Research on the model of staggered tooth phase to reduce vibration of single-stage gear transmission system: Theoretical analysis and experiments.

Aiming at the problems of high vibration and high noise in gear transmission systems, a model of gear with staggered tooth phase structure(GSTPS) for reducing vibration is proposed. Without changing the overall structure of the gear transmission system, the purpose of reducing mesh stiffness fluctuations is achieved by staggering adjacent gears at a certain angle along the axis, thereby the vibration of the gear transmission system could be reduced. The characterization method of time-varying mesh stiffness of the GSTPS is studied. Then, the impact of different staggered tooth phases(STP) on reducing vibration of the transmission system are researched, and the basis for selecting the optimal STP are obtained. The experimental platform for reducing vibration with STP is established. And some experimental studies were conducted to validate the theoretical model.

Retraction: Shen et al. Investigation of the Ordered Structure in Partially Melted Isotactic Polypropylene. Polymers 2021, 13, 3354.

The published article [...].

Investigation of the Ordered Structure in Partially Melted Isotactic Polypropylene.

The ordered structure of partially melted isotactic polypropylene (iPP) was investigated using polarized optical microscopy (POM) and small-/wide-angle X-ray scattering (SAXS/WAXS) measurements. The crystalline morphology was first examined by means of pulling a glass fiber through the iPP melt, which was generated by partially melting a preformed spherulite. The results from the POM experiments indicated that, even at a minimal pulling rate, the surviving ordered structure could also relocate along the direction of fiber pulling and grow into cylindrites eventually. In addition, during the quiescent crystallization from the partially melted sample, which had the same thermal history of fiber-pulling experiments, the obvious memory effect of melt was also observed from the results of X-ray experiments. Moreover, the SAXS profile derived from the partially melted iPP at 170 °C was fitted by the theory of scattering amplitude with the cylindrical form factor. The fit result implied that the surviving ordered structure is of cylindrical nanocrystals with a diameter D ≈ 30 ± 3 nm and height h ≈ 45 ± 3 nm, which can significantly influence the crystallization morphology and kinetics during the subsequent crystallization process.

Determination of eight pharmaceuticals in an aqueous sample using automated derivatization solid-phase microextraction combined with gas chromatography-mass spectrometry.

An automated aqueous derivatization solid-phase microextraction (SPME) coupled with a gas chromatography/mass spectrometry (GC/MS) method was developed for simultaneous determination of eight pharmaceuticals in water samples. Dimethyl sulfate and tetrabutylammonium hydrogen sulfate were selected as derivatization and activation reagents for the esterification reaction. An experimental design approach, central composition design (CCD), was employed to investigate and optimize the operative factors influencing the extraction efficiency, including extraction time, extraction temperature and ionic strength. The other parameters such as type of fiber coating, pH and derivatization conditions were also evaluated. SPME was finally carried out in headspace mode at 80°C for 60min with the presence of 3.00g Na2SO4, using a home-made 44µm PDMS fiber. Wide linear ranges and low limits of detection (0.06-1.24ng L(-1)) were obtained under the optimized conditions. The relative standard deviations (RSDs) and recoveries ranged from 0.5% to 12.3% and 85% to 110%, respectively. The proposed method was successfully applied to the analysis of the real surface water samples from the Pearl River Estuary.

Molecularly imprinted microspheres synthesized by a simple, fast, and universal suspension polymerization for selective extraction of the topical anesthetic benzocaine in human serum and fish tissues.

A simple, fast, and universal suspension polymerization method was used to synthesize the molecularly imprinted microspheres (MIMs) for the topical anesthetic benzocaine (BZC). The desired diameter (10-20 µm) and uniform morphology of the MIMs were obtained easily by changing one or more of the synthesis conditions, including type and amount of surfactant, stirring rate, and ratio of organic to water phase. The MIMs obtained were used as a molecular-imprinting solid-phase-extraction (MISPE) material for extraction of BZC in human serum and fish tissues. The MISPE results revealed that the BZC in these biosamples could be enriched effectively after the MISPE operation. The recoveries of BZC on MIMs cartridges were higher than 90% (n = 3). Finally, an MISPE-HPLC method with UV detection was developed for highly selective extraction and fast detection of trace BZC in human serum and fish tissues. The developed method could also be used for the enrichment and detection of BZC in other complex biosamples.

Nanoparticle-based systems for T(1)-weighted magnetic resonance imaging contrast agents.

Because magnetic resonance imaging (MRI) contrast agents play a vital role in diagnosing diseases, demand for new MRI contrast agents, with an enhanced sensitivity and advanced functionalities, is very high. During the past decade, various inorganic nanoparticles have been used as MRI contrast agents due to their unique properties, such as large surface area, easy surface functionalization, excellent contrasting effect, and other size-dependent properties. This review provides an overview of recent progress in the development of nanoparticle-based T1-weighted MRI contrast agents. The chemical synthesis of the nanoparticle-based contrast agents and their potential applications were discussed and summarized. In addition, the recent development in nanoparticle-based multimodal contrast agents including T1-weighted MRI/computed X-ray tomography (CT) and T1-weighted MRI/optical were also described, since nanoparticles may curtail the shortcomings of single mode contrast agents in diagnostic and clinical settings by synergistically incorporating functionality.

Chemometrics optimization of six antihistamines separations by capillary electrophoresis with electrochemiluminescence detection.

This work expanded the knowledge of the use of chemometric experimental design in optimizing of six antihistamines separations by capillary electrophoresis with electrochemiluminescence detection. Specially, central composite design was employed for optimizing the three critical electrophoretic variables (Tris-H(3)PO(4) buffer concentration, buffer pH value and separation voltage) using the chromatography resolution statistic function (CRS function) as the response variable. The optimum conditions were established from empirical model: 24.2mM Tris-H(3)PO(4) buffer (pH 2.7) with separation voltage of 15.9 kV. Applying theses conditions, the six antihistamines (carbinoxamine, chlorpheniramine, cyproheptadine, doxylamine, diphenhydramine and ephedrine) could be simultaneous separated in less than 22 min. Our results indicate that the chemometrics optimization method can greatly simplify the optimization procedure for multi-component analysis. The proposed method was also validated for linearity, repeatability and sensitivity, and was successfully applied to determine these antihistamine drugs in urine.

Designing bifunctionalized gold nanoparticle for colorimetric detection of Pb2+ under physiological condition.

In the present work, a kind of peptide functionalized gold nanoparticle (AuNP) has been synthesized and employed for colorimetric detection of Pb(2+) in both aqueous solution and living cell. The AuNPs are capped by two peptide ligands: glutathione (GSH) and pentapeptide (CALNN). The GSH is used as a functional group for selectively sensing Pb(2+) by coordination reaction, and CALNN is employed as a stabilize ligand for improving the stability of AuNPs under physiological condition, respectively. The AuNP enables to strongly interact with Pb(2+) that leads to distinct color change of solution. Under the optimized molar ratio of GSH to CALNN on the AuNP surface, the colorimetric assay for detecting Pb(2+) in living cell downs to 2.9 fmol Pb(2+)per cell (3 times of standard deviation, 3σ) with linear relationship from 2.9 to 37.7 fmol Pb(2+) per cell. In addition, the method also shows highly selective detection toward Pb(2+) against other common metal ions in both aqueous solution and living cell.

Simultaneous analysis of six cardiovascular drugs by capillary electrophoresis coupled with electrochemical and electrochemiluminescence detection, using a chemometrical optimization approach.

CE coupled with dual electrochemical (EC) and electrochemiluminescence (ECL) detection was optimized for simultaneous analysis of six cardiovascular drugs (alprenolol, propafenone, acebutolol, verapamil, atenolol and metoprolol) via central composite design. Following this study, three critical electrophoretic factors governing the CE separation were investigated: Tris-H(3)PO(4) buffer concentration, buffer pH value and separation voltage. A modified chromatographic response was adopted for evaluating CE separation quality. Optimum conditions were achieved using Tris-H(3)PO(4) buffer 35.6 mM (pH 2.3) separated at 13.9 kV, which was employed experimentally and led to the successful simultaneous separation of the above six drugs. The good agreement of the chromatographic response was observed between predicted data and actual experimental results using these optimized conditions (RSD=3.75%). The proposed method was validated for linearity, repeatability and sensitivity, and subsequently successfully applied to determine six basic drugs in urine samples.

Rapid authentication of ginseng species using microchip electrophoresis with laser-induced fluorescence detection.

Ginseng is one of the most expensive Chinese herbal medicines and the effectiveness of ginseng depends strongly on its botanical sources and the use of different parts of the plants. In this study, a microchip electrophoresis method coupled with the polymerase chain reaction (PCR)-short tandem repeats (STR) technique was developed for rapid authentication of ginseng species. A low viscosity hydroxypropyl methylcellulose (HPMC) solution was used as the sieving matrix for separation of the amplified STR fragments. The allele sizing of the amplified PCR products could be detected within 240 s or less. Good reproducibility and accuracy of the fragment size were obtained with the relative standard deviation for the allele sizes less than 1.0% (n=11). At two microsatellite loci (CT 12, CA 33), American ginseng had a different allele pattern on the electropherograms compared with that of the Oriental ginseng. Moreover, cultivated and wild American ginseng can be distinguished on the basis of allele sizing. This work establishes the feasibility of fast genetic authentication of ginseng species by use of microchip electrophoresis.

Native fluorescence detection of flavin derivatives by microchip capillary electrophoresis with laser-induced fluorescence intensified charge-coupled device detection.

To widen the scope of laser-induced fluorescence (LIF) for detection in microchip capillary electrophoresis (CE), a microchip CE LIF-ICCD (intensified charge-coupled device) system based on a tunable wavelength dye laser pumped by a pico-second pulse nitrogen laser for excitation and a spectrograph with ICCD for detection had developed to demonstrate the enhancement in detection sensitivity by the following three approaches: direct detection of native fluorescence, improvement of signal-to-noise ratio by pulse laser excitation and time delay detection, and selective spectral acquisition by multi-channel detection. Riboflavin, flavin mononucleotide (FMN) and flavin-adenine dinucleotide (FAD) have been selected as they are dietetically important and microchip CE provides a promising onsite detection method. The results indicate a strong effect of wavelength on detection sensitivity and the need to tune wavelength for direct detection. Under optimized conditions (excitation 450 nm, emission 520 nm, gate delay time 45 ns, 20 mM phosphate buffer at pH 7.1), the following results were obtained under static condition: Working ranges (0.6-350 microg/l, r > 0.99), detection limits (0.15-1.0 microg/l) and peak height repeatability (1.8-2.2% R.S.D.), all within the applicability range for body fluids or beverages such as human urine and cow milk. Baseline separation of three flavins was obtained under dynamic condition and the fluorescence spectra acquired assist the identification of alkaline-degraded products of riboflavin. Thus, the capability to check peak purity and identify unknown peaks has been demonstrated.

Study of adsorption behavior of bilirubin on human-albumin monolayer using a quartz crystal microbalance.

The quartz crystal microbalance was employed to study the adsorption behavior of bilirubin on human-albumin layer, which was chemically bound to the self-assembled monolayer of 4-aminothiophenol on the surface of a gold electrode of the crystal via glutaraldehyde. A long-time adsorption process of bilirubin that took place on a human-albumin-modified surface was observed, and the adsorption kinetic parameters were estimated from the in situ frequency measurements. The amount of adsorbed bilirubin increased with increasing of both hydrogen ions and bilirubin concentration and was larger than that estimated based on the conclusion that there are two affinity sites for bilirubin per albumin molecule. With the present method, the displacement of bilirubin from an albumin layer caused by aspirin was also examined. QCM measurement provides a facile method for in situ monitoring of the adsorption/desorption of bilirubin on proteins layers.