Wide-incident-angle, polarization-independent broadband-absorption metastructure without external resistive elements by using a trapezoidal structure.

The absorption of electromagnetic waves in a broadband frequency range with polarization insensitivity and incidence-angle independence is greatly needed in modern technology applications. Many structures based on metamaterials have been suggested for addressing these requirements; these structures were complex multilayer structures or used special materials or external electric components, such as resistive ones. In this paper, we present a metasurface structure that was fabricated simply by employing the standard printed-circuit-board technique but provides a high absorption above 90% in a broadband frequency range from 12.35 to 14.65 GHz. The metasurface consisted of structural unit cells of 4 symmetric substructures assembled with a metallic bar pattern, which induced broadband absorption by using a planar resistive interaction in the pattern without a real resistive component. The analysis, simulation, and measurement results showed that the metasurface was also polarization insensitive and still maintained an absorption above 90% at incident angles up to 45°. The suggested metasurface plays a role in the fundamental design and can also be used to design absorbers at different frequency ranges. Furthermore, further enhancement of the absorption performance is achieved by improved design and fabrication.

Investigation on the Potential Application of Na-Attapulgite as an Excipient in Domperidone Sustained-Release Tablets.

In this study, Na-attapulgite was explored as an excipient to prepare domperidone sustained-release tablets and test them in accordance with United States Pharmacopoeia requirements. Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC) were employed to explore the compatibility between Na-attapulgite and domperidone. The XRD and DSC show no interaction between the drug and Na-attapulgite. The FTIR spectrum indicates a shift in the absorption of N-H in the drug molecule, which can be explained by the hydrogen bonding interaction between the N-H in the DOM molecule and the -OH on the surface of Na-ATP. The diameter, hardness, friability and drug content of the tablets were measured, and they all met the relevant requirements of the United States Pharmacopoeia. In addition, the tablets with Na-attapulgite as excipient exhibit a better release performance within the release time of 12 h. These results demonstrate that the domperidone sustained-release tablets have been successfully prepared by using Na-attapulgite as an excipient. The doping of Na-ATP in domperidone sustained-release tablets improves the cytocompatibility. Moreover, with the increase of Na-ATP content, cells proliferate remarkably and cell activity is significantly enhanced.

Highly-dispersive transparency at optical frequencies in planar metamaterials based on two-bright-mode coupling.

Using a planar metamaterial, which consists of two silver strips, we theoretically demonstrate the plasmonic electromagnetically-induced transparency (EIT)-like spectral response at optical frequencies. The two silver strips serve as the bright modes, and are excited strongly by the incident wave. Based on the weak hybridization between the two bright modes, a highly-dispersive plasmonic EIT-like spectral response appears in our scheme. Moreover, the group index is higher than that of another scheme which utilizes the strong coupling between the bright and dark modes.

Plasmonic electromagnetically-induced transparency in symmetric structures.

A broken symmetry is generally believed to be a prerequisite for plasmonic electromagnetically-induced transparency (EIT), since the asymmetry allows the excitation of the otherwise forbidden dark mode. Nevertheless, according to the picture of magnetic plasmon resonance (MPR)-mediated plasmonic EIT, we show that plasmonic EIT can be achieved even in symmetric structures based on the second-order MPR. This not only sharpens our understanding of the existing concept, but also provides a profound insight into the plasmonic coherent interference in the near-field zone.

Characterization of volatile components in dry chrysanthemum flowers using headspace-liquid-phase microextraction-gas chromatography.

A headspace-liquid-phase microextraction (HS-LPME)-GC (gas chromatography) method for the characterization of volatile components in dry chrysanthemum flowers has been developed. In the proposed method, two extraction solvents, n-hexadecane and benzyl alcohol, are used for preconcentrating volatiles in the sample. A droplet of the extraction solvent is squeezed from the GC syringe and inserted in the headspace of the sample bottle with the dry flower, immersed in deionized water, and warmed in a water bath. The optimum HS-LPME parameters in terms of extraction solvent type, droplet magnitude, equilibrium (water bath) temperature, equilibrium time, extraction time, and ionic strength are achieved using GC-FID (flame ionization detection) by varying several levels of the factors that affect the HS-LPME procedure. After extraction under the optimized conditions, the extraction droplet is retracted into the syringe and injected for GC-MS (mass spectrometry) analysis. Thirty-three volatile components are extracted and identified using this HS-LPME-GC-MS method, with the aid of chemometric methods. It is shown that the volatiles in dry chrysanthemum flowers are mainly unsaturated organic compounds, such as monoterpenes, sesquiterpenes and their oxygenous derivatives, triterpenoids, and aliphatic compounds. Several representative components, in order of precedence of the retention time, are pinene (106.3 microg/g), camphene (112.7 microg/g), eucapyptol (52.1 microg/g), camphor (29.4 microg/g), borneol (4.2 microg g), bornyl acetate (67.3 microg/g), caryophyllene (0.7 microg/g), and caryophyllene oxide (20.0 microg/g). The relative standard error and detection limit of this method is 5-9% and 0.4 microg/g, respectively.