Operating characteristics of the spinning cone column

OBJECTIVE: To establish whether uniparental disomy (UPD) could represent an outcome of embryonic aneuploidy self-correction and its relevance to preimplantation genetic diagnosis, and to validate a method of UPD detection in limited quantities of cells and determine the frequency of UPD in a large sample size of human blastocysts. DESIGN: Retrospective observational. SETTING: Academic center for reproductive medicine. PATIENT(S): Couples undergoing in vitro fertilization (IVF) treatment whose embryos underwent trophectoderm biopsy single-nucleotide polymorphism (SNP) array-based 24-chromosome aneuploidy screening. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Rate of UPD observed in the human blastocyst. RESULT(S): After application of defined thresholds, 2 of 3,401 blastocysts were found to possess isodisomy, and 0 were found to possess heterodisomy. The overall frequency of UPD in the human blastocyst was therefore 0.06%. CONCLUSION(S): This validated method of detection indicates that UPD is extremely rare and suggests that routine screening during preimplantation genetic diagnosis (PGD) may not be necessary. Furthermore, chromosomal UPD is unlikely to explain or support the existence of embryonic self-correction

Determinants of farmers’ adaptation to climate change: A micro level analysis in Ghana

ABSTRACT This study analyzed socio-economic factors that influence farmers’ adaptation to climate change in agriculture. Perceptions regarding long-term changes in climate variables and the rate of occurrence of weather extremes were also investigated. Additionally, farmers’ perceived barriers to the use of adaptation practices were identified and ranked. A total of 100 farm-households were randomly selected from four communities in the Lawra district of Ghana and data were collected through semi-structured questionnaires, focused group discussions and field observations. A logistic regression model and weighted average index were used to analyze the data. The results showed that 87 % of respondents perceived a decrease in rainfall amount, while 82 % perceived an increase in temperature over the past 10 years. Results of the weighted average index indicate that dry spell and drought have a higher annual rate of occurrence than flood. Empirical results of the logistic regression model showed that education, household size, annual household income, access to information, credit and membership of farmer-based organization are the most important factors that influence farmers’ adaptation to climate change. The main constraints on adaptation include unpredictability of weather, high farm input cost, lack of access to timely weather information and water resources. The policy implication of this study is that governments should mainstream barriers to, and choice factors of, adaptation practices to climate change related projects and programs