Storage States in Ultracold Collective Atoms

We present a complete theoretical description of atomic storage states in the multimode framework by including spatial coherence in atomic collective operators and atomic storage states. We show that atomic storage states are Dicke states with the maximum cooperation number. In some limits, a set of multimode atomic storage states has been established in correspondence with multimode Fock states of the electromagnetic field. This gives better understanding of both the quantum and coherent information of optical field can be preserved and recovered in ultracold medium. In this treatment, we discuss in detail both the adiabatic and dynamic transfer of quantum information between the field and the ultracold medium.Comment: 22 pages, no figures;to be published in Euro. Phys. J.

Computational Study of the Magnetic Structure of Na2_2IrO3_3

The magnetic structure of honeycomb iridate Na$_2$IrO$_3$ is of paramount importance to its exotic properties. The magnetic order is established experimentally to be zigzag antiferromagnetic. However, the previous assignment of ordered moment to the $\bm{a}$-axis is tentative. We examine the magnetic structure of Na$_{2}$IrO$_{3}$ using first-principles methods. Our calculations reveal that total energy is minimized when the zigzag antiferromagnetic order is magnetized along $\bm{g}\approx\bm{a}+\bm{c}$. Such a magnetic configuration is explained by adding anisotropic interactions to the nearest-neighbor Kitaev-Heisenberg model. Spin-wave spectrum is also calculated, where the calculated spin gap of $10.4$ meV can in principle be measured by future inelastic neutron scattering experiments. Finally we emphasize that our proposal is consistent with all known experimental evidence, including the most relevant resonant x-ray magnetic scattering measurements [X. Liu \emph{et al.} {Phys. Rev. B} \textbf{83}, 220403(R) (2011)].Comment: 18 pages, 7 figure

Pyrolysis and catalytic pyrolysis of protein- and lipid-rich feedstock

Current biorefineries utilize only sugars or lipids in biomass for fuel production, leaving protein-rich residues underutilized. Improper disposal of those residues may cause economical or ecological problem. Research in this dissertation focuses on developing pyrolysis/catalytic pyrolysis as a pathway for producing biofuel or bio-based chemical from protein- and lipid- rich biomass. Fast pyrolysis of microalgae remnants after lipid extraction produced bio-oil with around 13% nitrogen content. This large amount of nitrogen can have deleterious effects on catalysts during bio-oil upgrading. Catalytic pyrolysis of protein-rich algal biomass with HZSM-5 catalyst yielded aromatic and olefinic hydrocarbons. Most of nitrogen in biomass was released as ammonia, which suggests feasibility for recycling nitrogen as a nutrient for microalgae cultivation. Catalytic pyrolysis of protein-rich biomass produced significantly higher yields of hydrocarbons compared with lignocellulosic biomass. Protein and lipid produced higher yield of hydrocarbons compared with carbohydrates and lignin in biomass. The lipid components in biomass have positive synergistic effect to enhance yields of aromatics. The effect of reactor configuration on the products of catalytic pyrolysis was also investigated. In-situ catalytic pyrolysis produced significantly more aromatics and less olefins compared with ex-situ catalytic pyrolysis. Selectivity of monocyclic aromatics such as benzene and toluene for ex-situ catalytic pyrolysis was higher than for the in-situ method. Variance of hydrocarbon yields for in-situ and ex-situ catalytic pyrolysis were explained by differences in gas flow and heat transfer for the two kinds of catalytic pyrolysis. The remarkably high olefin yield from ex-situ catalytic pyrolysis suggests the possibility of exploiting the process to preferentially obtain olefins from biomass. Techno-economic analysis was performed on an integrated biorefinery combining corn ethanol production and catalytic pyrolysis of dried distillers grains with solubles (DDGS) for hydrocarbon production. In addition to ethanol, a wide range of hydrocarbons including aromatics, olefins, and synthetic gasoline and diesel are produced from the integrated facility. The hydrocarbon products command a substantially higher market value than could be realized by selling the unprocessed DDGS. However, the capital costs and operating costs for the integrated biorefinery are higher than the conventional stand-alone corn ethanol biorefinery. The minimum fuel selling price (MFSP) for the integrated scenario is comparable to the MFSP for the stand-alone scenario. Combined with the benefit of product diversity, the proposed integrated corn biorefinery may be competitive with conventional stand-alone ethanol production