Fluid-structure interaction analysis of airflow, structural mechanics and aerosol dynamics in a four-generation acinar model.

Elucidating the aerosol dynamics in the pulmonary acinar region is imperative for both health risk assessment and inhalation therapy, especially nowadays with the occurrence of the global COVID-19 pandemic. During respiration, the chest's outward elastic recoil and the lungs' inward elastic recoil lead to a change of transmural pressure, which drives the lungs to expand and contract to inhale and expel airflow and aerosol. In contrast to research using predefined wall motion, we developed a four-generation acinar model and applied an oscillatory pressure on the model outface to generate structure deformation and airflow. With such tools at hand, we performed a computational simulation that addressed both the airflow characteristic, structural mechanics, and aerosol dynamics in the human pulmonary acinar region. Our results showed that there is no recirculating flow in the sac. The structural displacement and stress were found to be positively related to the change of model volume and peaked at the end of inspiration. It was noteworthy that the stress distribution on the acinar wall was significantly heterogeneous, and obvious concentrations of stress were found at the junction of the alveoli and the ducts or the junction of the alveoli and alveoli in the sac. Our result demonstrated the effect of breathing cycles and aerosol diameter on deposition fraction and location of aerosols in the size range of 0.1-5 µm. Multiple respiratory cycles were found necessary for adequate deposition or escape of submicron particles while having a negligible influence on the transport of large particles, which were dominated by gravity. Our study can provide new insights into the further investigation of airflow, structural mechanics, and aerosol dynamics in the acinar depth.

Experimental Investigation on the Low-Velocity Impact Response of Tandem Nomex Honeycomb Sandwich Panels.

Sandwich panels are often subjected to unpredictable impacts and crashes in applications. The core type and impactor shape affect their impact response. This paper investigates the responses of five tandem Nomex honeycomb sandwich panels with different core-types under low-velocity-impact conditions with flat and hemispherical impactors. From the force response and impact displacement, gradient-tandem and foam-filled structures can improve the impact resistance of sandwich panels. Compared with the single-layer sandwich panel, the first peak of contact force of the foam-gradient-filled tandem honeycomb sandwich panels increased by 34.84%, and maximum impact displacement reduced by 50.98%. The resistance of gradient-tandem Nomex honeycomb sandwich panels under low-velocity impact outperformed uniform-tandem structures. Foam-filled structures change the impact responses of the tandem sandwich panels. Impact damage with a flat impactor was more severe than the hemispherical impactor. The experimental results are helpful in the design of tandem Nomex honeycomb sandwich panels.

A self-contained and integrated microfluidic nano-detection system for the biosensing and analysis of molecular interactions.

Traditional detection methods have shortcomings such as time-consumption and requirement of large instruments, which cannot meet the demands for on-site detection or analysis. Silicon nanowire-field-effect transistor (SiNW-FET) biosensors have the advantages of high speed, high sensitivity, strong specificity, and ease of integration. However, SiNW-FET biosensors also have some demerits: they are too sensitive, environmental factors such as light, temperature, and pH easily cause interference, and their performance uniformity needs to be calibrated in advance. In this work, we constructed a self-contained and integrated microfluidic nano-detection system containing a SiNW-FET biosensor for bio-detection and analysis. All analysis processes including liquid sample delivery, optical modulation, constant temperature control, signal amplification and data acquisition, and result display were automatically performed. In series tests including light-guided ones by analyzing various types of samples with an automatic sample injection mode, the system shows good stability and robustness. Its signal accuracy was verified using a commercial high-precision ammeter (R2 = 0.9988), too. The feasibility of the system for bio-detection was verified using simulant samples of the typical microorganism Mycobacterium tuberculosis with a limit of detection of 1.0 fg mL-1. Furthermore, the process of the binding-dissociation of antibody-protein pairs was analyzed using the system, demonstrating the potential for molecular interaction analysis. This system is highly integrated, small in size, and easy to carry, which will be developed into a portable device for on-site bio-detection and analysis of molecular interactions to enable environmental testing, medical research, food and agricultural safety, military medicine, etc.

Visualization of the infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward.

Since December 2019, coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a great challenge to the world's public health system. Nosocomial infections have occurred frequently in medical institutions worldwide during this pandemic. Thus, there is an urgent need to construct an effective surveillance and early warning system for pathogen exposure and infection to prevent nosocomial infections in negative-pressure wards. In this study, visualization and construction of an infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward were performed to describe the distribution regularity and infection risk of SARS-CoV-2, the critical factors of infection, the air changes per hour (ACHs) and the viral variation that affect infection risk. The SARS-CoV-2 distribution data from this model were verified by field test data from the Wuhan Huoshenshan Hospital ICU ward. ACHs have a great impact on the infection risk from airborne exposure, while they have little effect on the infection risk from surface exposure. The variant strains demonstrated significantly increased viral loads and risks of infection. The level of protection for nurses and surgeons should be increased when treating patients infected with variant strains, and new disinfection methods, electrostatic adsorption and other air purification methods should be used in all human environments. The results of this study may provide a theoretical reference and technical support for reducing the occurrence of nosocomial infections.

[Numerical simulation on the deposition characteristics of inhaled particles in human pulmonary acinus region under the influence of multi-factors].

Research on the deposition of inhaled particles in human pulmonary acinus region is important to the pathogenesis investigation, prevention and treatment of lung diseases. Most of the current research focus on the final deposition fraction of inhaled particles in human acinar region, but little is involved in their dynamic deposition characteristics. In this paper, five multi-alveolar models, G3-G7, were built. The evaluation parameter 1/4 deposition time was introduced to study the particle deposition speed. The deposition characteristics of particles in the diameter ranging 0.1-5 µm were numerically simulated and summarized under the influence of factors such as the generation and structure of model, particle diameter and respiratory mode, shedding some new light on the further research of transport of inhaled particles. The results showed that the generation and structure of model had a significance effect on the deposition of particles. 0.1 µm particles were dominated by Brownian diffusion, which experienced a high deposition fraction, a fast deposition speed and a logarithmic deposition curve, while 5 µm particles were dominated by gravitational sedimentation, with a high deposition fraction, a fast deposition speed and an S-shaped deposition curve. The deposition of 0.3-1 µm particles were influenced greatly by convention and varied with the change of respiratory mode. The research methods and results in this paper can provide theoretical basis and data support for the further exploration of the mechanism, prevention and treatment of lung diseases.

Particle Self-Aligning, Focusing, and Electric Impedance Microcytometer Device for Label-Free Single Cell Morphology Discrimination and Yeast Budding Analysis.

Microfluidic electric impedance flow cytometry (IFC) devices have been applied in single cell analysis, such as cell counting, volume discrimination, cell viability, etc. A cell's shape provides specific information about cellular physiological and pathological conditions, especially in microorganisms such as yeast. In this study, the particle orientation focusing was theoretically analyzed and realized by hydrodynamics. The pulse width (passing time for the particles) of the conductance signal was used to discriminate particle shapes. Spherical and rod-shaped particles with similar volumes/lengths were differentiated by the IFC device, using the impedance pulse parameters of the events. Then, typical late-budding, early budding, and unbudded yeast cells were distinguished by the width, amplitude, and ratio of width to amplitude (R) of the impedance pulse. The pulse amplitude and the R combination gate for identifying the late-budding yeast was estimated through the statistic results. Using the gate, the late-budding rates under different conditions were calculated. Late-budding rates obtained using our method showed a high correlation (R2 = 0.83) with the manual cell counting result and represented the budding status of yeast cells under different conditions proficiently. Thus, the late-budding rate calculated using the above method can be used as a qualitative parameter to assess the reproductive performance of yeast and whether a yeast culturing environment is optimal. This IFC device and cell shape discrimination method is very simple and could be applied in the fermentation industry and other microorganisms' discrimination as a rapid analysis technique in the future.

[Progress on numerical simulation of the deposition of inhaled particles in human pulmonary acinus region].

The inhalation and deposition of particles in human pulmonary acinus region can cause lung diseases. Numerical simulation of the deposition of inhaled particles in the pulmonary acinus region has offered an effective gateway to the prevention and clinical treatment of these diseases. Based on some important affecting factors such as pulmonary acinar models, model motion, breathing patterns, particulate characteristics, lung diseases and ages, the present research results of numerical simulation in human pulmonary acinus region were summarized and analyzed, and the future development directions were put forward in this paper, providing new insights into the further research and application of the numerical simulation in the pulmonary acinus region.

[Experimental research on the effect of functional residual capacity on the deposition of inhalable particles in human alveoli region].

Research on the deposition of inhalable particles in the alveoli of the lungs is important to the causes, development for common respiratory diseases such as emphysema, and even the optimization of clinical treatment and prevention programs of them. In this paper, an in vitro experimental model was established to simulate the deposition of terminal bronchioles and pulmonary acinus particles. The deposition rate of inhalable particles with different particle sizes in the pulmonary acinus was studied under different functional residual capacity. The results showed that the particle diameter was an important factor affecting the deposition of particles in the lung alveoli. Particles with 1 µm diameter had the highest deposition rate. With the functional residual capacity increasing, particulate deposition rate significantly reduced. The results of this study may provide data support and optimization strategy for target inhalation therapy of respiratory diseases such as emphysema and pneumoconiosis. The established model may also provide a feasible in vitro experimental model for studying the deposition of inhalable particles in the pulmonary alveoli.

Dynamic sessile micro-droplet evaporation monitored by electric impedance sensing.

Studies of liquid evaporation on a solid surface are useful for wettability phenomena-related research, and can be applied in a series of scientific and industrial areas. However, traditional methods are not easy to be intergrated into small size to monitor evaporation process of a micro-droplet. In this paper, a micro-electrode array was used to measure the impedance of an electrolyte droplet, indicating the dynamic process of evaporation. This method uses the relationship between concentration and conductivity of the water solution to dynamically monitor the evaporation process. The dynamic impedance results were compared to weight and imaging data of droplet evaporation and demonstrate high correlation coefficient of the earlier 90% part of the sodium chloride droplet evaporation process (R 2 = 0.99). Our study proved that the height of the droplet will affect the impedance sensing result, and the solution used for droplet evaporation can be expanded to mixture of strong electrolyte solution such as phosphate buffered solution. Then the "impedance imaging" of the array monitored the evaporating speed differences of different sites of a sessile droplet. As the electrode array can be integrated into small size, this method is compatible for many other experimental systems and can be further used for evaporation studies and corresponding application areas.

A method to differentiate between ventricular fibrillation and asystole during chest compressions using artifact-corrupted ECG alone.

In recent years, numerous adaptive filtering techniques have been developed to suppress the chest compression (CC) artifact for reliable analysis of the electrocardiogram (ECG) rhythm without CC interruption. Unfortunately, the result of rhythm diagnosis during CCs is still unsatisfactory in many studies. The misclassification between corrupted asystole (ASY) and corrupted ventricular fibrillation (VF) is generally regarded as one of the major reasons for the poor performance of reported methods. In order to improve the diagnosis of VF/ASY corrupted by CCs, a novel method combining a least mean-square (LMS) filter and an amplitude spectrum area (AMSA) analysis was developed based only on the analysis of the surface of the corrupted ECG episode. This method was tested on 253 VF and 160 ASY ECG samples from subjects who experienced cardiac arrest using a porcine model and was compared with six other algorithms. The validation results indicated that this method, which yielded a satisfactory result with a sensitivity of 93.3%, a specificity of 96.3% and an accuracy of 94.8%, is superior to the other reported techniques. After improvement using the human ECG records in real cardiopulmonary resuscitation (CPR) scenarios, the algorithm is promising for corrupted VF/ASY detection with no hardware alterations in clinical practice.

[Progress in numerical simulation and experimental study on inhalable particles deposition in human respiratory system].

Inhalable particles deposition in the human respiratory system is the main cause of many respiratory and cardiovascular diseases. It plays an important role in related disease prevention and treatment through establishing computer or external entity models to study rules of particle deposition. The paper summarized and analyzed the present research results of various inhalable particle deposition models of upper respiratory tract and pulmonary area, and expounded the application in the areas of disease inducement analysis, drug inhale treatment etc. Based on the review, the paper puts forward the problems and application limitations of present research, especially pointing out future emphasis in development directions. It will have a value of reference guidance for further systematic and in-depth study on the inhalable particle deposition simulation, experiment and application.

[Numerical simulation on cycle change form of the pressure and wall shear in human upper respiratory tract].

The research on cycle change form of the pressure and the wall shear in human upper respiratory tract can strengthen understanding of the characteristics of the airflow in the place and provide us with a scientific basis for analyzing the diffusion, transition and deposition patterns of aerosol there. In our study, we used large eddy simulation to emulate the pressure and wall shear in human upper respiratory tract in conditions of the low intensive respiratory patterns, and discussed the distributing disciplinarian of the pressure and wall shear in mouth-throat model and trachea-triple bifurcation. The results showed that the pressure gradient variation in human upper respiratory tract was mainly fastened from root of epiglottis to trachea. The minimum pressure at the interim of inspiration was a duplication of the interim of expiration, and located on the posterior wall of the glottis. The pressure gradient variation was evident on trachea and its fork. The wall shear changed with the velocity of the air flow, and its direction changed periodically with breath cycle.