Search

Two neolignan glycosides including a new one (1), along with seven iridoid glycosides (3 − 9) and nine flavonoid glycosides (10 − 18), were isolated from the leaves of Vaccinium bracteatum. Their structures were established mainly on the basis of 1D/2D NMR and ESIMS analyses, as well as comparison to known compounds in the literature. The structure of 1 with absolute stereochemistry was also confirmed by chemical degradation and ECD calculation. Selective compounds showed antiradical activity against ABTS and/or DPPH. Moreover, several isolates also suppressed the production of ROS in RAW264.7 cells and exerted neuroprotective effect toward PC12 cells. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) is a promising degree of freedom for fundamental studies in electromagnetics and quantum mechanics. The unlimited state space of OAM shows a great potential to enhance channel capacities of classical and quantum communications. By exploring the Pancharatnam-Berry phase concept and engineering anisotropic scatterers in a metasurface with spatially varying orientations, a plane wave with zero OAM can be converted to a vortex beam carrying nonzero OAM. In this paper, we proposed two types of novel perfect electric conductor-perfect magnetic conductor anisotropic metasurfaces. One is composed of azimuthally continuous loops and the other is constructed by azimuthally discontinuous dipole scatterers. Both types of metasurfaces are mounted on a mushroom-type high impedance surface. Compared to previous metasurface designs for generating OAM, the proposed ones achieve nearly perfect conversion efficiency. In view of the eliminated vertical component of electric field, the continuous metasurface shows very smooth phase pattern at the near-field region, which cannot be achieved by convectional metasurfaces composed of discrete scatterers. On the other hand, the metasurface with discrete dipole scatterers shows a great flexibility to generate OAM with arbitrary topological charges. Our work is fundamentally and practically important to high-performance OAM generation. [ABSTRACT FROM AUTHOR]

In this work, for the first time the electromagnetic features of graphene are characterized by a circuit model derived instead of fitted from the electric field integral equation (EFIE). The atomically thick graphene is equivalently replaced by an impedance surface. When it is magnetized, the impedance surface is anisotropic with a tensor conductivity. Based on EFIE, the graphene's circuit model can be derived by the partial element equivalency circuit (PEEC) concept. The anisotropic resistivity is modeled using a serial resistor with current control voltage sources (CCVSs). From the derived circuit model, electromagnetic properties of graphene can be conveniently analyzed. This work also provides a new characterization method for dispersive and anisotropic materials. [ABSTRACT FROM AUTHOR]

This paper analyzed the impact and causal relation of outbound Chinese FDI on growth, employment and export performance of 16 selected US States by using Panel data. The contemporaneous panel fixed estimation results shows that the impact of Chinese outbound FDI on the economic growth, employment and export of selected states are insignificant. But the impact of FDI on growth turns positive and significant when interacted with States export to China. Applying heterogeneous panel causality approach on a refined dynamic panel model indicates that Chinese FDI does not cause GDP, exports and employment while the results of reverse causality confirm that US State GDP (market size) cause the inflow of Chinese outbound FDI. The overall impact of Chinese outbound investment, a small portion of the total FDI inflow to the US, varies from conditionally positive to utterly insignificant without any adverse impact on the local economy. [ABSTRACT FROM AUTHOR]

The fast multipole algorithm manifests in two very different forms at low frequencies and at mid frequencies. Each can operate in their respective regimes, but are not tenable in the other regimes. The paper reports on a way to factorize the Green's function for fast algorithm using a mixed form. The low-frequency fast multipole algorithm (LF-FMA) will be used at low frequencies or the long-wavelength regime, and the multilevel fast multipole algorithm (MLFMA) will be used for the mid frequencies or the shorter-wavelength regime. For object modeling where both long-wavelength and wave physics are important, we propose a mixed-form fast multipole algorithm (MF-FMA). This algorithm has no low frequency break down, and it can work seamlessly from static (where circuit physics is important) to dynamic (where wave physics is important). [ABSTRACT FROM AUTHOR]

We review recent advances in fast algorithms for fast integral equation solvers that are useful for IC applications. We review fast solvers for Laplace's equation, which is about 10 times faster than the conventional fast multipole method. Then we review the physics of low-frequency electromagnetics, and the relevant low-frequency method of moments. We describe a fast solver that allows us to solve over one million unknowns on a workstation recently. In addition, we demonstrate the applications of these fast integral equation solvers to the lithography problem. In addition, we propose a scheme whereby we first characterize blocks of linear circuits with network S, Y, or Z parameters. Then a fast real-time convolution scheme is used to calculate the Interaction of a linear circuit with nonlinear terminations such as transistors and diodes. Such a scheme requires no model-order reduction of the circuits. [ABSTRACT FROM AUTHOR]

Background: Congenital left atrial appendage aneurysm (LAAA) is a rare cardiac anomaly with potentially serious complications, including life-threatening systemic thromboembolism, atrial tachyarrhythmia, and cardiac dysfunction. Currently, early surgical intervention is generally recommended to prevent these complications.Case Presentation: We present a case of congenital giant LAAA in a female patient who successfully completed pregnancy and underwent caesarean section with no obvious complications. Surgical resection of the LAAA was performed 3 years later, at the onset of chest pain resulting from compression of adjacent cardiac structures by the LAAA.Conclusion: Surgical resection is recommended for the majority of patients with LAAA because of potential LAAA-related severe outcomes. However, clinical monitoring may be an optional strategy for asymptomatic patients without intra-atrial thrombus or other complications. Precise evaluation with echocardiography and brain magnetic resonance imaging is valuable for the subsequent management of LAAA. [ABSTRACT FROM AUTHOR]

The genes responsible for silk biosynthesis are switched on and off at particular times in the silk glands of Bombyx mori. This switch appears to be under the control of endogenous and exogenous hormones. However, the molecular mechanisms by which silk protein synthesis is regulated by the juvenile hormone (JH) are largely unknown. Here, we report a basic helix-loop-helix transcription factor, Bmdimm, its silk gland-specific expression, and its direct involvement in the regulation of fibroin H-chain (fib-H) by binding to an E-box (CAAATG) element of the fib-H gene promoter. Far-Western blots, enzyme-linked immunosorbent assays, and co-immunoprecipitation assays revealed that Bmdimm protein interacted with another basic helix-loop-helix transcription factor, Bmsage. Immunostaining revealed that Bmdimm and Bmsage proteins are co-localized in nuclei. Bmdimm expression was induced in larval silk glands in vivo, in silk glands cultured in vitro, and in B. mori cell lines after treatment with a JH analog. The JH effect on Bmdimm was mediated by the JH-Met-Kr-h1 signaling pathway, and Bmdimm expression did not respond to JH by RNA interference with double-stranded BmKr-h1 RNA. These data suggest that the JH regulatory pathway, the transcription factor Bmdimm, and the targeted fib-H gene contribute to the synthesis of fibroin H-chain protein in B. mori. [ABSTRACT FROM AUTHOR]

Tensor impedance metasurfaces have attracted much attention recently due to their ability to flexibly manipulate both propagating and surface waves. So far, the analysis of tensor impedance has not been fully supported by commercial electromagnetic simulation software. Also, the representation of formulas of penetrable tensor impedance for both propagating and surface waves is limited in the literature. Hence, a unified analysis framework is proposed for this purpose. It allows the calculation of wave reflection and transmission with arbitrary incident angles, or inversely, the calculation of surface impedance tensors given the desired wave propagation properties. It also allows surface eigenmode analysis, where surface modes with novel isofrequency contours are found for penetrable tensor impedance surfaces. The relationship between penetrable and impenetrable metasurfaces is derived so that the resultant formulas are applicable in both scenarios. A finite difference method code is implemented to validate the derived formulas. The proposed unified formulas are of closed form, hence offering very fast operation for research and design of tensor impedance metasurfaces. [ABSTRACT FROM AUTHOR]

We present a theoretical study of the characteristics of the nonlinear spin-orbital angular momentum coupling induced by second-harmonic generation in plasmonic and dielectric nanostructures made of centrosymmetric materials. In particular, the connection between the phase singularities and polarization helicities in the longitudinal components of the fundamental and second-harmonic optical fields and the scatterer symmetry properties are discussed. By in-depth comparison between the interaction of structured optical beams with plasmonic and dielectric nanostructures, we have found that all-dielectric and plasmonic nanostructures that exhibit magnetic and electric resonances have comparable second-harmonic conversion efficiency. In addition, mechanisms for second-harmonic enhancement for single and chiral clusters of scatterers are unveiled and the relationships between the content of optical angular momentum of the incident optical beams and the enhancement of nonlinear light scattering is discussed. In particular, we formulate a general angular momenta conservation law for the nonlinear spin-orbital angular momentum interaction, which includes the quasi-angular-momentum of chiral structures with different-order rotational symmetry. As a key conclusion of our study relevant to nanophotonics, we argue that all-dielectric nanostructures provide a more suitable platform to investigate experimentally the nonlinear interaction between spin and orbital angular momenta, as compared to plasmonic ones, chiefly due to their narrower resonance peaks, lower intrinsic losses, and higher sustainable optical power. [ABSTRACT FROM AUTHOR]

Implantable coils have been widely utilized in functional magnetic resonance imaging (fMRI) owing to their superior signal to noise ratio. To effectively minimize the magnetic field distortion and image artifacts, the magnetic susceptibility of the implantable coil needs to be evaluated before practical use. In this work, we experimentally identify the magnetic susceptibility of each component of the implantable coil with the 7T Bruker NMR imaging scanner and provide useful guidelines for the following manufacturing. A 5 x 5 mm² implantable surface coil with a tunable frequency range is subsequently introduced for the 7T fMRI of the rat primary somatosensory cortex (S1FL). A detachable external tuning circuit for the implantable coil is employed to facilitate in-vivo measurements in the rat model. [ABSTRACT FROM AUTHOR]

The shoot density, shoot length, and above-ground biomass of Equisetum fluviatile communities were characterized during the growing season at six lakes in the Jiuzhaigou wetland system during 2007. Shoot length, shoot density, and above-ground biomass of E. fluviatile showed significant seasonal changes in all sites. The shoot length increased significantly from April to August except in seasonally flooded sites in Arrow-Bamboo Lake. Stepwise multiple regressions indicated that shoot density was correlated with water depth in all growth months. Total nitrogen in soil correlated positively with the maximum above-ground biomass. [ABSTRACT FROM AUTHOR]

In the study of reaction kinetics between hydrogen and hydriding alloys, what is the most important is to obtain intrinsic kinetic data. The hydriding kinetics of 0.5 g La1.5Ni0.5Mg17 sample in the two-phase (α-β) region was investigated as a function of temperature and pressure in the ranges 553–573 K and 0.256–0.992 MPa H2 respectively. Mathematical analyses of the time-dependent hydrogen absorption curves indicate agreement with Jander diffusion model, [1 - (1 - ξ)1/3]2 = k(T, P)t, which suggests that the rate-controlling step for hydrogen absorption is three-dimensional diffusion. An apparent activation energy for such diffusion process of 83 ± 1 kJ/mol H2 has been obtained from the absorption data. [ABSTRACT FROM AUTHOR]

A passive chipless radio-frequency identification (RFID) tag based on a log-periodic (LP) dipole array is proposed, where the tailorable band-rejection property of the LP aperture is utilised to realise a large number of codes. The proposed tag principle is successfully validated by measurements, where the absence and presence of the band-rejection is shown to carry the bit information. Its fabrication simplicity is also demonstrated by its implementation on a flexible substrate. Finally, two different tag formation schemes, based on a specific set of resonance suppressions, are discussed in detail. [ABSTRACT FROM AUTHOR]