One-step green hydrothermal synthesis of biocompatible graphene/titanium dioxide nanocomposites: towards the development of highly sensitive and selective electrochemical immunosensor for dengue diagnosis

Biosensor platforms are powerful analytical devices capable of revolutionising medical diagnostics by providing highly accessible and effective diagnosis at the point-of-care stage. In this work, a high-performance electrochemical-based biosensing platform was developed using graphene/titanium dioxide (G/TiO2) nanocomposite. The graphene employed in the G/TiO2 electrode material was synthesised via a sonochemical liquid phase exfoliation method, eradicating the use of harsh chemicals and high temperature conditions. The simple and low temperature hydrothermal synthesis of the G/TiO2 nanocomposite also ensured the affordability and scalability of the process. Modifying electrodes with the as-synthesised nanocomposite resulted in enhanced electrochemical performances compared to bare electrodes and graphene-modified electrodes. As hydrogen peroxide (H2O2) is one of the most common by-products of biological metabolic reactions, a non-enzymatic hydrogen peroxide (H2O2) sensor platform was developed to investigate the potential of G/TiO2 nanocomposite in biosensing applications. The resulting H2O2 sensor exhibited high sensitivity with a limit of detection (LOD) of 56.89 nM. Subsequently, a versatile biosensor platform was constructed using 1-pyrenebutyric acid N-hydroxysuccinimide ester (PSE) as the biolinker. The performances of both graphene and G/TiO2 based immunosensing platforms were evaluated for the detection of Dengue virus antibodies (DENV IgG). For the first time, a consensus envelope glycoprotein domain III (cEDIII) of dengue virus was employed as the biorecognition element for improved selectivity towards DENV IgG, even when challenged against the structurally similar Zika virus antibodies (ZIKV IgG). Moreover, the cEDIII protein was obtained via a novel plant-based molecular pharming approach which offers remarkable scalability and safety. Both graphene and G/TiO2 platforms showed promising results in dengue sensing with good sensitivity and selectivity. In addition, the feasibility of the immunosensing platforms in real sample was investigated through the detection of dengue antibodies in mouse serum samples, where both platforms successfully discriminated positive samples from the negative control, suggesting the potential of the immunosensor platforms in replacing conventional diagnostic methods. The G/TiO2-based immunosensor displayed superior sensing performance compared to the graphene-based platform, with wider linear working range (62.5 pg/mL to 2 ng/mL) and lower limit of detection (LOD) of 2.81 pg/mL. Finally, the biocompatibility enhancement effect provided by the incorporation of TiO2 nanoparticles onto graphene was studied via cytotoxicity assessments and comparison study on both graphene and G/TiO2 nanocomposites. Results showed that the cytotoxicity of the nanomaterials is exposure time and dose-dependent, in which higher concentrations and prolonged incubation periods lead to higher magnitude of losses in cell viability. In general, G/TiO2 nanocomposites exhibited lesser cytotoxic effects on both cell lines compared to graphene with a half maximal inhibitory concentration (IC50) of greater than 500 µg/ml and around 25 µg/ml for MRC5 cells and HaCaT cells, respectively, at 24-hour time-point. The satisfactory biocompatibility of G/TiO2 nanocomposites indicated its potential in various delicate biomedical applications such as in-vivo biosensing where the attribute is highly required

基于雷电物理的风机叶片动态击距与 电气几何模型

The damage of wind turbine blades suffered lightning strikes has been a key factor of the safe and reliable operation of wind farms. The electric geometrical model of wind turbine blades (EGMTB) was presented based on the traditional electric geometrical method and the physical process of lightning leader. The concept of dynamic striking distance was introduced and clarified the physical meaning of striking distance. And the calculation method of blade lightning protection system (LPS) efficiency was deduced. Finally, the effectiveness of EGMTB was validated by the long gap breakdown experiment of blades. The EGMTB was used to analyze the influence factors of blade LPS efficiency. It is indicated that the efficiency of blade LPS reduces with the decrease of lightning current and the angle between the blade and horizontal, and the efficiency of blade LPS can be improved by increasing the side lightning receptors. The EGMTB is intended to provide a theory for lightning protection design and evaluation of wind turbine blades

Effective strengthening of RC beams using bamboo-fibre-reinforced polymer: A finite-element analysis

This paper presents a finite-element model of the structural behaviour of reinforced concrete (RC) beams with and without openings externally strengthened with bamboo-fibre-reinforced composite (BFRC) plates. The simulation was performed using ABAQUS Unified FEA 2021HF8 software. The stress–strain relationship of the RC was modelled using a model code for concrete structures, whereas the concrete-damaged plasticity model was used to simulate concrete damage. The predicted crack pattern of the beams was comparable to that from experimental observations. The ultimate load-bearing capacity of RC beams in flexure was predicted with an error of up to 1.50%, while the ultimate load-bearing capacity of RC beams with openings in shear was predicted with an error ranging from 1.89 to 13.43%. The most successful arrangement for strengthening a beam with openings in the shear zone was to place BFRC plates perpendicular to the crack on both sides of the beam’s surface, which increased the beam’s original load-bearing capacity by 110.06% compared to that of the control beam (CB). The most effective method for strengthening RC beams in flexure is to attach a BFRC plate to the entire bottom soffit of the RC beam. This maximises the ultimate load-bearing capacity at the expense of the beam’s ductility

Streamlining Attendance Management in Education: A Web-Based System Combining Facial Recognition and QR Code Technology

Attendance tracking has long posed challenges in educational institutions due to the inefficiency and error-prone nature of traditional paper-based methods. In response, many institutions have embraced web technologies and automated attendance systems, incorporating biometrics, QR codes, barcodes, and RFID-based technologies. However, the applicability of these systems may vary across different educational settings. This paper introduces a web-based student attendance management system that combines facial recognition technology and QR codes to address the challenges associated with manual attendance tracking in a university college. The system leverages a centralized database for streamlined monitoring and auditing of attendance records, offering the flexibility to choose between face recognition and QR code attendance marking options. User acceptance tests were conducted to evaluate the system's effectiveness, and the results indicate that the proposed system greatly improves attendance tracking transparency and demonstrates high usability based on positive user ratings. Additionally, the preference for face recognition over QR code scanning was evident. Incorporating these technologies into the automated attendance system represents a substantial advancement in educational technology, offering an accurate and efficient way of recording attendance

Non-destructive concrete strength evaluation using smart piezoelectric transducer - a comparative study, smart materials and structures

Concrete strength monitoring, providing information related to the readiness of the structure for service, is important for the safety and resource planning in the construction industry. In this paper, a semi-analytical model of surface bonded piezoelectric (lead zirconate titanate) based wave propagation (WP) technique was developed for strength evaluation of mortar with different mix, throughout the curing process. Mechanical parameters of the mortar specimen were mathematically evaluated from the surface wave (R-wave) and pressure wave (P-wave) using elastic wave equations. These parameters were then empirically correlated to the strength. The model was found to be very robust as it could be generalized to account for different water to cement (W/C) ratio. The performance of the WP technique was then compared to the electromechanical impedance technique and other conventional techniques, such as the ultrasonic pulse velocity (UPV) test and the rebound hammer test. Results showed that the WP technique performed equally well as the conventional counterparts. The proposed technique is also advantageous over embedded WP technique and the UPV test, in terms of its capability to capture two types of waves for the evaluation of dynamic modulus of elasticity and Poisson's ratio. A separate study was finally conducted to verify the applicability of this technique on heterogeneous concrete specimen. With the inherent capability of the WP technique in enabling autonomous, real-time, online and remote monitoring, it could potentially replace its conventional counterparts, in providing a more effective technique for the monitoring of concrete strength

Schizophyllum commune

Schizophyllum commune UTARA1 was used for lipase production under solid state fermentation (SSF) of sugarcane bagasse (SB) impregnated with used cooking oil medium. Pretreatments of steam, microwave, hydrochloric acid (HCl), sodium hydroxide (NaOH), and their combinations, such as steam-assisted HCl, steam-assisted NaOH, microwave-assisted HCl, and microwave-assisted NaOH, on the milled SB, were done prior to SSF to investigate their effects on lipase production via SSF. The highest lipase activity among the pretreated SB was 0.200 U/gSB, using steam-assisted HCl treated SB, which is lower than the lipase activity produced from the untreated SB, which was 0.413 U/gSB. Scanning Electron Microscope (SEM) imaging showed significant rupture of the SB structure after steam-assisted-HCl pretreatments where the thin walls of the SB pith were wrinkled and collapsed, with no distinctive cell wall structure. The HCl pretreated SB gave the highest crystallinity index (CrI), 91.43%, compared to the untreated, 61.90%. Conversely, microwave and NaOH pretreatments reduced the CrI, which were 46.15% and 43.36%, respectively. In this study, the results obtained indicated that pretreated SB did not improve the lipase production of Schizophyllum commune UTARA1 under SSF

Snowball: Another View on Side-Channel Key Recovery Tools

The performance of Side-Channel Attacks (SCAs) decays rapidly when considering more sub-keys, making the full-key recovery a very challenging problem. Limited to independent collision information utilization, collision attacks establish the relationship among sub-keys but do not significantly slow down this trend. To solve it, we first exploit the samples from the previously attacked S-boxes to assist attacks on the targeted S-box under an assumption that similar leakage occurs in program loop or code reuse scenarios. The later considered S-boxes are easier to be recovered since more samples participate in this assist attack, which results in the ``snowball\u27\u27 effect. We name this scheme as Snowball, which significantly slows down the attenuation rate of attack performance. We further introduce confusion coefficient into the collision attack to construct collision confusion coefficient, and deduce its relationship with correlation coefficient. Based on this relationship, we give two optimizations on our Snowball exploiting the ``values\u27\u27 information and ``rankings\u27\u27 information of collision correlation coefficients named Least Deviation from Pearson correlation coefficient (PLD) and Least Deviation from confusion coefficient (CLD). Experiments show that the above optimizations significantly improve the performance of our Snowball

Overview of citric acid production from Aspergillus niger

Citric acid has high economic potential owing to its numerous applications. It is mostly produced by microbial fermentation using Aspergillus niger. In view of surges in demand and growing markets, there is always a need for the discovery and development of better production techniques and solutions to improve production yields and the efficiency of product recovery. To support the enormous scale of production, it is necessary and important for the production process to be environmentally friendly by utilizing readily available and inexpensive agro-industrial waste products, while maintaining high production yields. This article reviews the biochemistry of citric acid formation, choices of citric-acid producing microorganisms and raw materials, fermentation strategies, the effects of various fermentation conditions, citric acid recovery options and the numerous applications of citric acid, based on information drawn from the literature over the past 10 years