Poly(vinyl alcohol) (PVA) is a cytocompatible synthetic polymer and has been commonly used to prepare hydrogels. Bile acids and β-cyclodextrin are both natural compounds and they form stable ...host–guest inclusion complexes. They are attached covalently onto a low molecular weight PVA separately. Self-healing hydrogels can be easily formed by mixing the aqueous solutions of these PVA based polymers. The mechanical properties of the hydrogels can be tuned by varying the molar fractions of bile acid units on PVA. The dynamic inclusion complexation of the host–guest pair of the hydrogel allows the self-healing rapidly under ambient atmosphere and their mechanical properties could recover their original values in 1 min after incision. These PVA based polymers exhibited the good cytocompatibility and high hemocompatibility as shown by their biological evaluations. The use of natural compounds for host–guest interaction make such gels especially convenient to use as biomaterials, an advantage over conventional hydrogels prepared through freeze–thaw method.
Corneal transplantation is the widely accepted treatment to restore sight for corneal blindness. To date, because of the global donor cornea shortage, there is a need for alternatives to human donor ...corneas. Biocompatible collagen is an excellent candidate material for corneal repair in the view of biomimetics. Herein a class of polyrotaxane multiple aldehyde (PRA) cross-linkers based on the host–guest supramolecules of α-cyclodextrins and poly(ethylene glycol) is prepared to cross-link with collagen to fabricate materials for corneal repair. Aldehyde groups from rotaxanes and α-cyclodextrin units can synergistically improve the mechanical and optical properties of PRA cross-linked collagen membranes (Col-PRAs). Compared with counterparts cross-linked by traditional a cross-linker of 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide and N-hydroxy-succinimide, Col-PRAs have better mechanical properties, especially suture resistance as well as optical properties. In vivo lamellar keratoplasty results indicate that Col-PRAs not only can bear tight suturing on a rabbit cornea but also are prone to the remodeling of the epithelium and stroma of the cornea due to the outstanding cell adhesion and proliferation. These novel Col-PRAs exhibit great potential for use in the corneal regeneration.
•Cracked asphalt models with and without repairing agents were established by MS.•Potential energy is the main driving force of micro crack repair process.•There was a positive correlation between ...temperature and repair action.•Light and long chain-like small molecule is more suitable for a core material.
The objective of this study is to analyze the behavior of repairing agent of microcapsule in asphalt micro crack based on molecular dynamics simulation. Based on the molecular dynamics software Material Studio 7.0 (MS), a four-fraction molecular model of asphalt and a molecular model of repairing agent of the microcapsule core material were constructed. Based on this, the micro crack models with and without repairing agents in asphalt were constructed, and the dynamics simulation calculations were carried out. The density and energy of the repairing agent moving in the micro crack after being released from microcapsule were studied, as well as the diffusion coefficient of molecules of the two models. The shear modulus of the models before and after crack repairing were analyzed. Additionally, the effects of temperature and molecular type on crack repairing were also analyzed. The results indicated that crack repairing was a process of mutual diffusion between the repairing agent and asphalt under the main driving force of potential energy. The repairing agent in the cracks accelerated the diffusion of the asphalt molecules to promote crack repairing rate; Crack repairing speed and temperature were positively correlated, that is, the repair rate increases with the increase of temperature. After the crack repair, the shear modulus of the models with and without repairing agent increased by 228.57% and 111.11%, respectively, indicating that the repairing agent also accelerated the mechanical property recovery of the crack model. The light and long chain-like small molecule type repairing agent could more promote the self-repairing process, and be more suitable for use as a core material repairing agent of microcapsules.
Multiparameter spectrophotometry (MPS) provides a powerful tool for accurate characterization of turbid materials in applications such as analysis of material compositions, assay of biological ...tissues for clinical diagnosis and food safety monitoring.
This work is aimed at development and validation of a rapid inverse solver based on a particle swarm optimization (PSO) algorithm to retrieve the radiative transfer (RT) parameters of absorption coefficient, scattering coefficient and anisotropy factor of a turbid sample.
Monte Carlo (MC) simulations were performed to obtain calculated signals for comparison to the measured ones of diffuse reflectance, diffuse transmittance and forward transmittance. An objective function has been derived and combined with the PSO algorithm to iterate MC simulations for MPS.
We have shown that the objective function can significantly reduce the variance in calculated signals by local averaging of an inverse squared error sum function between measured and calculated signals in RT parameter space. For validation of the new objective function for PSO based inverse solver, the RT parameters of 20% Intralipid solutions have been determined from 520 to 1000 nm which took about 2.7 minutes on average to complete signal measurement and inverse calculation per wavelength.
The rapid solver enables MPS to be translated into easy-to-use and cost-effective instruments without integrating sphere for material characterization by separating and revealing compositional profiles at the molecular and particulate scales.
Abstract Traditional air conditioner (AC) temperature control typically sets temperature goals or establishes a uniform temperature range without considering industrial characteristics and user ...comfort preferences. As a result, users cannot achieve differentiated and precise control. This paper proposes a data-driven approach to predict the range of AC set temperatures under the constraint of user comfort. Firstly, a random forest feature importance screening method is employed to extract key factors influencing AC set temperatures. Secondly, a convolutional neural network (CNN) model is constructed to estimate AC set temperatures for five typical user categories. Finally, based on the Predicted Mean Vote (PMV) model, user thermal comfort constraints are established to calculate the flexible adjustment range of AC for users. Through simulation analysis using real AC data from a certain region in Eastern China, the proposed standard for estimating user air conditioner set temperatures in this paper ensures a root mean square error not exceeding 0.5 and an average absolute percentage error not surpassing 1.8%. The obtained air conditioner adjustment ranges reflect the characteristics of users in different industries, meeting engineering requirements.
Multiparameter spectrophotometry (MPS) provides a powerful and environmental-friendly tool for the characterization of turbid materials, including foods, without additives. The existing methods of ...MPS, however, lack either modeling accuracy or capacity for translation into ease-of-use instrument. We have developed a novel method of MPS to rapidly retrieve the spectral data of absorption coefficient, scattering coefficient, and anisotropy factor within the framework of radiative transfer (RT) theory without using integrating spheres. To demonstrate the feasibility of our MPS method for food analysis, the RT parameters have been determined between 500 and 1000 nm for four types of milk samples and skim milk samples spiked with either Lactobacillus acidophilus (L. acid.) or DH<inline-formula> <tex-math notation="LaTeX">5\alpha </tex-math></inline-formula> Escherichia coli (E. coli) bacteria. The spectral data have been shown to agree with the published results on milk composition. We have also found the threshold of number density for the detection of E. coli in skim milk to be about <inline-formula> <tex-math notation="LaTeX">2\times 10^{4} </tex-math></inline-formula> (mm−3). These results show clearly the potential of the presented method for the development of accurate, ease-of-use, and cost-effective instrument for routine analysis of turbid materials by MPS.
Artery blood flow driven by pressure wave is essential for human life. The long-term research goal is to establish a foundation for future translation of the imaging photoplethysmography (iPPG) ...method into applications such as extraction of vital health biomarkers. For this dissertation research, we focus on development of a robust framework of hardware and data processing tools for rapid acquisition and analysis of in vivo iPPG data. Through this project, we have developed a multispectral imaging system for acquisition of time-sequenced iPPG data in vivo from hands of two volunteers with 12 wavelength bands ranging from 445 to 940 nm at a frame rate up to 250 Hz. A fluid dynamic model of blood flow and pressure wave was employed to quantify the effects of the artery wall deformation with different Young’s modulus, artery radius and other boundary conditions on flow rate and pressure. A voxel-based Monte Carlo (MC) simulation model has been established for quantitative analysis of the iPPG data based on the radiative transfer theory. The measured waveforms of iPPG signals at multiple locations in palmar artery have been compared to the waveforms of blood pressure waves calculated with the coupled model of MC and the fluid dynamic simulations. We have identified the optimal wavelength bands for iPPG illumination to detect palm artery tree and shown that the spatial and temporal distributions of the iPPG signals have strong potentials to monitor heartbeat rate and conditions of artery. The results of this dissertation study provide convincing evidences that iPPG data contain rich information on blood flow and propagation of pressure wave in artery. Consequently, future development of the iPPG method can yield a powerful and non-contact tool to rapidly acquire vital sign data and quantitatively assess cardiovascular conditions.
•Turbidity characterization by radiative transfer parameters from three measured signals.•Robustness of inverse solutions is quantified in the space of radiative transfer parameters.•Area descending ...rate (ADR) of contour lines correlates with convergence rate.•Effect of detection configuration is evaluated by ADR for different sample types.•The 3-photodiode design yields a robust approach for multiparameter spectrophotometry.
Spectroscopic characterization of turbid samples needs to solve inverse scattering problems (ISPs). With the radiative transfer (RT) theory as the framework for modeling light-matter interaction, accurate characterization becomes feasible but practical implementation remains challenging. We have evaluated the uniqueness and robustness of ISP solutions for a multiparameter spectrophotometer system without integrating spheres using different detection configurations for signal measurement. A novel parameter of area descending rate (ADR) has been developed to sample globally the distribution of an objective function in the 3D space of RT parameters and quantify uniqueness and robustness of ISP solutions. Analysis of the objective function for different sample types show the uniqueness of solutions for different detection configurations with increased complexity for samples of very larger single-scattering albedo values. The robustness of ISP solutions as quantified by ADR was found to be insensitive to the changes in detection configurations. Such stability provides strong evidences that the multiparameter spectrophotometry using only three photodiodes combined with Monte Carlo simulations yields a valuable and practical approach for turbidity characterization.
As an effective alternative to suture in wound closure, tissue adhesives often need to have excellent biocompatibility and suitable bioadhesion. To achieve long‐term adhesion on moist tissue, ...polyrotaxane (PR) crosslinked self‐healing hydrogels have been prepared by the introduction of dynamic borate bonds between PR bearing phenylboronic acid moieties (PR‐PBA) and dopamine grafted poly(vinyl alcohol) (PVA‐DOP). Synthesis of these precursor polymers PR‐PBA and PVA‐DOP is quite simple and the hydrogels combine dynamic borate bonds with the sliding motion of the phenylboronic acid moieties on PR. The sliding nature of the crosslinking points along the axle in the PR is thought to enhance the mechanical properties and adhesion ability of the resultant hydrogels. Meanwhile, catechol groups on dopamine units have been protected by borate bonds under alkaline conditions to avoid oxidation, and they then are released to react with various functional groups on tissue surface to ensure the switchable tissue adhesion. The self‐healing test and adhesion of hydrogels on pigskin demonstrate the ability to restore the original performance after repeated strain cycles and maintain strong tissue adhesion. The components of these hydrogels have satisfying biocompatibility. These results indicate that these self‐healing hydrogels have great potentials in tissue adhesion.
A self‐healing hydrogel is constructed by grafting dopamine onto poly(vinyl alcohol) with phenylboronic acid‐modified polyrotaxane to achieve long‐term adhesion on moist tissues. The catechol groups on the dopamine are protected from oxidation by borate bonds under alkaline conditions and then released to ensure switchable tissue adhesion. The hydrogel components are biocompatible and the gel has excellent adhesive self‐healing properties.
As a noncontact method, imaging photoplethysmography (iPPG) may provide a powerful tool to measure pulsatile pressure wave (PPW) in superficial arteries and extract biomarkers for monitoring of ...artery wall stiffness.
We intend to develop a approach for extraction of the very weak cardiac component from iPPG data by identifying locations of strong PPW signals with optimized illumination wavelength and determining pulse wave velocity (PWV).
Monochromatic in vivo iPPG datasets have been acquired from left hands to investigate various algorithms for retrieval of PPW signals, distribution maps and waveforms, and their dependence on arterial location and wavelength.
A robust algorithm of pixelated independent component analysis (pICA) has been developed and combined with spatiotemporal filtering to retrieve PPW signals. Spatial distributions of PPW signals have been mapped in 10 wavelength bands from 445 to 940 nm and waveforms were analyzed at multiple locations near the palmar artery tree. At the wavelength of 850 nm selected for timing analysis, we determined PWV values from 12 healthy volunteers in a range of 0.5 to 5.8 m/s across the hand region from wrist to midpalm and fingertip.
These results demonstrate the potentials of the iPPG method based on pICA algorithm for translation into a monitoring tool to characterize wall stiffness of superficial artery by rapid and noncontact measurement of PWV and other biomarkers within 10 s.
