4,079 research outputs found
Structure and correlates of cognitive aging in a narrow age cohort
Aging-related changes occur for multiple domains of cognitive functioning. An accumulating body of research indicates that, rather than representing statistically independent phenomena, aging-related cognitive changes are moderately to strongly correlated across domains. However, previous studies have typically been conducted in age-heterogeneous samples over longitudinal time lags of 6 or more years, and have failed to consider whether results are robust to a comprehensive set of controls. Capitalizing on 3-year longitudinal data from the Lothian Birth Cohort of 1936, we took a longitudinal narrow age cohort approach to examine cross-domain cognitive change interrelations from ages 70 to 73 years. We fit multivariate latent difference score models to factors representing visuospatial ability, processing speed, memory, and crystallized ability. Changes were moderately interrelated, with a general factor of change accounting for 47% of the variance in changes across domains. Change interrelations persisted at close to full strength after controlling for a comprehensive set of demographic, physical, and medical factors including educational attainment, childhood intelligence, physical function, APOE genotype, smoking status, diagnosis of hypertension, diagnosis of cardiovascular disease, and diagnosis of diabetes. Thus, the positive manifold of aging-related cognitive changes is highly robust in that it can be detected in a narrow age cohort followed over a relatively brief longitudinal period, and persists even after controlling for many potential confounders
Microgeographic Variation in Response of Red-Eared Slider (Trachemys scripta elegans) Embryos to Similar Incubation Environments
We examined site-specific variation in the response of red-eared slider (Trachemys elegans) embryos exposed to similar incubation environments, and collected at five nearby sites central Illinois. Overall, site was not a significant source of variance in change in egg mass during bation, in hatchling wet mass, and in hatchling carapace length. However, site was a significant source variance in incubation period. Nonetheless, significant site-specific differences in each trait were in pairwise comparisons. The actual difference between extremes was small. Eggs from the site longest incubation period also gained the most water during incubation. Our study has important cations for future studies of geographic variation in the physiological response of embryos to incubation environments. Comparisons between eggs and embryos from geographically distant sites would benefit inclusion of as many clutches as possible. Larger numbers of clutches reduce the possibility that ferences between geographically distant regions are due to maternal differences rather than region-differences. Studies comparing embryonic responses from geographically distant regions would be strengthened by including turtles from as many local collecting sites for each region as possible. Sampling site per region may be inadequate because any geographic variation in embryonic response could well be due to undetected local site-specific differences
A Complete Finite Equational Axiomatisation of the Fracterm Calculus for Common Meadows
We analyse abstract data types that model numerical structures with a concept
of error. Specifically, we focus on arithmetic data types that contain an error
flag whose main purpose is to always return a value for division. To
rings and fields we add a division operator and study a class of algebras
called \textit{common meadows} wherein . The set of equations true
in all common meadows is named the \textit{fracterm calculus of common
meadows}. We give a finite equational axiomatisation of the fracterm calculus
of common meadows and prove that it is complete and that the fracterm calculus
is decidable
Scale and Turbulence Effects on the Lift and Drag Characteristics of the NACA 65(Sub 3)-418, A=1.0 Airfoil Section
Wind-tunnel tests, investigating low drag wing performance in small-scale tests, showed a large increase in minimum drag coefficient, and a decrease of maximum lift coefficient occurred with decreasing Reynolds Number above certain designated values. The lift-curve slope varied up to 6% between high and low turbulence levels. Low Reynolds Number test data are unreliable for low drag airfoils either to estimate full-scale characteristics or to determine merits of airfoils for higher Reynolds numbers
Ultra-high energy cosmic rays may come from clustered sources
Clustering of cosmic-ray sources affects the flux observed beyond the cutoff
imposed by the cosmic microwave background and may be important in interpreting
the AGASA, Fly's Eye, and HiRes data. The standard deviation, sigma, in the
predicted number, N, of events above 10^{20} eV is sigma/N = 0.9(r_0/10
Mpc)^{0.9}, where r_0 is the unknown scale length of the correlation function
(r_0 = 10 Mpc for field galaxies). Future experiments will allow the
determination of r_0 through the detection of anisotropies in arrival
directions of ~ 10^{20} eV cosmic-rays over angular scales of Theta ~ r_0/30
Mpc.Comment: Accepted for publication in Astrophysical Journa
Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267
We report the results of a pilot program to use the Magellan/M2FS
spectrograph to survey the galactic populations and internal kinematics of
galaxy clusters. For this initial study, we present spectroscopic measurements
for quiescent galaxies observed along the line of sight to the galaxy
cluster Abell 267 (). We develop a Bayesian method for modeling the
integrated light from each galaxy as a simple stellar population, with free
parameters that specify redshift () and characteristic age,
metallicity (), alpha-abundance (), and
internal velocity dispersion () for individual galaxies.
Parameter estimates derived from our 1.5-hour observation of A267 have median
random errors of ,
, $\sigma_{\mathrm{[Fe/H]}}=0.11\
\mathrm{dex}\sigma_{[\alpha/\mathrm{Fe}]}=0.07\ \mathrm{dex}\sigma_{\sigma_\mathrm{int}}=20\ \mathrm{km\ s^{-1}}$. In a companion paper,
we use these results to model the structure and internal kinematics of A267.Comment: 16 pages, 11 figures, accepted for publication in The Astronomical
Journa
Systolic and diastolic ventricular function in zebrafish embryos: Influence of norepenephrine, MS-222 and temperature
<p>Abstract</p> <p>Background</p> <p>Zebrafish are increasingly used to study the influences of gene mutation and manipulation on cardiac development, structure and function. In this study, a video edge detection system was used to characterise, continuously, cardiac ventricle function in 2â5 days old zebrafish embryos embedded in 0.6% agar and examined under light microscopy at room temperature (22°C). Using video edge detection software (IonOptix Inc), the motion of a small region of the cardiac ventricle wall was converted to a continuous chart trace allowing analysis of wall motion amplitude (WMA) and myocardial wall velocity during systole (MWVs) and diastole (MWVd).</p> <p>Results</p> <p>Cardiac wall motion characteristics changed progressively from day 2 to 5 (WMA, 2-days, 17.6 ± 4.4 ÎŒm vs 5-days, 24.6 ± 4.7 ÎŒm, p < 0.01). MWVd was more rapid than MWVs at all developmental time points. Embryonic hearts were also assessed after increasing concentrations of norepenephrine (NE) and the anaesthetic agent MS222 (tricaine) were added to the bathing water. In response to NE, WMA increased significantly more in 4 day embryos compared with 2 day embryos (change in WMA,13.6 ± 8.2 ÎŒm vs 4.0 ± 8.8 ÎŒm, p = 0.01, respectively) while the decrease in WMA in response to MS222 was similar in both 2 and 4-day embryos. Heart rate, MWVs and MWVd were significantly higher at 28°C compared with 22°C. No differences in cardiac function were observed between AB and Golden strains.</p> <p>Conclusion</p> <p>Video edge detection appears sufficiently sensitive to detect subtle changes in diastolic and systolic cardiac function during development and changes resulting from pharmacological and environmental interventions. Such measurements could be valuable in assessment of altered cardiac function after genetic manipulation.</p
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