Well‐Defined High Molecular Weight Polystyrene with High Rates and High Livingness Synthesized via Two‐Stage RAFT Emulsion Polymerization

A highly living polymer with over 100 kg mol⁻¹ molecular weight is very difficult to achieve by controlled radical polymerization since the unavoidable side reactions of irreversible radical termination and radical chain transfer to monomer reaction become significant. It is reported that over 500 kg mol⁻¹ polystyrene with high livingness and low dispersity could be synthesized by a facile two‐stage reversible addition–fragmentation transfer emulsion polymerization. The monomer conversion reaches 90% within 10 h. High livingness of the product is ascribed to the extremely low initiator concentration and the chain transfer constant for monomer unexpectedly much lower than the well‐accepted values in the conventional radical polymerization. The two‐stage monomer feeding policy much decreases the dispersity of the product.

     

Phase‐preserved macroscopic visible‐light carpet cloaking beyond two dimensions

Transformation optics, a recent geometrical design strategy of light manipulation with both ray trajectories and optical phase controlled simultaneously, promises an invisibility cloaking device that can render a macroscopic object invisible even to a scientific instrument measuring optical phase. Recent “carpet” cloaks have extended their cloaking capability to broadband frequency ranges and macroscopic scales, but they only demonstrated the recovery of ray trajectories after passing through the cloaks, while whether the optical phase would reveal their existence still remains unverified. In this paper, a phase‐preserved macroscopic visible‐light carpet cloak is demonstrated in a geometrical construction beyond two dimensions. As an extension of previous two‐dimensional (2D) macroscopic carpet cloaks, this almost‐three‐dimensional carpet cloak exhibits three‐dimensional (3D) invisibility for illumination near its center (i.e. with a limited field of view), and its ideal wide‐angle invisibility performance is preserved in multiple 2D planes intersecting in the 3D space. Optical path length is measured with a broadband pulsed‐laser interferometer, which provides unique experimental evidence on the geometrical nature of transformation optics.

     

Ultrabroadband superoscillatory lens composed by plasmonic metasurfaces for subdiffraction light focusing

Conventional optics is diffraction limited due to the cutoff of spatial frequency components, and evanescent waves allow subdiffraction optics at the cost of complex near‐field manipulation. Recently, optical superoscillatory phenomena were employed to realize superresolution lenses in the far field, but suffering from very narrow working wavelength band due to the fragility of the superoscillatory light field. Here, an ultrabroadband superoscillatory lens (UBSOL) is proposed and realized by utilizing the metasurface‐assisted law of refraction and reflection in arrayed nanorectangular apertures with variant orientations. The ultrabroadband feature mainly arises from the nearly dispersionless phase profile of transmitted light through the UBSOL for opposite circulation polarization with respect to the incident light. It is demonstrated in experiments that subdiffraction light focusing behavior holds well with nearly unchanged focal patterns for wavelengths spanning across visible and near‐infrared light. This method is believed to find promising applications in superresolution microscopes or telescopes, high‐density optical data storage, etc.

     

The Analysis of Phenolic Compounds in Walnut Husk and Pellicle by UPLC-Q-Orbitrap HRMS and HPLC

Husk and pellicle as the agri-food waste in the walnut-product industry are in soaring demand because of their rich polyphenol content. This study investigated the differential compounds related to walnut polyphenol between husk and pellicle during fruit development stage. By using ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap), a total of 110 bioactive components, including hydrolysable tannins, flavonoids, phenolic acids and quinones, were tentatively identified, 33 of which were different between husk and pellicle. The trend of dynamic content of 16 polyphenols was clarified during walnut development stage by high-performance liquid chromatography (HPLC). This is the first time to comprehensive identification of phenolic compounds in walnut husk and pellicle, and our results indicated that the pellicle is a rich resource of polyphenols. The dynamic trend of some polyphenols was consistent with total phenols. The comprehensive characterization of walnut polyphenol and quantification of main phenolic compounds will be beneficial for understanding the potential application value of walnut and for exploiting its metabolism pathway.     

Progress of Jinping Underground laboratory for Nuclear Astrophysics (JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of~(25)Mg(p,γ)~(26)Al,~(19)F(p,α)~(16)O,~(13)C(α,n)~(16)O and ~(12)C(α,γ)~(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.     

Structural phase transition of vanadium at 69 GPa

A phase transition was observed at 63-69 GPa and room temperature in vanadium with synchrotron x-ray diffraction. The transition is characterized as a rhombohedral lattice distortion of the body-centered-cubic vanadium without a discontinuity in the pressure-volume data, thus representing a novel type of transition that has never been observed in elements. Instead of driven by the conventional s-d electronic transition mechanism, the phase transition could be associated with the softening of C44 trigonal elasticity tensor that originates from the combination of Fermi surface nesting, band Jahn-Teller distortion, and electronic topological transition.     

Spectroscopic evidence of the multiple- site structure of Eu(3+) ions incorporated in ZnO nanocrystals

Hexagonal Eu(3+):ZnO nanocrystals were synthesized by a modified solgel method. By means of the site-selective spectroscopy at 10 K, two kinds of luminescence sites of Eu(3+) are identified. One site exhibits a long lifetime of (5)D(0) and sharp emission and excitation peaks, which are ascribed to the inner lattice site with an ordered crystalline environment. The other site associated with the distorted lattice sites near the surface shows a relatively short lifetime of (5)D(0) and significantly broadened fluorescence lines. The energy transfer from the nanocrystal host to Eu(3+) confirms that Eu(3+) ions can, to some extent, be incorporated into the ZnO nanocrystal.     

Quantitative analysis of asymmetrical cortical activity in motor areas during sequential finger movement

Brain asymmetry is a phenomenon well known for handedness and has been studied in motor cortices. However, few quantitative studies on asymmetrical cortical activity in motor areas have been conducted. In this study, we systematically investigated asymmetrical cortical activity in motor areas during sequential finger movement by quantitatively analyzing functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) responses. The norm of BOLD signal percentage of change was introduced to quantitatively measure the BOLD signal intensity change difference between the left and right motor areas. The results of the data collected from six subjects show that the norm of BOLD signal percentage of change in the right motor area is higher than that in the left motor area for two-hand movement (P=.0059) and single-hand movement (P=.0279) with right-handedness. These results from fMRI show the asymmetry of motor areas and may suggest that the left hemisphere motor area comes into being as an adaptation system that needs few neuron cells only to finish any movement task for right-handedness. The activation intensity in the left motor area is reduced with normal right finger movement. The activation intensity in the right motor area is obviously higher than that in the left motor area.     

Antennal morphology, structure and sensilla distribution in Microplitis pallidipes (Hymenoptera: Braconidae)

Microplitis pallidipes (Hymenoptera: Braconidae) is an important larval parasitoid of noctuid larval pests. In this study, we describe the morphology, ultrastructure and distribution of sensilla on the antennae of both male and female adults using scanning electron microscopy; complemented with transmission electron microscopy. Observations determined that the antennae of M. pallidipes were threadlike and the flagella were composed of 16 sub-segments. Totally, there were six types of sensilla found on the antennae. They were identified as Sensilla trichodea, Sensilla chaetica, Sensilla basiconica type I, S. basiconica type II, Sensilla coeloconicum, and elongated Sensilla placodea, respectively. The S. trichodea were the most abundant sensilla and distributed over the entire antennae, while S. basiconica I and II, S. coeloconicum, and elongated S. placodea were limited to the flagellum. S. chaetica were found on the scape and pedicle in very low numbers. The S. basiconica II and elongated S. placodea walls were full of pores as evident in transmission electron micrographs. Though the shape and structure of antennae between male and female adults were not basically different, the length and width of the antennae on male wasps were significantly greater than that of females. Also, the number, size and density of S. placodea of the male were significantly greater than those of females. The morphology and structure of these sensilla were compared with that found in other braconid wasps. Their possible functions are discussed in light of previously published literature.     

Rapid determination of radon progeny concentration based on artificial neural networks

Journal of Radioanalytical and Nuclear Chemistry - The rapid measurement of radon progeny concentration is of great significance for improving the efficiency of radon exposure dose evaluation in a...