Modeling human observer detection in undersampled magnetic resonance imaging (MRI) reconstruction with total variation and wavelet sparsity regularization

Purpose: Task-based assessment of image quality in undersampled magnetic resonance imaging provides a way of evaluating the impact of regularization on task performance. In this work, we evaluated the effect of total variation (TV) and wavelet regularization on human detection of signals with a varying background and validated a model observer in predicting human performance. Approach: Human observer studies used two-alternative forced choice (2-AFC) trials with a small signal known exactly task but with varying backgrounds for fluid-attenuated inversion recovery images reconstructed from undersampled multi-coil data. We used a 3.48 undersampling factor with TV and a wavelet sparsity constraints. The sparse difference-of-Gaussians (S-DOG) observer with internal noise was used to model human observer detection. Results: We observed a trend that the human observer detection performance remained fairly constant for a broad range of values in the regularization parameter before decreasing at large values. A similar result was found for the normalized ensemble root mean squared error. Without changing the internal noise, the model observer tracked the performance of the human observers as the regularization was increased but overestimated the PC for large amounts of regularization for TV and wavelet sparsity, as well as the combination of both parameters. Conclusions: For the task we studied, the S-DOG observer was able to reasonably predict human performance with both TV and wavelet sparsity regularizers over a broad range of regularization parameters. We observed a trend that task performance remained fairly constant for a range of regularization parameters before decreasing for large amounts of regularization

Friction Stir Welding of Aluminum 6082 with Mild Steel and Its Joint Analyses

Energy-saving and reduction in CO2 emission are the two important challenging issues that must be resolved in the coming future. Introducing aluminum components in a standard steel car body or in the hulls of ship brings the reduction in weight of vehicles, thereby reducing the emission. In this research study, Aluminum 6082 alloy and mild steel were tried to join together (weld) by an eco-friendly and energy efficient technology named as Friction Stir Welding (FSW), which is far advantageous than the conventional fusion welding especially in the case of joining dissimilar materials. As this is a solid state welding process, most of the defects occurring in the molten state of the material could be completely eliminated. Also, welding takes place at low temperature (below the melting point of the material) due to which there is less chance of intermetallics formation at the heat affected region that will eventually degrade the mechanical properties of the weld

ACCELERATED FIRST PASS CARDIAC PERFUSION MRI USING IMPROVED k − t SLR

ABSTRACT Routinely trade-offs between the spatio-temporal resolution, volume coverage and SNR are done in first pass cardiac perfusion MRI due to the restricted imaging acquisition window (usually of the order of 300 to 400 msec per heart beat). In this paper, we demonstrate the use a low rank and sparse reconstruction scheme (k − t SLR) in obtaining highly accelerated first pass perfusion MR images and hence aim to reduce the above mentioned trade-offs. We introduce non-convex spectral norms and use a spatio-temporal total variation norm in recovering the dynamic signal matrix. We introduce an augmented Lagrangian optimization scheme in the context of matrix recovery to speed up the convergence of the algorithm. Extensive validations on in-vivo data are done to demonstrate the performance improvement of the proposed frame work

Reproducibility and repeatability of six high-throughput 16S rDNA sequencing protocols for microbiota profiling

Culture-independent molecular techniques and advances in next generation sequencing (NGS) technologies make large-scale epidemiological studies on microbiota feasible. A challenge using NGS is to obtain high reproducibility and repeatability, which is mostly attained through robust amplification. We aimed to assess the reproducibility of saliva microbiota by comparing triplicate samples. The microbiota was produced with simplified in-house 16S amplicon assays taking advantage of large number of barcodes. The assays included primers with Truseq (TS-tailed) or Nextera (NX-tailed) adapters and either with dual index or dual index plus a 6-nt internal index. All amplification protocols produced consistent microbial profiles for the same samples. Although, in our study, reproducibility was highest for the TS-tailed method. Five replicates of a single sample, prepared with the TS-tailed 1-step protocol without internal index sequenced on the HiSeq platform provided high alpha-diversity and low standard deviation (mean Shannon and Inverse Simpson diversity was 3.19 +/- 0.097 and 13.56 +/- 1.634 respectively). Large-scale profiling of microbiota can consistently be produced by all 16S amplicon assays. The TS-tailed-1S dual index protocol is preferred since it provides repeatable profiles on the HiSeq platform and are less labour intensive.Peer reviewe

Gender-Specific Associations Between Saliva Microbiota and Body Size

Objective: The human intestinal microbiota likely play an important role in the development of overweight and obesity. However, the associations between saliva microbiota and body mass index (BMI) have been sparsely studied. The aim of this study was to identify the associations between saliva microbiota and body size in Finnish children. Methods: The saliva microbiota of 900 Finnish children, aged 11-14 years with measured height and weight, was characterized using 16S rRNA (V3-V4) sequencing. Results: The core saliva microbiota consisted of 14 genera that were present in more than 95% of the Finnish children. The saliva microbiota profiles were gender-specific with higher alpha-diversity in boys than girls and significant differences between the genders in community composition and abundances. Alpha-diversity differed between normal weight and overweight girls and between normal weight and obese boys. The composition was dissimilar between normal weight and obese girls, but not in boys. The relative abundance profiles differed according to body size. Decrease in commensal saliva bacteria were observed in all the body sizes when compared to normal weight children. Notably, the relative abundance of bacteria related to, Veillonella, Prevotella, Selenomonas, and Streptococcus was reduced in obese children. Conclusion: Saliva microbiota diversity and composition were significantly associated with body size and gender in Finnish children. Body size-specific saliva microbiota profiles open new avenues for studying the potential roles of microbiota in weight development and management.Peer reviewe

Antimicrobial drug use in the first decade of life influences saliva microbiota diversity and composition

Background: The human microbiota contributes to health and well-being. Antimicrobials (AM) have an immediate effect on microbial diversity and composition in the gut, but next to nothing is known about their long-term contribution to saliva microbiota. Our objectives were to investigate the long-term impact of AM use on saliva microbiota diversity and composition in preadolescents. We compared the lifetime effects by gender and AMs. We used data from 808 randomly selected children in the Finnish Health In Teens (Fin-HIT) cohort with register-based data on AM purchases from the Social Insurance Institution of Finland. Saliva microbiota was assessed with 16S rRNA (V3-V4) sequencing. The sequences were aligned to the SILVA ribosomal RNA database and classified and counted using the mothur pipeline. Associations between AM use and alpha-diversity (Shannon index) were identified with linear regression, while associations between beta-diversity (Bray-Curtis dissimilarity) and low, medium or high AM use were identified with PERMANOVA. Results: Of the children, 53.6% were girls and their mean age was 11.7 (0.4) years. On average, the children had 7.4 (ranging from 0 to 41) AM prescriptions during their lifespan. The four most commonly used AMs were amoxicillin (n= 2622, 43.7%), azithromycin (n= 1495, 24.9%), amoxicillin-clavulanate (n= 1123, 18.7%) and phenoxymethylpenicillin (n= 408, 6.8%). A linear inverse association was observed between the use of azithromycin and Shannon index (b- 0.015,pvalue = 0.002) in all children, the effect was driven by girls (b- 0.032,pvalue = 0.001), while not present in boys. Dissimilarities were marked between high, medium and low users of all AMs combined, in azithromycin users specifically, and in boys with amoxicillin use. Amoxicillin and amoxicillin-clavulanate use was associated with the largest decrease in abundance ofRikenellaceae. AM use in general and phenoxymethylpenicillin specifically were associated with a decrease ofPaludibacterand pathways related to amino acid degradations differed in proportion between high and low AM users. Conclusions: A systematic approach utilising reliable registry data on lifetime use of AMs demonstrated long-term effects on saliva microbiota diversity and composition. These effects are gender- and AM-dependent. We found that frequent lifelong use of AMs shifts bacterial profiles years later, which might have unforeseen health impacts in the future. Our findings emphasise a concern for high azithromycin use, which substantially decreases bacterial diversity and affects composition as well. Further studies are needed to determine the clinical implications of our findings.Peer reviewe

Unified reconstruction and motion estimation in cardiac perfusion MRI

ABSTRACT We introduce a novel unifying approach to jointly estimate the motion and the dynamic images in first pass cardiac perfusion MR imaging. We formulate the recovery as an energy minimization scheme using a unified objective function that combines data consistency, spatial smoothness, motion and contrast dynamics penalties. We introduce a variable splitting strategy to simplify the objective function into multiple sub problems, which are solved using simple algorithms. These sub-problems are solved in an iterative manner using efficient continuation strategies. Preliminary validation using a numerical phantom and in-vivo perfusion data demonstrate the utility of the proposed scheme in recovering the perfusion images from considerably under-sampled data

Long-term ambient air-stable cubic CsPbBr3 perovskite quantum dots using molecular bromine

We report unprecedented phase stability of cubic CsPbBr3 quantum dots in ambient air obtained by using Br2 as halide precursor. Mechanistic investigation reveals the decisive role of temperature-controlled in situ generated, oleylammonium halide species from molecular halogen and amine for the long term stability and emission tunability of CsPbX3 (X = Br, I) nanocrystals

Controlling Cherenkov angles with resonance transition radiation

Cherenkov radiation provides a valuable way to identify high energy particles in a wide momentum range, through the relation between the particle velocity and the Cherenkov angle. However, since the Cherenkov angle depends only on material's permittivity, the material unavoidably sets a fundamental limit to the momentum coverage and sensitivity of Cherenkov detectors. For example, Ring Imaging Cherenkov detectors must employ materials transparent to the frequency of interest as well as possessing permittivities close to unity to identify particles in the multi GeV range, and thus are often limited to large gas chambers. It would be extremely important albeit challenging to lift this fundamental limit and control Cherenkov angles as preferred. Here we propose a new mechanism that uses constructive interference of resonance transition radiation from photonic crystals to generate both forward and backward Cherenkov radiation. This mechanism can control Cherenkov angles in a flexible way with high sensitivity to any desired range of velocities. Photonic crystals thus overcome the severe material limit for Cherenkov detectors, enabling the use of transparent materials with arbitrary values of permittivity, and provide a promising option suited for identification of particles at high energy with enhanced sensitivity.Comment: There are 16 pages and 4 figures for the manuscript. Supplementary information with 18 pages and 5 figures, appended at the end of the file with the manuscript. Source files in Word format converted to PDF. Submitted to Nature Physic