Feature Tracking Cardiac Magnetic Resonance via Deep Learning and Spline Optimization

Feature tracking Cardiac Magnetic Resonance (CMR) has recently emerged as an area of interest for quantification of regional cardiac function from balanced, steady state free precession (SSFP) cine sequences. However, currently available techniques lack full automation, limiting reproducibility. We propose a fully automated technique whereby a CMR image sequence is first segmented with a deep, fully convolutional neural network (CNN) architecture, and quadratic basis splines are fitted simultaneously across all cardiac frames using least squares optimization. Experiments are performed using data from 42 patients with hypertrophic cardiomyopathy (HCM) and 21 healthy control subjects. In terms of segmentation, we compared state-of-the-art CNN frameworks, U-Net and dilated convolution architectures, with and without temporal context, using cross validation with three folds. Performance relative to expert manual segmentation was similar across all networks: pixel accuracy was ~97%, intersection-over-union (IoU) across all classes was ~87%, and IoU across foreground classes only was ~85%. Endocardial left ventricular circumferential strain calculated from the proposed pipeline was significantly different in control and disease subjects (-25.3% vs -29.1%, p = 0.006), in agreement with the current clinical literature.Comment: Accepted to Functional Imaging and Modeling of the Heart (FIMH) 201

Simple and efficient synthesis of 5′ pre-adenylated DNA using thermostable RNA ligase

We report a simple method of enzymatic synthesis of pre-adenylated DNA linkers/adapters for next-generation sequencing using thermostable RNA ligase from Methanobacterium thermoautotrophicum (MthRnl). Using RNA ligase for the reaction instead of the existing chemical or T4 DNA ligase-based methods allows quantitative conversion of 5′-phosphorylated single-stranded DNA (ssDNA) to the adenylated form. The MthRnl adenylation reaction is specific for ATP and either ssDNA or RNA. In the presence of Mg+2, the reaction has a pH optimum of 6.0–6.5. Unlike reactions that use T4 DNA ligase, this protocol does not require synthesis of a template strand for adenylation. The high yield of the reaction simplifies isolation and purification of the adenylated product. Conducting the adenylation reaction at the elevated temperature (65°C) reduces structural constraints, while increased ATP concentrations allow quantitative adenylation of DNA with a 3′-unprotected end

Truth in Consequentiality: Theory and Field Evidence on Discrete Choice Experiments

This paper explores methodological issues surrounding the use of discrete choice experiments to elicit values for public goods. We develop an explicit game-theoretic model of individual decisions to a series of choice sets, providing general conditions under which surveys with repeated binary choices are incentive compatible. We complement the theory with a framed field experiment, with treatments that span the spectrum from incentive compatible, financially binding decisions to decisions with no direct financial consequences. The results suggest truthful preference revelation is possible in surveys, provided that respondents view their decisions as having more than a weak chance of influencing policy. Cette étude s’intéresse à des aspects méthodologiques associés à l’utilisation d’expériences avec choix discrets pour évaluer des biens publics. Nous avons développé un modèle explicite de jeux théoriques pour des décisions individuelles à des séries de choix, avec conditions générales sous lesquelles un questionnaire avec des choix binaires répétés incite la révélation des valeurs. Ce développement théorique est suivi d’expériences terrains avec traitements qui couvrent le spectre des incitatifs de la révélation des valeurs, passant de la décision avec mise en place réelle du projet et paiements réels de la part des participants, à celle sans aucune conséquence financière directe et avec projets hypothétiques. Les résultats indiquent qu’il est possible d’obtenir une révélation des valeurs réelles en situation hypothétique, si les participants pensent que leurs décisions ont un potentiel d’impact significatif sur une éventuelle politique.discrete choice experiment, framed field experiment, mechanism design theory, stated preferences, consequentiality , expériences avec choix discrets; expérience terrain; préférences révélées; conséquences, biais hypothétique

Models of Somatic Hypermutation Targeting and Substitution Based on Synonymous Mutations from High-Throughput Immunoglobulin Sequencing Data

Analyses of somatic hypermutation (SHM) patterns in B cell immunoglobulin (Ig) sequences contribute to our basic understanding of adaptive immunity, and have broad applications not only for understanding the immune response to pathogens, but also to determining the role of SHM in autoimmunity and B cell cancers. Although stochastic, SHM displays intrinsic biases that can confound statistical analysis, especially when combined with the particular codon usage and base composition in Ig sequences. Analysis of B cell clonal expansion, diversification, and selection processes thus critically depends on an accurate background model for SHM micro-sequence targeting (i.e., hot/cold-spots) and nucleotide substitution. Existing models are based on small numbers of sequences/mutations, in part because they depend on data from non-coding regions or non-functional sequences to remove the confounding influences of selection. Here, we combine high-throughput Ig sequencing with new computational analysis methods to produce improved models of SHM targeting and substitution that are based only on synonymous mutations, and are thus independent of selection. The resulting “S5F” models are based on 806,860 Synonymous mutations in 5-mer motifs from 1,145,182 Functional sequences and account for dependencies on the adjacent four nucleotides (two bases upstream and downstream of the mutation). The estimated profiles can explain almost half of the variance in observed mutation patterns, and clearly show that both mutation targeting and substitution are significantly influenced by neighboring bases. While mutability and substitution profiles were highly conserved across individuals, the variability across motifs was found to be much larger than previously estimated. The model and method source code are made available at http://clip.med.yale.edu/SH

Design of Packaging Vents for Cooling Fresh Horticultural Produce

Abstract This review focuses on the design of vents in packages used for handling horticulture produce. The studies on vent designs that are conducted to obtain fundamental understanding of the mechanisms by which different parameters affect the rate and homogeneity of the airflow and the cooling process are presented. Ventilated packages should be designed in such a way that they can provide a uniform airflow distribution and consequently uniform produce cooling. Total opening area and opening size and position show a significant effect on pressure drop, air distribution uniformity and cooling efficiency. Recent advances in measurement and mathematical modelling techniques have provided powerful tools to develop detailed investigations of local airflow rate and heat and mass transfer processes within complex packaging structures. The complexity of the physical structure of the packed systems and the biological variability of the produce make both experimental and model-based studies of transport processes challenging. In many of the available mathematical models, the packed structure is assumed as a porous medium; the limitations of the porous media approach are evident during vented package design studies principally when the containerto-produce dimension ratio is below a certain value. The complex and chaotic structure within horticultural produce ventilated packages during a forced-air precooling process complicates the numerical study of energy and mass transfer considering each individual produce. Future research efforts should be directed to detailed models of the vented package, the complex produce stacking within the package, as well as their interaction with adjacent produce, stacks and surrounding environment. For the validation of the numerical models, the development of better experimental techniques taking into account the complex packaging system is also very important

Salmonella Infection Drives Promiscuous B Cell Activation Followed by Extrafollicular Affinity Maturation

SummaryThe B cell response to Salmonella typhimurium (STm) occurs massively at extrafollicular sites, without notable germinal centers (GCs). Little is known in terms of its specificity. To expand the knowledge of antigen targets, we screened plasmablast (PB)-derived monoclonal antibodies (mAbs) for Salmonella specificity, using ELISA, flow cytometry, and antigen microarray. Only a small fraction (0.5%–2%) of the response appeared to be Salmonella-specific. Yet, infection of mice with limited B cell receptor (BCR) repertoires impaired the response, suggesting that BCR specificity was important. We showed, using laser microdissection, that somatic hypermutation (SHM) occurred efficiently at extrafollicular sites leading to affinity maturation that in turn led to detectable STm Ag-binding. These results suggest a revised vision of how clonal selection and affinity maturation operate in response to Salmonella. Clonal selection initially is promiscuous, activating cells with virtually undetectable affinity, yet SHM and selection occur during the extrafollicular response yielding higher affinity, detectable antibodies

Antipsychotics and Torsadogenic Risk: Signals Emerging from the US FDA Adverse Event Reporting System Database

Background: Drug-induced torsades de pointes (TdP) and related clinical entities represent a current regulatory and clinical burden. Objective: As part of the FP7 ARITMO (Arrhythmogenic Potential of Drugs) project, we explored the publicly available US FDA Adverse Event Reporting System (FAERS) database to detect signals of torsadogenicity for antipsychotics (APs). Methods: Four groups of events in decreasing order of drug-attributable risk were identified: (1) TdP, (2) QT-interval abnormalities, (3) ventricular fibrillation/tachycardia, and (4) sudden cardiac death. The reporting odds ratio (ROR) with 95 % confidence interval (CI) was calculated through a cumulative analysis from group 1 to 4. For groups 1+2, ROR was adjusted for age, gender, and concomitant drugs (e.g., antiarrhythmics) and stratified for AZCERT drugs, lists I and II (http://www.azcert.org, as of June 2011). A potential signal of torsadogenicity was defined if a drug met all the following criteria: (a) four or more cases in group 1+2; (b) significant ROR in group 1+2 that persists through the cumulative approach; (c) significant adjusted ROR for group 1+2 in the stratum without AZCERT drugs; (d) not included in AZCERT lists (as of June 2011). Results: Over the 7-year period, 37 APs were reported in 4,794 cases of arrhythmia: 140 (group 1), 883 (group 2), 1,651 (group 3), and 2,120 (group 4). Based on our criteria, the following potential signals of torsadogenicity were found: amisulpride (25 cases; adjusted ROR in the stratum without AZCERT drugs = 43.94, 95 % CI 22.82-84.60), cyamemazine (11; 15.48, 6.87-34.91), and olanzapine (189; 7.74, 6.45-9.30). Conclusions: This pharmacovigilance analysis on the FAERS found 3 potential signals of torsadogenicity for drugs previously unknown for this risk

Single T Cell Sequencing Demonstrates the Functional Role alpha beta TCR Pairing in Cell Lineage and Antigen Specificity

Although structural studies of individual T cell receptors (TCRs) have revealed important roles for both the alpha and beta chain in directing MHC and antigen recognition, repertoire-level immunogenomic analyses have historically examined the beta chain alone. To determine the amount of useful information about TCR repertoire function encoded within alpha beta pairings, we analyzed paired TCR sequences from nearly 100,000 unique CD4+ and CD8+ T cells captured using two different high-throughput, single-cell sequencing approaches. Our results demonstrate little overlap in the healthy CD4+ and CD8+ repertoires, with shared TCR sequences possessing significantly shorter CDR3 sequences corresponding to higher generation probabilities. We further utilized tools from information theory and machine learning to show that while alpha and beta chains are only weakly associated with lineage, of pairings appear to synergistically drive TCR-MHC interactions. V alpha beta gene pairings were found to be the TCR feature most informative of T cell lineage, supporting the existence of germline-encoded paired alpha beta TCR-MHC interaction motifs. Finally, annotating our TCR pairs using a database of sequences with known antigen specificities, we demonstrate that approximately a third of the T cells possess alpha and beta chains that each recognize different known antigens, suggesting that alpha beta pairing is critical for the accurate inference of repertoire functionality. Together, these findings provide biological insight into the functional implications of alpha beta pairing and highlight the utility of single-cell sequencing in immunogenomics