Accelerated Path-Following Iterative Shrinkage Thresholding Algorithm With Application to Semiparametric Graph Estimation

<p>We propose an accelerated path-following iterative shrinkage thresholding algorithm (APISTA) for solving high-dimensional sparse nonconvex learning problems. The main difference between APISTA and the path-following iterative shrinkage thresholding algorithm (PISTA) is that APISTA exploits an additional coordinate descent subroutine to boost the computational performance. Such a modification, though simple, has profound impact: APISTA not only enjoys the same theoretical guarantee as that of PISTA, that is, APISTA attains a linear rate of convergence to a unique sparse local optimum with good statistical properties, but also significantly outperforms PISTA in empirical benchmarks. As an application, we apply APISTA to solve a family of nonconvex optimization problems motivated by estimating sparse semiparametric graphical models. APISTA allows us to obtain new statistical recovery results that do not exist in the existing literature. Thorough numerical results are provided to back up our theory.</p

Positive Semidefinite Rank-Based Correlation Matrix Estimation With Application to Semiparametric Graph Estimation

<div><p>Many statistical methods gain robustness and flexibility by sacrificing convenient computational structures. In this article, we illustrate this fundamental tradeoff by studying a semiparametric graph estimation problem in high dimensions. We explain how novel computational techniques help to solve this type of problem. In particular, we propose a nonparanormal neighborhood pursuit algorithm to estimate high-dimensional semiparametric graphical models with theoretical guarantees. Moreover, we provide an alternative view to analyze the tradeoff between computational efficiency and statistical error under a smoothing optimization framework. Though this article focuses on the problem of graph estimation, the proposed methodology is widely applicable to other problems with similar structures. We also report thorough experimental results on text, stock, and genomic datasets.</p></div

Multication Cross-Linked Poly(<i>p</i>‑terphenyl isatin) Anion Exchange Membranes for Fuel Cells: Effect of Cross-Linker Length on Membrane Performance

As a key component of anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) have been investigated in the last decades. Herein, a series of multication cross-linkers were introduced into side-chain-type poly­(p-terphenyl isatin) to develop high-performance and long-term stable AEMs. Additionally, the effects of the hydrophilic cross-linker length on the membrane performance were systematically investigated. The resulting cross-linked membranes possess a low swelling ratio (<18% at 80 °C) and high tensile strength (51.1–58.3 MPa). Notably, the cross-linker length influences the AEM internal morphology. With hexyl as the spacer between backbones and cation groups in the cross-linker, 0.9q-PTI-6C exhibits the highest hydroxide ion conductivity of 118.5 mS/cm at 80 °C, which is ascribed to well-developed ion channels. Furthermore, alkyl spacer chains and cross-linked networks contribute to the excellent alkali stability of membranes. After immersion in 2 M NaOH for 1200 h at 80 °C, 0.9q-PTI-8C only shows 11 and 12.7% losses in ion conductivity and ion exchange capacity (IEC), respectively. The fuel cell fabricated using 0.9q-PTI-6C can achieve the maximum power density of 310 mW/cm2 at 80 °C

Effect of the Activation Process on the Microstructure and Electrochemical Properties of N‑Doped Carbon Cathodes in Li–O₂ Batteries

Lithium–oxygen (Li–O2) batteries have the potential to provide high energy densities; however, they suffer from low actual specific capacity and poor cycle performance. Hence, it is urgent to design a satisfactory oxygen electrode for a Li–O2 battery. In this study, carbonaceous materials, denominated CA, CB, and CC, from chitin were prepared by the three activators of H3PO4, KOH, and KHCO3 as oxygen electrode materials for Li–O2 batteries. The different carbon structural characteristics from the same precursor were regulated and controlled by different chemical reagents. Finally, the spherical particle cluster structure of CA has a high specific surface area, rich N doping, good connectivity, and uniform surface chemistry, so that CA acts as an oxygen electrode presenting excellent electron conductivity, providing sufficient, and stable electrochemical activity sites for oxygen reduction reaction and storing abundant discharge products. The electrochemical measurements indicate that at a current density of 0.02 mA/cm2, a CA-based battery delivers a high specific capacity of 16 600 mA h/g and a stable cycle performance of 210 cycles. This study proposes a functional carbonaceous material from chitin as a cathode oxygen electrode, which provides an economical and sustainable way for the improvement of oxygen electrodes and the application of Li–O2 batteries

Data_Sheet_1_Altered expression of inflammation-associated molecules in striatum: an implication for sensitivity to heavy ion radiations.docx

Background and objectiveHeavy ion radiation is one of the major hazards astronauts face during space expeditions, adversely affecting the central nervous system. Radiation causes severe damage to sensitive brain regions, especially the striatum, resulting in cognitive impairment and other physiological issues in astronauts. However, the intensity of brain damage and associated underlying molecular pathological mechanisms mediated by heavy ion radiation are still unknown. The present study is aimed to identify the damaging effect of heavy ion radiation on the striatum and associated underlying pathological mechanisms.Materials and methodsTwo parallel cohorts of rats were exposed to radiation in multiple doses and times. Cohort I was exposed to 15 Gy of 12C6+ ions radiation, whereas cohort II was exposed to 3.4 Gy and 8 Gy with 56Fe26+ ions irradiation. Physiological and behavioural tests were performed, followed by 18F-FDG-PET scans, transcriptomics analysis of the striatum, and in-vitro studies to verify the interconnection between immune cells and neurons.ResultsBoth cohorts revealed more persistent striatum dysfunction than other brain regions under heavy ion radiation at multiple doses and time, exposed by physiological, behavioural, and 18F-FDG-PET scans. Transcriptomic analysis revealed that striatum dysfunction is linked with an abnormal immune system. In vitro studies demonstrated that radiation mediated diversified effects on different immune cells and sustained monocyte viability but inhibited its differentiation and migration, leading to chronic neuroinflammation in the striatum and might affect other associated brain regions.ConclusionOur findings suggest that striatum dysfunction under heavy ion radiation activates abnormal immune systems, leading to chronic neuroinflammation and neuronal injury.</p