X‐ray speckle visibility spectroscopy in the single‐photon limit

The technique of speckle visibility spectroscopy has been employed for the measurement of dynamics using coherent X‐ray scattering. It is shown that the X‐ray contrast within a single exposure can be related to the relaxation time of the intermediate scattering function, and this methodology is applied to the diffusion of 72 nm‐radius latex spheres in glycerol. Data were collected with exposure times as short as 2 ms by employing a resonant shutter. The weak scattering present for short exposures necessitated an analysis formalism based on the spatial correlation function of individual photon charge droplets on an area detector, rather than the usual methods employed for intensity correlations. It is demonstrated that this method gives good agreement between theory and experiment and thus holds promise for extending area‐detector‐based coherent scattering methods to the study of faster dynamics than previously obtainable.     

The millimeter wave rotational spectrum of N-cyanomethanimine,CH2NCN

The rotational spectrum of the short-lived species N-cyanomethanimine, CH₂NCN, has been measured in the frequency range 100–250 GHz. The observed transitions allow the determination of the rotational and centrifugal distortion constants and the nitrogen quadrupole coupling constants for both nitrogen nuclei. The N-cyanomethanimine spectrum was measured directly in the products of the pyrolysis of trimethylenetetrazole. The rotational constants obtained are A = 63 372.995(11) MHz, B = 5 449.347 90(28) MHz, and C = 5 009.559 86(29) MHz; the quadrupole coupling constants are χ_aa = 2.057(39) MHz and χ_bb ? χ_cc = ?7.205(21) MHz for the imine nitrogen, and χ_aa = ?3.264(33) MHz and χ_bb ? χ_cc = ?1.630(18) MHz for the cyano-group nitrogen. The accurate constants obtained allow the calculation of the line position and hyperfine structure of any rotational transition appropriate for a radioastronomical search.     

Braiding of the attractor and the failure of iterative algorithms

Research partially supported by NSF Grant 8120790     

Starkes und überstarkes Auswahlaxiom

It is well known that equivalence holds between the weak axiom of choice (AC) and the well ordering principle (WOP) for sets, resp. between strong AC and WOP for classes. It will be shown that in a theory PC^* with inpredicative classes (i. e. with no restriction of quantification in the defining formula) the super-strong AC used by the informally working mathematician is equivalent to a superstrong WOP. The equivalence between strong AC and super-strong AC is implied by a conditionC refutable in PC^* but provable in PC which is PC^* with predicative classes only and with the general ordered pair axiom. PC^* [super-strong AC] is inconsistent because the super-strong AC impliesC. Therefore the application of choice functions to non-empty classes generally makes a predicative definition of these classes necessary. Connected with these problems is a statement equivalent to the conjunction of the axioms of power set and foundation based on a function which coincides with the von Neumann-function under the assumption of one of the mentioned axioms.     

Eine Erweiterung der Infinitesimalrechnung

Ohne Zusammenfassung     

Influence of a water rinse on the structure and properties of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) films

Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films exhibit a complex structure of interconnected conductive PEDOT domains in an insulating PSS matrix that controls their electrical properties. This structure is modified by a water rinse, which removes PSS with negligible PEDOT loss. Upon PSS removal, film thickness is reduced by 35%, conductivity is increased by 50%, and a prominent dielectric relaxation is eliminated. These results suggest that the removed PSS is not associated with PEDOT and that the conductive domain network is not substantially altered by the removal of a significant fraction of insulator. The removal of PSS may benefit organic light emitting diode fabrication by reducing acid attack on indium tin oxide electrodes and lead to more robust performance in switching circuits by extending the working frequency range.