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Subfraction 7-3 was further eluted on a silica gel (200-300 mesh) column with gradient dichloromethane-acetone (10:1-0:1) to give compound B 6 b (113.5 mg). SP 1 sp H NMR (400 MHz, DMSO B - b d SB 6 sb , , ppm, J/Hz): 7.99 (2H, dd, J = 7.8, 1.5, H-2", 6"), 7.60 (1H, t, J = 7.8, H-4"), 7.47 (2H, t, J = 7.8, H-3", 5"), 7.29 (1H, td, J = 7.6, 1.5, H-5), 7.18 (1H, dd, J = 7.6, 1.5, H-3), 7.10 (1H, d, J = 7.8, H-6), 7.02 (1H, td, J = 7.6, 1.4, H-4), 6.08 (1H, dt, J = 9.8, 3.6, H-13), 5.77 (1H, dt, J = 9.8, 1.7, H-14), 5.37 (1H, d, J = 7.6, H-1'), 5.30 (1H, d, J = 11.8, H-7a), 5.23 (1H, d, J = 11.8, H-7b), 5.08 (1H, m, H-2'), 3.96-3.25 (5H, m, H-3'-6'), 2.87 (1H, m, H-11a), 2.65 (1H, m, H-12a), 2.59 (1H, m, H-11b), 2.50 (1H, m, H-12b). Fraction 4 was chromatographed on a silica gel (200-300 mesh) column eluting with dichloromethane-acetone (15:1-0:1) to give compound B 10 b (249.4 mg). SP 1 sp H NMR (400 MHz, DMSO-d SB 6 sb , , ppm, J/Hz): 9.43 (1H, br.s, 3'-OH), 7.46 (1H, dd, J = 2.4, 8.4, H-6'), 7.44 (1H, d, J = 2.4, H-2'), 6.90 (1H, d, J = 8.4, H-5'), 6.79 (1H, d, J = 2.0, H-6), 6.78 (1H, s, H-3), 6.47 (1H, d, J = 2.0, H-8), 5.09 (1H, d, J = 7.0, H-1"), 3.42 (3H, OCH SB 3 sb ), 3.20-3.73 (sugar protons), 12.99 (1H, s, 5-OH). [Extracted from the article]

Subfraction 2-6 was eluted on a silica gel (200-300 mesh) column with gradient petroleum ether-acetone (20:1-1:1) and TLC (petroleum ether-acetone, 1:1) to give compound B 3 b (7.1 mg). The ethyl acetate extract was separated on a silica gel (100-200 mesh) column with gradient dichloromethane-methanol (15:0-0:1) to afford three fractions (Frs. Subfraction 2-2 was further separated on a Sephadex LH-20 column (methanol as eluent) and an ODS column (methanol-water, 40-80%), then subjected to semipreparative HPLC (methanol-water, 70%) to give compounds B 7 b (11.4 mg), B 9 b (8.7 mg), and B 10 b (18.2 mg). The butyl alcohol extract was subjected to column chromatography on silica gel (100-200 mesh) eluted with gradient dichloromethane-methanol (30:0-0:1) to afford fractions (Frs. [Extracted from the article]

In order to obtain a material with excellent microwave absorption performance, polyvinyl alcohol (PVA) sponge was employed as the template. The porous structure of the sponge can facilitate faster and more uniform diffusion of the ferric nitrate liquid during the dipping and obtain a uniform distribution of the ferromagnetic particles, which serves as a functional phase to enhance the microwave absorption properties. The Fe@Fe3O4-C nanocomposite can then be fabricated through a dipping/carbonization process. The special core–shell structure effectively improves the dielectric and magnetic loss and provides proper impedance matching. The results indicate that the prepared samples show excellent microwave absorption performance, with maximum effective absorption bandwidth up to 7.9 GHz at a thickness of 2.27 mm. The maximum reflection loss can reach −48.36 dB at 9.6 GHz. Therefore, it is feasible to use PVA sponge as a template to fabricate porous Fe@Fe3O4-C nanocomposite with excellent microwave absorption performance. [ABSTRACT FROM AUTHOR]

It is greatly meaningful but remains very challenging to obtain high-performance microwave absorber with thin thickness, lightweight, wide bandwidth, and strong absorption. Here, sulfur-enriched nitrogen-doped carbon nanofibers (S-NCFs) with excellent microwave absorption performance have been constructed through electrospinning technology and heat treatment with sublimed sulfur. Experimental results and the theoretical calculation evidenced that nitrogenous carbon nanofibers doping with sulfur could not only generate a large number of electric dipoles but also favor the promotion of conductivity. Benefiting from the unique architecture and heteroatoms doping that contributed to the well-matched impedance and dielectric enhancement, the S-NCFs exhibited the minimum reflection loss (RL) of − 48.67 dB at 16.1 GHz with a matching thickness of 1.39 mm at a filler loading of as low as 15%. In addition, the samples can obtain the broadest effective absorption bandwidth (EAB, RL < − 10 dB) of 4.90 GHz with the thickness of 1.53 mm. This work provides a facile and efficient approach for fabricating carbon materials as lightweight and highly efficient microwave absorbers. [ABSTRACT FROM AUTHOR]

In this paper, Ag/paper-based composites with low dielectric loss were obtained by introduce the concept of metamaterial into the fabrication process. In this kind of metacomposite, single-layer paper was used as basic block to build up a matrix with sandwich structure, in which Ag particles are embedded and silver particles are evenly distributed. The microstructure and phase composition were characterized by scanning electron microscope and X-ray diffractometer. The impedance spectrum of the composites in 20 Hz–1 MHz region was measured by using LCR Meter, which can be well fitted by equivalent circuit method. The results show that, compared to the composite in which Ag particles disorder distributed, the dielectric loss of the layer-by-layer structured metacomposite can be effectively reduced (tan θ ≤ 0.1), without negative effect on the dielectric constant. Moreover, the dielectric properties of metacomposites show obvious anisotropy in the horizontal and vertical directions, which might give a feasible way for flexible smart material in its design. [ABSTRACT FROM AUTHOR]

In this work, hierarchically porous carbons were synthesized by carbonizing chiffon cake at different carbonization temperature from 600 to 1200 °C. The synthesis method exhibits that bio-derived food waste is more nature-friendly as no external hazardous activators are used during the pyrolysis process, and it takes less cost. The corresponding microwave absorption properties were proved to be dependent on the carbonization temperature, as well as resulting crystal structures and graphitization degrees. With the carbonization temperature of 1000 °C, the obtained samples (C1000) showed excellent microwave absorption performance with a maximum reflection loss − 49.52 dB at 17.7 GHz. The broad effective absorption bandwidth reached 5.1 GHz (12.4–17.5 GHz) at the thickness of 1.52 mm. The optimal absorbing property can be attributed to the strong dielectric loss, good impedance matching and quarter-wavelength cancellation. This work provides a way to prepare low cost, green and sustainable microwave absorbent with efficient microwave absorption property. [ABSTRACT FROM AUTHOR]

Two new compounds, named ilexin L 1 and ilexin L 3, were isolated from the roots of Ilex pubescens. Their structures were elucidated as 1-[3-formyl-2-methoxyacetyl-( E)-3-pentenyl] cycloolivil ketal ( 1) and rhodioside-4,6- O-2'-methoxylacetyl-3'-formyl-( E)-3-pentenyl- β-D-glucoside ( 2), respectively. The absolute configuration in compound 1 was assigned as 7' S, p8' S, 8 S,10 R on the basis of the CD spectrum, and compound 2 was assigned as 7 R on the basis of the NOESY spectrum and chemical methods. [ABSTRACT FROM AUTHOR]

We report on a novel non-enzymatic sensor for hydrogen peroxide (HP) that is based on a biocomposite made up from chitosan (CS), hemoglobin (Hb), and silver nanoparticles (AgNPs). The AgNPs were prepared in the presence of CS and glucose in an ultrasonic bath, and CS is found to act as a stabilizing agent. They were then combined with Hb and CS to construct a carbon paste biosensor. The resulting electrode gave a well-defined redox couple for Hb, with a formal potential of about −0.17 V (vs. SCE) at pH 6.86 and exhibited a remarkable electrocatalytic activity for the reduction of HP. The sensor was used to detect HP by flow injection analysis, and a linear response is obtained in the 0.08 to 250 μM concentration range. The detection limit is 0.05 μM (at S/N = 3). These characteristics, along with its long-term stability make the sensor highly promising for the amperometric determination of HP. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A study of the response behavior of anion to surface plasmon resonance (SPR) based sensor, in which a Poly(pyrrole) (Ppy) modified thin gold film was used as a sensor chip is described. In situ surface plasmon resonance and electrochemical methods were used to investigate the electropolymerization and doping/dedoping processes of thin Ppy film. The electropolymerization of pyrrole was carried out under cyclic voltammetric conditions, and simultaneously monitored by in situ SPR. It has revealed that the transition between the reduced state and oxidized state of the Ppy, corresponding to the doping/dedoping of anions, can lead to very distinct changes in SPR signal at a fixed angle of incident laser beam. Furthermore, it has demonstrated that the concentration, the charge and size of anions, as well as the film thickness play important roles in the ingress/egress process of anions. Based on this, this combination of experimental approaches can be used to detect Cl. SPR signal exhibited a good linear relationship with the concentration of Cl. [ABSTRACT FROM AUTHOR]

The changes in the contents of adenosine 5’-triphosphate (ATP) and its related breakdown compounds were investigated in the adductor muscle, mantle, gill and body trunk of oyster ( Crassostrea gigas) during frozen storage at −20°C and −30°C and compared with that of the fresh oyster. The investigation was performed using an HPLC system. Different extents of ATP decomposition were found in various tissues frozen at the two temperatures. The K, K’ and A.E.C values were calculated as the chemical freshness indices. Considering the results of sensory evaluation, the A.E.C. value in body trunk at −20°C and −30°C could be used as the best freshness index for frozen oyster. [ABSTRACT FROM AUTHOR]

Two new compounds, named ilexin L 1 and ilexin L 3, were isolated from the roots of Ilex pubescens. Their structures were elucidated as 1-[3-formyl-2-methoxyacetyl-( E)-3-pentenyl] cycloolivil ketal ( 1) and rhodioside-4,6- O-2'-methoxylacetyl-3'-formyl-( E)-3-pentenyl- β-D-glucoside ( 2), respectively. The absolute configuration in compound 1 was assigned as 7' S, p8' S, 8 S,10 R on the basis of the CD spectrum, and compound 2 was assigned as 7 R on the basis of the NOESY spectrum and chemical methods. [ABSTRACT FROM AUTHOR]