Stripe Disordering Transition

We have recently begun Monte Carlo simulations of the dynamics of stripe phases in the cuprates. A simple model of spinodal decomposition of the holes allows us to incorporate Coulomb repulsion and coherency strains. We find evidence for a possible stripe disordering transition, at a temperature below the pseudogap onset. Experimental searches for such a transition can provide constraints for models of stripe formation.Comment: 4 pages LaTex, 2 ps figures (U. of Miami Conference HTS99

Heat-load simulator for heat sink design

Heat-load simulator is fabricated from 1/4-inch aluminum plate with a contact surface equal in dimensions and configuration to those of the electronic installation. The method controls thermal output to simulate actual electronic component thermal output

SO(6)-Generalized Pseudogap Model of the Cuprates

The smooth evolution of the tunneling gap of Bi_2Sr_2CaCu_2O_8 with doping from a pseudogap state in the underdoped cuprates to a superconducting state at optimal and overdoping reflects an underlying SO(6) instability structure of the (pi,0) saddle points. The pseudogap is probably not associated with superconductivity, but is related to competing nesting instabilities, which are responsible for the stripe phases. We earlier introduced a simple Ansatz of this competition in terms of a pinned Balseiro-Falicov (pBF) model of competing charge density wave and (s-wave) superconductivity. This model gives a good description of the phase diagram and the tunneling and photoemission spectra. Here, we briefly review these results, and discuss some recent developments: experimental evidence for a non-superconducting component to the pseudogap; and SO(6) generalizations of the pBF model, including flux phase and d-wave superconductivity.Comment: 6 pages LaTex, 4 ps figures (U. of Miami Conference HTS99

Introduction to mathematical physics

A comprehensive survey of all the mathematical methods that should be available to graduate students in physics. In addition to the usual topics of analysis, such as infinite series, functions of a complex variable and some differential equations as well as linear vector spaces, this book includes a more extensive discussion of group theory than can be found in other current textbooks. The main feature of this textbook is its extensive treatment of geometrical methods as applied to physics. With its introduction of differentiable manifolds and a discussion of vectors and forms on such manifolds as part of a first-year graduate course in mathematical methods, the text allows students to grasp at an early stage the contemporary literature on dynamical systems, solitons and related topological solutions to field equations, gauge theories, gravitational theory, and even string theor

Feasibility demonstration for electroplating ultra-thin polyimide film

The effect of electrodeposition variables on film thickness was investigated using a dilute polyimide solution as a bath into which aluminum (as foil or as a vapor deposited coating) was immersed. The electrodeposited film was dried for 2 hours at 93 C (primarily to remove solvent) and cured for 18 hours at 186 C. Infrared studies indicate that imide formation (curing) occurs at 149 C under vacuum. From a conceptual viewpoint, satisfactory film metallized on one side can be obtained by this method. The cured ultra thin polyimide film exhibits properties equivalent to those of commercial film, and the surface appearance of the strippable polyimide film compares favorably with that of a sample of commercial film of thicker gauge. The feasibility of manufacturing approximately one million sq m of ultra thin film capable of being joined to fabricate an 800 m by 9 800 m square from starting material 0.5 to 1 m wide for space erectable structures was demonstrated

Sequencing and analysis of the gastrula transcriptome of the brittle star Ophiocoma wendtii

Background The gastrula stage represents the point in development at which the three primary germ layers diverge. At this point the gene regulatory networks that specify the germ layers are established and the genes that define the differentiated states of the tissues have begun to be activated. These networks have been well-characterized in sea urchins, but not in other echinoderms. Embryos of the brittle star Ophiocoma wendtii share a number of developmental features with sea urchin embryos, including the ingression of mesenchyme cells that give rise to an embryonic skeleton. Notable differences are that no micromeres are formed during cleavage divisions and no pigment cells are formed during development to the pluteus larval stage. More subtle changes in timing of developmental events also occur. To explore the molecular basis for the similarities and differences between these two echinoderms, we have sequenced and characterized the gastrula transcriptome of O. wendtii. Methods Development of Ophiocoma wendtii embryos was characterized and RNA was isolated from the gastrula stage. A transcriptome data base was generated from this RNA and was analyzed using a variety of methods to identify transcripts expressed and to compare those transcripts to those expressed at the gastrula stage in other organisms. Results Using existing databases, we identified brittle star transcripts that correspond to 3,385 genes, including 1,863 genes shared with the sea urchin Strongylocentrotus purpuratus gastrula transcriptome. We characterized the functional classes of genes present in the transcriptome and compared them to those found in this sea urchin. We then examined those members of the germ-layer specific gene regulatory networks (GRNs) of S. purpuratus that are expressed in the O. wendtii gastrula. Our results indicate that there is a shared ‘genetic toolkit’ central to the echinoderm gastrula, a key stage in embryonic development, though there are also differences that reflect changes in developmental processes. Conclusions The brittle star expresses genes representing all functional classes at the gastrula stage. Brittle stars and sea urchins have comparable numbers of each class of genes and share many of the genes expressed at gastrulation. Examination of the brittle star genes in which sea urchin orthologs are utilized in germ layer specification reveals a relatively higher level of conservation of key regulatory components compared to the overall transcriptome. We also identify genes that were either lost or whose temporal expression has diverged from that of sea urchins