Ballistocardiograms (BCG) is an essential signal for vital sign monitoring. Obtaining the beat-to-beat intervals from BCG signal is of great significance for home-care applications, such as sleep staging, heart disease alerting, etc. The current approaches of detecting beat-to-beat intervals from BCG signals are complex. In this paper, we develop a non-invasive BCG monitoring system, and propose an effective and accurate algorithm for beat-to-beat detection. Firstly, a heartbeat shape is adaptively modeled based on a two-step procedure by taking advantage of the J-peak and the K-valley of BCG signals. Then, forward and backward detections with the criteria of both the morphological distance and the cross-correlation are jointly employed to find the position of each BCG signal, and in turn, to determine the beat-to-beat intervals of BCG signals. The proposed method was validated in at least 90 minutes recording from 10 subjects in various setups. The mean absolute beat-to-beat intervals error was 10.72 ms and on an average 97.93% of the beat-to-beat intervals were detected.
The chemical and SCMP pulping properties with chips compressed by screw extrusion machine were discussed in the paper. The results showed that parts of extractive and hemicellulose of compressed chips were dissolved; also fibers were damaged in certain degree. The compression improved impregnability of solutions obviously, which led to reduce the dosage of active alkali from 20% to 14% in conventional KP and soda-AQ pulping and produce the pulp with similar kappa number and screened pulp yield, but rejects and alkali consumption were decreased obviously. The pulp strength was deteriorated due to the damaged fibers, but beating performance was improved. Comparatively screw extrusion pretreatment was more suitable for soda-AQ pulping process particularly for the knot wood chips. Sulfonation of chips was improved after compressing, however the strength of SCMP was not increased, it was possibly attributed to the heavy damage of the fibers.
Abstract Sulfonated cellulose (SC) with varying degrees of substitution (DS) were prepared with the pyridine sulfur trioxide complex (Py-SO 3 ) as a sulfonation reagent (as a source of sulfur trioxide) in dimethyl formamide (DMF) as a solvent, where the DS was primarily affected by the molar ratio between Py-SO 3 and the anhydroglucose (AHG) unit. Sulfonation temperature and residence time have less effect on DS. The ratio of the crystalline domain of SC decreased gradually with incremental DS, and the crystalline cellulose I of SC at DS 0.81 nearly disappeared, and the moiety of the paracrystalline SC with high hydrophilicity increased. The thermostability decreased with increasing DS as a consequence of crystalline domain decrement. The adsorption performance of SC to metal ions was enhanced with increasing DS. However, above DS 0.62, the adsorption capacity enhancement is negligible. For an economic adsorption of heavy meatal ions in effluents, the DS of SC must be optimized.
Cellulose nanocrystals (CNCs) are nanoscale particles made from cellulose. They have many unique properties such as being lightweight, stiff, and renewable, making them promising for a variety of applications in a wide range of industries, including materials science, energy storage, and biomedicine. In this paper, a two-stage (swelling-SA-catalyzed) method including IL pretreatment and solid acid hydrolysis process was developed to extract CNCs with high purity and good thermal stability from microcrystalline cellulose (MCC). In the first stage, the swelling of MCC in ionic liquid was studied with the assistance of ultrasonication, and it was found that the amorphous regions became more disordered while the crystalline areas were selectively retained under the conditions of 30 min of reaction time, 45 °C of temperature, 2% of ionic liquid water content and 1:4 mass ratio of cellulose to ionic liquid. CNCs were extracted using solid acid hydrolysis, with a 45 wt% solid acid to cellulose ratio and a 5.0 h hydrolysis process at 45 °C. The morphology, crystallinity, surface characteristics and thermo stability of the sample were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Results demonstrated the highly thermostable CNCs were successful extracted with rodlike shape of 300 ± 100 nm in length and 20 ± 10 nm in width. Solid acid recovery and reuse were also studied, revealing a promising candidate that can reduce the environmental impact associated with chemical products.
Reversible thermochromic paper able to resist counterfeiting was prepared by adding reversible thermochromic microcapsules (RTM) to a slurry of cellulosic fibers, a process that is difficult to imitate. However, the loss of RTM is one of the biggest problems that inhibits industrial use of this approach. So, the retention of RTM in pulp was investigated. The RTM was synthesized by in-situ polymerization, and its properties were characterized. It exhibited strong color contrast between cool and heated conditions, and such behavior could be used to achieve distinctive anticounterfeiting characteristics in the paper. The surface of each microcapsule was smooth, and there was no coherence between particles. The diameters of the microcapsules were mainly in the range 3.0 μm to 5.0 μm. Retention of RTM was closely related to beating degree and pulp composition; the higher the beating degree and hardwood pulp content, the higher the retention of RTM. On the other hand, the retention of RTM was influenced by filler and retention aid. Retention aid promoted retention of RTM to some degree; however, filler was not conductive to retention of RTM. Different addition sequences between RTM and filler or retention aid also influenced the retention of RTM.
Exploring an efficient technique for carbon sphere preparation has attracted extensive attention. Herein, acidic lithium bromide hydrate (ALBH) was used in the hydrothermal carbonization (HTC) process to overcome the recalcitrance of lignocellulose, such that nano-carbon spheres were prepared at mild condition: 140 °C for 150 min with 0.8 M of HCl from 20-40 meshed corn stover. That carbon spheres showed decent morphology properties and abundant functional groups, which was better than that from pine and poplar wood. The corn stover derived carbon nanospheres could efficiently adsorb both heavy ions and methyl orange in wastewater. Meanwhile, the ALBH after reaction could be recovered and reused. Specifically, the morphologies and adsorption capability of the prepared carbon nanospheres using recovered ALBH were negligibly affected even after 5 cycles. These results verified the practical production of carbon nanospheres from lignocellulose at mild conditions, which provided more potential for the synthesis of novel biomass-based materials for comprehensive applications.
We developed a ballistocardiography (BCG)-based Internet-of-Medical-Things (IoMT) system for remote monitoring of cardiopulmonary health. The system composes of BCG sensor, edge node, and cloud platform. To improve computational efficiency and system stability, the system adopted collaborative computing between edge nodes and cloud platforms. Edge nodes undertake signal processing tasks, namely approximate entropy for signal quality assessment, a lifting wavelet scheme for separating the BCG and respiration signal, and the lightweight BCG and respiration signal peaks detection. Heart rate variability (HRV), respiratory rate variability (RRV) analysis and other intelligent computing are performed on cloud platform. In experiments with 25 participants, the proposed method achieved a mean absolute error (MAE)±standard deviation of absolute error (SDAE) of 9.6±8.2 ms for heartbeat intervals detection, and a MAE±SDAE of 22.4±31.1 ms for respiration intervals detection. To study the recovery of cardiopulmonary function in patients with coronavirus disease 2019 (COVID-19), this study recruited 186 discharged patients with COVID-19 and 186 control volunteers. The results indicate that the recovery performance of the respiratory rhythm is better than the heart rhythm among discharged patients with COVID-19. This reminds the patients to be aware of the risk of cardiovascular disease after recovering from COVID-19. Therefore, our remote monitoring system has the ability to play a major role in the follow up and management of discharged patients with COVID-19.
Abstract An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO 2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr⋅3.5H 2 O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO 2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13 C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.
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