Abstract:
In this work, in order to find a method for the accurate determination of chemical oxygen demand (COD_{Cr}) in high chloride oilfield wastewater, the interferences of chloridion (Cl^{-}) on COD_{Cr} determination were first studied based on the Chinese national standard GB 11914-89. The results showed that the COD_{Cr} values and deviations determined by the classical potassium dichromate (K_{2}Cr_{2}O_{7}) method increased gradually with the increase of Cl^{-} mass concentration in water samples. Then, theoretical and experimental studies on reducing interferences of Cl^{-} on COD_{Cr} determination were carried out. The results showed that different concentrations of K_{2}Cr_{2}O_{7} exhibited different oxidation capacities on Cl^{-}, while having little effects on the oxidation of organic compounds. More specifically, when the concentration of K_{2}Cr_{2}O_{7} was 0.025 mol·L^{-1} and the mass ratio of HgSO_{4}:Cl^{-} was 10:1, the interferences of Cl^{-} on COD_{Cr} determination were the slightest. Finally, a low concentration oxidant method was proposed for the accurate determination of COD_{Cr} in high chloride oilfield wastewaters. The performances of the proposed method were verified by the simulated and actual high chloride oilfield wastewater. The results showed that when Cl^{-} ≤ 20,000 mg·L^{-1} and COD < 100 mg·L^{-1}, the relative prediction errors of COD_{Cr} provided by the proposed method were acceptable, which revealed that the low concentration oxidant method is feasible and reliable for the determination of COD_{Cr} in high chloride oilfield wastewater.

Biomass tar is an obstacle in biomass gasification. Partial combustion is a potential method for tar elimination. To better study the tar conversion conditions and design reasonable partial combustion reactor, 2D/3D throat models are establish to calculate the tar reduction during partial combustion using numerical method. Different number of nozzles, injection directions and injection velocities were investigated. SIMPLE algorithm was used in this calculation. The results indicated that the best performance of partial combustion was obtained when ER (equivalent ratio)=0.34. A performance of 3 nozzles, perpendicular injection and 20 m/s injection velocity could reach lowest tar content of 3.09 wt%.

Abstract:
Background Src homology 2 (SH2) domain is a conserved module involved in various biological processes. Tensin family member was reported to be involved in tumor suppression by interacting with DLC-1 (deleted-in-liver-cancer-1) via its SH2 domain. We explore here the important questions that what the structure of tensin2 SH2 domain is, and how it binds to DLC-1, which might reveal a novel binding mode. Principal Findings Tensin2 SH2 domain adopts a conserved SH2 fold that mainly consists of five β-strands flanked by two α-helices. Most SH2 domains recognize phosphorylated ligands specifically. However, tensin2 SH2 domain was identified to interact with nonphosphorylated ligand (DLC-1) as well as phosphorylated ligand. Conclusions We determined the solution structure of tensin2 SH2 domain using NMR spectroscopy, and revealed the interactions between tensin2 SH2 domain and its ligands in a phosphotyrosine-independent manner.

Abstract:
The duality in the Chalker-Coddington network model is examined. We are able to write down a duality relation for the edge state transmission coefficient, but only for a specific symmetric Hall geometry. Looking for broader implication of the duality, we calculate the transmission coefficient $T$ in terms of the conductivity $\sigma_{xx}$ and $\sigma_{xy}$ in the diffusive limit. The edge state scattering problem is reduced to solving the diffusion equation with two boundary conditions $(\partial_y-(\sigma_{xy})/(\sigma_{xx})\partial_x)\phi=0$ and $[\partial_x+(\sigma_{xy}-\sigma_{xy}^{lead})/(\sigma_{xx}) \partial_y]\phi=0$. We find that the resistances in the geometry considered are not necessarily measures of the resistivity and $\rho_{xx}=L/W R/T h/e^2$ ($R=1-T$) holds only when $\rho_{xy}$ is quantized. We conclude that duality alone is not sufficient to explain the experimental findings of Shahar et al and that Landauer-Buttiker argument does not render the additional condition, contrary to previous expectation.

Abstract:
The understanding of far-field thermal radiation had directly led to the discovery of quantum mechanics a century ago, and is of great current practical importance for applications in energy conversions, radiative cooling, and thermal control. It is commonly assumed that for any macroscopic thermal emitter, its maximal emitted power within any given frequency range cannot exceed that of a blackbody with the same surface area. In contrast to such conventional wisdom, here we propose, and experimentally demonstrate, that the emitted power from a finite size macroscopic blackbody to far field vacuum can be significantly enhanced, within the constraint of the second law of thermodynamics. To achieve such an enhancement, the thermal body needs to have internal electromagnetic density of states (DOS) greater than that of vacuum, and one needs to provide a thermal extraction mechanism to enable the contributions of all internal modes to far field radiation.

Abstract:
We study stimulated emission from an excited two-level atom coupled to a waveguide containing an incident single-photon pulse. We show that the strong photon correlation, as induced by the atom, plays a very important role in stimulated emission. Additionally, the temporal duration of the incident photon pulse is shown to have a marked effect on stimulated emission and atomic lifetime.

Abstract:
The tunneling into the {\em bulk} of a 2D electron system (2DES) in strong magnetic field is studied near the integer quantum Hall transitions. We present a nonperturbative calculation of the tunneling density of states (TDOS) for both Coulomb and short-ranged electron-electron interactions. In the case of Coulomb interaction, the TDOS exhibits a 2D quantum Coulomb gap behavior, $\nu(\ve)=C_Q\ave/e^4$, with $C_Q$ a nonuniversal coefficient of quantum mechanical origin. For short-ranged interactions, we find that the TDOS at low bias follows $\nu(\ve)/\nu (0)=1+(\ave/\ve_0)^\gamma$, where $\gamma$ is a universal exponent determined by the scaling dimension of short-ranged interactions.

Abstract:
We develop a general perturbation theory to treat small parameter changes in dispersive plasmonic nanostructures and metamaterials. We specifically apply it to dielectric refractive index, and metallic plasma frequency modulation in metal- dielectric nanostructures. As a numerical demonstration, we verify the theory's accu- racy against direct calculations, for a system of plasmonic rods in air where the metal is defined by a two-pole fit of silver's dielectric function. We also discuss new optical behavior related to plasma frequency modulation in such systems. Our approach provides new physical insight for the design of plasmonic devices for biochemical sensing and optical modulation, and future active metamaterial applications.

Abstract:
Light trapping for solar cells can reduce production cost and improve energy conversion efficiency. Understanding some of the basic theoretical constraints on light trapping is therefore of fundamental importance. Here, we develop a general angular constraint on the absorption enhancement in light trapping. We show that there is an upper limit for the angular integration of absorption enhancement factors. This limit is determined by the number of accessible resonances supported by an absorber.

Abstract:
We present a theory for Fano interference in light scattering by individual obstacle, based on a temporal coupled-mode formalism. This theory is applicable for obstacles that are much smaller than the incident wavelength, or for systems with two-dimensional cylindrical or three-dimensional spherical symmetry. We show that for each angle momentum channel, the Fano interference effect can be modeled by a simple temporal coupled-mode equation, which provides a line shape formula for scattering and absorption cross-section. We validate the analysis with numerical simulations. As an application of the theory, we design a structure that exhibits strong absorption and weak scattering properties at the same frequency.