The dynamic response of an inhomogeneous plasma diode to an appliedpotential drop

Recent measurements of the response to an applied step voltage in collisionless plasmas have demonstrated the importance of the initial ion density distribution for the resulting time evolution and the formation of electric double layers. The dynamic response of a plasma diode to an applied step voltage is studied by particle-in-cell simulations and an analytical model. It is shown that an ion-density cavity (a local ion-density minimum with a width of many Debye lengths) can support large potential drops for several electron transit times. The potential drop extends over a distance related to the cavity width. When the applied potential drop exceeds a certain critical value, which depends on the cavity depth, the drop instead concentrates in a cathode sheath, which also is the response obtained for homogeneous initial plasma. The existence regions for the two different response in the appropriate parameter plane are found from the simulations and shown to agree with the regions predicted analytically. The analytical potential profiles agree with those simulated     

The implicate order and Prigogine's notions of irreversibility

In this paper, a very close relationship between Prigogine's notions of irreversibility and the implicate order is brought out. Certain of Prigogine's basic assumptions with regard to irreversible processes are also shown to be the equivalent of the introduction of nilpotent operators in the algebra underlying the implicate order.     

Growth of carbon nanotubes from waste blast furnace gases at atmospheric pressure

Carbon emissions from industrial sources are of major global concern, especially contributions from the steel manufacturing process which accounts for the majority of emissions. Typical blast furnace gases consist of CO₂ (20‐25%), CO (20‐25%), H₂ (3‐5%) and N₂ (40‐50%) and trace amounts of other gases. It is demonstrated that gas mixtures with these compositions can be used at atmospheric pressure to grow carbon nanotubes (CNTs) by chemical vapor deposition (CVD) on to steel substrates, which act as catalysts for CNT growth. Computational modelling was used to investigate the CNT growth conditions inside the CVD chamber. The results show that industrial waste pollutant gases can be used to manufacture materials with significant commercial value, in this case CNTs.     

Complex energies and beginnings of time suggest a theory of scattering and decay

Many useful concepts for a quantum theory of scattering and decay (like Lippmann-Schwinger kets, purely outgoing boundary conditions, exponentially decaying Gamow vectors, causality) are not well defined in the mathematical frame set by the conventional (Hilbert space) axioms of quantum mechanics. Using the Lippmann-Schwinger equations as the takeoff point and aiming for a theory that unites resonances and decay, we conjecture a new axiom for quantum mechanics that distinguishes mathematically between prepared states and detected observables. Suggested by the two signs ±i? of the Lippmann-Schwinger equations, this axiom replaces the one Hilbert space of conventional quantum mechanics by two Hardy spaces. The new Hardy space theory automatically provides Gamow kets with exponential time evolution derived from the complex poles of the S-matrix. It solves the causality problem since it results in a semigroup evolution. But this semigroup brings into quantum physics a new concept of the semigroup time t = 0, a beginning of time. Its interpretation and observations are discussed in the last section.     

The time reversal operator for semigroup evolutions

A quantum theory combining an irreversible time evolution semigroup with a time reversal operator is presented.