Efficient Edge-AI Models for Robust ECG Abnormality Detection on Resource-Constrained Hardware.

This study introduces two models, ConvLSTM2D-liquid time-constant network (CLTC) and ConvLSTM2D-closed-form continuous-time neural network (CCfC), designed for abnormality identification using electrocardiogram (ECG) data. Trained on the Telehealth Network of Minas Gerais (TNMG) subset dataset, both models were evaluated for their performance, generalizability capacity, and resilience. They demonstrated comparable results in terms of F1 scores and AUROC values. The CCfC model achieved slightly higher accuracy, while the CLTC model showed better handling of empty channels. Remarkably, the models were successfully deployed on a resource-constrained microcontroller, proving their suitability for edge device applications. Generalization capabilities were confirmed through the evaluation on the China Physiological Signal Challenge 2018 (CPSC) dataset. The models' efficient resource utilization, occupying 70.6% of memory and 9.4% of flash memory, makes them promising candidates for real-world healthcare applications. Overall, this research advances abnormality identification in ECG data, contributing to the progress of AI in healthcare.

S4D-ECG: A Shallow State-of-the-Art Model for Cardiac Abnormality Classification.

PURPOSE: This study introduces an algorithm specifically designed for processing unprocessed 12-lead electrocardiogram (ECG) data, with the primary aim of detecting cardiac abnormalities. METHODS: The proposed model integrates Diagonal State Space Sequence (S4D) model into its architecture, leveraging its effectiveness in capturing dynamics within time-series data. The S4D model is designed with stacked S4D layers for processing raw input data and a simplified decoder using a dense layer for predicting abnormality types. Experimental optimization determines the optimal number of S4D layers, striking a balance between computational efficiency and predictive performance. This comprehensive approach ensures the model's suitability for real-time processing on hardware devices with limited capabilities, offering a streamlined yet effective solution for heart monitoring. RESULTS: Among the notable features of this algorithm is its strong resilience to noise, enabling the algorithm to achieve an average F1-score of 81.2% and an AUROC of 95.5% in generalization. The model underwent testing specifically on the lead II ECG signal, exhibiting consistent performance with an F1-score of 79.5% and an AUROC of 95.7%. CONCLUSION: It is characterized by the elimination of pre-processing features and the availability of a low-complexity architecture that makes it suitable for implementation on numerous computing devices because it is easily implementable. Consequently, this algorithm exhibits considerable potential for practical applications in analyzing real-world ECG data. This model can be placed on the cloud for diagnosis. The model was also tested on lead II of the ECG alone and has demonstrated promising results, supporting its potential for on-device application.

Thermal Properties of MXenes and Relevant Applications.

The properties and applications of MXenes (a family of layered transition metal carbides, nitrides, and carbonitrides) have aroused enormous research interests for a decade since the successful synthesis of few-layer transition metal carbides in 2011. Though MXenes, as the building blocks, have already been applied in various fields (such as wearable electronics) owing to the distinctive optical, mechanical and electrical properties, their thermal stability and intrinsic thermal properties were less thoroughly investigated compared to other characteristics in early reports. The pioneering theoretical prediction of the thermoelectric nature of MXenes was performed in 2013 while the first experiment-based report concerning the degradation behavior of the 2D structure at elevated temperatures in a controlled atmosphere was published in 2015, followed by numerous discoveries regarding the thermal properties of MXenes. Herein, after a brief description of the synthesis, this Review summarized the latest insights into the thermal stability and thermophysical properties of MXenes, and further associated these unique properties with relevant applications by multiple examples. Finally, current hurdles and challenges in this field were provided along with some advices on potential research directions in the future.

Recent Developments of Nanomaterials and Nanostructures for High-Rate Lithium Ion Batteries.

Lithium ion batteries have been considered as a promising energy-storage solution, the performance of which depends on the electrochemical properties of each component, including cathode, anode, electrolyte and separator. Currently, fast charging is becoming an attractive research field due to the widespread application of batteries in electric vehicles, which are designated to replace conventional diesel automobiles in the future. In these batteries, rate capability, which is closely linked to the topology and morphology of electrode materials, is one of the determining parameters of interest. It has been revealed that nanotechnology is an exceptional tool in designing and preparing cathodes and anodes with outstanding electrochemical kinetics due to the well-known nanosizing effect. Nevertheless, the negative effects of applying nanomaterials in electrodes sometimes outweigh the benefits. To better understand the exact function of nanostructures in solid-state electrodes, herein, a comprehensive review is provided beginning with the fundamental theory of lithium ion transport in solids, which is then followed by a detailed analysis of several major factors affecting the migration of lithium ions in solid-state electrodes. The latest developments in characterisation techniques, based on either electrochemical or radiology methodologies, are covered as well. In addition, state-of-the-art research findings are provided to illustrate the effect of nanomaterials and nanostructures in promoting the rate performance of lithium ion batteries. Finally, several challenges and shortcomings of applying nanotechnology in fabricating high-rate lithium ion batteries are summarised.

Electrically Sorted Single-Walled Carbon Nanotubes-Based Electron Transporting Layers for Perovskite Solar Cells.

Incorporation of as prepared single-walled carbon nanotubes (SWCNTs) into the electron transporting layer (ETL) is an effective strategy to enhance the photovoltaic performance of perovskite solar cells (PSCs). However, the fundamental role of the SWCNT electrical types in the PSCs is not well understood. Herein, we prepared semiconducting (s-) and metallic (m-) SWCNT families and integrated them into TiO2 photoelectrodes of the PSCs. Based on experimental and theoretical studies, we found that the electrical type of the nanotubes plays an important role in the devices. In particular, the mixture of s-SWCNTs and m-SWCNTs (2:1 w/w)-based PSCs exhibited a remarkable efficiency of up to 19.35%, which was significantly higher than that of the best control cell (17.04%). In this class of PSCs, semiconducting properties of s-SWCNTs play a critical role in extracting and transporting electrons, whereas m-SWCNTs provide high conductance throughout the electrode.

Synthesis, purification, properties and characterization of sorted single-walled carbon nanotubes.

Single-walled carbon nanotubes (SWCNTs) have attracted significant attention due to their outstanding mechanical, chemical and optoelectronic properties, which makes them promising candidates for use in a wide range of applications. However, as-produced SWCNTs have a wide distribution of various chiral species with different properties (i.e. electronic structures). In order to take full advantage of SWCNT properties, highly purified and well-separated SWCNTs are of great importance. Recent advances have focused on developing new strategies to effectively separate nanotubes into single-chirality and/or semiconducting/metallic species and integrating them into different applications. This review highlights recent progress in this cutting-edge research area alongside the enormous development of their identification and structural characterization techniques. A comprehensive review of advances in both controlled synthesis and post-synthesis separation methods of SWCNTs are presented. The relationship between the unique structure of SWCNTs and their intrinsic properties is also discussed. Finally, important future directions for the development of sorting and purification protocols for SWCNTs are provided.

Measuring the Density of States of the Inner and Outer Wall of Double-Walled Carbon Nanotubes.

The combination of ultraviolet photoelectron spectroscopy and metastable helium induced electron spectroscopy is used to determine the density of states of the inner and outer coaxial carbon nanotubes. Ultraviolet photoelectron spectroscopy typically measures the density of states across the entire carbon nanotube, while metastable helium induced electron spectroscopy measures the density of states of the outermost layer alone. The use of double-walled carbon nanotubes in electronic devices allows for the outer wall to be functionalised whilst the inner wall remains defect free and the density of states is kept intact for electron transport. Separating the information of the inner and outer walls enables development of double-walled carbon nanotubes to be independent, such that the charge transport of the inner wall is maintained and confirmed whilst the outer wall is modified for functional purposes.

Efficiency Improvement Using Molybdenum Disulphide Interlayers in Single-Wall Carbon Nanotube/Silicon Solar Cells.

Molybdenum disulphide (MoS2) is one of the most studied and widely applied nanomaterials from the layered transition-metal dichalcogenides (TMDs) semiconductor family. MoS2 has a large carrier diffusion length and a high carrier mobility. Combining a layered structure of single-wall carbon nanotube (SWCNT) and MoS2 with n-type silicon (n-Si) provided novel SWCNT/n-Si photovoltaic devices. The solar cell has a layered structure with Si covered first by a thin layer of MoS2 flakes and then a SWCNT film. The films were examined using scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The MoS2 flake thickness ranged from 5 to 90 nm while the nanosheet’s lateral dimensions size ranged up to 1 μm². This insertion of MoS2 improved the photoconversion efficiency (PCE) of the SWCNT/n-Si solar cells by approximately a factor of 2.

Direct-Patterning SWCNTs Using Dip Pen Nanolithography for SWCNT/Silicon Solar Cells.

Dip pen nanolithography (DPN) is used to pattern single-walled carbon nanotube (SWCNT) lines between the n-type Si and SWCNT film in SWCNT/Si solar cells. The SWCNT ink composition, loading, and DPN pretreatment are optimized to improve patterning. This improved DPN technique is then used to successfully pattern >1 mm long SWCNT lines consistently. This is a 20-fold increase in the previously reported direct-patterning of SWCNT lines using the DPN technique, and demonstrates the scalability of the technique to pattern larger areas. The degree of the uniformity of SWCNTs in these lines is further characterized by Raman spectroscopy and scanning electron microscopy. The patterned SWCNT lines are used as thin conductive pathways in SWCNT/Si solar cells, similar to front contact electrodes. The critical parameters of these solar cells are measured and compared to control cells without SWCNT lines. The addition of SWCNT lines increases power conversion efficiency by 40% (relative). Importantly, the SWCNT lines reduce average series resistance by 44%, and consequently increase average fill factor by 24%.

Adsorption and Desorption of Single-Stranded DNA from Single-Walled Carbon Nanotubes.

The chemical affinity of single-stranded DNA (ssDNA) to adsorb to the surface of single-walled carbon nanotubes (SWCNTs) is used for SWCNT purification, separation and in bio-devices. Despite the popularity of research on SWCNT-ssDNA conjugates, very little work has studied the removal of adsorbed ssDNA on SWCNTs. This paper reports a comprehensive study of biological, physical and chemical treatments for the removal of ssDNA from SWCNT-ssDNA suspensions. These include enzymatic cleavage, heat treatment under vacuum up to 400 °C, chemical treatments with high or low pH, oxidizing conditions, and high-ionic-strength solvents. Complimentary characterization techniques including fluorescence from a DNA-intercalating dye (YO-PRO-1) and photoelectron spectroscopy are used to exhaustively study and compare the methods investigated. Enzyme treatment is found to remove the phosphate backbone only, leaving nucleosides adsorbed to SWCNTs. Heating in inert atmosphere is ineffective at removing ssDNA. Acid, base and oxidative treatment are found to be effective for the removal of ssDNA from SWCNTs. Where possible the mechanism of desorption is described and from the findings suggestions for "best practices" are provided.

Recent Development of Carbon Nanotube Transparent Conductive Films.

Transparent conducting films (TCFs) are a critical component in many personal electronic devices. Transparent and conductive doped metal oxides are widely used in industry due to their excellent optoelectronic properties as well as the mature understanding of their production and handling. However, they are not compatible with future flexible electronics developments where large-scale production will likely involve roll-to-roll manufacturing. Recent studies have shown that carbon nanotubes provide unique chemical, physical, and optoelectronic properties, making them an important alternative to doped metal oxides. This Review provides a comprehensive analysis of carbon nanotube transparent conductive films covering detailed fabrication methods including patterning of the films, chemical doping effects, and hybridization with other materials. There is a focus on optoelectronic properties of the films and potential in applications such as photovoltaics, touch panels, liquid crystal displays, and organic light-emitting diodes in conjunction with a critical analysis of both the merits and shortcomings of carbon nanotube transparent conductive films.

Investigating the Effect of Carbon Nanotube Diameter and Wall Number in Carbon Nanotube/Silicon Heterojunction Solar Cells.

Suspensions of single-walled, double-walled and multi-walled carbon nanotubes (CNTs) were generated in the same solvent at similar concentrations. Films were fabricated from these suspensions and used in carbon nanotube/silicon heterojunction solar cells and their properties were compared with reference to the number of walls in the nanotube samples. It was found that single-walled nanotubes generally produced more favorable results; however, the double and multi-walled nanotube films used in this study yielded cells with higher open circuit voltages. It was also determined that post fabrication treatments applied to the nanotube films have a lesser effect on multi-walled nanotubes than on the other two types.

Heterojunction Solar Cells Based on Silicon and Composite Films of Graphene Oxide and Carbon Nanotubes.

Graphene oxide (GO) sheets have been used as the surfactant to disperse single-walled carbon nanotubes (CNT) in water to prepare GO/CNT electrodes that are applied to silicon to form a heterojunction that can be used in solar cells. GO/CNT films with different ratios of the two components and with various thicknesses have been used as semitransparent electrodes, and the influence of both factors on the performance of the solar cell has been studied. The degradation rate of the GO/CNT-silicon devices under ambient conditions has also been explored. The influence of the film thickness on the device performance is related to the interplay of two competing factors, namely, sheet resistance and transmittance. CNTs help to improve the conductivity of the GO/CNT film, and GO is able to protect the silicon from oxidation in the atmosphere.

[Evaluation of risk factors for retinopathy of prematurity].

OBJECTIVE: To evaluate the incidence and risk factors of ROP (retinopathy of prematurity) through a prospective multicenter study. METHODS: Eleven children's or maternal & child hospitals participated in a collective network. All infants of birth weight < 2000 g, born in or transferred to one of the participating centers from January 1st 2005 to February 28th 2006 were recruited. Timely ophthalmologic examinations were performed. The relevant data at baseline and endpoints were collected at each unit. RESULTS: A total of 882 preterm infants fulfilled the screening criteria and 752 finished a followup. And 123 infants (16.4%) had some degree of ROP. Infants with ROP had a lower gestational age, birth weight and a longer duration of oxygen versus those without ROP [(30.82 +/- 0.20) weeks vs (32.56 +/- 0.09) weeks, (1430 +/- 25) g vs (1636 +/-10) g, (11.6 +/- 1.4) d vs (4.4 +/- 0.3) d]. Through a univariate analysis, birth weight, gestational age, asphyxia, oxygen duration > 5 days, apnea, surfactant usage, pneumonia, anemia, blood transfusion, acidosis and neonatal respiratory distress syndrome (NRDS) were associated with ROP (P < 0.05). Logistic regression analysis showed that birth weight (OR = 0.998), apnea (OR = 1.653) and blood transfusion (OR = 1.763) were independent risk factors for ROP. CONCLUSION: Asphyxia, oxygen duration > 5 days, surfactant usage, anemia, acidosis and NRDS, lower birth weight, apnea and blood transfusion may improve the risks of ROP.