1,076 research outputs found
Finite mixtures of matrix-variate Poisson-log normal distributions for three-way count data
Three-way data structures, characterized by three entities, the units, the
variables and the occasions, are frequent in biological studies. In RNA
sequencing, three-way data structures are obtained when high-throughput
transcriptome sequencing data are collected for n genes across p conditions at
r occasions. Matrix-variate distributions offer a natural way to model
three-way data and mixtures of matrix-variate distributions can be used to
cluster three-way data. Clustering of gene expression data is carried out as
means to discovering gene co-expression networks. In this work, a mixture of
matrix-variate Poisson-log normal distributions is proposed for clustering read
counts from RNA sequencing. By considering the matrix-variate structure, full
information on the conditions and occasions of the RNA sequencing dataset is
simultaneously considered, and the number of covariance parameters to be
estimated is reduced. A Markov chain Monte Carlo expectation-maximization
algorithm is used for parameter estimation and information criteria are used
for model selection. The models are applied to both real and simulated data,
giving favourable clustering results
Density functional study of FeS, FeSe and FeTe: Electronic structure, magnetism, phonons and superconductivity
We report density functional calculations of the electronic structure, Fermi
surface, phonon spectrum, magnetism and electron-phonon coupling for the
superconducting phase FeSe, as well as the related compounds FeS and FeTe. We
find that the Fermi surface structure of these compounds is very similar to
that of the Fe-As based superconductors, with cylindrical electron sections at
the zone corner, cylindrical hole surface sections, and depending on the
compound, other small hole sections at the zone center. As in the Fe-As based
materials, these surfaces are separated by a 2D nesting vector at
(,). The density of states, nesting and Fermi surface size increase
going from FeSe to FeTe. Both FeSe and FeTe show spin density wave ground
states, while FeS is close to an instability. In a scenario where
superconductivity is mediated by spin fluctuations at the SDW nesting vector,
the strongest superconductor in this series would be doped FeTe.Comment: Added note regarding recent experimental observations of
superconductivity under pressure. Some additional discussio
Agro-environmental project duration and effectiveness in South-east Asia
Considerable emphasis has been placed on developing technologies for agricultural sustainability. Many bilateral projects are working to achieve this outcome. A desk review was conducted to study the importance of project duration for the effectiveness of sustainable agricultural projects. Longer-duration projects were successful in addressing more holistic issues than short projects. However, funding agencies tend to fund shorter-duration projects, so projects become progressively shorter. At the same time, the number of projects implemented each year is increasing. Despite the decrease in total development assistance, increases in project numbers, particularly since 1986, appear to be at the cost of project duration. Short project duration was one of the most cited reasons for not completing essential dissemination activities for wider adoption, whereas longer- duration projects were usually considered more successful in addressing more holistic issues. It is difficult to produce tangible outputs from agricultural and soil conservation projects within five years. Considering the slow changes in the system and in agricultural and environmental sustainability, the authors suggest that project developers should be advised to plan for a minimum of 5â10 years, depending on the nature of activities. It is time for funding agencies to reconsider their tendency to fund shorter-duration projects
Integrating immunology and microfluidics for single immune cell analysis
The field of immunoengineering aims to develop novel therapies and modern vaccines to manipulate and modulate the immune system and applies innovative technologies toward improved understanding of the immune system in health and disease. Microfluidics has proven to be an excellent technology for analytics in biology and chemistry. From simple microsystem chips to complex microfluidic designs, these platforms have witnessed an immense growth over the last decades with frequent emergence of new designs. Microfluidics provides a highly robust and precise tool which led to its widespread application in single-cell analysis of immune cells. Single-cell analysis allows scientists to account for the heterogeneous behavior of immune cells which often gets overshadowed when conventional bulk study methods are used. Application of single-cell analysis using microfluidics has facilitated the identification of several novel functional immune cell subsets, quantification of signaling molecules, and understanding of cellular communication and signaling pathways. Single-cell analysis research in combination with microfluidics has paved the way for the development of novel therapies, point-of-care diagnostics, and even more complex microfluidic platforms that aid in creating in vitro cellular microenvironments for applications in drug and toxicity screening. In this review, we provide a comprehensive overview on the integration of microsystems and microfluidics with immunology and focus on different designs developed to decode single immune cell behavior and cellular communication. We have categorized the microfluidic designs in three specific categories: microfluidic chips with cell traps, valve-based microfluidics, and droplet microfluidics that have facilitated the ongoing research in the field of immunology at single-cell level
Electronic Structure, Magnetism and Superconductivity of Layered Iron Compounds
The layered iron superconductors are discussed using electronic structure
calculations. The four families of compounds discovered so far, including
Fe(Se,Te) have closely related electronic structures. The Fermi surface
consists of disconnected hole and electron cylinders and additional hole
sections that depend on the specific material. This places the materials in
proximity to itinerant magnetism, both due to the high density of states and
due to nesting. Comparison of density functional results and experiment
provides strong evidence for itinerant spin fluctuations, which are discussed
in relation to superconductivity. It is proposed that the intermediate phase
between the structural transition and the SDW transition in the oxy-pnictides
is a nematic phase.Comment: Proceedings ISS200
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