Brachistochrone of Entanglement for Spin Chains

We analytically investigate the role of entanglement in time-optimal state evolution as an appli- cation of the quantum brachistochrone, a general method for obtaining the optimal time-dependent Hamiltonian for reaching a target quantum state. As a model, we treat two qubits indirectly cou- pled through an intermediate qubit that is directly controllable, which represents a typical situation in quantum information processing. We find the time-optimal unitary evolution law and quantify residual entanglement by the two-tangle between the indirectly coupled qubits, for all possible sets of initial pure quantum states of a tripartite system. The integrals of the motion of the brachistochrone are determined by fixing the minimal time at which the residual entanglement is maximized. Entan- glement plays a role for W and GHZ initial quantum states, and for the bi-separable initial state in which the indirectly coupled qubits have a nonzero value of the 2-tangle.Comment: 9 pages, 4 figure

Upgrade of the X3 super-orbital expansion tube

Expansion tubes are important facilities for the study of high enthalpy hypersonic flows which avoid the non-equilibrium chemical and thermal effects associated with the flow stagnation intrinsic to reflected shock tunnels. X3 is one of the largest freepiston super-orbital expansion tube in the world with an overall length of approximately 69 m and is capable of generating reentry speed flows equivalent to those experienced during a hyperbolic re-entry trajectory. It was originally built with a twostage free-piston driver to achieve the high compression ratio of a large diameter compression tube without the high construction costs of designing the large diameter tube to be strong enough to resist peak driver pressure loads. However, this arrangement proved difficult in operation. This paper describes the upgrades to X3, in respect to its physical layout. The facility has been recommissioned to incorporate a single-piston driver, a steady expansion nozzle and a new test section. Major changes have been made to the free-piston driver with a re-designed piston and launcher and a new end cap tube which is 200 mm thick to contain driver pressures up to 80 MPa. The re-designed piston introduces an area change at the primary diaphragm, ensuring that the maximum increase in total pressure and temperature can be gained as the driver gas undergoes unsteady expansion from sonic to supersonic conditions. The compression process steadily increases up to Mach 1 at the throat then gains of up to an order of magnitude in total temperature and pressure can be realised as the unsteady expansion process takes over. The area change will also increase test times; with a throat at the primary diaphragm, the piston mechanics can be more readily tuned to minimise reflection of waves off the piston which would otherwise reduce the test time. A new Mach 10 steady expansion nozzle has been developed which has increased the core flow and the test time for appropriate conditions. The dump tank has been replaced with a larger tank and test section giving a larger volume with greater potential for instrumentation

The response of four calcium hydroxides on monkey pulps

. Dentinal bridge formation and pulpal responses of four calcium hydroxide materials, pulp capping medicaments, MFC®, Experimental MFC-12, Dycal® and Pulpdent®, were evaluated in primary and permanent monkey teeth. A total of 60 primary and 60 permanent teeth were used with each material placed in a Class V cavity exposure in Rhesus monkey teeth. The materials were placed on the exposed pulp tissue and were histologically evaluated at 3 days, 5 weeks and 8 weeks. After perfusion the teeth were processed using routine histological procedures. The 3-day pulpal responses in both primary and permanent teeth were moderate, characterized by disruption of the pulpal tissue directly beneath the exposure site and a zone of acute inflammation and hemorrhage in the underlying pulp. The 5-week response showed histological differences between the four medicaments, with Dycal producing the least amount of pulpal irritation with reparative dentin bridges occurring in 50% of the permanent teeth. Experimental MFC-12 stimulated one reparative dentin bridge, while Pulpdent and MFC showed no evidence of bridge formation. Pulpal responses to Dycal were moderate and moderate to severe for the other calcium hydroxide compounds. No reparative dentin bridges were seen in the primary teeth at 5 weeks with any of the materials, and the pulpal responses were of a moderate degree at that time. Eight-week responses were similar to the 5-week responses. Dycal provoked a slight to moderate pulpal response with 50% success at bridging. Experimental MFC-12 initiated pulpal responses in the moderate to severe range with some bridging evident. Pulpdent incited moderate to severe histological responses with three teeth demonstrating bridge formation, and MFC provoked severe pulpal responses with no bridging. Primary teeth showed some bridging for all compounds except those treated with MFC, in which no evidence of bridging occurred, and moderate to severe pulpal responses were present.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72823/1/j.1600-0714.1980.tb00393.x.pd

Trends in source gases

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form

Relativistic Klein-Gordon charge effects by information-theoretic measures

The charge spreading of ground and excited states of Klein-Gordon particles moving in a Coulomb potential is quantitatively analyzed by means of the ordinary moments and the Heisenberg measure as well as by use of the most relevant information-theoretic measures of global (Shannon entropic power) and local (Fisher's information) types. The dependence of these complementary quantities on the nuclear charge Z and the quantum numbers characterizing the physical states is carefully discussed. The comparison of the relativistic Klein-Gordon and non-relativistic Schrodinger values is made. The non-relativistic limits at large principal quantum number n and for small values of Z are also reached.Comment: Accepted in New Journal of Physic

The Mechanism of CO and CO₂ Hydrogenation to Methanol over Cu-Based Catalysts

Methanol, an important chemical, fuel additive, and precursor for clean fuels, is produced by hydrogenation of carbon oxides over Cu-based catalysts. Despite the technological maturity of this process, the understanding of this apparently simple reaction is still incomplete with regard to the reaction mechanism and the active sites. Regarding the latter, recent progress has shown that stepped and ZnOx-decorated Cu surfaces are crucial for the performance of industrial catalysts. Herein, we integrate this insight with additional experiments into a full microkinetic description of methanol synthesis. In particular, we show how the presence or absence of the Zn promoter dramatically changes not only the activity, but unexpectedly the reaction mechanism itself. The Janus-faced character of Cu with two different sites for methanol synthesis, Zn-promoted and unpromoted, resolves the long-standing controversy regarding the Cu/Zn synergy and adds methanol synthesis to the few major industrial catalytic processes that are described on an atomic level

Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey

This paper provides a tutorial and survey for a specific kind of illustrative visualization technique: feature lines. We examine different feature line methods. For this, we provide the differential geometry behind these concepts and adapt this mathematical field to the discrete differential geometry. All discrete differential geometry terms are explained for triangulated surface meshes. These utilities serve as basis for the feature line methods. We provide the reader with all knowledge to re-implement every feature line method. Furthermore, we summarize the methods and suggest a guideline for which kind of surface which feature line algorithm is best suited. Our work is motivated by, but not restricted to, medical and biological surface models.Comment: 33 page