Glutaraldehyde Fixation Chemistry A Scheme for Rapid Crosslinking and Evidence for Rapid Oxygen Consumption

The chemical literature suggests that pyridine derivatives are the major reaction products of amine-aldehyde reactions. A scheme is proposed for pyridine synthesis which is derived from a classic synthesis of pyridines from one amine molecule and 3 aldehyde molecules. The pyridine polymers are considered as a major class of cross-links in glutaraldehyde fixed cells. This scheme for pyridine synthesis accounts for the following observations of amine-glutaraldehyde react ions: 1) large quantities of acid are rapidly produced, 2) oxygen uptake occurs at a high rate, 3) a variety of products distinguished by molecular size are rapidly and irreversibly synthesized, and 4) the major reaction products share physical and chemical characteristics with highly substituted pyridine compounds. When formaldehyde is added to glutaraldehyde-amine reactions, oxygen uptake is sharply reduced and the product spectrum is changed in a complex manner. Formaldehyde may thus have an entirely different role in the mixed glutaraldehyde-form-aldehyde fixatives than has previously been suggested

Quantitative magnetic resonance image analysis via the EM algorithm with stochastic variation

Quantitative Magnetic Resonance Imaging (qMRI) provides researchers insight into pathological and physiological alterations of living tissue, with the help of which researchers hope to predict (local) therapeutic efficacy early and determine optimal treatment schedule. However, the analysis of qMRI has been limited to ad-hoc heuristic methods. Our research provides a powerful statistical framework for image analysis and sheds light on future localized adaptive treatment regimes tailored to the individual's response. We assume in an imperfect world we only observe a blurred and noisy version of the underlying pathological/physiological changes via qMRI, due to measurement errors or unpredictable influences. We use a hidden Markov random field to model the spatial dependence in the data and develop a maximum likelihood approach via the Expectation--Maximization algorithm with stochastic variation. An important improvement over previous work is the assessment of variability in parameter estimation, which is the valid basis for statistical inference. More importantly, we focus on the expected changes rather than image segmentation. Our research has shown that the approach is powerful in both simulation studies and on a real dataset, while quite robust in the presence of some model assumption violations.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS157 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Effects of Selection Systems on Job Search Decisions

On the basis of Gilliland\u27s (1993) model of selection system fairness, the present study investigated the relationships between selection procedures, perceived selection system fairness, and job search decisions in both hypothetical and actual organizations. We conducted two studies to test the model. In Study 1, we used an experimental method to examine job seekers\u27 perceptions of, and reactions to, five widely used selection procedures. Results suggested that applicants viewed employment interviews and cognitive ability tests as more job related than biographical inventories (biodata), personality tests, and drug tests, and that job relatedness significantly affected fairness perceptions, which in turn affected job search decisions. Study 2 examined the hypothesized relationships between the selection systems and job seekers\u27 pursuit of actual, relevant organizations. Results from both studies offer support for the hypothesized model, suggesting that selection tests have differential effects on perceived selection system validity and fairness, which affect subsequent job search decisions

Employee Age as a Moderator of the Relationship Between Ambition and Work Role Affect

Past research has demonstrated a negative relationship between ambition, or the desire to get ahead, and job satisfaction. In the present paper, age was hypothesized to moderate the relationship between ambition and job satisfaction such that the relationship between ambition and satisfaction is more negative for older employees than for younger employees. Three studies, with three criterion variables (promotion satisfaction, extrinsic job satisfaction, overall job satisfaction), were used to test the hypothesis. Results indicated support for the hypothesized interaction. The discussion focuses on the implications of the results for organizational and individual career management strategies

T-maze learning in weanling lambs

A major advantage of sheep models in experimental studies of neurodevelopmental disorders (e.g., with prenatal neurotoxicant exposure) is that the equivalent of all three trimesters of human brain development occurs in sheep entirely in utero. However, studies of learning and memory in sheep are limited. The goal of this study was to extend the analysis of spatial learning and memory in adolescent sheep using several traditional T-maze tasks. Both 9- and 14-week-old lambs acquired a delayed non-matching to place task, but the older lambs learned the task significantly faster. In contrast, acquisition of a matching to place task was significantly more difficult. Lambs, like rodents, appear to have a predisposition toward learning “win-shift” spatial problems in a T-maze under appetitive motivation. Lambs also rapidly acquired a position habit and showed typical reversal learning curves. These findings support the use of T-maze tasks to assess behavioral outcomes in various sheep models