Mattress-Based Non-Influencing Sleep Apnea Monitoring System.

A mattress-type non-influencing sleep apnea monitoring system was designed to detect sleep apnea-hypopnea syndrome (SAHS). The pressure signals generated during sleep on the mattress were collected, and ballistocardiogram (BCG) and respiratory signals were extracted from the original signals. In the experiment, wavelet transform (WT) was used to reduce noise and decompose and reconstruct the signal to eliminate the influence of interference noise, which can directly and accurately separate the BCG signal and respiratory signal. In feature extraction, based on the five features commonly used in SAHS, an innovative respiratory waveform similarity feature was proposed in this work for the first time. In the SAHS detection, the binomial logistic regression was used to determine the sleep apnea symptoms in the signal segment. Simulation and experimental results showed that the device, algorithm, and system designed in this work were effective methods to detect, diagnose, and assist the diagnosis of SAHS.

Ni-catalyzed asymmetric hydrophosphinylation of conjugated enynes and mechanistic studies.

The catalytic asymmetric synthesis of P-stereogenic phosphines is an efficient strategy to access structurally diverse chiral phosphines that could serve as organocatalysts and ligands to transition metals and motifs of antiviral drugs. Herein, we describe a Ni catalyzed highly regio and enantioselective hydrophosphinylation reaction of secondary phosphine oxides and enynes. This method afforded a plethora of alkenyl phosphine oxides which could serve as valuable precursors to bidentate ligands. A new type of mechanism was discovered by combined kinetic studies and density functional theory (DFT) calculations, which was opposed to the widely accepted Chalk-Harrod type mechanism. Notably, the alkene moiety which could serve as a directing group by coordinating with the Ni catalyst in the transition state, plays a vital role in determining the reactivity, regio and enantioselectivity.

Study on a quartz crystal microbalance sensor based on chitosan-functionalized mesoporous silica for humidity detection.

Chitosan-functionalized mesoporous silica MCM-41 (Chi/M41) was prepared by a mild method. In the composite materials, the spherical MCM-41 particles were regarded as supporting skeletons, which reduced the effect of chitosan swelling on the repeatability and reliability of quartz crystal microbalance (QCM) sensors at high relative humidity (RH), and chitosan provided good film-forming properties of the final composite. The composite structure effectively improved the sensitivity of the QCM sensors compared to that of chitosan and MCM-41 sensors. The QCM sensor based on the Chi/M41 composites showed excellent sensitivity (58.4 ± 0.3 Hz/% RH). In addition, the optimal sensor exhibited excellent reliability, such as negligible humidity hysteresis (0.8 ± 0.1% RH), a small variation coefficient (1.1 ± 0.1), short response and recovery times (18 s/15 s) and good long-term stability. Furthermore, the Langmuir adsorption isotherm model and the Gibbs free energy were used to investigate the adsorption mechanism of water molecules on the sensitive films in this work.

Chitosan wrapped multiwalled carbon nanotubes as quartz crystal microbalance sensing material for humidity detection.

In this work, the chitosan wrapped multiwalled carbon nanotubes (MWCNTs-CS) composited material was prepared by surface deposition and crosslinking method. This mild process can maintain the unique properties of the original carbon nanotubes intact. The morphological character of MWCNTs-CS was examined via Fourier transform infrared spectroscopy and field emission scanning electron microscopy. MWCNTs-CS was used as sensing film to fabricate quartz crystal microbalance (QCM) humidity sensors. The optimized sensor possesses high response sensitivity (46.7 Hz/% RH), negligible humidity hysteresis (around 1.1% RH), quick response and recovery time (75 s/34 s), and remarkable reversibility, repeatability, long-term stability and selectivity. Langmuir adsorption isotherm model was used to study the adsorption process of water molecules on MWCNTs-CS film, and the Gibbs free adsorption energy was calculated as -21.85 kJ/mol. By combining the good mechanic properties of MWCNTs and the high hydrophilia of chitosan, the MWCNTs-CS composites are promising for humidity sensing application.