Mapping quantitative trait loci for economic traits in chickens

Identification of genomic regions harboring genes affecting economic traits is the primary step for the improvement of agricultural species through marker-assisted selection. Many important traits are difficult and expensive to measure, and, thus, selection can be improved by selecting directly upon genomic regions affecting these traits (QTL). White meat percentage (WM%) and Marek\u27s disease (MD) resistance are examples of important traits in commercial chickens. One objective of the research presented herein was to identify QTL affecting WM%, other growth-related traits, and MD resistance. Another objective was to compare statistical models for identifying these QTL. Phenotypes and genetic markers on an F2 broiler cross were analyzed using half-sib, line cross, combined, and parent of origin models to identify QTL affecting WM% and other growth related traits. Sixty-eight QTL were identified at the 5% chromosome-wise level, including six QTL affecting WM% and 20 putative imprinted QTL. The use of multiple segregation and expression models proved to be beneficial for identifying QTL. A commercial egg-layer backcross was used to identify QTL affecting MD resistance based on marker genotypes of long and short survivors (selective genotyping). Seventeen markers associated with MD survival were identified at P \u3c 0.10 using linear regression (LR) and Cox proportional hazards (CPH) models. Using simulated data reflecting the MD virus-challenged population, analyses using LR, CPH, and Weibull models were compared. Little difference in power was found between CPH and LR models when few individuals survived to the end of the experimental period (low censoring) and when all or selected individuals were genotyped. Simulated data did not follow a Weibull distribution, and thus the Weibull model generally resulted in less power than the other two models. The LR model was recommended for analyzing survival data when the amount of censoring is low because of ease of implementation of the model and interpretation of estimates. Including non-genotyped individuals in the selective genotyping analysis increased power, but resulted in LR having an inflated false positive rate. The QTL identified in this research can be an integral step for improvement of commercial chickens through marker assisted selection programs or identification of candidate genes

Teenage Childbearing and Its Life Cycle Consequences: Exploiting a Natural Experiment

In this paper, we exploit a 'natural experiment' associated with human reproduction to identify the effect of teen childbearing on subsequent educational attainment, family structure, labor market outcomes and financial self-sufficiency. In particular, we exploit the fact that a substantial fraction of women who become pregnant experience a miscarriage (spontaneous abortion) and thus do not have a birth. If miscarriages were purely random and if miscarriages were the only way, other than by live births, that a pregnancy ended, then women, who had a miscarriage as a teen, would constitute an ideal control group with which to contrast teenage mothers. Exploiting this natural experiment, we devise an Instrumental Variables (IV) estimators for the consequences of teen mothers not delaying their childbearing, using data from the National Longitudinal Survey of Youth, 1979 (NLSY79). Our major finding is that many of the negative consequences of not delaying childbearing until adulthood are much smaller than has been estimated in previous studies. While we do find adverse consequences of teenage childbearing immediately following a teen mother's first birth, these negative consequences appear short- lived. By the time a teen mother reachers her late twenties, she appears to have only slightly more children, is only slightly more likely to be single mother, and has no lower levels of educational attainment than if she had delayed her childbearing to adulthood. In fact, by this age teen mothers appear to be better off in some aspects of their lives. Teenage childbearing appears to raise levels of labor supply, accumulated work experience and labor market earnings and appears to reduce the chances of living in poverty and participating in the associated social welfare programs. These estimated effects imply that the cost of teenage childbearing to U.S. taxpayers is negligible. In particular, our estimates imply that the widely held view that teenage childbearing imposes a substantial cost on government is an artifact of the failure to appropriately account for pre- existing socioeconomic differences between teen mothers and other women when estimating the causal effects of early childbearing. While teen mothers are very likely to live in poverty and experience other forms of adversity, our results imply that little of this would be changed just by getting teen mothers to delay their childbearing into adulthood.

Thermal improvement of existing dwellings

This report describes the outcome from a study to determine the impact of energy efficiency measures applied to the Scottish housing stock. Assuming conventional property type classifications, the present performance of the housing stock is quantified using available survey data. Building simulation techniques were then employed to generate a Web-based, decision-support tool for use by policy makers to estimate the impact of deploying energy efficiency measures in different combinations over time. The process of tool formulation is described and an example is given of tool use to identify best-value retrofitting options while taking factors such as future climate change and improved standard of living into account

Spitzer Warm Mission Transition and Operations

Following the successful dynamic planning and implementation of IRAC Warm Instrument Characterization activities, transition to Spitzer Warm Mission operations has gone smoothly. Operation teams procedures and processes required minimal adaptation and the overall composition of the Mission Operation System retained the same functionality it had during the Cryogenic Mission. While the warm mission scheduling has been simplified because all observations are now being made with a single instrument, several other differences have increased the complexity. The bulk of the observations executed to date have been from ten large Exploration Science programs that, combined, have more complex constraints, more observing requests, and more exo-planet observations with durations of up to 145 hours. Communication with the observatory is also becoming more challenging as the Spitzer DSN antenna allocations have been reduced from two tracking passes per day to a single pass impacting both uplink and downlink activities. While IRAC is now operating with only two channels, the data collection rate is roughly 60% of the four-channel rate leaving a somewhat higher average volume collected between the less frequent passes. Also, the maximum downlink data rate is decreasing as the distance to Spitzer increases requiring longer passes. Nevertheless, with well over 90% of the time spent on science observations, efficiency has equaled or exceeded that achieved during the cryogenic mission

In-Situ Thermal Image Correlation with Mechanical Properties of Nylon-12 in SLS

Selective laser sintering (SLS) of Nylon is a significant portion of the additive manufacturing market for structurally sensitive applications. Current methods of acceptance for such parts are based on the inclusion of ASTM tensile test specimens within the build volume to assess the overall build quality. Ultimate strength and elongation of these specimens oriented both in-plane and normal to the layer build direction are the primary quality metrics. This paper looks at a more complete method of certifying parts for acceptance based on examination of the build conditions in each layer of the part by comparing layer-by-layer thermal conditions during the part build to the resulting ASTM specimen tensile properties. Through such a comparison, a more complete three-dimensional assessment of part quality during the build process can be constructed. The layer-by-layer assessment used here is derived from infrared thermal imaging; mapping temperature profiles of SLS-built tensile bars with data collected before, during, and after each layer-wise laser melting sequence. Mechanical properties and fracture conditions are then quantified and correlated with the conditions where the fractures occur. Build conditions associated with poor failure conditions may then be used to assess poor SLS bonding throughout the part volume, improving overall part quality assessment and certification. As the method is matured, real time layer-by-layer assessment will be linked to SLS control, to correct for observed defects during the build and improve overall part quality and repeatability.Mechanical Engineerin

Hemodynamic, ventilatory and metabolic effects of light isometric exercise in patients with chronic heart failure

AbstractLight isometric exercise, such as lifting or carrying loads that require 25% of a maximal voluntary contraction, is frequently reported to cause dyspnea in patients with heart failure. The pathophysiologic mechanisms responsible for the appearance of this symptom, however, are unknown. Accordingly, hemodynamic, metabolic and ventilatory responses to 6 min of light isometric forearm exercise were examined and compared in 20 patients with chronic heart failure and abnormal ejection fraction (24 ± 9%) and 17 normal individuals. In contrast to findings in normal volunteers, exercise cardiac index did not increase whereas exercising forearm and mixed venous lactate concentrations increased (p < 0.05) above levels at rest in patients with heart failure; at 90 s of recovery, blood lactate concentration remained elevated (p < 0.05). The venous lactate concentration of the nonexercising arm, unlike that of the exercising forearm, was not altered. Oxygen uptake, carbon droxide production and minute ventilation increased similarly in patients and nomal subjects durings exercise, but only in patients did each increase further (p < 0.05) during recovery.Thus, in patients with heart failure, light iaometric forearm exercise represents an anaerobic contraction with lactate production. The subsequent increase in carbon dioxide production leads to a disproportionate increase in minute ventilation and oxygen uptake during recovery that may be perceived as breathlessness

Copy number variation in African Americans

<p>Abstract</p> <p>Background</p> <p>Copy number variants (CNVs) have been identified in several studies to be associated with complex diseases. It is important, therefore, to understand the distribution of CNVs within and among populations. This study is the first report of a CNV map in African Americans.</p> <p>Results</p> <p>Employing a SNP platform with greater than 500,000 SNPs, a first-generation CNV map of the African American genome was generated using DNA from 385 healthy African American individuals, and compared to a sample of 435 healthy White individuals. A total of 1362 CNVs were identified within African Americans, which included two CNV regions that were significantly different in frequency between African Americans and Whites (17q21 and 15q11). In addition, a duplication was identified in 74% of DNAs derived from cell lines that was not present in any of the whole blood derived DNAs.</p> <p>Conclusion</p> <p>The Affymetrix 500 K array provides reliable CNV mapping information. However, using cell lines as a source of DNA may introduce artifacts. The duplication identified in high frequency in Whites and low frequency in African Americans on chromosome 17q21 reflects haplotype specific frequency differences between ancestral groups. The generation of the CNV map will be a valuable tool for identifying disease associated CNVs in African Americans.</p

Comparison of methods for analysis of selective genotyping survival data

Survival traits and selective genotyping datasets are typically not normally distributed, thus common models used to identify QTL may not be statistically appropriate for their analysis. The objective of the present study was to compare models for identification of QTL associated with survival traits, in particular when combined with selective genotyping. Data were simulated to model the survival distribution of a population of chickens challenged with Marek disease virus. Cox proportional hazards (CPH), linear regression (LR), and Weibull models were compared for their appropriateness to analyze the data, ability to identify associations of marker alleles with survival, and estimation of effects when all individuals were genotyped (full genotyping) and when selective genotyping was used. Little difference in power was found between the CPH and the LR model for low censoring cases for both full and selective genotyping. The simulated data were not transformed to follow a Weibull distribution and, as a result, the Weibull model generally resulted in less power than the other two models and overestimated effects. Effect estimates from LR and CPH were unbiased when all individuals were genotyped, but overestimated when selective genotyping was used. Thus, LR is preferred for analyzing survival data when the amount of censoring is low because of ease of implementation and interpretation. Including phenotypic data of non-genotyped individuals in selective genotyping analysis increased power, but resulted in LR having an inflated false positive rate, and therefore the CPH model is preferred for this scenario, although transformation of the data may also make the Weibull model appropriate for this case. The results from the research presented herein are directly applicable to interval mapping analyses