Parametric Testing of Metasurface Stirrers for Metasurfaced Reverberation Chambers.

In this paper, the correlation coefficients and the total scattering cross sections (TSCSs) for different types of metasurfaced stirrers and the traditional metallic stirrer, and the effects on field uniformity when such stirrers are used in reverberation chambers, are analyzed. Three metasurfaced stirrers are considered: A stirrer with two unit cells arranged alternatively (#1), a stirrer with two unit cells arranged in a chessboard-like manner (#2), and a stirrer with two unit cells in random arrangement (#3). From the correlation coefficient and TSCS results obtained in simulations, it follows that metasurfaced stirrer #1 is the best option. Field uniformity analysis of the resulting metasurface reverberation chambers (MRC) equipped with the different stirrers also supports this conclusion.

Enhancing the Number of Modes in Metasurfaced Reverberation Chambers for Field Uniformity Improvement.

The use of metasurfaces to increase the number of modes, lower the operating frequency, and improve the field uniformity in reverberation chambers (RCs) is investigated in this paper. The method used to improve the field uniformity and decrease the resonance frequencies is based on increasing the number of modes by using the concept of subwavelength cavities. The resonance frequencies of a RC with metasurface wall are derived and expressed analytically in terms of macroscopic characteristics. Simulation of the reflection phase of the unit cell is then given as a guideline to choose the required microscopic parameters of the designed metasurface. The mode density in such subwavelength RCs is then obtained using a numerical eigenmode solver. Compared to traditional RCs, a much higher modal density is obtained at low frequencies. The standard deviation of the field uniformity in the test volume of the RC corresponding to different types of metasurface walls is finally compared. It is shown that by increasing the number of modes in the RC at the lower band, the operating frequency decreases and the field uniformity of the RC is improved.

Tuning the dispersion of effective surface plasmon polaritons with multilayer systems.

Recently, effective surface plasmon polaritons (ESPPs) induced by structural dispersion in bounded waveguides were theoretically demonstrated and experimentally verified. Despite the theoretical and experimental efforts, whether ESPPs can mimic real SPPs in every aspect still remains an open question. In this work, we go one step further to study the hybridization of ESPPs in multilayer systems. We consider transverse electric (TE) modes in a conventional rectangular waveguide and a parallel-plate waveguide (PPW) and derive analytically the dispersion relations and asymptotic frequencies of the corresponding ESPPs modes in sandwiched structures consisting of alternating dielectrics of different permittivities. Our results show that the ESPPs can be categorized into odd and even parities (owing to the 'plasmon' hybridization) in a similar way as natural SPPs supported by the insulator/metal/insulator (IMI) and metal/insulator/metal (MIM) heterostructures in the optical regime. The similarities and differences between ESSPs and their optical counterparts are also discussed in details, which may provide valuable guidance for future application of ESPPs at the microwave and terahertz frequencies.

Metasurfaced Reverberation Chamber.

The concept of metasurfaced reverberation chamber (RC) is introduced in this paper. It is shown that by coating the chamber wall with a rotating 1-bit random coding metasurface, it is possible to enlarge the test zone of the RC while maintaining the field uniformity as good as that in a traditional RC with mechanical stirrers. A 1-bit random coding diffusion metasurface is designed to obtain all-direction backscattering under normal incidence. Three specific cases are studied for comparisons, including a (traditional) mechanical stirrer RC, a mechanical stirrer RC with a fixed diffusion metasurface, and a RC with a rotating diffusion metasurface. Simulation results show that the compact rotating diffusion metasurface can act as a stirrer with good stirring efficiency. By using such rotating diffusion metasurface, the test region of the RC can be greatly extended.

Step-Up Synthesis of Periodic Mesoporous Organosilicas with a Tyrosine Framework and Performance in Horseradish Peroxidase Immobilization.

New amino-acid-bridged periodic mesoporous organosilicas (PMOs) were constructed by hydrolysis and condensation reactions under acid conditions in the presence of a template. The tyrosine bissilylated organic precursor (TBOS) was first prepared through a multistep reaction by using tyrosine (a natural amino acid) as the starting material. PMOs with the tyrosine framework (Tyr-PMOs) were constructed by simultaneously using TBOS and tetraethoxysilane as complex silicon sources in the condensation process. All the Tyr-PMOs materials were characterized by XRD, FTIR spectroscopy, N2 adsorption-desorption, TEM, SEM, and solid-state 29 Si NMR spectroscopy to confirm the structure. The horseradish peroxidase (HRP) enzyme was first immobilized on these new Tyr-PMOs materials. Optimal conditions for enzyme adsorption included a temperature of 40 °C, a time of 8 h, and a pH value of 7. Furthermore, the novel Tyr-PMOs materials could store HRP for approximately 40 days and maintained the enzymatic activity, and the Tyr-PMOs-10 % HRP with the best immobilization effect could be reused at least eight times.

Broadband and Broad-angle Polarization-independent Metasurface for Radar Cross Section Reduction.

In this work, a broadband and broad-angle polarization-independent random coding metasurface structure is proposed for radar cross section (RCS) reduction. An efficient genetic algorithm is utilized to obtain the optimal layout of the unit cells of the metasurface to get a uniform backscattering under normal incidence. Excellent agreement between the simulation and experimental results show that the proposed metasurface structure can significantly reduce the radar cross section more than 10 dB from 17 GHz to 42 GHz when the angle of incident waves varies from 10° to 50°. The proposed coding metasurface provides an efficient scheme to reduce the scattering of the electromagnetic waves.

Localized Spoof Surface Plasmons based on Closed Subwavelength High Contrast Gratings: Concept and Microwave-Regime Realizations.

In this work, we report the existence of spoof localized surface plasmons (spoof-LSPs) arising with closed high contrast gratings (HCGs) at deep subwavelength scales, another platform for field localization at microwave frequencies. The HCGs are in the form of a periodic array of radial dielectric blocks with high permittivity around a metal core supporting spoof-LSPs of transverse magnetic (TM) form. Simulation results validate the phenomenon and a metamaterial approach is also given to capture all the resonant features of this kind of spoof-LSPs. In addition, experimental verification of the existence of spoof-LSPs supported by a three dimensional (3D) HCGs resonance structure in the microwave regime is presented. This work expands the original spoof-LSPs theory and opens up a new avenue for obtaining resonance devices in the microwave frequencies.

High-Contrast Gratings based Spoof Surface Plasmons.

In this work, we explore the existence of spoof surface plasmons (SSPs) supported by deep-subwavelength high-contrast gratings (HCGs) on a perfect electric conductor plane. The dispersion relation of the HCGs-based SSPs is derived analyt- ically by combining multimode network theory with rigorous mode matching method, which has nearly the same form with and can be degenerated into that of the SSPs arising from deep-subwavelength metallic gratings (MGs). Numerical simula- tions validate the analytical dispersion relation and an effective medium approximation is also presented to obtain the same analytical dispersion formula. This work sets up a unified theoretical framework for SSPs and opens up new vistas in surface plasmon optics.

Coplanar waveguide wideband band-stop filter based on localized spoof surface plasmons.

In this work, a wideband band-stop plasmonic filter based on localized spoof surface plasmons is reported, which consists of a coplanar waveguide (CPW) and an ultra-thin periodic corrugated metallic strip with defect units at the back of the substrate. Defect units are used to localize the transmission energy along the CPW. Each defect unit can introduce a narrow stop band, and a series of defect units is judiciously designed to form a broadband CPW band-stop filter. The center frequency and bandwidth of the filter can be tuned by the heights and numbers of the defect units. In addition, a T-shaped unit is designed to increase the equivalent height of the lateral branch so as to realize the miniaturization of the vertical geometric dimension. Theoretical analysis of the filter has been conducted, and a sample at microwave frequency has been fabricated and measured to validate our design. This simple band-stop plasmonic filter can find potential applications in plasmonic circuits and antennas at microwave and terahertz frequencies.

Tunable band-notched coplanar waveguide based on localized spoof surface plasmons.

This Letter proposes a simple band-notched coplanar waveguide (BNCPW), which consists of a coplanar waveguide (CPW) and an ultra-thin periodic corrugated metallic strip that supports spoof surface plasmon polaritons (SSPPs) with defect units on the back of the substrate. By introducing a defect unit or multiple defect units into the strip, a narrow stopband or multiple narrow stopbands would be generated flexibly and conveniently. The band-notch function is based on the idea that a defect mode, which exists in the bandgap between the fundamental and the first higher mode of the SSPPs, can be introduced to form a stopband. Thus, the SSPPs field is localized around the defect units, which is another form of localized spoof surface plasmons (LSSPs). By properly tuning the dimensions of each defect unit, the absorption level and center frequency of the stopband could be adjusted independently. We offer theoretical analysis and experimental results to validate our idea and design. In this framework, a variety of band-notched devices and antennas in the microwave and terahertz (THz) frequencies can be easily designed without additional band-stop filters.

Smooth bridge between guided waves and spoof surface plasmon polaritons.

In this work, we build a smooth bridge between a coaxial waveguide and a plasmonic waveguide with subwavelength periodically cylindrical radial grooves, to realize high-efficiency mode conversion between conventional guided waves and spoof surface plasmon polaritons in broadband. This bridge consists of a flaring coaxial waveguide connected with a metal cylindrical wire corrugated with subwavelength gradient radial grooves. Experimental results of the transmission and reflection coefficients show excellent agreement with the numerical simulations. The proposed scheme can be extended readily to other bands and the bridge structure can find potential applications in the integration of conventional microwave or terahertz devices with plasmonic circuits.

Multiband localized spoof plasmons in closed textured cavities.

In this work, we explore the existence of multiband localized spoof plasmons (LSPs) in closed textured cavities with multiple groove depths. It is interesting to note that the spoof LSPs in each band resemble those generated by the textured 2D cavities of the same periodicity with the corresponding single groove depth, and the field distributions and confinement characteristics of the plasmon-like modes in such a corrugated cavity are different from the conventional cavity. Hence, these multiple resonance band structures can find potential applications in the microwave and terahertz frequencies.

A corrugated perfect magnetic conductor surface supporting spoof surface magnon polaritons.

In this paper, we demonstrate that spoof surface magnon polaritons (SSMPs) can propagate along a corrugated perfect magnetic conductor (PMC) surface. From duality theorem, the existence of surface electromagnetic modes on corrugated PMC surfaces are manifest to be transverse electric (TE) mode compared with the transverse magnetic (TM) mode of spoof surface plasmon plaritons (SSPPs) excited on corrugated perfect electric conductor surfaces. Theoretical deduction through modal expansion method and simulation results clearly verify that SSMPs share the same dispersion relationship with the SSPPs. It is worth noting that this metamaterial will have more similar properties and potential applications as the SSPPs in large number of areas.

A novel structure for tunable terahertz absorber based on graphene.

Graphene can be used as a platform for tunable absorbers for its tunability of conductivity. In this paper, we proposed an "uneven dielectric slab structure" for the terahertz (THz) tunable absorber based on graphene. The absorber consists of graphene-dielectric stacks and an electric conductor layer, which is easy to fabricate in the manufacturing technique. Fine tuning of the absorption resonances can be conveniently achieved by adjusting the bias voltage. Both narrowband and broadband tunable absorbers made of this structure are demonstrated without using a patterned graphene. In addition, this type of graphene-based absorber exhibits stable resonances with a wide range angles of obliquely incident electromagnetic waves.

[2-Acet-oxy-3-(naphthalen-1-yl-oxy)prop-yl](propan-2-yl)aza-nium chloride monohydrate.

The title compound, C18H24NO3 (+)·Cl(-)·H2O, was synthesized by the reaction of propranolol hydro-chloride with acetyl chloride in chloro-form followed by slow evaporation in air. In the cation, the dihedral angle between the planes of the naphthalene ring system and the acetate group is 71.1 (2)°. An intra-molecular N-H⋯O hydrogen bond results in the formation of a non-planar pseudo-ring, with the ether O and the H atom displaced by -1.328 (2) and 0.65 Å, respectively, from the plane of the other ring atoms. The cation and anion are linked by an N-H⋯Cl hydrogen bond. The water molecule is linked to a methyl H atom by C-H⋯O hydrogen bond.

Isolation, identification and function of a novel anti-HSV-1 protein from Grifola frondosa.

A novel antiviral protein was purified from an extract of Grifola frondosa fruiting bodies using a procedure that included 40% ammonium sulfate precipitation and DEAE-cellulose ion exchange chromatography, and designated GFAHP. This protein inhibited herpes simplex virus type 1 (HSV-1) replication in vitro with an IC(50) value of 4.1 microg/ml and a therapeutic index >29.3. Higher concentrations of GFAHP (125 and 500 microg/ml) also significantly reduced the severity of HSV-1 induced blepharitis, neovascularization, and stromal keratitis in a murine model. Topical administration of GFAHP to the mouse cornea resulted in a significant decrease in virus production (mean virus yields: 3.4log10PFU in the treated group and 4.19log10PFU in the control group). We proved that GFAHP directly inactivates HSV-1 while simultaneously inhibiting HSV-1 penetration into Vero cells. Gel electrophoresis showed that GFAHP had a molecular weight of 29.5 kDa. GFAHP was tryptic digested and analyzed from the PMF of matrix assisted desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and nanoelectrospray ionization tandem mass spectrometry. The N-terminal sequence of GFAHP consisted of an 11 amino acid peptide, NH(2)-REQDNAPCGLN-COOH that did not match any known amino acid sequences, indicating that GFAHP is likely to be a novel antivirus protein. To our knowledge, this is the first report that characterizes an anti-HSV protein from G. frondosa.

Inhibition of hepatitis B virus by D-fraction from Grifola frondosa: synergistic effect of combination with interferon-alpha in HepG2 2.2.15.

In this study, D-fraction extracted from Grifola frondosa (GF-D) and its combination with human interferon alpha-2b (IFN) were investigated for the inhibitory effect on hepatitis B virus (HBV) in HepG2 2.2.15 cells (2.2.15 cells). HBV DNA and viral antigens were analyzed by a quantitative real-time polymerase chain reaction and end-point titration in radioimmunoassays, respectively. The results showed that GF-D or IFN alone could inhibit HBV DNA in 2.2.15 cells with the 50% inhibitory concentration (IC50) of 0.59 mg/ml and 1399 IU/ml, respectively. We further investigated the combination of GF-D and IFN for anti-HBV activity and found that they synergistically inhibited HBV replication in 2.2.15 cells. In combination with 0.45 mg/ml GF-D, the apparent IC50 value for IFN was 154 IU/ml. This 9-fold increase in antiviral activity of IFN suggested that GF-D could synergize with IFN. These results indicate that GF-D, in combination with IFN, might provide a potentially effective therapy against chronic HBV infections.

Excretion and detection of SARS coronavirus and its nucleic acid from digestive system.

AIM: To study whether severe acute respiratory syndrome coronavirus (SARS-CoV) could be excreted from digestive system. METHODS: Cell culture and semi-nested RT-PCR were used to detect SARS-CoV and its RNA from 21 stool and urine samples, and a kind of electropositive filter media particles was used to concentrate the virus in 10 sewage samples from two hospitals receiving SARS patients in Beijing in China. RESULTS: It was demonstrated that there was no live SARS-CoV in all samples collected, but the RNA of SARS-CoV could be detected in seven stool samples from SARS patients with any one of the symptoms of fever, malaise, cough, or dyspnea, in 10 sewage samples before disinfection and 3 samples after disinfection from the two hospitals. The RNA could not be detected in urine and stool samples from patients recovered from SARS. CONCLUSION: Nucleic acid of SARS-CoV can be excreted through the stool of patients into sewage system, and the possibility of SARS-CoV transmitting through digestive system cannot be excluded.

Concentration and detection of SARS coronavirus in sewage from Xiao Tang Shan Hospital and the 309th Hospital.

The transmission of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is associated with close contact to SARS patients and droplet secretions of those patients. The finding of positive RT-PCR results from stools of SARS patients suggests that stools of SARS patients or sewage containing stools of patients could transmit SARS-CoV. We used a novel style of electropositive filter media particle to concentrate the SARS-CoV from the sewage of two hospitals receiving SARS patients in Beijing. We also used cell culture, RT-PCR and gene sequencing to detect and identify the viruses from sewage. No infectious SARS-CoV contamination was found in any of the samples collected, but the nucleic acid of SARS-CoV could be detected in the sewage from the two hospitals before disinfection. While the RNA was only detected in three samples from the 309th Hospital, the others were negative after disinfection. These findings provide strong evidence that SARS-CoV can be excreted through the stool/urine of patients into sewage system, thus making the sewage system a possible route of transmission.

[Detection of RNA of SARS coronavirus in hospital sewage].

OBJECTIVE: In order to explore the existence of SARS coronavirus (Co-V) and/or its RNA in sewage of hospitals administered SARS patients. METHODS: A novel electropositive filter was used to concentrate the SARS-CoV from the sewage of two hospitals administered SARS patients in Beijing, including twelve 2,500 ml sewage samples from the hospitals before disinfection, and ten 25,000 ml samples after disinfection; as well as cell culture, RT-PCR and sequencing of gene to detect and identify the viruses from sewage. RESULTS: There was no live SARS-CoV detected in the sewage in this study. The nucleic acid of SARS-CoV had been found in the 12 sewage samples before disinfection from both hospitals by semi-nested PCR. After disinfection, SARS-CoV RNA could only be detected from the samples from the 309th Hospital, and the others were negative. CONCLUSION: It provides evidence that there is no live SARS-Cov in the sewage from hospitals with SARS patients though SARS-CoV RNA can be detected.