12,574 research outputs found

    Recent developments in classical density functional theory: Internal energy functional and diagrammatic structure of fundamental measure theory

    Full text link
    An overview of several recent developments in density functional theory for classical inhomogeneous liquids is given. We show how Levy's constrained search method can be used to derive the variational principle that underlies density functional theory. An advantage of the method is that the Helmholtz free energy as a functional of a trial one-body density is given as an explicit expression, without reference to an external potential as is the case in the standard Mermin-Evans proof by reductio ad absurdum. We show how to generalize the approach in order to express the internal energy as a functional of the one-body density distribution and of the local entropy distribution. Here the local chemical potential and the bulk temperature play the role of Lagrange multipliers in the Euler-Lagrange equations for minimiziation of the functional. As an explicit approximation for the free-energy functional for hard sphere mixtures, the diagrammatic structure of Rosenfeld's fundamental measure density unctional is laid out. Recent extensions, based on the Kierlik-Rosinberg scalar weight functions, to binary and ternary non-additive hard sphere mixtures are described.Comment: 15 pages, 6 figure

    The Uncertainty of Fluxes

    Full text link
    In the ordinary quantum Maxwell theory of a free electromagnetic field, formulated on a curved 3-manifold, we observe that magnetic and electric fluxes cannot be simultaneously measured. This uncertainty principle reflects torsion: fluxes modulo torsion can be simultaneously measured. We also develop the Hamilton theory of self-dual fields, noting that they are quantized by Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is Z/2-graded, so typically contains both bosonic and fermionic states. Significantly, these ideas apply to the Ramond-Ramond field in string theory, showing that its K-theory class cannot be measured.Comment: 33 pages; minor modifications for publication in Commun. Math. Phy

    Northern Record for the Zooxanthellate Scleractinian Coral Siderastrea siderea (Ellis and Solander) from the Gulf of Mexico

    Get PDF
    We report a northward range extension of the zooxanthellate scleractinian coral Siderastrea siderea (Ellis and Solander) in the Gulf of Mexico. Several small, living colonies of S. siderea have been obtained in dredge samples from a site located at 29º 55.5\u27 N, 087º 28.4\u27 W in the northeastern Gulf of Mexico. Prior to these collections the northernmost occurrence of S. siderea in the Gulf of Mexico was reported as 27º 54.5\u27 N, 093º 35.8\u27 W, on the East Flower Garden Bank, in the western Gulf of Mexico. In the eastern Gulf of Mexico, S. siderea is not reported occurring on the west Florida shelf north of the Florida Keys-Dry Tortugas or approximately 24º 55\u27 N

    Repetitive Segmental Structure of the Transducin β Subunit: Homology with the CDC4 Gene and Identification of Related mRNAs

    Get PDF
    Retinal transducin, a guanine nucleotide regulatory protein (referred to as a G protein) that activates a cGMP phosphodiesterase in photoreceptor cells, is comprised of three subunits. We have identified and analyzed cDNA clones of the bovine transducin β subunit that may be highly conserved or identical to that in other G proteins. From the cDNA nucleotide sequence of the entire coding region, the primary structure of a 340-amino acid protein was deduced. The encoded β subunit has a Mr of 37,375 and is comprised of repetitive homologous segments arranged in tandem. Furthermore, significant homology in primary structure and segmental sequence exists between the β subunit and the yeast CDC4 gene product. The Mr 37,375 β subunit polypeptide is encoded by a 2.9-kilobase (kb) mRNA. However, there exists in retina other β-related mRNAs that are divergent from the 2.9-kb mRNA on the basis of oligonucleotide and primer-extended probe hybridizations. All mammalian tissues and clonal cell lines that have been examined contain at least two β-related mRNAs, usually 1.8 and 2.9 kb in length. These results suggest that the mRNAs are the processed products of a small number of closely related genes or of a single highly complex β gene

    INCOME, WEALTH, AND THE ECONOMIC WELL-BEING OF FARM HOUSEHOLDS

    Get PDF
    Agricultural policy is rooted in the 1930s notion that providing transfers of money to the farm sector translates into increased economic well-being of farm families. This report shows that changes in income for the farm sector or for any particular group of farm businesses do not necessarily reflect changes confronting farm households. Farm households draw income from various sources, including off-farm work, other businesses operated, and increasingly nonfarm investments. Likewise, focus on a single indicator of well-being, like income, overlooks other indicators such as the wealth held by the household and the level of consumption expenditures for health care, food, housing, and other items. Using an expanded definition of economic well-being, we show that farm households as a whole are relatively better off than the average U.S. household, but that about 6 percent remain economically disadvantaged relative to the rest of the population.Consumption, farm households, income, wealth, well-being, off-farm employment, Consumer/Household Economics,

    Reusable Agena study. Volume 2: Technical

    Get PDF
    The application of the existing Agena vehicle as a reusable upper stage for the space shuttle is discussed. The primary objective of the study is to define those changes to the Agena required for it to function in the reusable mode in the 100 percent capture of the NASA-DOD mission model. This 100 percent capture is achieved without use of kick motors or stages by simply increasing the Agena propellant load by using optional strap-on-tanks. The required shuttle support equipment, launch and flight operations techniques, development program, and cost package are also defined

    Furnace and support equipment for space processing

    Get PDF
    A core facility capable of performing a majority of materials processing experiments is discussed. Experiment classes are described, the needs peculiar to each experiment type are outlined, and projected facility requirements to perform the experiments are treated. Control equipment (automatic control) and variations of the Czochralski method for use in space are discussed

    Records of Zygopa michaelis Holthuis, 1960 (Decapoda: Anomura: Albuneidae) from the Gulf of Mexico

    Get PDF
    The albuneid mole crab, Zygopa michaelis Holthuis, 1960, which was originally described from Curaçao and recently reported from the Florida East coast (Gore and Becker 1977), is reported from the Gulf of Mexico off the Florida West coast. Of the seven specimens collected, six were taken in 38 m of water off Fort Myers and one in 42 m on the Florida Middle Ground. All seven specimens occurred in substrata composed primarily of carcareous sand
    corecore