe authors erect Costatoria costata var. subrotunda (Bittner) from Hungarian Lower Triassic to species level. Its subgeneric position is also discussed here. Thus, Costatoria is represented in the Werfen Formation of Dolomites area by two species: C. (Costatoria?) subrotunda (Bittner) from the upper part of Campil Member (Smithian) and C. (Costatoria) costata (Zenker) from Cencenighe and S. Lucano Members (Spathian). C. subrotunda shows a wide geographic distribution and could be considered as a helpful marker of Smithian age.-Author
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Allelic association between marker loci
No full textAllelic association has proven useful to refine the location of major genes prior to positional cloning, but it is of uncertain value for genome scans in complex inheritance. We have extended kinship theory to give information content for linkage and allelic association. Application to pairs of closely linked markers as a surrogate for marker x oligogene pairs indicates that association is largely determined by regional founders, with little effect of subsequent demography. Sub-Saharan Africa has the least allelic association, consistent with settlement of other regions by small numbers of founders. Recent speculation about substantial advantages of isolates over large populations, of constant size over expansion, and of F1 hybrids over incrosses is not supported by theory or data. On the contrary, fewer affected cases, less opportunity for replication, and more stochastic variation tend to make isolates less informative for allelic association, as they are for linkage.</p
Memorandum from A. E. Demaray to E. C. Finney
No full textFour letters of correspondence about the purchase of Bright Angel Trail between A. E. Demaray, Acting Director of the Grand Canyon National Park; E. C. Finney, Department of the Interior First Assistant Secretary; Carl T. Hayden, Representative (AZ); and Stephen T. Mather, Director of the National Park Service
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
[Texas Historical Commission Marker: Samuel E. and Mary C. Marshall House]
No full textPhotograph of the Texas Historical Commission marker for Samuel E. and Mary C. Marshall House in Whitewright, Texas. Text: Civil War veteran Sam Marshall (1838-1911), his wife, Mary (1840-1924), and their family came from Kentucky to Grayson county in the late 1860s, and moved to the new railroad town of Whitewright by 1880. After achieving success with their land investments and commercial businesses, the Marshalls built this Queen Anne Free Classic house in 1899-1900. The gabled roof, decorative woodwork, classical columns, porch and balcony are all notable elements of this style. After Mary Marshall's death in 1924, the house subsequently was owned and occupied by the Carter, Sanders, and Stuteville families
Prediction of haplotypes for ungenotyped animals and its effect on marker-assisted breeding value estimation
No full textBackground: In livestock populations, missing genotypes on a large proportion of animals are a major problem to implement the estimation of marker-assisted breeding values using haplotypes. The objective of this article is to develop a method to predict haplotypes of animals that are not genotyped using mixed model equations and to investigate the effect of using these predicted haplotypes on the accuracy of marker-assisted breeding value estimation. Methods: For genotyped animals, haplotypes were determined and for each animal the number of haplotype copies (nhc) was counted, i.e. 0, 1 or 2 copies. In a mixed model framework, nhc for each haplotype were predicted for ungenotyped animals as well as for genotyped animals using the additive genetic relationship matrix. The heritability of nhc was assumed to be 0.99, allowing for minor genotyping and haplotyping errors. The predicted nhc were subsequently used in marker-assisted breeding value estimation by applying random regression on these covariables. To evaluate the method, a population was simulated with one additive QTL and an additive polygenic genetic effect. The QTL was located in the middle of a haplotype based on SNP-markers. Results: The accuracy of predicted haplotype copies for ungenotyped animals ranged between 0.59 and 0.64 depending on haplotype length. Because powerful BLUP-software was used, the method was computationally very efficient. The accuracy of total EBV increased for genotyped animals when marker-assisted breeding value estimation was compared with conventional breeding value estimation, but for ungenotyped animals the increase was marginal unless the heritability was smaller than 0.1. Haplotypes based on four markers yielded the highest accuracies and when only the nearest left marker was used, it yielded the lowest accuracy. The accuracy increased with increasing marker density. Accuracy of the total EBV approached that of gene-assisted BLUP when 4-marker haplotypes were used with a distance of 0.1 cM between the markers. Conclusions: The proposed method is computationally very efficient and suitable for marker-assisted breeding value estimation in large livestock populations including effects of a number of known QTL. Marker-assisted breeding value estimation using predicted haplotypes increases accuracy especially for traits with low heritabilit
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Cystatin C as a marker of renal function immediately after liver transplantation.
No full textTo verify whether cystatin C may be of some use as a renal function marker immediately after orthotopic liver transplantation (OLT), we compared serum cystatin C (S(Cyst)), serum creatinine (S(cr)), and creatinine clearance (C(cr)) levels with the glomerular filtration rate (GFR). On postoperative days 1, 3, 5, and 7, S(Cyst) and S(cr) was measured in simultaneously drawn blood samples, whereas C(cr) was calculated using a complete 24-hour urine collection. The GFR was determined on the same days by means of iohexol plasma clearance (I-GFR). The correlation between 1/S(Cyst) and I-GFR was stronger than that of 1/S(cr) or C(cr) (P or = 30% lower than that recorded on the first postoperative day, S(Cyst)(P< 0.0001) and S(cr) (P< 0.01) levels were increased, whereas C(cr) remained unchanged (P = 0.09). Receiver operating characteristic (ROC) area-under-the-curve analysis showed that the diagnostic accuracy of S(cyst) was better than that of S(cr) and C(cr). S(cyst) levels of 1.4, 1.7, and 2.2 mg/L respectively predicted I-GFR levels of 80, 60, and 40 mL/minute/1.73 m. In conclusion, cystatin C is a reliable marker of renal function during the immediate post-OLT period, especially when the goal is to identify moderate changes in GFR
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