Solving a fluid-plate interaction problem using finite element methods with domain decomposition strategies

This thesis studies numerically a fluid-plate interaction problem which models the coupled vibration between an acoustic field and an elastic thin plate. Since the thickness of the plate is negligible, the plate serves a dual role in the model. It is the solid medium and at the same time it is the interface between the acoustic field and the solid. Mathematically, the interaction problem is described by the acoustic wave equation in the fluid and the fourth order plate vibration equation on the plate. The pressure in the fluid and the vertical displacement of the plate are the primary variables to be solved numerically. The objectives of the thesis are to propose and to implement on computers a numerical scheme for computing the solution of the interaction problem. In the scheme, the finite element method is used for the spatial discretization, and the finite difference method is employed for the temporal discretization. The fully discrete finite element equations are then solved by using a parallelizable domain decomposition algorithm. A computer code is developed, and its efficiency and accuracy are tested on the specific examples

Margaret M. Gibson Correspondence

Entries include letters of correspondence about the author. Date range: 1939-1

Earth Radiation Budget Research at the NASA Langley Research Center

In the 1970s research studies concentrating on satellite measurements of Earth's radiation budget started at the NASA Langley Research Center. Since that beginning, considerable effort has been devoted to developing measurement techniques, data analysis methods, and time-space sampling strategies to meet the radiation budget science requirements for climate studies. Implementation and success of the Earth Radiation Budget Experiment (ERBE) and the Clouds and the Earth's Radiant Energy System (CERES) was due to the remarkable teamwork of many engineers, scientists, and data analysts. Data from ERBE have provided a new understanding of the effects of clouds, aerosols, and El Nino/La Nina oscillation on the Earth's radiation. CERES spacecraft instruments have extended the time coverage with high quality climate data records for over a decade. Using ERBE and CERES measurements these teams have created information about radiation at the top of the atmosphere, at the surface, and throughout the atmosphere for a better understanding of our climate. They have also generated surface radiation products for designers of solar power plants and buildings and numerous other application

Model of heterogeneous microscale in SOFI for Monte Carlo simulations

We present a methodology for creating a simulated foam microstructure for use in forward simulations of wave equations to quantitatively analyze the expected scattering phenomenon primarily responsible for the attenuation of interrogating signals in Sprayed-On Foam Insulation (SOFI). Our approach builds off of the popular use of Voronoi Tessalations for crystal growth modeling by using the Laguerre variant (Apollonius Graph) applied to close-packed spheres. A fi lled-in random raindrop algorithm is used to generate the packing confi guration. Lastly, variation of diameter mean values is used to model knitlines, i.e., the interfaces between sprayed-on layers

Automatic Brain Tumor Segmentation using Convolutional Neural Networks with Test-Time Augmentation

Automatic brain tumor segmentation plays an important role for diagnosis, surgical planning and treatment assessment of brain tumors. Deep convolutional neural networks (CNNs) have been widely used for this task. Due to the relatively small data set for training, data augmentation at training time has been commonly used for better performance of CNNs. Recent works also demonstrated the usefulness of using augmentation at test time, in addition to training time, for achieving more robust predictions. We investigate how test-time augmentation can improve CNNs' performance for brain tumor segmentation. We used different underpinning network structures and augmented the image by 3D rotation, flipping, scaling and adding random noise at both training and test time. Experiments with BraTS 2018 training and validation set show that test-time augmentation helps to improve the brain tumor segmentation accuracy and obtain uncertainty estimation of the segmentation results.Comment: 12 pages, 3 figures, MICCAI BrainLes 201

Recombination and its impact on the genome of the haplodiploid parasitoid wasp Nasonia

Homologous meiotic recombination occurs in most sexually reproducing organisms, yet its evolutionary advantages are elusive. Previous research explored recombination in the honeybee, a eusocial hymenopteran with an exceptionally high genome-wide recombination rate. A comparable study in a non-social member of the Hymenoptera that would disentangle the impact of sociality from Hymenoptera-specific features such as haplodiploidy on the evolution of the high genome-wide recombination rate in social Hymenoptera is missing. Utilizing single-nucleotide polymorphisms (SNPs) between two Nasonia parasitoid wasp genomes, we developed a SNP genotyping microarray to infer a high-density linkage map for Nasonia. The map comprises 1,255 markers with an average distance of 0.3 cM. The mapped markers enabled us to arrange 265 scaffolds of the Nasonia genome assembly 1.0 on the linkage map, representing 63.6% of the assembled N. vitripennis genome. We estimated a genome-wide recombination rate of 1.4-1.5 cM/Mb for Nasonia, which is less than one tenth of the rate reported for the honeybee. The local recombination rate in Nasonia is positively correlated with the distance to the center of the linkage groups, GC content, and the proportion of simple repeats. In contrast to the honeybee genome, gene density in the parasitoid wasp genome is positively associated with the recombination rate; regions of low recombination are characterized by fewer genes with larger introns and by a greater distance between genes. Finally, we found that genes in regions of the genome with a low recombination frequency tend to have a higher ratio of non-synonymous to synonymous substitutions, likely due to the accumulation of slightly deleterious non-synonymous substitutions. These findings are consistent with the hypothesis that recombination reduces interference between linked sites and thereby facilitates adaptive evolution and the purging of deleterious mutations. Our results imply that the genomes of haplodiploid and of diploid higher eukaryotes do not differ systematically in their recombination rates and associated parameters.Publisher PDFPeer reviewe

Association of handgrip strength with suicidal ideation among adults aged ≥50 years from low- and middle-income countries

IntroductionThis study aimed to investigate the association between handgrip strength and suicidal ideation in representative samples of adults aged >= 50 years from six LMICs (China, Ghana, India, Mexico, Russia, and South Africa).MethodsCross-sectional, community-based data from the World Health Organization's Study on Global Aging and Adult Health were analyzed. Handgrip strength quintiles by sex were created based on the average value of two handgrip measurements of the dominant hand. Self-reported information on past 12-month suicidal ideation was collected. Multivariable logistic regression analysis was conducted to assess associations.ResultsData on 34,129 individuals were analyzed [mean (SD) age 62.4 (16.0) years; age range 50-114 years; 52.1% females]. After adjustment for potential confounders, in the overall sample, compared to the handgrip strength quintile with the highest values [Quintile 1 (Q1)], Q2, Q3, Q4, and Q5 were associated with significant 2.15 (95% CI = 1.05-4.39), 2.78 (95% CI = 1.06-7.32), 3.53 (95% CI = 1.68-7.42), and 6.79 (95% CI = 2.80-16.48) times higher odds for suicidal ideation.ConclusionsLower handgrip strength was significantly and dose-dependently associated with higher odds for suicidal ideation in adults aged >= 50 years from LMICs. Future longitudinal studies are needed to understand the underlying mechanisms, and whether increasing general muscular strength and physical function may lead to reduction in suicidal ideation

Covariant equations for the three-body bound state

The covariant spectator (or Gross) equations for the bound state of three identical spin 1/2 particles, in which two of the three interacting particles are always on shell, are developed and reduced to a form suitable for numerical solution. The equations are first written in operator form and compared to the Bethe-Salpeter equation, then expanded into plane wave momentum states, and finally expanded into partial waves using the three-body helicity formalism first introduced by Wick. In order to solve the equations, the two-body scattering amplitudes must be boosted from the overall three-body rest frame to their individual two-body rest frames, and all effects which arise from these boosts, including the Wigner rotations and rho-spin decomposition of the off-shell particle, are treated exactly. In their final form, the equations reduce to a coupled set of Faddeev-like double integral equations with additional channels arising from the negative rho-spin states of the off-shell particle.Comment: 57 pages, RevTeX, 6 figures, uses epsf.st

Kiwifruit fermentation drives positive gut microbial and metabolic changes irrespective of initial microbiota composition

It is well established that individuals vary greatly in the composition of their core microbiota. Despite differing ecology, we show here that metabolic capacity converges under the pressure of kiwifruit substrates in a model gut system. The impact of pre-digested green and gold kiwifruit on the human colonic microbiota and their metabolic products was assessed using in vitro, pH-controlled, anaerobic batch culture fermenters. Phylogenetic analyses revealed that bacterial composition changed over time, irrespective of whether a substrate was added or not, indicating a natural adjustment period to the gut model environment. Adding kiwifruit substrate caused additional changes in terms of growth of specific bacterial groups, bacterial diversity and metabolite profiles. Relative abundance of Bacteroides spp. increased with both green and gold kiwifruit substrate while Bifidobacterium spp. increased only with green kiwifruit. NMR spectroscopy and GC demonstrated an increase in organic acids (primarily acetate, butyrate, and propionate) and a concomitant decrease in several amino acids and oligosaccharides following addition of green and gold kiwifruit substrate. The experiments demonstrated that despite markedly different baseline profiles in individual donor inoculum, kiwifruit components can induce substantive change in microbial ecology and metabolism which could have consequences for human health