56 research outputs found
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PMINR: Pointwise Mutual Information-Based Network Regression β With Application to Studies of Lung Cancer and Alzheimerβs Disease
Complex diseases are believed to be the consequence of intracellular network(s) involving a range of factors. An improved understanding of a disease-predisposing biological network could lead to better identification of genes and pathways that confer disease risk and therefore inform drug development. The group difference in biological networks, as is often characterized by graphs of nodes and edges, is attributable to effects of these nodes and edges. Here we introduced pointwise mutual information (PMI) as a measure of the connection between a pair of nodes with either a linear relationship or nonlinear dependence. We then proposed a PMI-based network regression (PMINR) model to differentiate patterns of network changes (in node or edge) linking a disease outcome. Through simulation studies with various sample sizes and inter-node correlation structures, we showed that PMINR can accurately identify these changes with higher power than current methods and be robust to the network topology. Finally, we illustrated, with publicly available data on lung cancer and gene methylation data on aging and Alzheimerβs disease, an evaluation of the practical performance of PMINR. We concluded that PMI is able to capture the generic inter-node correlation pattern in biological networks, and PMINR is a powerful and efficient approach for biological network analysis
ΠΡΠΎΡΠΈΠ»Π°ΠΊΡΠΈΠΊΠ° Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΡΡ ΡΠΎΡΡΠΎΡΠ½ΠΈΠΉ Π½Π° ΡΡΠΎΠΌΠ°ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠΌ ΠΏΡΠΈΠ΅ΠΌΠ΅
Π½Π΅ΠΎΡΠ»ΠΎΠΆΠ½ΡΠ΅ ΡΠΎΡΡΠΎΡΠ½ΠΈΡΡΡΠΎΠΌΠ°ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΏΠΎΠΌΠΎΡ
A new insight into underlying disease mechanism through semi-parametric latent differential network model
Background
In genomic studies, to investigate how the structure of a genetic network differs between two experiment conditions is a very interesting but challenging problem, especially in high-dimensional setting. Existing literatures mostly focus on differential network modelling for continuous data. However, in real application, we may encounter discrete data or mixed data, which urges us to propose a unified differential network modelling for various data types. Results
We propose a unified latent Gaussian copula differential network model which provides deeper understanding of the unknown mechanism than that among the observed variables. Adaptive rank-based estimation approaches are proposed with the assumption that the true differential network is sparse. The adaptive estimation approaches do not require precision matrices to be sparse, and thus can allow the individual networks to contain hub nodes. Theoretical analysis shows that the proposed methods achieve the same parametric convergence rate for both the difference of the precision matrices estimation and differential structure recovery, which means that the extra modeling flexibility comes at almost no cost of statistical efficiency. Besides theoretical analysis, thorough numerical simulations are conducted to compare the empirical performance of the proposed methods with some other state-of-the-art methods. The result shows that the proposed methods work quite well for various data types. The proposed method is then applied on gene expression data associated with lung cancer to illustrate its empirical usefulness. Conclusions
The proposed latent variable differential network models allows for various data-types and thus are more flexible, which also provide deeper understanding of the unknown mechanism than that among the observed variables. Theoretical analysis, numerical simulation and real application all demonstrate the great advantages of the latent differential network modelling and thus are highly recommended
Phase evolution and superconductivity enhancement in Se-substituted MoTe thin films
The strong spinorbit coupling (SOC) and numerous crystal phases in
fewlayer transition metal dichalcogenides (TMDCs) MX (MW, Mo, and
XTe, Se, S) has led to a variety of novel physics, such as Ising
superconductivity and quantum spin Hall effect realized in monolayer 2H and
TdMX, respectively. Consecutive tailoring of the MX structure from
2H to Td phase may realize the longsought topological superconductivity in
one material system by incorporating superconductivity and quantum spin Hall
effect together. In this work, by combing Raman spectrum, X-ray photoelectron
spectrum (XPS), scanning transmission electron microscopy imaging (STEM) as
well as electrical transport measurements, we demonstrate that a consecutively
structural phase transitions from Td to 1T to 2H polytype can be realized as
the Se-substitution concentration increases. More importantly, the
Sesubstitution has been found to notably enhance the superconductivity of
the MoTe thin film, which is interpreted as the introduction of the
twoband superconductivity. The chemical constituent induced phase transition
offers a new strategy to study the s superconductivity and the possible
topological superconductivity as well as to develop phasesensitive devices
based on MX materials.Comment: 27 pages, 5 figure
Transport evidence of asymmetric spin-orbit coupling in fewlayer superconducting 1TdMoTe
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) MX2 (M=W, Mo,
Nb, and X=Te, Se, S) with strong spin-orbit coupling (SOC) possess plenty of
novel physics including superconductivity. Due to the Ising SOC, monolayer
NbSe and gated MoS of 2H structure can realize the Ising
superconductivity phase, which manifests itself with in-plane upper critical
field far exceeding Pauli paramagnetic limit. Surprisingly, we find that a
few-layer 1Td structure MoTe also exhibits an in-plane upper critical field
() which goes beyond the Pauli paramagnetic limit. Importantly, the
in-plane upper critical field shows an emergent two-fold symmetry which is
different from the isotropic in 2H structure TMDCs. We show that
this is a result of an asymmetric SOC in 1Td structure TMDCs. The asymmetric
SOC is very strong and estimated to be on the order of tens of meV. Our work
provides the first transport evidence of a new type of asymmetric SOC in TMDCs
which may give rise to novel superconducting and spin transport properties.
Moreover, our findings mostly depend on the symmetry of the crystal and apply
to a whole class of 1Td TMDCs such as 1Td-WTe which is under intense study
due to its topological properties.Comment: 34 pages, 12 figure
A novel Markov Blanket-based repeated-fishing strategy for capturing phenotype-related biomarkers in big omics data
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
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