Adjustable Ultra-Light Mechanical Negative Poisson's Ratio Metamaterials with Multi-Level Dynamic Crushing Effects.

Mechanical metamaterials with multi-level dynamic crushing effects (MM-MLs) are designed in this study through coordinate transformation and mirror arrays. The mechanical effects of the diameter and length ratio of the struts and connecting rods, the Euler angles, and the cell numbers on the mechanical properties are investigated separately. MM-ML can exhibit significant two-level platform stress, and the local cells in the first platform stress stage undergo rotational motion, while the second platform stress stage mainly involves collapse compression and bending. Although increasing the length of the connecting rods can increase the range of Poisson's ratio, it will reduce the level of platform stress and energy absorption. Increasing the Euler angle will reduce the strain interval of the first platform stress and can improve the energy absorption capacity. In addition, increasing the cell number while maintaining a constant relative density can effectively enhance energy absorption. MM-ML has significant parameter controllability, can achieve different platform stress regions, different ranges of Poisson's ratios, and energy absorption requirements according to the application scenario, and can demonstrate functional diversity compared to existing research. The design scheme can provide ideas for adaptive crushing protection requirements.

Study on the Effect of Type III Recombinant Humanized Collagen on Human Vascular Endothelial Cells.

The effect and mechanism of type III recombinant humanized collagen (hCOLIII) on human vascular endothelial EA.hy926 cells at the cellular and molecular levels were investigated. The impact of hCOLIII on the proliferation of EA.hy926 cells was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid assay, the effect of hCOLIII on cell migration was investigated by scratch assay, the impact of hCOLIII on cell cycle and apoptosis was detected by flow cytometry, the ability of hCOLIII to induce angiogenesis of EA.hy926 cells was evaluated by angiogenesis assay, and the effect of hCOLIII on vascular endothelial growth factor (VEGF) expression was detected by real-time reverse transcription-polymerase chain reaction analysis. The hCOLIII at concentrations of 0.5, 0.25, and 0.125 mg/mL all showed specific effects on the proliferation and migration of human vascular endothelial cells. It could also affect the cell cycle, increase the proliferation index, and increase the expression level of VEGF in human vascular endothelial cells. In the meantime, hCOLIII at the concentration of 0.5 mg/mL also showed a promoting effect on vessel formation. hCOLIII can potentially promote the endothelization process of blood vessels, mainly by affecting the proliferation, migration, and vascular-like structure of human endothelial cells. At the same time, hCOLIII can promote the expression of VEGF. This collagen demonstrated its potential as a raw material for cardiovascular implants.

Fabrication and performance evaluation of PLCL-hCOLIII small-diameter vascular grafts crosslinked with procyanidins.

Cardiovascular disease has become one of the main causes of death. It is the common goal of researchers worldwide to develop small-diameter vascular grafts to meet clinical needs. Collagen is a valuable biomaterial that has been used in the preparation of vascular grafts and has shown good results. Recombinant humanized collagen (RHC) has the advantages of clear chemical structure, batch stability, no virus hazard and low immunogenicity compared with animal-derived collagen, which can be developed as vascular materials. In this study, Poly (l-lactide- ε-caprolactone) with l-lactide/ε-caprolactone (PLCL) and type III recombinant humanized collagen (hCOLIII) were selected as raw materials to prepare vascular grafts, which were prepared by the same-nozzle electrospinning apparatus. Meanwhile, procyanidin (PC), a plant polyphenol, was used to cross-link the vascular grafts. The physicochemical properties and biocompatibility of the fabricated vascular grafts were investigated by comparing with glutaraldehyde (GA) crosslinked vascular grafts and pure PLCL grafts. Finally, the performance of PC cross-linked PLCL-hCOLIII vascular grafts were evaluated by rabbit carotid artery transplantation model. The results indicate that the artificial vascular grafts have good cell compatibility, blood compatibility, and anti-calcification performance, and can remain unobstructed after 30 days carotid artery transplantation in rabbits. The grafts also showed inhibitory effects on the proliferation of SMCs and intimal hyperplasia, demonstrating its excellent performance as small diameter vascular grafts.

[Quality Control of Appliance Products of Medical Devices for Human Assisted Reproductive Technology].

Infertility has become one of the global problems, with the continuous improvement and penetration of human assisted reproductive technology, appliance products of medical devices for assisted reproductive technology, such as aspiration needles, micromanipulator and embryo transfer catheter, have been widely used. In order to ensure the safety and effectiveness of such products, it is necessary to establish an appropriate quality control system. This paper mainly discusses the quality control points of human assisted reproductive medical devices from the aspects of raw materials, product design, production process, key performance, packaging, preservation and transportation, so as to provide technical reference for the research and development, production and supervision of such products.

Digital Health Technologies Respond to the COVID-19 Pandemic In a Tertiary Hospital in China: Development and Usability Study.

BACKGROUND: The outbreak of COVID-19 has caused a continuing global pandemic. Hospitals are integral to the control and prevention of COVID-19; however, they are facing numerous challenges during the epidemic. OBJECTIVE: Our study aimed to introduce the practical experience of the design and implementation of a web-based COVID-19 service platform at a tertiary hospital in China as well as the preliminary results of the implementation. METHODS: The web-based COVID-19 service platform was deployed within the health care system of the Guangdong Second Provincial General Hospital and Internet Hospital; the function of the platform was to provide web-based medical services for both members of the public and lay health care workers. The focal functions of this system included automated COVID-19 screening, related symptom monitoring, web-based consultation, and psychological support; it also served as a COVID-19 knowledge hub. The design and process of each function are introduced. The usage data for the platform service were collected and are represented by three periods: the pre-epidemic period (December 22, 2019, to January 22, 2020, 32 days), the controlled period (January 23 to March 31, 2020, 69 days), and the postepidemic period (April 1 to June 30, 2020, 91 days). RESULTS: By the end of June 2020, 96,642 people had used the automated COVID-19 screening and symptom monitoring systems 161,884 and 7,795,194 times, respectively. The number of general web-based consultation services per day increased from 30 visits in the pre-epidemic period to 122 visits during the controlled period, then dropped to 73 visits in the postepidemic period. The psychological counseling program served 636 clients during the epidemic period. For people who used the automated COVID-19 screening service, 160,916 (99.40%) of the total users were classified in the no risk category. 464 (0.29%) of the people were categorized as medium to high risk, and 12 people (0.01%) were recommended for further COVID-19 testing and treatment. Among the 96,642 individuals who used the COVID-19 related symptoms monitoring service, 6696 (6.93%) were symptomatic at some point during the monitoring period. Fever was the most frequently reported symptom, with 2684/6696 symptomatic people (40.1%) having had this symptom. Cough and sore throat were also relatively frequently reported by the 6696 symptomatic users (1657 people, 24.7%, and 1622 people, 24.2%, respectively). CONCLUSIONS: The web-based COVID-19 service platform implemented at a tertiary hospital in China is exhibited to be a role model for using digital health technologies to respond to the COVID-19 pandemic. The digital solutions of automated COVID-19 screening, daily symptom monitoring, web-based care, and knowledge propagation have plausible acceptability and feasibility for complementing offline hospital services and facilitating disease control and prevention.

Three-surface model for the ray tracing of an imaging acousto-optic tunable filter.

A three-surface model is proposed for the ray tracing of an imaging acousto-optic tunable filter (AOTF) in the optical design of an AOTF imaging system. The first and last surfaces are two refractive planes corresponding to the incident and exit facets of the AOTF, while the property of the second surface is defined particularly to describe the change of the ray trace owing to the interaction of the acoustic and optic waves. One parameter, the acoustic angle, is first corrected using the test tuning relation to compensate for the nonideality of the acoustic wave. The model has been verified with a two-piezotransducer AOTF to show its usefulness. The differences between the measured diffracted angles and the modeling value are below 0.01°. The comparison demonstrates the accuracy and the efficiency of the three-surface model.

Improvement in the synchronization between the radio frequency signal and the image detector in an acousto-optic tunable filter imaging spectrometer.

An improved synchronization between the radio frequency (RF) signal and the image detector in an acousto-optic tunable filter (AOTF) imaging spectrometer is proposed to optimize power consumption and eliminate image smear. The RF signal is controlled on and off alternately to match the exposure of the image sensor. This scheme reduces the RF power and rejects the light illumination on the image sensor in the interval of charge transfer. An experiment using a visible AOTF, a frame transfer charge-coupled device camera, and an incandescent lamp is conducted for demonstration. The average RF power decreases 7.6%, and the image smear is eliminated.

Combined laser and broadband light for measuring the tuning relation of an acousto-optic tunable filter.

To improve the tuning relation accuracy of an acousto-optic tunable filter, the conventional separated laser and broadband light methods were combined. The single laser test measured one accurate point and corrected the large amounts of data obtained from the broadband light method. The final tuning relation was fitted by the corrected data. A simulation and an experiment for several methods were conducted for comparison. The relative error was reduced from 0.2% to 0.05% in the 430~785 nm range. The equivalent wavelength accuracy improved from 1 to 0.2 nm. This method solved the problems associated with the use of a single laser source with few test data values and a single broadband light source with poor collimation.

[Lateral chromatic aberrations correction for AOTF imaging spectrometer based on doublet prism].

An user defined surface function method was proposed to model the acousto-optic interaction of AOTF based on wave-vector match principle. Assessment experiment result shows that this model can achieve accurate ray trace of AOTF diffracted beam. In addition, AOTF imaging spectrometer presents large residual lateral color when traditional chromatic aberrations correcting method is adopted. In order to reduce lateral chromatic aberrations, a method based on doublet prism is proposed. The optical material and angle of the prism are optimized automatically using global optimization with the help of user defined AOTF surface. Simulation result shows that the proposed method provides AOTF imaging spectrometer with great conveniences, which reduces the lateral chromatic aberration to less than 0.000 3 degrees and improves by one order of magnitude, with spectral image shift effectively corrected.

[Analysis of the noise and signal-to-noise of AOTF imaging spectrometer based on EMCCD].

Imaging spectrometer based on acousto-optic tunable filter (AOTF) is a novel hyperspectral imaging system. In order to rectify the non-uniformity of radiation sensitivity on different waveband, especially the low signal-to-noise (SNR) in low-light conditions, the electron-multiplying CCD (EMCCD) sensor was proposed. The noise of AOTF imaging spectrometer was analyzed in both normal and EM modes of the CCD sensor with derived SNR calculating model which has been experimentally validated. On that basis, a new evaluation method of the dynamic range in EM mode and a novel method of calculating spectral radiance at the entrance aperture were adopted. The experimental result shows that the theoretic SNR models are fit, and better selection of EM mode is effective to improve the SNR and non-uniformity of radiation sensitivity in low light level conditions.