Analysis of physical-chemical processes governing SSME internal fluid flows

The efforts to adapt CHAM's computational fluid dynamics code, PHOENICS, to the analysis of flow within the high pressure fuel turbopump (HPFTP) aft-platform seal cavity of the SSME are summarized. In particular, the special purpose PHOENICS satellite and ground station specifically formulated for this application are listed and described, and the preliminary results of the first part two-dimensional analyses are presented and discussed. Planned three-dimensional analyses are also briefly outlined. To further understand the mixing and combustion processes in the SSME fuelside preburners, a single oxygen-hydrogen jet element was investigated

Synthetic experiments in the benzophyrone series. Part XXXVI. Nuclear methylation of nor-Eugenin and Chrysin, and synthesis and study of related C-methyl compounds

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Synthetic experiments in the benzopyrone series. Part XXI. Isomerisation of C-(6 or 8)-methyl-5: 7-dihydroxy chromones

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Bose Hubbard Model in a Strong Effective Magnetic Field: Emergence of a Chiral Mott Insulator Ground State

Motivated by experiments on Josephson junction arrays, and cold atoms in an optical lattice in a synthetic magnetic field, we study the "fully frustrated" Bose-Hubbard (FFBH) model with half a magnetic flux quantum per plaquette. We obtain the phase diagram of this model on a two-leg ladder at integer filling via the density matrix renormalization group approach, complemented by Monte Carlo simulations on an effective classical XY model. The ground state at intermediate correlations is consistently shown to be a chiral Mott insulator (CMI) with a gap to all excitations and staggered loop currents which spontaneously break time reversal symmetry. We characterize the CMI state as a vortex supersolid or an indirect exciton condensate, and discuss various experimental implications.Comment: 4 pages, 4 figs, Significantly revised version, to appear in PRA-Rapi

Preparation and characterization of epitaxial Fe2-xTixO3 films with various Ti concentrations (0.5 < x < 1.0)

An ilmenite-hematite solid solution ( Fe2-xTixO3 ) is one of the candidates for practical magnetic semiconductors with a high Curie temperature. We have prepared well-crystallized epitaxial Fe2-xTixO3 films with a wide range of Ti concentrations - x=0.50, 0.60, 0.65, 0.76, 0.87, and 0.94 - on &#945;-Al2O3(001) substrates. The films are prepared by a reactive helicon plasma sputtering technique to evaporate Fe and TiO targets simultaneously under optimized oxygen pressure conditions. The structural characterizations of the films reveal that all films have a single phase of the ordered structure with R3 symmetry, where Ti-rich and Fe-rich layers are stacked alternately along the c axis. All films have large ferrimagnetic moments at low temperature, and room temperature magnetization is clearly observed at x&#60;0.7. The inverse temperature dependence of the resistivities of the films indicates their semiconducting behavior. The film resistivities decrease with decreasing Ti concentration.</p

Fluctuation modes in color-superconductors

We investigate fluctuation effects of a gap parameter in color-superconductors. The fluctuation modes in the super phase are described by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and the other is a diquark boson whose mass is about twice of the gap energy (an extended quasi-supersymmetry). In the normal phase the fluctuation becomes a precursory (soft) mode whose amplitude increases near the critical temperature.Comment: 6 page

Hidden Sp(2s+1)- or SO(2s+1)-symmetry and new exactly solvable models in ultracold atomic systems

The high spin ultracold atom models with a special form of contact interactions, i.e., the scattering lengthes in the total spin-$2,4 \cdots$ channels are equal but may be different from that in the spin-0 channel, is studied. It is found that those models have either $Sp(2s+1)$-symmetry for the fermions or $SO(2s+1)$-symmetry for the bosons in the spin sector. Based on the symmetry analysis, a new class of exactly solvable models is proposed and solved via the Bethe ansatz. The ground states for repulsive fermions are also discussed.Comment: 6 pages, 2 figure

A Compact, Low-Power Cantilever-Based Sensor Array for Chemical Detection

A compact and low-power cantilever-based sensor array has been developed and used to detect various vapor analytes. This device employs sorptive polymers that are deposited onto piezoresistive cantilevers. We have successfully detected several organic vapors, representing a breadth of chemical properties and over a range of concentrations. Comparisons of the polymer/vapor partition coefficient to the cantilever deflection responses show that a simple linear relationship does not exist, emphasizing the need to develop an appropriate functional model to describe the chemical-to-mechanical transduction that is unique to this sensing modality

On the cyclotron line in Cepheus X-4

Context. Accreting X-ray pulsars provide us with laboratories for the study of extreme gravitational and magnetic fields, hence accurate descriptions of their observational properties contribute to our understanding of this group of objects. Aims. We aim to detect a cyclotron resonance scattering feature in the Be/X-ray binary Cep X-4 and to investigate pulse profile and spectral changes through the outburst. Methods. Spectral fitting and timing analysis are employed to probe the properties of Cep X-4 during an outburst in 2002 June. Results. A previously announced cyclotron feature at 30.7 keV is confirmed, while the source shows spectral behaviour and luminosity related changes similar to those observed in previous outbursts. The long-term X-ray lightcurve shows a periodicity at 20.85 d, which could be attributed to the orbit in this Be system

Interaction-driven giant thermopower in magic-angle twisted bilayer graphene

Magic-angle twisted bilayer graphene has proved to be a fascinating platform to realize and study emergent quantum phases arising from the strong correlations in its flat bands. Thermal transport phenomena, such as thermopower, are sensitive to the particle-hole asymmetry, making them a crucial tool to probe the underlying electronic structure of this material. Here we have carried out thermopower measurements of magic-angle twisted bilayer graphene as a function of carrier density, temperature and magnetic field. We report the observation of an unusually large thermopower reaching a value of the order of 100 mu V K-1 at a low temperature of 1 K. The thermopower exhibits peak-like features that violate the Mott formula in close correspondence to the resistance peaks appearing around the integer filling of the moire bands, including the Dirac point. We show that the large thermopower peaks and their associated behaviour arise from the emergent highly particle-hole-asymmetric electronic structure, due to the sequential filling of the moire flat bands and the associated recovery of Dirac-like physics. Furthermore, the thermopower shows an anomalous peak around the superconducting transition, which points towards the possible role of superconducting fluctuations in magic-angle twisted bilayer graphene. Thermal transport measurements provide a complementary view of the electronic structure of a material to electronic transport. This technique is applied to twisted bilayer graphene, and highlights the particle-hole asymmetry of its band structure