Investigating exceptional points in dark-bright mode-coupled plasmonic systems.

Exceptional points (EPs) of non-Hermitian systems are gaining more and more attention due to their important applications in unidirectional transmitters, sensors, etc. However, theoretical studies on EPs of reflection, transmission, and absorption spectra are less available. In this paper, in the dark-bright mode-coupled plasmonic systems, the variations of EPs of reflection, transmission, and absorption spectra are numerically investigated using temporal coupled-mode theory, and an assumption is given using the representation transformation theory. The intermediate representation (IR) is firstly proposed and related to the reflection spectrum, while the normal representation (NR) is associated with the absorption spectrum. In the region far from EPs, the IR (or NR) describes the reflection (or absorption) spectrum well. Near EPs, modified formulas similar to the representation transformation theory are given. In order to verify the correctness of the assumption, two metasurfaces are designed. And the simulation results are in good agreement with the assumption and it is found in the near-infrared and visible-light band that the absorption loss of the dark mode is linearly related to the EPs of reflection, transmission, and absorption spectra, while the radiation loss of the bright mode is only linearly related to the EPs of the absorption spectrum. These laws can help to manipulate the splitting of spectral lines for reflection, transmission, and absorption by adjusting the radiation loss and absorption loss of bright mode, the absorption loss of dark mode, and the coupling coefficients between two resonant modes. This research provides a guiding scheme for the design of micro and nano photonics devices.

Efficient planar plasmonic directional launching of linearly polarized light in a catenary metasurface.

Efficient directional excitation of planar surface plasmon polaritons (SPPs) has important and wide applications in micro-nano photonic technology. Recently, by using the geometric phase and spin-orbit interaction, catenary structures have been applied to the directional control of SPPs and showed excellent performance. However, due to the need to use the chirality of the subwavelength catenary apertures, the previously studied systems were only suitable for circularly polarized light. Here, based on a catenary metasurface we theoretically design and experimentally demonstrate a SPP directional launcher used for linearly polarized light. The numerical calculation results show that the directional extinction ratio reaches up to 35 dB under the normal incidence of p-polarized light at 750 nm which is 5 dB higher than the maximum extinction ratio in the existing results as we know. The experimental results show that the resonant wavelength position, bandwidth and extinction ratio change trend well match the theoretical results. The physical mechanism is analyzed and it is found that the asymmetric quadrupole mode is the key factor leading to the directional SPPs which is completely different from the geometric phase modulation mechanism to excite the directional SPPs of circularly polarized light in the catenary metasurface. These principles and methods could open new doors for future chip-level photonic device or system design such as multi-directional beam splitters and polarization detectors.

Broadband terahertz absorption enabled by coating an ultrathin antireflection film on doped semiconductor.

We show that perfect absorption of terahertz wave can be achieved in a compact system where an ultrathin film of lossless dielectric is coated on a doped semiconductor substrate. Due to the nontrivial reflection phase shift at the interface between the two media, strong resonant behavior and the concomitant antireflection occur at wavelengths that are much larger than the thickness of the dielectric film, resulting in strong absorption of the incident wave in a wide frequency range. Using this mechanism, we design a broadband terahertz absorber by coating a Ge film on a highly doped GaAs substrate. We show that such a system not only has a perfect absorption peak, but also exhibits high absorptance (over 0.9) within a fractional bandwidth of over 20%. By varying the free carrier density in the GaAs substrate, the central frequency of the absorption band can be tuned from 1.79 to 2.69 THz. In addition, the absorption performance of the proposed system is shown to be insensitive to both incident angle and polarization. Our results offer a low-cost way for the design of absorption-based THz devices.

Broadband, Spectrally Flat, Graphene-based Terahertz Modulators.

Advances in the efficient manipulation of terahertz waves are crucial for the further development of terahertz technology, promising applications in many diverse areas, such as biotechnology and spectroscopy, to name just a few. Due to its exceptional electronic and optical properties, graphene is a good candidate for terahertz electro-absorption modulators. However, graphene-based modulators demonstrated to date are limited in bandwidth due to Fabry-Perot oscillations in the modulators' substrate. Here, a novel method is demonstrated to design electrically controlled graphene-based modulators that can achieve broadband and spectrally flat modulation of terahertz beams. In our design, a graphene layer is sandwiched between a dielectric and a slightly doped substrate on a metal reflector. It is shown that the spectral dependence of the electric field intensity at the graphene layer can be dramatically modified by optimizing the structural parameters of the device. In this way, the electric field intensity can be spectrally flat and even compensate for the dispersion of the graphene conductivity, resulting in almost invariant absorption in a wide frequency range. Modulation depths up to 76% can be achieved within a fractional operational bandwidth of over 55%. It is expected that our modulator designs will enable the use of terahertz technology in applications requiring broadband operation.

Tunable all-optical plasmonic diode based on Fano resonance in nonlinear waveguide coupled with cavities.

Tunable all-optical plasmonic diode is proposed based on the Fano resonance in an asymmetric and nonlinear system, comprising metal-insulator-metal waveguides coupled with nanocavities. The spatial asymmetry of the system gives rise to the nonreciprocity of the field localizations at the nonlinear gap between the coupled cavities and to the nonreciprocal nonlinear response. Nonlinear Fano resonance, originating from the interference between the discrete cavity mode and the continuum traveling mode, is observed and effectively tuned by changing the input power. By combining the unidirectional nonlinear response with the steep dispersion of the Fano asymmetric line shape, a transmission contrast ratio up to 41.46 dB can be achieved between forward and backward transmission. Our all-optical plasmonic diode with compact structure can find important applications in integrated optical nanocircuits.

[Preliminary Study of Lonicera hypoglauca on Germination Conditions of Sand Culture Seeds and Sterilization Method of Sand Culture Seedling Sterilization].

OBJECTIVE: To explore the germination conditions of Lonicera hypoglauca sand culture seeds and the effects of sand culture seedlings sterilization. METHODS: 0.1% HgCl2 with different sterilization time, different illumination time and temperature culture condition were adopted to study the germination conditions of sand culture seeds. Different sterilization treatments and different hardening-seedling days were used to test the sterilization effect of sand culture seedlings. RESULTS: The sterilization effect of the combination of 75% ethanol 30 s + 0.1% HgCl2 5 min on Lonicera hypoglauca seeds was the optimum,with the average pollution rate of 15.56%, and the average germination rate reached 51.11%. The combination of varied temperature-room temperature under light for 12 h/d was the best, with the average germination rate peaked at 75.49%, and the average germination potential reached 68.36%. The treatment of detergent liquor scrub-tap water wash on the part above the hypocotyl, which was sand cultured under the opening condition and had no root, showed the best sterilization effect, with the average pollution rate was zero, and the average survival rate peaked at 100.00%. The sterilization effect of sand culture seedlings, which was disinfected after cleaning by detergent liquor scrub-tap water wash after hardening-seeding for 30 days, was the best, with the average pollution rate of 50.00%, and the average survival rate of 100.00%. CONCLUSION: The best sterilization effect is the combination of 75% ethanol 30 s + 0.1% HgCl2 5 min; Lighting for 12 h/d of varied temperature-room temperature is regarded as the optimum culture condition. The treatment of detergent liquor scrub-tap water wash treatment on the part above the hypocotyl,which is sand cultured under the opening condition and had no root, shows the best sterilization effect. For the sand culture seedlings, before inoculated in subculture medium, should be hardening-seedling for some days and sterilized after detergent liquor scrub-tap water wash.

[Determination of chlorogenic acid and luteoloside in lonicerae flos of different habitats and germplasms].

OBJECTIVE: To establish an UPLC-PDA method for simultaneous determination of chlorogenic acid and luteoloside in Lonicerae Flos. On the basis of developed method, the quality of Lonicerae Flos from nine habitats and two local germplasms introduced from Qufu in Shandong to Wuming in Guangxi was evaluated. METHODS: The analysis was performed on a Waters Acquity UPLC H-Class system. An Acquity UPLC BEH RP18 (100 mm x 2.1 mm,1.7 µm) column was used for all analyses. The investigated compounds were separated with a gradient mobile phase consisting of acetonitrile and 0.4% phosphoric acid solution at a flow rate of 0.2 mL/min, and the detection wavelength was set at 242 nm. RESULTS: The quality of Lonicerae Flos from Qufu was the best among Lonicerae Flos of nine habitats for its content of chlorogenic acid and luteoloside at 35.715 and 1.270 mg/g, respectively. The content of chlorogenic acid and luteoloside in Lonicerae Flos of "Jiufengyihao" and "Shuxing" introduced from Qufu to Wuming both complied with the standard of Chinese Pharmacopoeia (2010 edition). CONCLUSION: The developed UPLC-PDA method is simple, reliable and repeatable, which is helpful for the quality control of Lonicerae Flos. "Jiufengyihao" and "Shuxing" are potential germplasms for the introduction of Lonicerae Flos in Wuming.

Baricitinib alleviates lipopolysaccharide­induced human periodontal ligament stem cell injury and promotes osteogenic differentiation by inhibiting JAK/STAT signaling.

Periodontitis is the chronic inflammation of the periodontal tissue. The present study aimed to investigate the role of baricitinib, a Janus kinase (JAK)1/2 inhibitor, in periodontitis by using a lipopolysaccharide (LPS)-induced human periodontal ligament stem cell (PDLSC) model. The viability of PDLSCs stimulated by LPS was assessed in the presence of baricitinib by Cell Counting Kit-8 assay. The induction of oxidative stress was evaluated by detecting the intracellular reactive oxygen species (ROS) levels, superoxide dismutase (SOD) activity and glutathione (GSH) content. ELISA and reverse transcription-quantitative PCR were used to determine the levels of inflammatory factors TNF-α, IL-1ß and IL-6. Alkaline phosphatase (ALP) activity and alizarin red staining were used to assess the osteogenic differentiation of PDLSCs. The expression levels of osteogenic differentiation- and JAK/signal transducer and activator of transcription (STAT) signaling-associated proteins were estimated with western blotting. RO8191, an agonist of the JAK/STAT pathway, was used to treat PDLSCs to investigate the regulatory mechanism of baricitinib. The results indicated that baricitinib elevated the LPS-induced decrease in cell viability. LPS-triggered oxidative stress and inflammation were inhibited by baricitinib, as demonstrated by the decreased levels of ROS, TNF-α, IL-1ß, IL-6 and increased levels of SOD and GSH. In addition, baricitinib caused a marked elevation in ALP activity and mineralization ability of PDLSCs, as determined by the upregulated osteocalcin and Runt-related transcription factor 2 expression. Moreover, the expression levels of phosphorylated (p)-JAK1, p-JAK2 and p-STAT3 were downregulated by baricitinib in a dose-dependent manner. Furthermore, addition of RO8191 restored the effect of baricitinib on the induction of oxidative stress, inflammation and osteogenic differentiation of PDLSCs exposed to LPS. Collectively, these findings suggested that baricitinib alleviated oxidative stress and inflammation and promoted osteogenic differentiation of LPS-induced PDLSCs by inhibiting JAK/STAT signaling.

Sidelobe suppression in structured light sheet fluorescence microscopy by the superposition of two light sheets.

Light sheet microscopy has emerged as a powerful technique for three-dimensional and long-term vivo imaging within neuroscience and developmental biology. A light sheet illumination with structured light fields allows a better tradeoff between the field of view and axial resolution but suffers from strong side lobes. Here, we propose a method of producing structured light sheet illumination with suppressed side lobes by applying the superposition of two light sheets. The side lobe suppression results from the destructive interference between the side lobes and constructive interference between the main lobe of the two light sheets. In the proposed method, the incident light pattern in the rear pupil plane of the illumination objective is a combination of the incident light line beams required for the generation of the two interfering light sheets. We present a fast and simple calculation method to determine the incident light pattern in the rear pupil plane. Simulation results demonstrate the effectiveness of the proposed sidelobe suppression method for double-line light sheet, four-line light sheet, as well as line Bessel sheet. In particular, an 81% decrease in the relative side lobe energy can be achieved in case of double-line light sheet with an almost nonchanging propagation length. We show a way of using combined incident light patterns to generate structured light sheets with interference-resulted side lobe suppression, which is straightforward in design and with advantages of improved imaging performance.

The construction of an Agrobacterium-mediated transformation system of Gynostemma pentaphyllum using the phosphomannose-isomerase/mannose selection system.

In this study, the transformed system mediated by Agrobacterium tumefaciens of Gynostemma pentaphyllum was constructed by using the phosphomannose-isomerase (PMI) gene as a marker. To investigate the cefotaxime sodium salt (Cef) concentration of bacteriostatic medium and the appropriate mannose concentration in the selectable medium, explants of the stems with buds were cultured in a basic medium supplemented with different Cef and mannose concentrations, respectively. After these were optimized, 288 explants were transformed according the protocol described above to verify their availability by using the polymerase chain reaction (PCR), reverse transcription-PCR and chlorophenol red. The results showed that the appropriate Cef concentration for bacteriostatic culture and mannose concentration for selectable culture were 150 mg l-1 and 3 g l-1 for stem with buds, respectively. According to the PCR results, the transformation frequency of stems with buds was 20.49% with a regeneration rate of 29.16%. In future, the CPR assay could be the auxiliary method of choice as it is moderately accurate, but it has good maneuverability and is cost effective for large-scale use.

[Preliminary study on the effect of climate factors on pollen fertility in Platycodon grandiflorum].

OBJECTIVE: To have a better utilization of male sterile lines in heterozygotic breeding of Platycodon grandiflorum and provide theoretical basis for Platycodon grandiflorum hyboridization. METHODS: The pollen viability was detected by the means of aceto carmine dyeing, and the correlation analysis between climate factors of each anther development stage and pollen viability was estimated by Pearson coefficients. RESULTS: Pollen viability variation range of male-sterile line GP1BC1-12 was 0% - 27%. That of male-sterile line GP12BC4-10 and chifeng germplasm was respectively 1.3% - 17.9% and 75.9% - 98.5%. Further linear regression analysis between climate factors of each anther development stage and pollen viability indicated that the degree of sensitivity varied with different germplasm of Platycodon grandiflorum. Among three germplasm, male sterile line GP12BC4-10 was the most stable one to the climate factors, and the male-sterile line GP1BC1-12 was the most sensitive one. CONCLUSION: Temperature and solar irradiation are the most important climate factors to affect pollen viability in Platycodon grandflorum, and microspore mother cells stage (MMC) is its sensetive stage.

[The performance of agronomic traits in F1 crossing combinations derived from male sterile line of Platycodon grandiflorum].

OBJECTIVE: To determine the possibility of heterosis utilization by male sterility in Platycodon grandiflorum. METHODS: The analysis of variance, heterosis over standard and correlation on 12 agronomic in 18 crossing combinations were carried out. RESULTS: Except the dry weight of upground part of plant, the length of main root and the diameter of middle part of the main root, all other agricultural traits were different significantly among the 18 F1 combinations. The diameter of middle part of the main root had the highest coefficient of variation and the ratio of fresh weight of main root and total root had the lowest coefficient of variation,which was 85.42% and 3.66%, respectively. For the traits related to the yield of root,average heterosis over standard in fresh main root and total root was 42.35% and 45.50%, respectively; For the traits related to the form of root, the diameter of up part and middle part of main root had a middle heterosis over standard, which was 12.38% and 29.97%, respectively. The shoot growth was significantly related to its root growth in combination (0.651). The number of nodes on main stem was significantly related to five out of six traits of root in hybrids. CONCLUSION: Variation of agricultural traits in crossing combination is rich, heterosis of traits in root is evident,and F1 hybrids with good yield and the forms could be selected from these combinations. The Platycodon grandiflorum of crossing combinations have reasonable morphological characteristics, and the number of nodes of main stem could be taken as the selected index. All show us that the heterosis by the male-sterility could be utilized in the breeding of Platycodon grandiflorum.

[Heterosis analysis of the main agronomic characters of Platycodon grandiflorum].

OBJECTIVE: Breeding the good varieties characters of Platycodon grandiflorum. METHODS: 20 combination, derived from 2 x 10 incomplete diallel cross with 2 male sterile lines and 10 four-generation inbred lines, analysis the 13 agronomic characters. RESULTS: The agronomic characters of F1 has obvious heterosis. Dry plant weight and fresh root weight have the largest heterosis. Their middle parent heterosis (MPH), high parent heterosis (HPH) and heterosis over CK (CH) were 96.07%, 62.62%, 116.21%, 108.99%, and 111.98%, 113.47%, respectively. CONCLUSION: The F1 hybrids derived from the crossing of male sterile lines and in-bred lines have obvious heterosis. It applied the hybrid heterosis breeding is an effective way for the new variety of Platycodon grandiflorum.

Tunable plasmon lensing in graphene-based structure exhibiting negative refraction.

We propose a novel method to achieve tunable plasmon focusing in graphene/photonic-crystal hybrid structure exhibiting all-angle negative refraction at terahertz frequencies. A two-dimensional photonic crystal composed of a square lattice of dielectric rods is constructed on the substrate of a graphene sheet to provide the hyperbolic dispersion relations of the graphene plasmon, giving rise to the all-angle plasmonic negative refraction. Plasmon lensing induced from the negative refraction is observed. We show that the ultracompact graphene-based system can produce sub-diffraction-limited images with the resolution significant smaller than the wavelength of the incident terahertz wave. Moreover, by adjusting the Fermi energy of the graphene, the imaging performance of the proposed system can remain almost invariant for different frequencies. Our results may find applications in diverse fields such as subwavelength spatial light manipulation, biological imaging, and so forth.

Controlling graphene plasmons with a zero-index metasurface.

Graphene plasmons, owing to their diverse applications including electro-optical modulation, optical sensing, spectral photometry and tunable lighting at the nanoscale, have recently attracted much attention. One key challenge in advancing this field is to precisely control the propagation of graphene plasmons. Here, we propose an on-chip integrated platform to engineer the wave front of the graphene plasmons through a metasurface with a refractive index of zero. We demonstrate that a well-designed graphene/photonic-crystal metasurface can possess conical plasmonic dispersion at the Brillouin zone center with a triply degenerate state at the Dirac frequency, giving rise to the zero-effective-index of graphene plasmons. Plane-wave-emission and focusing effects of the graphene plasmons are achieved by tailoring such a zero-index metasurface. In addition to the tunable Dirac point frequency enabled by the electrical tuning of the graphene Fermi level, our highly integrated system also provides stable performance even when defects exist. This actively controllable on-chip platform can potentially be useful for integrated photonic circuits and devices.

Enhanced endocytosis of acid-sensitive doxorubicin derivatives with intelligent nanogel for improved security and efficacy.

Three derivatives of doxorubicin (DOX) were prepared by modifying DOX with succinic anhydride, cis-aconitic anhydride and 2,3-dimethylmaleic anhydride, generating acid-insensitive succinyl-DOX (SAD), acid-sensitive cis-aconityl-DOX (CAD) and 2,3-dimethylmaleyl-DOX (DAD) respectively. The pH and reduction dual-responsive methoxy poly(ethylene glycol)-poly(l-lysine-co-l-cystine) nanogel was employed to encapsulate the DOX derivatives. In vitro release studies showed that drug release could be accelerated in the intracellular acidic and reductive conditions. Confocal laser scanning microscopy and flow cytometry results demonstrated that an enhanced intracellular drug release was observed in glutathione monoester pretreated HeLa cells (a human cervical cell line). The DOX derivatives exhibited a lower accumulation in the nuclei than DOX. Moreover, the CAD and DAD-loaded nanogels showed a comparable anti-proliferative activity to the DOX-loaded nanogel against HeLa and HepG2 cells (a human hepatoma cell line). As a comparison, the SAD-loaded nanogel almost never inhibited cellular proliferation. The above results suggested that the pH and reduction dual-responsive nanogel can efficiently deliver acid-sensitive DOX derivatives into the nuclei of cancer cells for minimizing the side effects and enhancing the inhibition of cellular proliferation.

Redox-sensitive shell-crosslinked polypeptide-block-polysaccharide micelles for efficient intracellular anticancer drug delivery.

Redox-responsive SCMs based on amphiphilic PBLG-b-dextran with good biocompatibility are synthesized and used for efficient intracellular drug delivery. The molecular structures and SCMs characteristics are characterized by (1) H NMR, FT-IR, TEM, and DLS. The hydrodynamic radius of SCMs increases gradually in PBS due to the cleavage of disulfide bond in micellar shell caused by the presence of GSH. The encapsulation efficiency and release kinetics of DOX are investigated. The fastest DOX release is observed under intracellular-mimicking reductive environments. An MTT assay demonstrates that DOX-loaded SCMs show higher cellular proliferation inhibition against GSH-OEt pretreated HeLa and HepG2 than that of the non-pretreated and BSO-pretreated ones.

[Study on removal of nitrobenzene in water by O3/H2O2].

Comparative experiments of ozonation and O3/H2O2 processes were conducted with nitrobenzene as the model organic pollutant. It was found that O3/H2O2 greatly increased the removal efficiency of nitrobenzene compared with that achieved by ozonation alone. It was believed that both in ozonation and O3/H2O2 processes nitrobenzene was primarily oxidized by OH.. Several factors that are likely to influence O3/H2O2 process in practical application were investigated. Experimental results demonstrated that with the same dosage of applied ozone and hydrogen peroxide, the multiple steps addition of ozone and hydrogen peroxide showed a much higher removal efficiency than that obtained by adding hydrogen peroxide within one step before the start of the experiment. Under the conditions of this experiment, the optimum molar ratios of hydrogen peroxide to ozone for the removal of nitrobenzene in distilled water and tap water were proved to be both 0.5, no significant negative effect was observed when the alkalinity levels (as CaCO3) were less than 100 mg/L.

[Comparative study on O3/H2O2 and O3/Mn processes for removal of refractory organics in water].

A comparative study of O3/H2O2 and O3/Mn was made to evaluate their respective effectiveness and mechanism for removal of refractory organics from water with nitrobenzene as the model pollutant. It was found that both processes enhanced the degradation of nitrobenzene that can be hardly degraded by ozonation and had respective optimum dosage of H2O2 and Mn(II) under the experimental conditions. By comparing the mechanism of O3/H2O2 process and considering the chemical character of nitrobenzene and variation of residual aqueous ozone, it is speculated that the degradation of nitrobenzene by O3/Mn might follow a radical pathway. As shown by the experimental result, the addition of H2O2 and Mn(II) both improved the mass transfer efficiency of ozone and thus more ozone was consumed for degradation of nitrobenzene, which is also an indication of the radical type reaction mechanism. The characteristic of O3/H2O2 and O3/Mn processes and their application in the drinking water treatment were finally discussed.