Government Information Quarterly. Volume 7, no. 2: National Aeronautics and Space Administration Scientific and Technical Information Programs. Special issue

NASA scientific and technical information (STI) programs are discussed. Topics include management of information in a research and development agency, the new space and Earth science information systems at NASA's archive, scientific and technical information management, and technology transfer of NASA aerospace technology to other industries

Knowing what you know in brain segmentation using Bayesian deep neural networks

In this paper, we describe a Bayesian deep neural network (DNN) for predicting FreeSurfer segmentations of structural MRI volumes, in minutes rather than hours. The network was trained and evaluated on a large dataset (n = 11,480), obtained by combining data from more than a hundred different sites, and also evaluated on another completely held-out dataset (n = 418). The network was trained using a novel spike-and-slab dropout-based variational inference approach. We show that, on these datasets, the proposed Bayesian DNN outperforms previously proposed methods, in terms of the similarity between the segmentation predictions and the FreeSurfer labels, and the usefulness of the estimate uncertainty of these predictions. In particular, we demonstrated that the prediction uncertainty of this network at each voxel is a good indicator of whether the network has made an error and that the uncertainty across the whole brain can predict the manual quality control ratings of a scan. The proposed Bayesian DNN method should be applicable to any new network architecture for addressing the segmentation problem.Comment: Submitted to Frontiers in Neuroinformatic

The Nature of the Red Giant Branches in the Ursa Minor and Draco Dwarf Spheroidal Galaxies

Spectra for stars located redward of the fiducial red giant branches of the Ursa Minor and Draco dwarf spheroidal galaxies have been obtained with the Hobby-Eberly telescope and the Marcario Low Resolution Spectrometer. From a comparison of our radial velocities with those reported in previous medium-resolution studies, we find an average difference of 10 km/s with a standard deviation of 11 km/s. On the basis of these radial velocities, we confirm the membership of five stars in Ursa Minor, and find two others to be nonmembers. One of the confirmed members is a known carbon star which lies redward of RGB; three others are previously unidentified carbon stars. The fifth star is a red giant which was found previously by Shetrone et al. (2001) to have [Fe/H] =-1.68+/-0.11 dex. In Draco, we find eight nonmembers, confirm the membership of one known carbon star, and find two new members. One of these stars is a carbon star, while the other shows no evidence for C2 bands or strong atomic bands, although the signal-to-noise ratio of the spectrum is low. Thus, we find no evidence for a population of stars more metal-rich than [Fe/H] \~ -1.45 dex in either of these galaxies. Indeed, our spectroscopic survey suggests that every candidate suspected of having a metallicity in excess of this value based on its position in the color-magnitude diagram is, in actuality, a carbon star. Based on the census of 13 known carbon stars in these two galaxies, we estimate of the carbon star specific frequency to be e(dSph) ~ 2.4E-5/Lsolarv, 25-100 times higher than that of Galactic globular clusters.Comment: 8 pages including 3 figures accepted in the Publications of the Astronomical Society of the Pacific. This work is based on observations obtained with the Hobby-Eberly Telescop

Age Differences in Striatal Delay Sensitivity during Intertemporal Choice in Healthy Adults

Intertemporal choices are a ubiquitous class of decisions that involve selecting between outcomes available at different times in the future. We investigated the neural systems supporting intertemporal decisions in healthy younger and older adults. Using functional neuroimaging, we find that aging is associated with a shift in the brain areas that respond to delayed rewards. Although we replicate findings that brain regions associated with the mesolimbic dopamine system respond preferentially to immediate rewards, we find a separate region in the ventral striatum with very modest time dependence in older adults. Activation in this striatal region was relatively insensitive to delay in older but not younger adults. Since the dopamine system is believed to support associative learning about future rewards over time, our observed transfer of function may be due to greater experience with delayed rewards as people age. Identifying differences in the neural systems underlying these decisions may contribute to a more comprehensive model of age-related change in intertemporal choice

N-terminal pro-B-type natriuretic peptide and risk of future cognitive impairment in the REGARDS cohort

Background: Improved understanding of the etiology of cognitive impairment is needed to develop effective preventive interventions. Higher amino-terminal pro-B-type natriuretic peptide (NT-proBNP) is a biomarker of cardiac dysfunction associated with risk of cardiovascular diseases and stroke in apparently healthy people. Objective: To study the association of NT-proBNP with risk of incident cognitive impairment. Methods: The Reasons for Geographic and Racial Differences in Stroke is a national cohort study of 30,239 black and white Americans age 45 and older at baseline, enrolled in 2003-7. Among participants without prebaseline stroke or cognitive impairment, baseline NT-proBNP was measured in 470 cases of incident cognitive impairment and 557 controls. Cases were participants scoring below the 6th percentile of demographically-adjusted means on at least 2 of 3 serially administered tests (word list learning, word list recall and semantic fluency) over 3.5 years follow-up. Results: Adjusting for age, gender, race, region of residence, education, and income, there was an increased odds ratio of incident cognitive impairment with increasing NT-proBNP; participants in the 4th versus 1st quartile (>127 versus ≤33 pg/ml) had a 1.69-fold increased odds (95% CI 1.11–2.58). Adjustment for cardiovascular risk factors and presence of an apolipoprotein E4 allele had no substantial impact on the odds ratio. Results did not differ by age, race, gender, or presence of an apolipoprotein E4 allele. Conclusion: Higher NT-pro-BNP was associated with incident cognitive impairment in this prospective study, independent of atherogenic and Alzheimer’s disease risk factors. Future work should clarify pathophysiologic connections of NT-proBNP and cognitive dysfunction

The Association of Parasitic Infections in Pregnancy and Maternal and Fetal Anemia: A Cohort Study in Coastal Kenya

Background: Relative contribution of these infections on anemia in pregnancy is not certain. While measures to protect pregnant women against malaria have been scaling up, interventions against helminthes have received much less attention. In this study, we determine the relative impact of helminthes and malaria on maternal anemia. Methods: A prospective observational study was conducted in coastal Kenya among a cohort of pregnant women who were recruited at their first antenatal care (ANC) visit and tested for malaria, hookworm, and other parasitic infections and anemia at enrollment. All women enrolled in the study received presumptive treatment with sulfadoxine-pyrimethamine, iron and multi-vitamins and women diagnosed with helminthic infections were treated with albendazole. Women delivering a live, term birth, were also tested for maternal anemia, fetal anemia and presence of infection at delivery. Principal Findings: Of the 706 women studied, at the first ANC visit, 27% had moderate/severe anemia and 71% of women were anemic overall. The infections with highest prevalence were hookworm (24%), urogenital schistosomiasis (17%), trichuria (10%), and malaria (9%). In adjusted and unadjusted analyses, moderate/severe anemia at first ANC visit was associated with the higher intensities of hookworm and P. falciparum microscopy-malaria infections. At delivery, 34% of women had moderate/severe anemia and 18% of infants' cord hemoglobin was consistent with fetal anemia. While none of the maternal infections were significantly associated with fetal anemia, moderate/severe maternal anemia was associated with fetal anemia. Conclusions: More than one quarter of women receiving standard ANC with IPTp for malaria had moderate/severe anemia in pregnancy and high rates of parasitic infection. Thus, addressing the role of co-infections, such as hookworm, as well as under-nutrition, and their contribution to anemia is needed

A cohort study of Plasmodium falciparum malaria in pregnancy and associations with uteroplacental blood flow and fetal anthropometrics in Kenya

To use ultrasound to explore the impact of malaria in pregnancy on fetal growth and newborn outcomes among a cohort of women enrolled in an intermittent presumptive treatment in pregnancy (IPTp) with sulfadoxine/pyrimethamine (SP) program in coastal Kenya