Visualization of Higher-Order Topological Insulating Phases in Two-Dimensional Dielectric Photonic Crystals.

The studies of topological phases of matter have been developed from condensed matter physics to photonic systems, resulting in fascinating designs of robust photonic devices. Recently, higher-order topological insulators have been investigated as a novel topological phase of matter beyond the conventional bulk-boundary correspondence. Previous studies of higher-order topological insulators have been mainly focused on the topological multipole systems with negative coupling between lattice sites. Here we experimentally demonstrate that second-order topological insulating phases without negative coupling can be realized in two-dimensional dielectric photonic crystals. We visualize both one-dimensional topological edge states and zero-dimensional topological corner states by using the near-field scanning technique. Our findings open new research frontiers for photonic topological phases and provide a new mechanism for light manipulating in a hierarchical way.

Theoretical study of the spectroscopic and nonlinear optical properties of trans- and cis-4-hydroxyazobenzene.

We investigate the molecular structure, vibrational and electronic absorption spectra, and electronic hyperpolarizabilities of trans and cis isomers of 4-hydroxyazobenzene (HOAB) via density functional theory. Results show that the azo dye exhibits a high third-order nonlinear optical response and good optical transparency. Both the basis set and the functional are important influences on the results obtained when calculating the absorption spectrum and NLO response. We also study the effect of the solvent on the electronic absorption spectrum to assess the ability of the functional to reproduce the experimental spectrum in combination with a suitable solvent model. Our calculations show that the SMD model of Truhlar et al. handles the electrostatic and the non-electrostatic effects of hydrogen-bonding solvents on the absorption spectrum better than the traditional polarizable continuum model does. In addition, our results indicate that the dye trans-HOAB exhibits a high second hyperpolarizability and excellent optical transparency. Also, although the second hyperpolarizability of cis-HOAB is much lower than that of trans-HOAB, it is non-negligible when calculating the optical nonlinearity of HOAB under an optical pump. We also examine the effect of frequency dispersion on second harmonic generation. This study provides the basis for further research on the spectroscopic and nonlinear optical properties of novel azo dyes and other π-conjugated compounds.

Solvent effects on polarizability and hyperpolarizability of spirobifluorene derivative.

We studied the solvent effect on the geometric structure and (hyper)polarizability of spirobifluorene derivative by using quantum chemistry calculations. We found that the geometric structure is slightly affected by the solvent polarity. However, solvent polarity significantly influences first hyperpolarizability and second hyperpolarizability respectively. In addition, the linear polarizability is less affected by the solvent than the hyperpolarizabilities. We also first studied the solvent effect on frontier molecular orbitals and found that the frontier molecular orbitals energy gap is strongly influenced by the surrounding solvent. Our results demonstrate frontier molecular orbitals energy gap and molecular hyperpolarizabilities can be tuned by a suitable choice of the solvent respectively. Such findings have crucial implications for organic nonlinear optical materials applications.

TE-mode coplanar imaging using weakly anisotropic metasurface.

We analyze and experimentally realize coplanar imaging of transverse-electric (TE) modes surface waves using weakly anisotropic metasurface consisting of non-periodic subwavelength U-shaped metallic structures. Such metallic structures with the exciting coplanar dipole are integrated on the top surface of a thin dielectric board. A circuit model is utilized to analyze the characteristics of the surface waves supported by the metasurface. By varying the geometrical parameters of the U-shaped metallic structures, the phases of surface waves are modulated, from which a planar lens is presented for the TE-mode coplanar imaging. The analyses and measurements show that anisotropies of the U-shaped metallic structures have little influence on the imaging properties of the planar lens. The measurement results have good agreements to numerical simulations.

[Influence of enteral administration of hypertonic electrolyte glucose solution on the intestinal barrier and organ functions in dogs with severe burn].

OBJECTIVE: To study the change in intestinal barrier and organ functions of burned dog after enteral administration of hypertonic electrolyte glucose solution (HEGS) in shock stage. METHODS: Twenty-four Beagle dogs inflicted with 35% TBSA full-thickness burn were divided into no-fluid group (NF), intravenous infusion with isotonic electrolyte glucose solution (IEGS) group (II group), enteral infusion with IEGS group (EI), and enteral infusion with HEGS group (EH) according to the random number table, with 6 dogs in each group. Saline, containing 50 g/L glucose, was intravenously or enterally infused into dogs in II group and EI group respectively 0.5 hour post injury (PIH) for resuscitation. Total infusion volume within PIH 24 was 4 mL x kg(-1) x %TBSA(-1) (half of the total volume was infused in the first 8 hours in a constant speed, the other half volume was infused in the rest 16 hours in a constant speed). HEGS, containing 18 g/L NaCl and 50 g/L glucose, was enterally infused into dogs in EH group. Total infusion volume within PIH 24 was 2 mL x kg(-1) x %TBSA(-1), with the same infusion speed as that in II and EI groups. Liver and kidney function indexes [activity of ALT and CK-MB, expression levels of creatinine and blood urea nitrogen (BUN) in serum], activity of diamine oxidase (DAO), and activity of Na(+)-K(+)-ATPase in intestinal mucosa at PIH 24 were determined. RESULTS: ALT activity in each group was close to one another. Serum levels of creatinine and BUN in II, EI, and EH groups were significantly lower than those in NF group. CK-MB activity obviously increased at PIH 2 in every group. CK-MB activity in EH group at PIH 2 to 8 was respectively lower than that in NF and II groups. DAO activity in serum in II, EI, and EH groups decreased since PIH 4 or PIH 6, respectively from (3.9 + or - 0.6) U/L to (3.6 + or - 0.5) U/L, (4.8 + or - 0.4) U/L to (2.8 + or - 0.8) U/L, (6.4 + or - 1.8) U/L to (3.5 + or - 0.8) U/L, all were significantly lower than those in NF group [from (12.5 + or - 0.4) U/L to (9.7 + or - 1.1) U/L, comparison between EH group and NF group, t value at PIH 4, 6, 8, 24 was respectively 10.25, 12.44, 17.99, 16.21, P values all below 0.05]. The order of Na(+)-k(+)-ATPase activity in intestinal mucosa at PIH 24 in each group from high to low was II group, EH group, EI group, and NF group (comparison between former 3 groups and NF group, t value was respectively 10.09, 4.96, 8.32, F value was 26.79, P values all below 0.05). CONCLUSIONS: HEGS does not cause significant harm to the barrier function of intestinal mucosa of shock dog after burn. Compared with NF, HEGS can significantly improve functions of heart, liver, and kidney, and it can achieve the same resuscitation effect as enteral or intravenous infusion of IEGS with only half of the solution volume.

[The curative effect of 1.8% hypertonic electrolyte glucose solution in enteral resuscitation of burn shock].

OBJECTIVE: To study the resuscitative effect of hypertonic electrolyte glucose solution (HEGS) in enteral resuscitation of burn shock. METHODS: Eighteen Beagle dogs with 35% TBSA full-thickness flame injury were used in this study. They were randomized to a control group (no-fluid resuscitation, N group), a HEGS resuscitation group (H group) or an isotonic electrolyte glucose solution (IEGS) resuscitation group (I group). The solution enterally was given for resuscitation from half an hour after burn. The volumes and rates of fluid infusion in the H group were basically in accordance with 2 ml/(kg x 1%TBSA), those in the I group were basically in accordance with parkland formula [4 ml/(kg x 1%TBSA)]. The haemodynamic parameters, global end-diastolic volume index, plasma volume, osmotic pressure of plasma, intestinal absorptive rates of water and Na(+), and intestine mucosa blood flow were continuously assessed. RESULTS: The cardiac output index, global end-diastolic volume index, plasma volume and intestine blood mucosa flow reduced markedly after burn in the three groups, and then gradually returned from 2 h after burn in two resuscitation groups, which were higher than that in the N group (P < 0.05). The activities of diamine oxidase in plasma in the two resuscitation groups were higher than that in N group (P < 0.05). The intestinal absorption rates of water and Na(+) reduced markedly after burn in two resuscitation groups with the lowest levels, and then returned from 6 h after burn. The rates of water in H group were lower than that in I group (P < 0.05); the rates of Na(+) in H group were higher than in I group (P < 0.05). CONCLUSION: The results indicated that 35%TBSA III degrees burn-injury dogs be resuscitated effectively with 1.8% hypertonic electrolyte-glucose solution by enteral, which 1/2 volume of an isotonic electrolyte glucose solution.