vations of a discontinuity near 1150 km in subduction arcas [(3, 6), for example] indicates that this may be a global feature o t yet unknou.n nature.T h e observation of reflectors at mid-1ua11tle iiepths comparable to those in subduction zones, hut in a different environment, indicates that a search for yet unidentitied nlineral asscnlblagcs o t global significance may he ~\.orthn.hilc. Recent cxperiments have shown the possihle existence of phase tra~lsitions at lolvcr mantle conditions: orthorhomhic-to-c~113ic silicate pcrovskite (3d) a i d rutile SiOz to CaClz structure ( 3 1 ). T h e role ancl proportions of volatiles such as water or carbon dioxide in the nlantle remain largely unknown and co~lld he o t importance (32). Additional seismic observations with the great resolving power of BB arrays s110~11ci help answer the yucstio~n o t the global character of our observations.

We investigate the index sensing characteristics of plasmonic arrays based on square lattice slablike gold nanorings ͑NRs͒ with different ring widths. The gold NR arrays exhibit two extinction peaks in the visible and near-infrared corresponding to antibonding and bonding modes. Redshift and blueshift in antibonding and bonding modes when broadening the average ring width are observed. We experimentally demonstrate the sensitivity of bonding mode can be tuned by varying the average ring width. However, the sensing performance is limited because the enhanced fields concentrate inside the shell-like structures. The nanoring ͑NR͒ structure surmounts this limitation due to the extension of inside field to the environment. This leads to significant increase in the detection sensitivity. 20 The NR plasmonic properties can be seen as the electromagnetic interaction between the nanodisc and the nanohole plasmons. [21][22][23] This results in the splitting of the plasmon mode into two resonance modes, which are the low energy "bonding" mode and the high energy "antibonding" mode. The resonance frequencies of both resonance modes can be easily tuned in the visible ͑VIS͒ and NIR range by adjusting the geometry of NR, which is useful for various optical sensing applications.In this letter, we report our experimental investigation of bonding and antibonding modes in plasmonic arrays based on square lattice slablike gold NRs with different ring widths. The refractive index sensing experiments of such structures are performed by immersing the samples in index matching liquids. We show that the sensitivities of NR arrays exhibit a linear relationship with ring widths for the bonding mode in the NIR regime. These results are crucial in designing LSP resonance ͑LSPR͒ sensors based on periodic metallic nanostructures.The scheme of square lattice gold NR array with ring thickness t, periodicity p, diameter d, and average width w is shown in Fig. 1͑a͒. The periodicity, diameter, and thickness are fixed at 1 m, 500 nm, and 50 nm. In fabrication, the ITO glass is utilized as the substrate to avoid the charge accumulation effect during electron beam lithography ͑EBL͒. First, the ITO glass was spin-coated a 150 nm polymethylmethacrylate ͑PMMA͒ layer. The NR patterns with area of 300ϫ 300 m 2 and different ring widths were defined on the PMMA layer by EBL. After the development process, a gold thin film with thickness of 50 nm was deposited by thermal evaporation. Then the liftoff process is applied by rinsing the sample in acetone for a few hours. The periodicity p of array is 1 m, the ring diameter is 500 nm, and the ring thickness t is 50 nm.APPLIED PHYSICS LETTERS 98, 153108 ͑2011͒

In this report, we propose a square lattice photonic crystal hetero-slab-edge microcavity design. In numerical simulations, three surface modes in this microcavity are investigated and optimized by tuning the slab-edge termination τ and gradual mirror layer. High simulated quality (Q) factor of 2.3 × 10(5) and small mode volume of 0.105 μm(3) are obtained from microcavity with τ = 0.80. In experiments, we obtain and identify different surface modes lasing. The surface mode in the second photonic band gap shows a very-low threshold of 140 μW and high Q factor of 5,500, which could be an avenue to low-threshold optical lasers and highly sensitive sensor applications with efficient light-matter interactions.

The microstructure and mechanical properties of permanent mold low-pressure casting (PMLPC) and sand mold gravity casting (SMGC) of A357 alloy were studied. The grain size of alloys formed by PMLPC is finer than that formed by sand mold gravity casting because of higher freezing rate of the former. The secondary dendrite arm spacing of PMLPC is approximately 15.2 μm (SD=4) while that of SMGC is 33.2 μm (SD=6). The ultimate tensile strength of PMLPC has a wider range from 350 MPa to 299.9 MPa and an elongation from 1.2 to 4.9. In comparison, the ultimate tensile strength of SMGC ranges from 307 MPa to 315 MPa and its elongation ranges from 2.1 to 3.7. These differences may be attributed to various factors, such as filling speed, filling pressure, and cooling rate, that affect the quality of permanent molds during the filling process.