BESPRECHUNGEN COMPTES RENDUS - REVIEWS

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72613/1/j.1467-6435.1957.tb00243.x.pd

Accuracy of direct genomic values in Holstein bulls and cows using subsets of SNP markers

Background: At the current price, the use of high-density single nucleotide polymorphisms (SNP) genotyping assays in genomic selection of dairy cattle is limited to applications involving elite sires and dams. The objective of this study was to evaluate the use of low-density assays to predict direct genomic value (DGV) on five milk production traits, an overall conformation trait, a survival index, and two profit index traits (APR, ASI). Methods. Dense SNP genotypes were available for 42,576 SNP for 2,114 Holstein bulls and 510 cows. A subset of 1,847 bulls born between 1955 and 2004 was used as a training set to fit models with various sets of pre-selected SNP. A group of 297 bulls born between 2001 and 2004 and all cows born between 1992 and 2004 were used to evaluate the accuracy of DGV prediction. Ridge regression (RR) and partial least squares regression (PLSR) were used to derive prediction equations and to rank SNP based on the absolute value of the regression coefficients. Four alternative strategies were applied to select subset of SNP, namely: subsets of the highest ranked SNP for each individual trait, or a single subset of evenly spaced SNP, where SNP were selected based on their rank for ASI, APR or minor allele frequency within intervals of approximately equal length. Results: RR and PLSR performed very similarly to predict DGV, with PLSR performing better for low-density assays and RR for higher-density SNP sets. When using all SNP, DGV predictions for production traits, which have a higher heritability, were more accurate (0.52-0.64) than for survival (0.19-0.20), which has a low heritability. The gain in accuracy using subsets that included the highest ranked SNP for each trait was marginal (5-6%) over a common set of evenly spaced SNP when at least 3,000 SNP were used. Subsets containing 3,000 SNP provided more than 90% of the accuracy that could be achieved with a high-density assay for cows, and 80% of the high-density assay for young bulls. Conclusions: Accurate genomic evaluation of the broader bull and cow population can be achieved with a single genotyping assays containing ∼ 3,000 to 5,000 evenly spaced SNP

Midlatitude shelf seas in the Cenomanian-Turonian greenhouse world: Temperature evolution and North Atlantic circulation

An 8 million year record of subtropical and midlatitude shelf-sea temperatures, derived from oxygen isotopes of well-preserved brachiopods from a variety of European sections, demonstrates a long-term Cenomanian temperature rise (16–20°C, midlatitudes) that reached its maximum early in the late Turonian (23°C, midlatitudes). Superimposed on the long-term trend, shelf-sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations. In the mid-Cenomanian and the late Turonian, two minor shelf-sea cooling events (2–3°C) coincide with carbon cycle perturbations and times of high-amplitude sea level falls. Although this evidence supports the hypothesis of potential glacioeustatic effects on Cretaceous sea level, the occurrence of minimum shelf-sea temperatures within transgressive beds argues for regional changes in shelf-sea circulation as the most plausible mechanism. The major carbon cycle event in the latest Cenomanian (oceanic anoxic event 2) is accompanied by a substantial increase in shelf-sea temperatures (4–5°C) that occurred ∼150 kyr after the commencement of the δ13C excursion and is related to the spread of oceanic conditions in western European shelf-sea basins. Our oxygen isotope record and published δ18O data of pristinely preserved foraminifera allow the consideration of North Atlantic surface water properties in the Cenomanian along a transect from the tropics to the midlatitudes. On the basis of fossil-derived δ18O, estimated δw ranges, and modeled salinities, temperature-salinity-density ranges were estimated for tropical, subtropical, and midlatitude surface waters. Accordingly, the Cenomanian temperate shelf-seas waters have potentially the highest surface water density and could have contributed to North Atlantic intermediate to deep waters in the preopening stage of the equatorial Atlantic gateway

Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

Small stationary diesel engines, like in generator sets, have limited emission control measures and are therefore responsible for 44% of the particulate matter (PM) emissions in the United States. The diesel exhaust composition depends on operating conditions of the combustion engine. Furthermore, the measurements are influenced by the used sampling method. This study examines the effect of engine loading and exhaust gas dilution on the composition of small-scale power generators. These generators are used in different operating conditions than road-transport vehicles, resulting in different emission characteristics. Experimental data were obtained for gaseous volatile organic compounds (VOC) and PM mass concentration, elemental composition and nitrate content. The exhaust composition depends on load condition because of its effect on fuel consumption, engine wear and combustion temperature. Higher load conditions result in lower PM concentration and sharper edged particles with larger aerodynamic diameters. A positive correlation with load condition was found for K, Ca, Sr, Mn, Cu, Zn and Pb adsorbed on PM, elements that originate from lubricating oil or engine corrosion. The nitrate concentration decreases at higher load conditions, due to enhanced nitrate dissociation to gaseous NO at higher engine temperatures. Dilution on the other hand decreases PM and nitrate concentration and increases gaseous VOC and adsorbed metal content. In conclusion, these data show that operating and sampling conditions have a major effect on the exhaust gas composition of small-scale diesel generators. Therefore, care must be taken when designing new experiments or comparing literature results

Addressing Endogeneity in International Marketing Applications of Partial Least Squares Structural Equation Modeling

Partial least squares structural equation modeling (PLS-SEM) has become a key method in international marketing research. Users of PLS-SEM have, however, largely overlooked the issue of endogeneity, which has become an integral component of regression analysis applications. This lack of attention is surprising because the PLS-SEM method is grounded in regression analysis, for which numerous approaches for handling endogeneity have been proposed. To identify and treat endogeneity, and create awareness of how to deal with this issue, this study introduces a systematic procedure that translates control variables, instrumental variables, and Gaussian copulas into a PLS-SEM framework. We illustrate the procedure's efficacy by means of empirical data and offer recommendations to guide international marketing researchers on how to effectively address endogeneity concerns in their PLS-SEM analyses

Measuring Risk Attitudes Controlling for Personality Traits*

Abstract: This study measures risk attitudes using two paid experiments: the Holt and Laury (2002) procedure and a variation of the game show Deal or No Deal. The participants also completed a series of personality questionnaires developed in the psychology literature including the risk domains of Weber, Blais, and Betz (2002). As in previous studies risk attitudes vary within subjects across elicitation methods. However, this variation can be explained by individual personality traits. Specifically, subjects behave as though the Holt and Laury task is an investment decision while the Deal or No Deal task is a gambling decision

Individual and social determinants of multiple chronic disease behavioral risk factors among youth

<p>Abstract</p> <p>Background</p> <p>Behavioral risk factors are known to co-occur among youth, and to increase risks of chronic diseases morbidity and mortality later in life. However, little is known about determinants of multiple chronic disease behavioral risk factors, particularly among youth. Previous studies have been cross-sectional and carried out without a sound theoretical framework.</p> <p>Methods</p> <p>Using longitudinal data (n = 1135) from Cycle 4 (2000-2001), Cycle 5 (2002-2003) and Cycle 6 (2004-2005) of the National Longitudinal Survey of Children and Youth, a nationally representative sample of Canadian children who are followed biennially, the present study examines the influence of a set of conceptually-related individual/social distal variables (variables situated at an intermediate distance from behaviors), and individual/social ultimate variables (variables situated at an utmost distance from behaviors) on the rate of occurrence of multiple behavioral risk factors (physical inactivity, sedentary behavior, tobacco smoking, alcohol drinking, and high body mass index) in a sample of children aged 10-11 years at baseline. Multiple behavioral risk factors were assessed using a multiple risk factor score. All statistical analyses were performed using SAS, version 9.1, and SUDAAN, version 9.01.</p> <p>Results</p> <p>Multivariate longitudinal Poisson models showed that social distal variables including parental/peer smoking and peer drinking (Log-likelihood ratio (LLR) = 187.86, degrees of freedom (DF) = 8, <it>p </it>< .001), as well as individual distal variables including low self-esteem (LLR = 76.94, DF = 4, <it>p </it>< .001) increased the rate of occurrence of multiple behavioral risk factors. Individual ultimate variables including age, sex, and anxiety (LLR = 9.34, DF = 3, <it>p </it>< .05), as well as social ultimate variables including family socioeconomic status, and family structure (LLR = 10.93, DF = 5, <it>p </it>= .05) contributed minimally to the rate of co-occurrence of behavioral risk factors.</p> <p>Conclusions</p> <p>The results suggest targeting individual/social distal variables in prevention programs of multiple chronic disease behavioral risk factors among youth.</p

Análisis de la demanda : un estudio de econometría

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