Showing papers by "National University of Singapore published in 2021"

Coordinate Attention for Efficient Mobile Network Design

Abstract: Recent studies on mobile network design have demonstrated the remarkable effectiveness of channel attention (e.g., the Squeeze-and-Excitation attention) for lifting model performance, but they generally neglect the positional information, which is important for generating spatially selective attention maps. In this paper, we propose a novel attention mechanism for mobile networks by embedding positional information into channel attention, which we call "coordinate attention". Unlike channel attention that transforms a feature tensor to a single feature vector via 2D global pooling, the coordinate attention factorizes channel attention into two 1D feature encoding processes that aggregate features along the two spatial directions, respectively. In this way, long-range dependencies can be captured along one spatial direction and meanwhile precise positional information can be preserved along the other spatial direction. The resulting feature maps are then encoded separately into a pair of direction-aware and position-sensitive attention maps that can be complementarily applied to the input feature map to augment the representations of the objects of interest. Our coordinate attention is simple and can be flexibly plugged into classic mobile networks, such as MobileNetV2, MobileNeXt, and EfficientNet with nearly no computational overhead. Extensive experiments demonstrate that our coordinate attention is not only beneficial to ImageNet classification but more interestingly, behaves better in down-stream tasks, such as object detection and semantic segmentation. Code is available at https://github.com/Andrew-Qibin/CoordAttention.

Intelligent Reflecting Surface-Aided Wireless Communications: A Tutorial

Abstract: Intelligent reflecting surface (IRS) is an enabling technology to engineer the radio signal propagation in wireless networks. By smartly tuning the signal reflection via a large number of low-cost passive reflecting elements, IRS is capable of dynamically altering wireless channels to enhance the communication performance. It is thus expected that the new IRS-aided hybrid wireless network comprising both active and passive components will be highly promising to achieve a sustainable capacity growth cost-effectively in the future. Despite its great potential, IRS faces new challenges to be efficiently integrated into wireless networks, such as reflection optimization, channel estimation, and deployment from communication design perspectives. In this paper, we provide a tutorial overview of IRS-aided wireless communications to address the above issues, and elaborate its reflection and channel models, hardware architecture and practical constraints, as well as various appealing applications in wireless networks. Moreover, we highlight important directions worthy of further investigation in future work.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

Abstract: In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Global epidemiology of NAFLD-related HCC: trends, predictions, risk factors and prevention

Abstract: One quarter of the global population is estimated to have nonalcoholic fatty liver disease (NAFLD). The incidence of nonalcoholic steatohepatitis (NASH) is projected to increase by up to 56% in the next 10 years. NAFLD is already the fastest growing cause of hepatocellular carcinoma (HCC) in the USA, France and the UK. Globally, the prevalence of NAFLD-related HCC is likely to increase concomitantly with the growing obesity epidemic. The estimated annual incidence of HCC ranges from 0.5% to 2.6% among patients with NASH cirrhosis. The incidence of HCC among patients with non-cirrhotic NAFLD is lower, approximately 0.1 to 1.3 per 1,000 patient-years. Although the incidence of NAFLD-related HCC is lower than that of HCC of other aetiologies such as hepatitis C, more people have NAFLD than other liver diseases. Urgent measures that increase global awareness and tackle the metabolic risk factors are necessary to reduce the impending burden of NAFLD-related HCC. Emerging evidence indicates that reduced immune surveillance, increased gut inflammation and gut dysbiosis are potential key steps in tumorigenesis. In this Review, we discuss the global epidemiology, projections and risk factors for NAFLD-related HCC, and propose preventive strategies to tackle this growing problem.

COVID-19 and the workplace: Implications, issues, and insights for future research and action.

Abstract: The impacts of COVID-19 on workers and workplaces across the globe have been dramatic. This broad review of prior research rooted in work and organizational psychology, and related fields, is intended to make sense of the implications for employees, teams, and work organizations. This review and preview of relevant literatures focuses on (a) emergent changes in work practices (e.g., working from home, virtual teamwork) and (b) emergent changes for workers (e.g., social distancing, stress, and unemployment). In addition, potential moderating factors (demographic characteristics, individual differences, and organizational norms) are examined given the likelihood that COVID-19 will generate disparate effects. This broad-scope overview provides an integrative approach for considering the implications of COVID-19 for work, workers, and organizations while also identifying issues for future research and insights to inform solutions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Hunger games search: Visions, conception, implementation, deep analysis, perspectives, and towards performance shifts

Abstract: A recent set of overused population-based methods have been published in recent years. Despite their popularity, most of them have uncertain, immature performance, partially done verifications, similar overused metaphors, similar immature exploration and exploitation components and operations, and an insecure tradeoff between exploration and exploitation trends in most of the new real-world cases. Therefore, all users need to extensively modify and adjust their operations based on main evolutionary methods to reach faster convergence, more stable balance, and high-quality results. To move the optimization community one step ahead toward more focus on performance rather than change of metaphor, a general-purpose population-based optimization technique called Hunger Games Search (HGS) is proposed in this research with a simple structure, special stability features and very competitive performance to realize the solutions of both constrained and unconstrained problems more effectively. The proposed HGS is designed according to the hunger-driven activities and behavioural choice of animals. This dynamic, fitness-wise search method follows a simple concept of “Hunger” as the most crucial homeostatic motivation and reason for behaviours, decisions, and actions in the life of all animals to make the process of optimization more understandable and consistent for new users and decision-makers. The Hunger Games Search incorporates the concept of hunger into the feature process; in other words, an adaptive weight based on the concept of hunger is designed and employed to simulate the effect of hunger on each search step. It follows the computationally logical rules (games) utilized by almost all animals and these rival activities and games are often adaptive evolutionary by securing higher chances of survival and food acquisition. This method's main feature is its dynamic nature, simple structure, and high performance in terms of convergence and acceptable quality of solutions, proving to be more efficient than the current optimization methods. The effectiveness of HGS was verified by comparing HGS with a comprehensive set of popular and advanced algorithms on 23 well-known optimization functions and the IEEE CEC 2014 benchmark test suite. Also, the HGS was applied to several engineering problems to demonstrate its applicability. The results validate the effectiveness of the proposed optimizer compared to popular essential optimizers, several advanced variants of the existing methods, and several CEC winners and powerful differential evolution (DE)-based methods abbreviated as LSHADE, SPS_L_SHADE_EIG, LSHADE_cnEpSi, SHADE, SADE, MPEDE, and JDE methods in handling many single-objective problems. We designed this open-source population-based method to be a standard tool for optimization in different areas of artificial intelligence and machine learning with several new exploratory and exploitative features, high performance, and high optimization capacity. The method is very flexible and scalable to be extended to fit more form of optimization cases in both structural aspects and application sides. This paper's source codes, supplementary files, Latex and office source files, sources of plots, a brief version and pseudocode, and an open-source software toolkit for solving optimization problems with Hunger Games Search and online web service for any question, feedback, suggestion, and idea on HGS algorithm will be available to the public at https://aliasgharheidari.com/HGS.html .

RUN beyond the metaphor: An efficient optimization algorithm based on Runge Kutta method

Abstract: The optimization field suffers from the metaphor-based “pseudo-novel” or “fancy” optimizers. Most of these cliche methods mimic animals' searching trends and possess a small contribution to the optimization process itself. Most of these cliche methods suffer from the locally efficient performance, biased verification methods on easy problems, and high similarity between their components' interactions. This study attempts to go beyond the traps of metaphors and introduce a novel metaphor-free population-based optimization method based on the mathematical foundations and ideas of the Runge Kutta (RK) method widely well-known in mathematics. The proposed RUNge Kutta optimizer (RUN) was developed to deal with various types of optimization problems in the future. The RUN utilizes the logic of slope variations computed by the RK method as a promising and logical searching mechanism for global optimization. This search mechanism benefits from two active exploration and exploitation phases for exploring the promising regions in the feature space and constructive movement toward the global best solution. Furthermore, an enhanced solution quality (ESQ) mechanism is employed to avoid the local optimal solutions and increase convergence speed. The RUN algorithm's efficiency was evaluated by comparing with other metaheuristic algorithms in 50 mathematical test functions and four real-world engineering problems. The RUN provided very promising and competitive results, showing superior exploration and exploitation tendencies, fast convergence rate, and local optima avoidance. In optimizing the constrained engineering problems, the metaphor-free RUN demonstrated its suitable performance as well. The authors invite the community for extensive evaluations of this deep-rooted optimizer as a promising tool for real-world optimization. The source codes, supplementary materials, and guidance for the developed method will be publicly available at different hubs at http://imanahmadianfar.com and http://aliasgharheidari.com/RUN.html .

Epidemiology of COVID-19: A systematic review and meta-analysis of clinical characteristics, risk factors, and outcomes.

Abstract: Coronavirus disease 2019 (COVID-19) has become a pandemic, but its reported characteristics and outcomes vary greatly amongst studies. We determined pooled estimates for clinical characteristics and outcomes in COVID-19 patients including subgroups by disease severity (based on World Health Organization Interim Guidance Report or Infectious Disease Society of America/American Thoracic Society criteria) and by country/region. We searched Pubmed, Embase, Scopus, Cochrane, Chinese Medical Journal, and preprint databases from 1 January 2020 to 6 April 2020. Studies of laboratory-confirmed COVID-19 patients with relevant data were included. Two reviewers independently performed study selection and data extraction. From 6007 articles, 212 studies from 11 countries/regions involving 281 461 individuals were analyzed. Overall, mean age was 46.7 years, 51.8% were male, 22.9% had severe disease, and mortality was 5.6%. Underlying immunosuppression, diabetes, and malignancy were most strongly associated with severe COVID-19 (coefficient = 53.9, 23.4, 23.4, respectively, all P < .0007), while older age, male gender, diabetes, and hypertension were also associated with higher mortality (coefficient = 0.05 per year, 5.1, 8.2, 6.99, respectively; P = .006-.0002). Gastrointestinal (nausea, vomiting, abdominal pain) and respiratory symptoms (shortness of breath, chest pain) were associated with severe COVID-19, while pneumonia and end-organ failure were associated with mortality. COVID-19 is associated with a severe disease course in about 23% and mortality in about 6% of infected persons. Individuals with comorbidities and clinical features associated with severity should be monitored closely, and preventive efforts should especially target those with diabetes, malignancy, and immunosuppression.

High-entropy-stabilized chalcogenides with high thermoelectric performance.

Abstract: Thermoelectric technology generates electricity from waste heat, but one bottleneck for wider use is the performance of thermoelectric materials. Manipulating the configurational entropy of a material by introducing different atomic species can tune phase composition and extend the performance optimization space. We enhanced the figure of merit (zT) value to 1.8 at 900 kelvin in an n-type PbSe-based high-entropy material formed by entropy-driven structural stabilization. The largely distorted lattices in this high-entropy system caused unusual shear strains, which provided strong phonon scattering to largely lower lattice thermal conductivity. The thermoelectric conversion efficiency was 12.3% at temperature difference ΔT = 507 kelvin, for the fabricated segmented module based on this n-type high-entropy material. Our demonstration provides a paradigm to improve thermoelectric performance for high-entropy thermoelectric materials through entropy engineering.

Covalent organic frameworks: an ideal platform for designing ordered materials and advanced applications

Abstract: Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended two- and three-dimensional polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores. This polymer architecture is unique as it enables predesigning both primary- and high-order structures, greatly enhancing our capabilities of designing organic materials to produce predictable structures and to achieve unique properties and functions. Progress over the past 15 years in the design, synthesis and functional exploration of COFs has successively established the basis of the COF field and COFs have shown the great potential of chemistry in developing a class of amazing organic materials. In this review, we focus on analysing the historic developments of COFs to uncover a full materials and application picture by providing comprehensive yet clear guidance for molecular design, synthetic control and functional exploration. We scrutinise the structural components of COFs including building blocks, reactive sites and functional groups with the aim of finding the origins of structural designability and diversity, as well as multiple functionalities. We disclose strategies for designing and synthesising frameworks to construct various tailor-made interfaces, and for exploring skeletons and pores to design properties and functions. With well-defined skeletons, pores and interfaces that offer a chemical basis to trigger and control interactions with photons, excitons, phonons, polarons, electrons, holes, spins, ions and molecules, we illustrate the current status of our understandings of structure-property correlations, and unveil the principles for establishing a regime to design unique functions that originate from and are inherent to structures. We predict the key central issues in design and synthesis, the challenges in functional design and the future directions from the perspectives of chemistry, physics and materials science.

Esophageal motility disorders on high-resolution manometry: Chicago classification version 4.0©

Abstract: Chicago Classification v4.0 (CCv4.0) is the updated classification scheme for esophageal motility disorders using metrics from high-resolution manometry (HRM). Fifty-two diverse international experts separated into seven working subgroups utilized formal validated methodologies over two-years to develop CCv4.0. Key updates in CCv.4.0 consist of a more rigorous and expansive HRM protocol that incorporates supine and upright test positions as well as provocative testing, a refined definition of esophagogastric junction (EGJ) outflow obstruction (EGJOO), more stringent diagnostic criteria for ineffective esophageal motility and description of baseline EGJ metrics. Further, the CCv4.0 sought to define motility disorder diagnoses as conclusive and inconclusive based on associated symptoms, and findings on provocative testing as well as supportive testing with barium esophagram with tablet and/or functional lumen imaging probe. These changes attempt to minimize ambiguity in prior iterations of Chicago Classification and provide more standardized and rigorous criteria for patterns of disorders of peristalsis and obstruction at the EGJ.

A single-cell and spatially resolved atlas of human breast cancers.

Abstract: Breast cancers are complex cellular ecosystems where heterotypic interactions play central roles in disease progression and response to therapy. However, our knowledge of their cellular composition and organization is limited. Here we present a single-cell and spatially resolved transcriptomics analysis of human breast cancers. We developed a single-cell method of intrinsic subtype classification (SCSubtype) to reveal recurrent neoplastic cell heterogeneity. Immunophenotyping using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) provides high-resolution immune profiles, including new PD-L1/PD-L2+ macrophage populations associated with clinical outcome. Mesenchymal cells displayed diverse functions and cell-surface protein expression through differentiation within three major lineages. Stromal-immune niches were spatially organized in tumors, offering insights into antitumor immune regulation. Using single-cell signatures, we deconvoluted large breast cancer cohorts to stratify them into nine clusters, termed 'ecotypes', with unique cellular compositions and clinical outcomes. This study provides a comprehensive transcriptional atlas of the cellular architecture of breast cancer.

ZnS-SnS@NC Heterostructure as Robust Lithiophilicity and Sulfiphilicity Mediator toward High-Rate and Long-Life Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur (Li-S) batteries are severely hindered by the low sulfur utilization and short cycling life, especially at high rates. One of the effective solutions to address these problems is to improve the sulfiphilicity of lithium polysulfides (LiPSs) and the lithiophilicity of the lithium anode. However, it is a great challenge to simultaneously optimize both aspects. Herein, by incorporating the merits of strong absorbability and high conductivity of SnS with good catalytic capability of ZnS, a ZnS-SnS heterojunction coated with a polydopamine-derived N-doped carbon shell (denoted as ZnS-SnS@NC) with uniform cubic morphology was obtained and compared with the ZnS-SnS2@NC heterostructure and its single-component counterparts (SnS@NC and SnS2@NC). Theoretical calculations, ex situ XANES, and in situ Raman spectrum were utilized to elucidate rapid anchoring-diffusion-transformation of LiPSs, inhibition of the shuttling effect, and improvement of the sulfur electrochemistry of bimetal ZnS-SnS heterostructure at the molecular level. When applied as a modification layer coated on the separator, the ZnS-SnS@NC-based cell with optimized lithiophilicity and sulfiphilicity enables desirable sulfur electrochemistry, including high reversibility of 1149 mAh g-1 for 300 cycles at 0.2 C, high rate performance of 661 mAh g-1 at 10 C, and long cycle life with a low fading rate of 0.0126% each cycle after 2000 cycles at 4 C. Furthermore, a favorable areal capacity of 8.27 mAh cm-2 is maintained under high sulfur mass loading of 10.3 mg cm-2. This work furnishes a feasible scheme to the rational design of bimetal sulfides heterostructures and boosts the development of other electrochemical applications.

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications.

Abstract: Among the recent developments in metal-organic frameworks (MOFs), porous layered coordination polymers (CPs) have garnered attention due to their modular nature and tunable structures. These factors enable a number of properties and applications, including gas and guest sorption, storage and separation of gases and small molecules, catalysis, luminescence, sensing, magnetism, and energy storage and conversion. Among MOFs, two-dimensional (2D) compounds are also known as 2D CPs or 2D MOFs. Since the discovery of graphene in 2004, 2D materials have also been widely studied. Several 2D MOFs are suitable for exfoliation as ultrathin nanosheets similar to graphene and other 2D materials, making these layered structures useful and unique for various technological applications. Furthermore, these layered structures have fascinating topological networks and entanglements. This review provides an overview of different aspects of 2D MOF layered architectures such as topology, interpenetration, structural transformations, properties, and applications.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

Abstract: I. Executive summary BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document. Methods ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided. Conclusion This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Carbazole isomers induce ultralong organic phosphorescence

Abstract: Commercial carbazole has been widely used to synthesize organic functional materials that have led to recent breakthroughs in ultralong organic phosphorescence1, thermally activated delayed fluorescence2,3, organic luminescent radicals4 and organic semiconductor lasers5. However, the impact of low-concentration isomeric impurities present within commercial batches on the properties of the synthesized molecules requires further analysis. Here, we have synthesized highly pure carbazole and observed that its fluorescence is blueshifted by 54 nm with respect to commercial samples and its room-temperature ultralong phosphorescence almost disappears6. We discover that such differences are due to the presence of a carbazole isomeric impurity in commercial carbazole sources, with concentrations <0.5 mol%. Ten representative carbazole derivatives synthesized from the highly pure carbazole failed to show the ultralong phosphorescence reported in the literature1,7–15. However, the phosphorescence was recovered by adding 0.1 mol% isomers, which act as charge traps. Investigating the role of the isomers may therefore provide alternative insights into the mechanisms behind ultralong organic phosphorescence1,6–18. A carbazole isomer, typically present as an impurity in commercially produced carbazole batches, is shown to be responsible for the ultralong phosphorescence observed in these compounds and their derivatives.

Fundamentals, status and promise of sodium-based batteries

Abstract: Na-based batteries have shown substantial progress in recent years and are promising candidates for mitigating the supply risks associated with Li-based batteries. In this Review, Na and Li batteries are compared in terms of fundamental principles and specific materials. Principles for the rational design of a Na battery architecture are discussed. Recent prototypes are surveyed to demonstrate that Na cells offer realistic alternatives that are competitive with some Li cells in terms of performance. Sodium batteries are promising candidates for mitigating the supply risks associated with lithium batteries. This Review compares the two technologies in terms of fundamental principles and specific materials, and assesses the performance of commercial prototype sodium cells.

Model-Contrastive Federated Learning

Abstract: Federated learning enables multiple parties to collaboratively train a machine learning model without communicating their local data. A key challenge in federated learning is to handle the heterogeneity of local data distribution across parties. Although many studies have been proposed to address this challenge, we find that they fail to achieve high performance in image datasets with deep learning models. In this paper, we propose MOON: model-contrastive federated learning. MOON is a simple and effective federated learning framework. The key idea of MOON is to utilize the similarity between model representations to correct the local training of individual parties, i.e., conducting contrastive learning in model-level. Our extensive experiments show that MOON significantly outperforms the other state-of-the-art federated learning algorithms on various image classification tasks.