Magnetic and superfluid phases of confined fermions in two-dimensional optical lattices

We examine antiferromagnetic and d-wave superfluid phases of cold fermionic atoms with repulsive interactions in a two-dimensional optical lattice combined with a harmonic trapping potential. For experimentally realistic parameters, the trapping potential leads to the coexistence of magnetic and superfluid ordered phases with the normal phase. We study the intriguing shell structures arising from the competition between the magnetic and superfluid order as a function of the filling fraction. In certain cases antiferromagnetism induce superfluidity by charge redistributions. We furthermore demonstrate how these shell structures can be detected as distinct anti-bunching dips and pairing peaks in the density-density correlation function probed in expansion experiments.Comment: 4 pages, 3 figure

Apellicon: a web-based tool for constructing and curating Textpresso databases.

As more research literature in the biological sciences is made available in electronic format, text mining systems are increasingly being used to improve the ability of investigators to retrieve relevant information. Through the use of advanced indexing techniques that utilize biological ontologies, semantic databases, and other formal representations of biological concepts text mining systems have been able to effectively parse biological literature. While text mining systems are increasingly effective at creating the linkages required to provide context-specific search results, the systems themselves are difficult to set up and use by novice computer users due to the highly technical nature of the applications. Because most researchers in the biological sciences do not have a strong computer science background we have focused on improving the quality of existing, proven text mining systems by implementing a web-based GUI that greatly improves the workflow of these systems. Textpresso in particular has an excellent web-based interface for searching literature but does not have an easy to use administrative interface. We developed the Apellicon interface to enable a wide range of users to build and manage a Textpresso database. An important feature of Apellicon is that it can enable groups to collaborate in building a Textpresso database

A Palladium-Catalyzed Vinylcyclopropane (3 + 2) Cycloaddition Approach to the Melodinus Alkaloids

A palladium-catalyzed (3 + 2) cycloaddition of a vinylcyclopropane and a β-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials

Is Gold a Hedge or a Safe Haven? An Analysis of Stocks, Bonds and Gold

This paper addresses two questions. First, we investigate whether gold is a hedge against stocks and/or bonds and second, we investigate whether gold is a safe haven for investors if either stocks or bonds fall. A safe haven is defined as a security that loses none of its value in case of a market crash. This is counterpoised against a hedge, defined as a security that does not co-move with stocks or bonds on average. We study constant and time-varying relationships between stocks, bonds and gold in order to investigate the existence of a hedge and a safe haven. The empirical analysis examines US, UK and German stock and bond prices and returns and their relationship with the Gold price. We find that (i) Gold is a hedge against stocks, (ii) Gold is a safe haven in extreme stock market conditions and (iii) Gold is a safe haven for stocks only for 15 trading days after an extreme shock occurred.Safe haven, gold, stock-bond correlation, flight-to-quality

Imide/arylene ether copolymers

Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties

A simple variational method for calculating energy and quantum capacitance of an electron gas with screened interactions

We describe a variational procedure for calculating the energy of an electron gas in which the long-range Coulomb interaction is truncated by the screening effect of a nearby metallic gate. We use this procedure to compute the quantum capacitance of the system as a function of electron density and spin polarization. The accuracy of the method is verified against published Monte-Carlo data. The results compare favorably with a recent experiment.Comment: 4 pages, 3 figure

Application of Swept-Sine Excitation for Acoustic Impedance Education

The NASA Langley Normal Incidence Tube (NIT) and Grazing Flow Impedance Tube (GFIT) are regularly employed to characterize the frequency response of acoustic liners through the eduction of their specific acoustic impedance. Both test rigs typically use an acoustic source that produces sine wave signals at discrete frequencies (Stepped-Sine) to educe the impedance. The current work details a novel approach using frequency-swept sine waveforms normalized to a constant sound pressure level for excitation. Determination of the sound pressure level and phase from microphone measurements acquired using swept-sine excitation is performed using a modified Vold-Kalman order tracking filter. Four acoustic liners are evaluated in the NIT and GFIT with both stepped-sine and swept-sine sources. Using these two methods, the educed impedance spectra are shown to compare favorably. However, the new (Swept-Sine) approach provides much greater frequency resolution in less time, allowing the acoustic liner properties to be studied in much greater detail