Flexible Resistive Gas Sensor Based on Molybdenum Disulfide-Modified Polypyrrole for Trace NO2 Detection.

High sensitivity and selectivity and short response and recovery times are important for practical conductive polymer gas sensors. However, poor stability, poor selectivity, and long response times significantly limit the applicability of single-phase conducting polymers, such as polypyrrole (PPy). In this study, PPy/MoS2 composite films were prepared via chemical polymerization and mechanical blending, and flexible thin-film resistive NO2 sensors consisting of copper heating, fluorene polyester insulating, and PPy/MoS2 sensing layers with a silver fork finger electrode were fabricated on a flexible polyimide substrate using a flexible electronic printer. The PPy/MoS2 composite films were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and field-emission scanning electron microscopy. A home-built gas sensing test platform was built to determine the resistance changes in the composite thin-film sensor with temperature and gas concentration. The PPy/MoS2 sensor exhibited better sensitivity, selectivity, and stability than a pure PPy sensor. Its response to 50 ppm NO2 was 38% at 150 °C, i.e., 26% higher than that of the pure PPy sensor, and its selectivity and stability were also higher. The greater sensitivity was attributed to p-n heterojunction formation after MoS2 doping and more gas adsorption sites. Thus, PPy/MoS2 composite film sensors have good application prospects.

Seascapes Shaped the Local Adaptation and Population Structure of South China Coast Yellowfin Seabream (Acanthopagrus latus).

Understanding the genetic composition and regional adaptation of marine species under environmental heterogeneity and fishing pressure is crucial for responsible management. In order to understand the genetic diversity and adaptability of yellowfin seabream (Acanthopagrus latus) along southern China coast, this study was conducted a seascape genome analysis on yellowfin seabream from the ecologically diverse coast, spanning over 1600 km. A total of 92 yellowfin seabream individuals from 15 sites were performed whole-genome resequencing, and 4,383,564 high-quality single nucleotide polymorphisms (SNPs) were called. By conducting a genotype-environment association analysis, 29,951 adaptive and 4,328,299 neutral SNPs were identified. The yellowfin seabream exhibited two distinct population structures, despite high gene flow between sites. The seascape genome analysis revealed that genetic structure was influenced by a variety of factors including salinity gradients, habitat distance, and ocean currents. The frequency of allelic variation at the candidate loci changed with the salinity gradient. Annotation of these loci revealed that most of the genes are associated with osmoregulation, such as kcnab2a, kcnk5a, and slc47a1. These genes are significantly enriched in pathways associated with ion transport including G protein-coupled receptor activity, transmembrane signaling receptor activity, and transporter activity. Overall, our findings provide insights into how seascape heterogeneity affects adaptive evolution, while providing important information for regional management in yellowfin seabream populations.

Asymmetric and Skin-Mimicking Hydrogels with Wide Temperature Tolerance and Superior Elasticity for High-Performance Strain Sensors.

Wide temperature tolerance and superior mechanical properties are highly required for composite hydrogels in electronic applications such as electronic skins and soft robotics. In this work, a unique polyacrylamide-based and double-network hydrogel system is designed and fabricated by introducing graphene oxide and glycerol to improve mechanical properties as well as antifreezing and antiheating properties. Maximum stress of the graphene oxide-incorporated hydrogel increases rapidly to 500.0 kPa which is much higher than that of polymetric acrylamide/carboxymethylcellulose sodium hydrogel (281.7 kPa), probably due to the inhibition from graphene oxide in generation and propagation of cracks. With constantly adding glycerol, total elongation and antifreezing and heating properties of the composite hydrogels increase gradually. Especially, sample with 20 vol % of glycerol not only shows stable conductivity and wide temperature tolerance (-50 to 50 °C) but also has ideal strength-toughness match (597.6 kPa and 1263.4%), suggesting that synergistic effect of different layers in the asymmetric structure plays an active role in improvement of mechanical properties.

Triazole-stabilized fluorescence sensor for highly selective detection of copper in tea and animal feed.

A triazole-stabilized fluorescence sensor is developed for copper detection in the study. Tris-(benzyltriazolylmethyl)amine (TBTA) is used to improve the sensitivity and stability for the sensing system. A series of comparative experiments are performed with and without TBTA. In the presence of TBTA, the fluorescence decrease ratio is enhanced from 2.46 to 118.25; the detection limit is reduced from 67 nM to 3.6 nM; the higher selectivity toward copper compared to the other metal ions is verified, including K+, Ca2+, Cd2+, Zn2+, Mg2+, Mn2+, Pb2+, Hg2+, Fe3+ and Cr3+. Besides, the sensing system is successfully applied for copper determination in complex tea samples and chicken feed samples with the recovery range of 91.67-116.8%. A good consistency between the presented sensor and the flame atom absorbance spectrometry (FAAS) is confirmed by the low relative errors with the range from -2.39% to 7.02%.

DNA template-mediated click chemistry-based portable signal-on sensor for ochratoxin A detection.

A novel signal-on portable sensing system has been developed for OTA detection using personal glucose meter (PGM) as signal transducer. In the study, we explore the potential of using a short dsDNA as template to trigger the "click" ligation of two DNA strands, further improve the stability of DNA strand on the magnetic beads (MBs) surface, and thereby reduce the background signal. Compared with no "click" ligation, the background signal decreases 7.5 times. Both the sensitivity and selectivity are greatly promoted. A high sensitivity with OTA detection down to 72 pg/mL is achieved, which is comparable with several existing detectors, such as fluorescence-based detectors and electrochemical detectors. The feasibility of the strategy in real samples is well verified and evaluated by detecting OTA in feed samples, indicating the potential application in the food safety field.

Diagnosis of carpal tunnel syndrome assessed using high-frequency ultrasonography: cross-section areas of 8-site median nerve.

This study aimed to determine the most suitable site for diagnosis of carpal tunnel syndrome (CTS) by examining an 8-site measurement of the median nerve's cross-sectional area (CSA). A total of 36 wrists of 26 patients with nerve conduction study (NCS) proven CTS, along with 34 wrists of 23 controls whose age and gender were matched with the patients, were evaluated with ultrasonography. The CSAs of the median nerve at eight predetermined sites including at the sites of 3, 2, and 1 cm proximal to the wrist crease, wrist crease, as well as at the sites of 1, 2, 3. and 4 cm distal to the wrist crease were obtained. The correlation between CSA and NCS severity, and duration of clinical CTS symptoms was analyzed. Receiver operating characteristic (ROC) curves was applied to determine the optimum cut-off point and to evaluate the diagnostic sensitivity and specificity of sonographic measurements. The CSAs of the median nerves at the eight sites were significantly higher in the CTS subjects, relative to the controls. Moreover, anatomical variation of the median nerve was found in the CTS group. ROC results indicated the areas under curve (AUC) at the site of 4 cm distal to the wrist crease were the largest with 0.874 cm(2), and an optimal cut-off value of 0.095 yielded a sensitivity of 88.9 % and a specificity of 76.5 %. The CSAs of "CTS-wrists" positively correlated with NCS severities and the CTS symptoms duration. Using 8-site CSAs measurement of the median nerve from inlet to outlet has positive correlations with NCS severity and duration of CTS symptoms.

Identification of cultivable bacteria in the intestinal tract of Bactrocera dorsalis from three different populations and determination of their attractive potential.

BACKGROUND: This study aimed to identify the cultivable bacteria inhabiting the intestinal tract of adult oriental fruit flies (Bactrocera dorsalis) from laboratory-reared, laboratory sterile sugar-reared, and field-collected populations, and to evaluate the attractiveness of the metabolites produced by the above bacteria to their hosts. RESULTS: Fifteen bacterial isolates chosen from the three populations were determined at species level. These 15 strains were cultured and the attractiveness of the whole Luria-Bertani broth, filtered and autoclaved supernatants to B. dorsalis adults was determined using bioassays. The bioassays showed that all bacterial strains were significantly more attractive to B. dorsalis adults than the media-only control. Among them, Bacillus cereus, Enterococcus faecalis, Enterobacter cloacae and Citrobacter freundii were the most attractive bacteria. Furthermore, results of a subsequent field test showed that the six bacterial strains were significantly more attractive than the control, with B. cereus and E. faecalis attracting significantly more flies. CONCLUSIONS: A cultivable bacterial community composed of Enterobacteriaceae, Enterococcaceae, and Bacillaceae was identified in the intestinal tract of B. dorsalis. Metabolites from B. cereus attracted the greatest number of B. dorsalis adults in the laboratory and field. These results provide useful information for the development of bacterial biocontrol agents or implementation as an insecticide.

Immobilization and characterization of tannase from a metagenomic library and its use for removal of tannins from green tea infusion.

Tannase (Tan410) from a soil metagenomic library was immobilized on different supports, including mesoporous silica SBA-15, chitosan, calcium alginate, and amberlite IRC 50. Entrapment in calcium alginate beads was comparatively found to be the best method and was further characterized. The optimum pH of the immobilized Tan410 was shifted toward neutrality compared with the free enzyme (from pH 6.4 to pH 7.0). The optimum temperature was determined to be 45°C for the immobilized enzyme and 30°C for the free enzyme, respectively. The immobilized enzyme had no loss of activity after 10 cycles, and retained more than 90% of its original activity after storage for 30 days. After immobilization, the enzyme activity was only slightly affected by Hg(2+), which completely inhibited the activity of the free enzyme. The immobilized tannase was used to remove 80% of tannins from a green tea infusion on the first treatment. The beads were used for six successive runs resulting in overall hydrolysis of 56% of the tannins.