Biosensors for the Determination of SARS-CoV-2 Virus and Diagnosis of COVID-19 Infection

Monitoring and tracking infection is required in order to reduce the spread of the coronavirus disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To achieve this goal, the development and deployment of quick, accurate, and sensitive diagnostic methods are necessary. The determination of the SARS-CoV-2 virus is performed by biosensing devices, which vary according to detection methods and the biomarkers which are inducing/providing an analytical signal. RNA hybridisation, antigen-antibody affinity interaction, and a variety of other biological reactions are commonly used to generate analytical signals that can be precisely detected using electrochemical, electrochemiluminescence, optical, and other methodologies and transducers. Electrochemical biosensors, in particular, correspond to the current trend of bioanalytical process acceleration and simplification. Immunosensors are based on the determination of antigen-antibody interaction, which on some occasions can be determined in a label-free mode with sufficient sensitivity.

Analysis of Errors Committed by Students in Writing English Essays

Error analysis in linguistics is a systematic process of collecting, identifying, describing, explaining and evaluating unaccepted linguistic forms committed by learners in their writings or speeches. This article attempts to assess the errors committed by 128 bachelor first year education students studying English as a foreign language at Makawanpur Multiple Campus, Hetauda, Nepal in the year 2021. Every student was assigned to write an essay on ‘The Impact of Corona Pandemic on Students’ in about 500 words as the written language sample in a free mode. 128 essays were selected as a sample through the simple random sampling method lottery from 190 essays. All the errors in their essays were identified, described, classified, explained and analyzed. The results revealed that most of the students committed errors in omission at the sentence level, and the causes of the errors were due to intralingual transfer, whereas the highest frequency of errors at the word level was preposition resulted due to mother tongue transfer and overgeneralization.

An empirical investigation on the correlation between solar cell cracks and hotspots

In recent years, solar cell cracks have been a topic of interest to industry because of their impact on performance deterioration. Therefore, in this work, we investigate the correlation of four crack modes and their effects on the temperature of the solar cell, well known as hotspot. We divided the crack modes to crack free (mode 1), micro-crack (mode 2), shaded area (mode 3), and breakdown (mode 4). Using a dataset of 12 different solar cell samples, we have found that there are no hotspots detected for a solar cell affected by modes 1 or 2. However, we discovered that the solar cell is likely to have hotspots if affected by crack mode 3 or 4, with an expected increase in the temperature from 25$$^\circ $$ ∘ C to 100$$^\circ $$ ∘ C. Additionally, we have noticed that an increase in the shading ratio in solar cells can cause severe hotspots. For this reason, we observed that the worst-case scenario for a hotspot to develop is at shading ratios of 40% to 60%, with an identified increase in the cell temperature from 25$$^\circ $$ ∘ C to 105$$^\circ $$ ∘ C.

Label-free concurrent 5-modal microscopy (Co5M) resolves unknown spatio-temporal processes in wound healing

The non-invasive investigation of multiple biological processes remains a methodological challenge as it requires capturing different contrast mechanisms, usually not available with any single modality. Intravital microscopy has played a key role in dynamically studying biological morphology and function, but it is generally limited to resolving a small number of contrasts, typically generated by the use of transgenic labels, disturbing the biological system. We introduce concurrent 5-modal microscopy (Co5M), illustrating a new concept for label-free in vivo observations by simultaneously capturing optoacoustic, two-photon excitation fluorescence, second and third harmonic generation, and brightfield contrast. We apply Co5M to non-invasively visualize multiple wound healing biomarkers and quantitatively monitor a number of processes and features, including longitudinal changes in wound shape, microvascular and collagen density, vessel size and fractality, and the plasticity of sebaceous glands. Analysis of these parameters offers unique insights into the interplay of wound closure, vasodilation, angiogenesis, skin contracture, and epithelial reformation in space and time, inaccessible by other methods. Co5M challenges the conventional concept of biological observation by yielding multiple simultaneous parameters of pathophysiological processes in a label-free mode.

Different Neutralization Sensitivity of SARS-CoV-2 Cell-to-Cell and Cell-Free Modes of Infection to Convalescent Sera

The COVID-19 pandemic caused by SARS-CoV-2 has posed a global threat to human lives and economics. One of the best ways to determine protection against the infection is to quantify the neutralizing activity of serum antibodies. Multiple assays have been developed to validate SARS-CoV-2 neutralization; most of them utilized lentiviral or vesicular stomatitis virus-based particles pseudotyped with the spike (S) protein, making them safe and acceptable to work with in many labs. However, these systems are only capable of measuring infection with purified particles. This study has developed a pseudoviral assay with replication-dependent reporter vectors that can accurately quantify the level of infection directly from the virus producing cell to the permissive target cell. Comparative analysis of cell-free and cell-to-cell infection revealed that the neutralizing activity of convalescent sera was more than tenfold lower in cell cocultures than in the cell-free mode of infection. As the pseudoviral system could not properly model the mechanisms of SARS-CoV-2 transmission, similar experiments were performed with replication-competent coronavirus, which detected nearly complete SARS-CoV-2 cell-to-cell infection resistance to neutralization by convalescent sera. These findings suggest that the cell-to-cell mode of SARS-CoV-2 transmission, for which the mechanisms are largely unknown, could be of great importance for treatment and prevention of COVID-19.

An investigation into the free vibration analysis of intact and defective laminated coposite beams subjected to combined axial force and end moment

This research is focusing on the bending-torsion coupled free vibration modeling as well as the analysis of intact and defective pre-stressed beams subjected to combined axial force and end moment. In the recent years, many studies have been conducted in an attempt to investigate the free vibration of pre-stressed beams using numerical and analytical techniques. However, despite their numerous applications, there is limited research done on pre-stressed beams subjected to both axial force and end moment in addition to the coupled behavior caused by the latter one. In the present study, current trends in the literature are critically examined, new models are proposed, and numerical and semi-analytical formulations are developed to find the natural frequencies and mode shapes of different pre-stressed slender beam configurations. The proposed methods are compared in terms of accuracy and convergence. Furthermore, the effects of axial force, end moment and delamination defect on the vibrational behavior of each model are also investigated. Four different general types of thin beams, including isotropic, layered, composite and delaminated beams, are modeled using traditional Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) technique. The DFE formulation is distinct from the conventional FEM by the fact that the former exploits frequency-dependent basis and shape functions of approximation space, whereas the polynomial ones are used in the latter method. With regard to layered beams, a novel layer-wise method is introduced for both DFE and FEM. Delaminated beam is also modeled using both ‘free mode’ and ‘constrained mode’ models showing that the continuity (both kinematic and force) conditions at delamination tips, in particular, play a large role in formulation of ‘free mode’ model. In this case, the defect is assumed to be a single-symmetric through the thickness delamination. However, the presented models and formulations could be readily extended to more general cases. Where available, the results were validated against existing limited experimental, analytical, and numerical data in literature. In addition, the investigated cases are modeled in the commercial finite element suite ANSYS® for further validation. Finally, general concluding remarks are made on the performance of the presented models and solution techniques, where the advantages and disadvantages of the proposed formulations as well as possible future research works are highlighted.

Free Vibration Analysis Of Layered Beams With Delamination Damage-An ANSYS®-Based FEM Investigation

Identifying delamination has been a focal point for many researchers. The reason for this interest arises from criticality of delamination in a variety of industries: automotive, aerospace, and construction. Therefore, vibration-based damage identification method is applied to detect, locate and characterize the damage in a mechanical structure. In this method, natural frequency as a diagnostic tool to determine the integrity of a structure has been utilized. The current research presents a FEM-based investigation into free vibrational analysis of defective layered beams with free mode delamination. It is shown that the size, type and location of delamination directly influence system non-dimensional frequencies. Based on an existing 1D model, the investigation is extended to 2D modelling for single-and-double-delamination cases. In each case, Fixed-Fixed and cantilevered beam configurations, both centred and off-centred delamination conditions are studied. Further, a 3D model is also developed for single delamination of a Fixed-Fixed beam. All simulation results show excellent agreement with the data available in the literature. The ANSYS ® FEM-based modelling approach presented here is general and accurately predicts delamination effects on the frequency response of beam structures.

An investigation into the free vibration analysis of intact and defective laminated coposite beams subjected to combined axial force and end moment

This research is focusing on the bending-torsion coupled free vibration modeling as well as the analysis of intact and defective pre-stressed beams subjected to combined axial force and end moment. In the recent years, many studies have been conducted in an attempt to investigate the free vibration of pre-stressed beams using numerical and analytical techniques. However, despite their numerous applications, there is limited research done on pre-stressed beams subjected to both axial force and end moment in addition to the coupled behavior caused by the latter one. In the present study, current trends in the literature are critically examined, new models are proposed, and numerical and semi-analytical formulations are developed to find the natural frequencies and mode shapes of different pre-stressed slender beam configurations. The proposed methods are compared in terms of accuracy and convergence. Furthermore, the effects of axial force, end moment and delamination defect on the vibrational behavior of each model are also investigated. Four different general types of thin beams, including isotropic, layered, composite and delaminated beams, are modeled using traditional Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) technique. The DFE formulation is distinct from the conventional FEM by the fact that the former exploits frequency-dependent basis and shape functions of approximation space, whereas the polynomial ones are used in the latter method. With regard to layered beams, a novel layer-wise method is introduced for both DFE and FEM. Delaminated beam is also modeled using both ‘free mode’ and ‘constrained mode’ models showing that the continuity (both kinematic and force) conditions at delamination tips, in particular, play a large role in formulation of ‘free mode’ model. In this case, the defect is assumed to be a single-symmetric through the thickness delamination. However, the presented models and formulations could be readily extended to more general cases. Where available, the results were validated against existing limited experimental, analytical, and numerical data in literature. In addition, the investigated cases are modeled in the commercial finite element suite ANSYS® for further validation. Finally, general concluding remarks are made on the performance of the presented models and solution techniques, where the advantages and disadvantages of the proposed formulations as well as possible future research works are highlighted.

Free Vibration Analysis Of Layered Beams With Delamination Damage-An ANSYS®-Based FEM Investigation

Identifying delamination has been a focal point for many researchers. The reason for this interest arises from criticality of delamination in a variety of industries: automotive, aerospace, and construction. Therefore, vibration-based damage identification method is applied to detect, locate and characterize the damage in a mechanical structure. In this method, natural frequency as a diagnostic tool to determine the integrity of a structure has been utilized. The current research presents a FEM-based investigation into free vibrational analysis of defective layered beams with free mode delamination. It is shown that the size, type and location of delamination directly influence system non-dimensional frequencies. Based on an existing 1D model, the investigation is extended to 2D modelling for single-and-double-delamination cases. In each case, Fixed-Fixed and cantilevered beam configurations, both centred and off-centred delamination conditions are studied. Further, a 3D model is also developed for single delamination of a Fixed-Fixed beam. All simulation results show excellent agreement with the data available in the literature. The ANSYS ® FEM-based modelling approach presented here is general and accurately predicts delamination effects on the frequency response of beam structures.

On the Finite Element Free Vibration Analysis of Delaminated Layered Beams: A New Assembly Technique

The dynamic analysis of flexible delaminated layered beams is revisited. Exploiting Boolean vectors, a novel assembly scheme is developed which can be used to enforce the continuity requirements at the edges of delamination region, leading to a delamination stiffness term. The proposed assembly technique can be used to form various beam configurations with through width delaminations, irrespective of the formulation used to model each beam segment. The proposed assembly system and the Galerkin Finite Element Method (FEM) formulation are subsequently used to investigate the natural frequencies and modes of 2- and 3-layer beam configurations. Using the Euler-Bernoulli bending beam theory and free mode delamination, the governing differential equations are exploited and two beam finite elements are developed. The free bending vibration of three illustrative example problems, characterized by delamination zones of variable length, is investigated. The intact and defective beam natural frequencies and modes obtained from the proposed assembly/FEM beam formulations are presented along with the analytical results and those available in the literature